摘要:

ANALYST, JANUARY 1993, VOL. I18 89 Determination of Malonaldehyde in Human Plasma: Elimination of Spectral Interferences in the 2-Thiobarbituric Acid Reaction Anunciacion Espinosa-Mansilla, Francisco Salinas and Amparo Rubio Leal Department of Analytical Chemistry, University of Extremadura, 06077 Badajoz, Spain A selective, derivative spectrophotometric method has been developed for the determination of malonal- dehyde (MLD), based on a reaction with 2-thiobarbituric acid (TBA). The proposed method has been applied t o the determination of MLD in human plasma. A study t o eliminate several spectral interferences is described. A comparative study of the results obtained using the proposed derivative method and a conventional TBA method applied t o human plasma is presented and the advantages of the proposed method over the conventional method for the determination of MLD in human plasma are evaluated.Keywords: Human plasma; malonaldeh yde determination; derivative spectrophotometry; 2-thiobarbituric acid test Malonaldehyde (MLD) is a volatile side product generated in the enzymic oxygenation of arachidonic acid and an end product of the oxidative degradation of lipids. The metabolic- ally uncoupled oxygenation of polyunsaturated fatty acid leading to lipid-derived MLD is a degenerative process of oils, foodstuffs and lipid-rich biomolecular assemblies (mem- branes, lipoproteins), which has been somewhat imprecisely termed auto-oxidation. 1 The ability of MLD to alter and/or cross-link a variety of biological molecules might contribute to its toxicity,2 and its mutagenic and/or carcinogenic properties could reflect adduct formation with nucleic acid bases.3.4 Covalent modification of lipoproteins with MLD might play a pathogenic role in atherosclerosis .s The major urinary metabolite of MLD in humans is 2-N-acetyl-6-N-( 1-formylvinyl)lysine, which appears to be derived from the degradation of proteins, phospholipids and nucleic acids, which have reacted with MLD via their amino groups.6.7 Stocks et a1.8 employed the MLD level as a measure of human red cell lipid auto-oxidation by H202 and their assay has become the standard (conventional method) for the determination of the susceptibility of red blood cells to lipid peroxidation. In its free form, MLD can be determined by ultraviolet (UV) absorptiome try ,Y polarography 1 0 and high-performance liquid chromatography (HPLC). 1 1.12 The 2-thiobarbituric acid (TBA) test is an extensively used procedure for determining MLD; one molecule of MLD reacts with two molecules of TBA with the elimination of two molecules of water.'3 This reaction produces a fluorescent red pigment with a high molar absorptivity, between 5- and 10-fold greater than that of MLD itself in the UV.1.' The colour intensity and its ready formation have prompted detailed investigation of the reaction between MLD and TBA.15.16 During the TBA reaction, many lipid-derived monofunc- tional aldehydes [2-furaldehyde (FIJR), 5-hydroxymethyl-2- furaldehyde (HMF), ethanal-sucrose (ETA-SUC) binary mixtures and glyoxal (GLY), etc.] form adducts with TBA which fluoresce and/or contribute, with a yellow or orange colour, to the reaction.17-20 Hence, these reactions can directly interfere with the spectrophotometric quantification of MLD.Another source of error arises from the presence of pigments, particularly in plant materials, contributing to spuriously high estimates of MLD content (e.g., biliverdin, BIL) .20 In addition, sample acidification can induce turbidity or precipitate non-lipid sample constituents (e.g., proteins), and clarification of the sample prior to the reaction is generally accomplished by centrifugation." Pigments can be easily extracted into organic solvents from the TBA-test mix- tures,22923 although no solvent extraction procedure yet reported is selective toward any particular pigment.In a recently published review,24 it was concluded that the determination of MLD and interpretation of sample MLD content and TBA response in studies of lipid peroxidation require caution, especially for biological systems. In human plasma, increased susceptibility to lipid peroxida- tion of the erythrocyte membrane has been described in haematological disorders, as well as in a b-lipoproteinaemia and tocopherol deficiency.25 Largilliere and Melanconl2 have found in normal plasma samples a concentration of 3.8 pmol 1 - 1 of material that reacts with TBA using the conventional method, and no detectable MLD content when HPLC is used. Hence, whether the elevated MLD content reported in diverse pathological conditions is genuinely due to an increased production of MLD or to other unknown substances reacting with TBA remains to be elucidated.In this work, a derivative spectrophotometric method for MLD determination, based on its reaction with TBA, is described. Owing to the advantageous nature of derivative spectrophotometry for the determination of absorbent ana- lytes, in the presence of several interferent species with overlapped spectra, and for the elimination of the background signal,26 it has been possible to determine MLD selectively in human plasma. Experimental Apparatus A Milton Roy Spectronic 3000 array spectrophotometer provided with Milton Roy software was used for all absorption measurements, storage and analysis of the spectrophotometric data. Differentiation was performed by the simplified least- squares procedure of Savitzky and Golay.27 A thermostatic- ally controlled bath, Selecta Unitronic 320 OR, was used for temperature control.Reagents I, 1,3,3-Tetraethoxypropane (TET) was prepared by dissolv- ing 0.01 g of reagent (Sigma) in 100 ml of water. Malon- appropriate was prepared by generation in situ from TET in acid medium. A 3 x 10-2 mol I-' TBA standard solution was prepared by dissolving 0.45 g of reagent (Sigma) in 100 ml of water and sonicating for 15 min. A 0.01% m/v HMF solution was prepared by dissolving 0.01 g of reagent (Sigma) in 100 ml of water. A 0.01% m/v FUR standard solution was prepared by dissolving 0.01 g of reagent (Sigma) in 100 ml of water. A90 W C m n n 0.40 v) a 0.20 ANALYST, JANUARY 1993, VOL. 118 - - 0.01% m/v GLY solution was prepared by dilution of the appropriate volume of reagent solution (30% in aqueous medium) (Sigma) in 100 ml of water. A 0.01% m/v BIL solution was prepared by dissolving 0.01 g of reagent in 100 ml of water previously made basic.A 0.01% m/v (in each component) ETA-SUC solution was prepared by dissolving 0.01 g of sucrose reagent plus 0.01 g of ethanal reagent (Sigma) in 100 ml of water. Demineralized water was used and all experiments were performed with analytical-reagent grade chemicals. B - 0 e = - - e I I Procedures for Determining MLD General procedure Place an aliquot of TET solution containing an amount of TET equivalent to 1.25-12.5 pg of MLD, 1 ml of 12 rnol I-* hydrochloric acid and 12 ml of 3 x 10-2 moll-' TBA solution in a 25 ml calibrated flask and dilute to the mark with de-ionized water.Heat the samples at 60°C for 60 min in a thermostatically controlled bath and then record the absorp- tion spectra of the samples between 450 and 600 nm and the first-derivative spectra using a AL of 17 nm. Determine the MLD content from the first-derivative spectrum by automatic- ally measuring the peak-to-peak amplitude ,5J3 and using the appropriate calibration graph. Human plasma Direct procedure. Plasma samples were analysed imme- diately after centrifugation. Samples were prepared in 25 ml calibrated flasks to contain 500 pl of human plasma and the General Procedure was followed. Procedure with previous precipitation of the proteins. Acetonitrile (2000 pI) was vigorously mixed with 1000 pl of plasma and centrifuged.The supernatant was filtered through a 0.4 pm filter, an aliquot of 1500 pl was transferred into a 25 ml calibrated flask and the General Procedure followed. Results and Discussion Free MLD is a strongly reactive compound that is unstable in aqueous media and which shows an absorption spectrum in the UV region with a maximum at 244 nm. The MLD reacts with TBA in acidic media and gives rise to a stable and soluble derivatized compound with an absorption maximum located at 532 nm, when the 2 : 1, TBA-MLD adduct is preferentially formed; for low TBA concentrations, a second absorption maximum is located at 395 nm. The absorption spectra for samples containing 0.47 pg ml- 1 of derivatized MLD and free MLD are shown in Fig. 1. An elevated bathochromic shift and a highly sensitive absorption signal are observed for the derivatized MLD.MLD + TBL 0.79 - z e $ n m 4 0.39 - .Q MLD 0 300 400 500 600 700 Wavelengthhm Fig. 1 Absorption spectra of derivatized and free MLD Optimization of the MLD Generation Owing to the instability of aqueous solutions of MLD, standard samples of MLD generated in situ from TET were employed. The optimum chemical and physical conditions for its generation were studied. The rate of MLD generation depends on the acid concentration. The kinetic curves for different hydrochloric acid concentrations at room temperat- ure are shown in Fig. 2. About 2-3 min are sufficient for the development of the reaction using a 1 rnol 1-1 hydrochloric acid concentration. A waiting time of 5 min was selected as sufficient for the MLD generation.A calibration graph was obtained at 244 nm for an MLD concentration of up to 5.95 pg rnl-l, generated in situ from standard samples of TET. The generation was quantitative over the concentration range studied. Study of the TBA-MLD Reaction Optimization of the chemical conditions Several chemical parameters affect the TBA-MLD forma- tion, such as temperature, heating time and acid concentra- tion. Numerous and sometimes drastic chemical conditions have been reportedhJ8.29 for diverse specific applications, but the chemical conditions for the determination of MLD have been studied here, with the aim of selecting the mildest possible chemical conditions for this reaction. A certain amount of MLD can be originated during the reaction with TBA at elevated temperature, from thermal decomposition of fatty peroxide, giving rise to false results in the determination of MLD in real samples.24 The influence of the acidic medium was studied using different hydrochloric acid concentrations for samples con- taining 1.19 pg ml-1 of MLD and 8.4 x 10-3 rnol 1-1 L I I I 0 5.00 10.00 15.00 20.00 Ti m e/m i n Fig.2 rnol I-' HCI; B, 0.5 rnol 1-1 HCl and C, 1.0 rnol 1-1 HCI Kinetic curves for MLD generation in acidic media. A , 0.1 0.80 F 0.60 h AANALYST, JANUARY 1993, VOL. 118 0.400 91 - ?a I 0 -0.100 ' 1 I _. 0 40 80 120 Heating time/min Fig. 4 Influcncc of heating time on the formation of TBA-MLD at A and C, 60 "C and B and D, 80 "C. Absorbance monitored at 531 nm (A and B) and 395 nm (C and D) /I 1.200 0.003 0.008 0.013 Fig.5 Influcncc of TBA concentration on the formation of TBA-MLD. A and D, 0.5 moll-' HCl; B and C. 5.0 moll-1 HCI. 0 = 532 nm; 0 = 395 nm [TBA]/mol I- concentration of TBA; the samples were maintained at 40°C for 30 min. The absorbance at 532 nm was constant between 0.1 and 1.2 moll- 1 hydrochloric acid and decreased for higher concentrations (Fig. 3). The absorbance at 39.5 nm increased slightly when the acid concentration increased. A 0.5 mol 1-1 HCl concentration was selected as optimum for the complete development of the red colour. The influence of the TBA concentration was studied for two different acidity values, 0.5 and 5.0 mol 1-1 HCl. In both media, an increase of the TBA concentration favoured the formation of a species that absorbed at 532 nm; however the absorbance maximum, located at 359 nm, decreased when the TBA concentration increased (Fig.4). A 0.014 mol 1-1 TBA concentration was selected as optimum, because TBA solubil- ity does not allow the use of higher TBA concentrations. Influence of temperature and heating time The effect of temperature on the reaction was examined whilst maintaining a constant heating time of 30 min. The tempera- ture was varied between 20 and 80°C and the samples were cooled to room temperature, before the absorption spectra were recorded. The absorbance at 395 nm was constant over the range of temperatures studied whereas the absorbance at 532 nm increased markedly with temperature up to 6O"C, while the absorbance was constant in the range from 60 to 80°C.The influence of the length of heating time between 20 and 100 min at 60 and 80°C was examined. At 60°C the absorbance was constant for a heating time of between 50 and 100 min, however, at 80 "C the reaction product was unstable for heating times of longer than 50 min (Fig. 5 ) . An optimum heating time of 60 min at 60°C was selected. 1.200 0.800 0 m f! % a a 0.400 0 0.020 1 (b) 0.01 0 I a m .- c .- & O Iz U w .- LL -0.010 -0.020 320 420 520 620 Wavelengthlnm (a) Zero-order and (b) first-derivative absorption spectra of Fig. 6 TBA-MLD in the 0.054.5 pg ml-l concentration rangc Conventional and first-derivative spectral characteristics Under optimum conditions, the derivatized MLD shows an absorption maximum at 531 nm. First-derivative spectra were obtained with different AX values and 17 nm was considered as suitable.The conventional and first-derivative spectra are shown in Fig. 6 for different MLD concentrations. Calibration graphs for MLD concentrations of up to 0.5 pg ml-1 can be established using measurements of the absorbance at 531 nm and the first-derivative peak-to-peak signal 1D521,543. Relative errors of 0.92 and 0.98% ( n = 11, 95% confidence level) were obtained for the conventional and derivative methods, respectively. The equations and the statistical parameters are summarized in Table I. Influence and Elimination of Diverse Interferent Species Study of the interferences Many diverse interferent species are described in the literature for the reaction of TBA with MLD. Some aldehydes produced in hexose degeneration react with TBA, forming pigments that absorb strongly in the visible spectral region and which are, therefore, potential interferents in the determination of MLD with TBA using the conventional method.The chemical behaviour of MLD with TBA in the presence of GLY, HMF, FUR, SUC-ETA mixtures and BIL was investigated under the optimum conditions previously ascer- tained, with the aim of establishing the reaction characteristics of each interferent and hence of avoiding interference. In order to investigate the degree of interference of the above-mentioned species in the reaction of MLD with TBA, the following experiments were carried out. Maintaining a constant concentration of MLD of 0.177 pg ml-1, under optimized chemical conditions and in the presence of the interferent species over a range of concentrations of between 1.8 and 18 pg ml-l (1 : 10 to 1 : 100 MLD: interferent m/m92 ANALYST, JANUARY 1993.VOL. 118 40 -- 30 - 0 - - -10 Table 1 Statistical parameters for thc determination of MLD -'L I I I I I Analytical Linear LOD*/ Method signal Equation regression ng ml-1 Conventional 531 nm A = 2.32[MLD]T + 0.009 0.9990 0.36 Derivative '0521.543 1052i,543 = O.O77[MLD]t + 0.0001 0.9997 1.30 * LOD = limit of dctection. t pg rn1-l. 0.50 r I 0.40 0.30 0.20 0.10 0 0.004 0 .- CI > -0 .- & O 4- r .- L -0.004 I I 375 475 575 675 Wavelengthhm Fig. 7 ( a ) Absorption spectra: A, TBA-MLD (0.17 pg ml-1); B. TBA-FUR (18 pg ml-I): C, TBA-FUR (10 pg ml-I); D, TBA-FUR (1.8 pg mi-1); F, TBA-MLD-FUR (MLD-to-interferent ratio = 1 : 10); and G.TBA-MLD-FUR (MLD-to-interferent ratio = 1 : 100). (b) First-derivative spectra: A, TBA-MLD (0.17 pg ml-1): B, TBA-FUR (18 pg ml-1) and G. TBA-MLD-FUR (MLD-to-inter- ferent ratio = 1 : 100) -0.008 2.000 I I 1.500 0 c: m e 1.000 z n a 0.500 320 420 520 620 Fig. 8 Absorption spectra: A, TRA-MLD (0.17 pg ml-l); B, TBA-HMF (18 pg ml-1); C, SUC-ETA (18 ygml-1); D, TBA-GLY (18 pg ml-1) and E, TBA-BIL (18 pg ml-I) Wavelengthhm Interference leve Is 1 50 1 (a) I s FUR HMF SUC-ETA GLY BIL 2 -Conventional E S Derivative L W 16 14 6 4 2 0 I I I I FUR HMF SUC-ETA GLY BIL = Conventional Derivative Types of interference interferences 71 Vl a : No competitive reaction with TBA b: No reaction with TBA c: Competitive reaction with TBA Fig. 9 Levels and types of interferents in the determination of MLD with TBA.( a ) lnterferent-to-MLD ratio = 100 : 1 and (6) interfcrcnt- to-MLD ratio = 10: 1 ratio), the conventional and first-derivative spectra were obtained against THA solution. The absorption spectrum of the product of the reaction between FUR and TBA is shown in Fig. 7(a), and is compared with the absorption spectra obtained for FUR-TBA in the presence of MLD for a 1 : 100 MLD : FUR ratio. The absorption spectrum obtained for the product of the reaction between TBA and MLD is alsoANALYST, JANUARY 1993, VOL. 118 I 1 I 93 0.600 0.400 0.200 0.600 0.400 0.200 0 1 I I 325 425 525 62 5 325 425 525 625 0.01 0 0.005 o, .- 4- > U .- G o 4- z .- LL -0.005 0.008 o, 0.003 .- 4- > .- G z -0.002 .- LL -0.007 included.The TBA-FUR product exhibits a continuous absorption between 475 and 575 nm and a second absorption maximum is located at about 420 nm. It is well known that derivative spectrophotometry is often used for reducing the effect of background spectral interfer- ences. The first-derivative spectra for the samples mentioned previously are shown in Fig. 7(6). The derivative signal 1Ds21,s43 for FUR-TBA is zero and the values obtained for MLD determination both in the presence and absence of FUR are similar. Behaviour similar to that previously described is also observed in the presence of HMF. The absorption spectrum for the TBA-HMF product shows an absorption maximum located at about 435 nm and a second absorption region in the range between 490 and 620 nm.The absorption spectrum of the GLY-TBA product only shows an absorption maximum in the range between 420 and 490 nm and this product does not absorb at higher wavelengths. However, in the presence of GLY the results obtained for the determination of MLD are less than the expected results; a small relative error is also obtained. In this case, a chemical interference is produced due to the consump- tion of TBA in the reaction with GLY. Similar behaviour is observed for SUC-ETA mixtures, but the relative interfer- ence level is higher. The pigment BIL exhibits continuous absorption through- out the visible spectrum, with absorption maxima located at 630 and 350 nm and it does not react with TBA. Bilverdine produces a spectral interference from overlapping spectra in the conventional TBA method.The absorption spectra for TBA interferents are shown in Fig. 8. Elimination of Interferences and Comparative Study With the aim of eliminating the above-mentioned interfer- ences, the proposed derivative method was applied. The conventional method was also applied and the results obtained were compared with those obtained using the derivative method. The results obtained for two different inter- ferent:MLD ratios and a schematic diagram of the types of interferences found are shown in Fig. 9. In all cases, a very notable decrease of the errors is observed when the derivative method was applied, except for the chemical interference of SUC-ETA. Applications The amount of material that reacts with TBA (MLD plus MLD-like compounds) present in human plasma is described in the literature; 3.8 pmoll-* is obtained using a conventional TBA method, however, MLD remains undetected using a direct HPLC method.12 In this work, the proposed derivative and conventional methods were applied to the determination of MLD in human plasma and a comparative study of proteinized and deproteinized samples was made.Blood was collected from 15 control subjects by venipunc- ture and a pool of the samples was made. After centrifugation, the plasma was immediately divided into two similar aliquots. The first aliquot was deproteinized as described above and the other was not pre-treated. The standard additions method was applied to both samples, proteinized and deproteinized. The absorption and derivative spectra were obtained (Fig.10) and the recovery ratios of known amounts of MLD added to the plasma were calculated for both series by applying both conventional and derivative methods using calibration graphs obtained under the same chemical conditions. The amounts of MLD in the plasma (taking into account that a 1 + 16 dilution of the samples was made) and the interference of the plasma matrix in the determinations were established. The recovery values obtained show that MLD had not been generated during the TBA reaction with plasma samples (Tables 2 and 3). The MLD content obtained using the derivative and94 ANALYST, JANUARY 1993, VOL. 118 Table 2 Results obtained by application of conventional and derivative methods to previously deproteinized human plasma Conventional method" Derivative method? Added/pg ml-1-t Found/pg ml-l$ Recovery(%) Added/pg ml-'-1 Found/pg ml- l$ Recovery(%) 0.00 0.48 - 0.00 0.04 2.95 3.46 101 2.95 3.22 5.90 6.54 103 5.90 6.25 8.85 9.3s 100 8.85 9.03 11.80 12.49 102 3 1.80 12.45 " Slope/pg-I ml cm-1 = 2.31.-1 Slope/Lg-l ml cm - 1 = 0.079. $ A 1 + 49 dilution was made in the original plasma sample prior to measurements. - I07 105 101 105 Table 3 Results obtained by direct application of conventional and derivative methods to human plasma Conventional method" Derivative methodt Added/pgml-l Found& ml-l$ Recovery(%) Added/pgmlkL Found/pg ml- l $ Recovery(%) - 0.00 0.00 - 0.00 0.24 2.95 3.46 110 2.95 2.32 78 5.90 5.80 94 5.90 4.38 74 8.85 9.13 101 8.85 6.71 76 11.80 12.12 101 11 .80 8.77 74 * Slopdpg-1 ml cm-I = 2.31.-1 Slopc/pg-' ml cm - 1 = 0.059. $ A I + 49 dilution was made in the original plasma sample prior to measurements. 0.5 r 0.4 - E 0.3 G = 0.2 0.1 0 Direct Deprotei n ized Sample = Conventional Derivative Cl TBA-test(literature1 E HPLC Fig. 11 using different methods Comparative diagram of the human plasma MLD content conventional methods and the literature data obtained using the TBA test and HPLC are compared in Fig. 11. Conclusions When using the conventional method, appreciable amounts of MLD are measured in human plasma, similar to the amounts described previously;" these results are false because several MLD-like TBA compounds absorb at 532 nm. However, when the proposed derivative method was applied a very low MLD content, less than the limit of detection, was detected in human plasma in accordance with the results described for the HPLC method.12 Adequate recovery values for MLD in deproteinized human plasma samples are obtained and this indicates that the established chemical conditions are adequate to determine MLD in plasma.Smaller recovery values for MLD are obtained owing to interference from precipitation of the sample matrix, when the samples have not been deproteinized. The authors are grateful to the DGICYT of Spain for financial support (Project No. PBSS-0431) and to Dr. F. Henao Davila for helpful discussions. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 References Miller, D. M., Buettner, G . R., and Aust, S. D., Free Radicals Biol. Med.. 1990, 8, 95. Nair, V., Cooper, C.S . , and Vietti, D. E., LipidA, 1986, 21, 6. Nair. V., Turner, G. A., and Offerman, R . J . , J. Am. Chem. SOC., 1984, 106, 3370. Basu, A . K.. O'Hara, S . M., Valladier, P., Stone, K.. Mols, O., and Marnctt, L. J., Chern. Res. Toxicol., 1988. 1, 53. Steinberg. D., Parthasarathy, S . , Carew. T. E.. Khoo, J. C., and Witztum, J . L., New Engl. J . Med., 1989, 320, 915. Hadley, M., and Draper, H . H . , Free Radicals Biol. Med., 1989, 6, 49. Draper, H. H., McGirr, L. G., and Hadley. M., Lipidy, 1986, 21, 305. Stocks, J., Kemp, M., and Dormandy, T. L., Br. 1. Haemaf., 1971, 20. 95. Kwan, T. W., and Watts, B. M., Anal. Chem., 1963, 35, 733. Bond, A. M.. Deprez, P. P.. Jones, R. D., Wallace, G. G., and Briggs, M. H.. Anal. Chem., 1980. 52, 2211. Sterbauer, H . , and Slater, 7'. F.. IFCS Med. Sci., 1981, 9, 749. Largilliere, C., and Melancon, S. B., Anal. Biochem., 1988, 170, 123. Sinnhuber, R. O., Yu, I . C., and Yu 7'. C., Food RPS., 19.58,23, 620. Sawicki. E.. Stanley. T. W., and Johnson. H., Anal. Chem., 1963, 35, 199. Nair, V.. and Turner, G. A., Lipids, 1984, 19, 804. Yu, L. W.. Latriano. L.. Duncan. S . , Hartwick, R. A.. and Witz, G., Anal. Biochem.. 1086, 156, 326. Kosugi, H., and Kikugawa, K., Lipids, 1986, 21. 537. Kosugi, H.. Kato, T . , and Kikugawa. K., Anal. Biochem., 1987, 165, 456. Kosugi. H., and Kikugawa, K., Free Radicals Biol. Med., 1989, 7. 205. Levillain, P., and Fompeydie, D . , Analusis, 1986. 14, 1. Ottolenghi, A., Arch. Biochem. Biophys.. 1959, 77, 355.ANALYST, JANUARY 1993, VOL. 118 95 22 Asakawa, T., and Matsushita. S., Lipids, 1980, 15, 137. 23 Kosugi. H., Kato, T., and Kikugawa, K . , Lipids, 1988,23,1024. 24 Janero, D. R., Free Radicals Biol. Med., 1990, 9, 515. 25 Stocks, J., Kcmp, M., and Dormandy, T. L., Lancet, 1971, 1, 266. 26 Salinas, F., Espinosa-Mansilla, A . , and Berzas, J. J., Anal. Clzim. Acta, 1990, 233. 289. 27 Savitzky, A., and Golay, M. J . E., Anal. Chern.. 1964,36, 1627. 28 McKnight, R. C., and Hunter, F. E., Biochim. Biophys. Acra, 1965, 98, 640. 29 Ramirez, M. A., and Spillman, D. H . , J. Food Sci., 1987, 52. 500. Paper 210,3876E Received July 21, 1992 Accepted September 10, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800089

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 97 Spectrophotometric Determination of Stability Constants of Anti-stepwise Complexes Shi-Fu Zou, Jie Zhou* and Wei-An Liangt Department of Chemistry, Shandong University, Jinan, Shandong, People‘s Republic of China There is a considerable knowledge of chemical equilibria of the stepwise formation of complexes in coordination chemistry. However, the coordination equilibria of complex formation of the type, M + R e MR s M2R e M3R e ... e M,R is less well understood. As their compositions are contrary t o the formation of stepwise complexes, they are called ’anti-stepwise complexes’. The existence of such complexes is not unusual and often causes difficulties in speciation analyses. Therefore, it is essential t o investigate further the chemical equilibria in solution.In this paper, based on Bjerrum’s function ( f i ) and the method of corresponding solutions, a method is suggested for determining the stability constants of this kind of complex. For demonstration purposes it has been used with the iron(ll1) and Eriochrome Cyanine R system and satisfactory results were obtained. This method is generally applicable and could be used for most ’anti-stepwise‘ systems. Keywords: Polynuclear complex; stability constant; iron; Eriochrome Cyanine R; spectrophotometry Stepwise coordination reactions are very common in coordi- nation chemistry and their equilibria in solution is well understood. However, for coordination equilibria of the type M + R f MR M,,R, investigations carried out so far seem insufficient. The latter, in which the complexes formed are called ‘anti-stepwise complexes’, is different from the former; as M is increased, the series from mononuclear to polynuclear complexes are formed.Although they are less widely known than the normal analytically useful complexes, they are not uncommon.1-7 The methods used in the determi- nation of the stability constants of the former can hardly be used in that of the latter, based on Bjerrum’s function (2)8 and the method of corresponding solutions,v so a method has been developed here for the latter. It has been applied to the iron(m) and Eriochrome Cyanine R system and satisfactory results were obtained. M2R f ... Theory Suppose that an anti-stepwise complexing system consists of the following reactions: M + R = MR K11 = [MR]/[M][R] (1) 2M + R = M2R K21 = [M,R]/[M]2[R] (2) (the charges are omitted for simplicity).If there are three coloured species, R, MR and M?R, in the system, EO, E~ and €2 are their respective molar absorptivities, the absorbance of the solution is expressed as A = EO[R] + E~[MR] + E ~ [ M ~ R ] CM = [MI + [MR] + 2[M?R] CR = [R] + [MR] + [M2R] (3) (4) ( 5 ) From mass balance equations, we obtain where cM and cR represent the total concentrations of the metal ion and the ligand, respectively. Substituting eqns. (4) and ( 5 ) into eqn. (3) yields A = ( E ~ - q))[MR] + (E? - EO)[M~R] + EOCR (3a) AA = A - EOCR = (11 - E,,)[MR] + (E? - E ~ ) [ M ~ R ] (3b) * Present address: Department of Basic Sciences, Shandong Agricultural University, Taian, Shandong, People’s Republic of China.t To whom correspondcncc should bc addrcsscd. We define E = AA/cR Substituting eqns. (l), (2), (3b) and ( 5 ) into eqn. (6) yields E = {(El - E*)Kll[MI + (E2 - EO)K21[Ml2V (1 + KlI[MI + &,[MI2) (6a) (7) We define 6 = (cM - [M])/cK % is different from 6, and is called the ‘average anti- coordination number’. Substituting eqns. (l), (2), (4) and ( 5 ) into eqn. (7), we obtain f i = ([MR] + 2[M,R])/([R] + [MR] + [MZR]) = (KlI[MI[RI + 2K21[M12[R1)/([Rl + Kll[M”l = (KIl[M] + 2K21[MI2)/(1 + KlI[MI + K21[M12) + K21[M12[R1> (7a) As E(), E ~ , E ~ , KI1 and K21 in eqns. (6a) and (7a) are constants under given conditions, this indicates that E and 6 are only a function of [MI. Therefore, it follows that solutions having the same E must have the same value of [MI. As % is a function of [MI only, it also follows that these solutions have the same value of f i .Hence we call these ‘anti-corresponding’ solu- tions. The experimental method to find these solutions is as follows. Several series of solutions are prepared with cR fixed and CM gradually increased. AA is measured for each of the solutions, then E is evaluated using eqn. (6). A series of graphs of E versus cM are plotted then lines parallel with the abscissa are drawn that intersect the curves at points a l , b , , ..., e l , and a2, b2, ..., e2, etc. The solutions corresponding to the points of intersec- tion are anti-corresponding solutions. They have the same When the anti-corresponding solutions have been obtained, [MI. eqn. (7) is rewritten in the form CM = 6 c R + [MI (7b) A linear plot of cM versus cR is constructed from a set of anti-corresponding solutions.The slope and the intercept of the line are % and [MI, respectively. According to the treatments mentioned above, several pairs of values ( f i , [MI) are obtained from several sets of anti-corresponding solutions. Each pair of values (%, [MI) are substituted into eqn. (7a) to give linear equations, where KI1 and Kzl are unknown values. By arbitrarily taking two of the equations to form simul- taneous equations, K l l and K21 can be evaluated.98 ANALYST, JANUARY 1993, VOL. 118 For a system that consists of more than two anti-stepwise complexes, the stability constants of these complexes can be evaluated by a similar treatment and selecting the appropriate equations for solution.Experimental Apparatus A Shimadzu Model UV-3000 recording spectrophotometer and a Model pHs-2 acidimeter were used. Reagents All chemicals were of analytical-reagent grade. A 1.00 x 10-3 rnol 1-1 stock standard solution of iron(rr1) was prepared by dissolving calculated amounts of NH4Fe- (S04)2-12H20 in 0.01 moll-' hydrochloric acid. Working standard solutions were prepared by appropriate dilution of the stock standard solution. Eriochrome Cyanine R (ECR) was purified according to the procedure of Dixon et al.,lO which uses slightly modified dextran chromatography,"ll and was used to prepare a 1.00 X 10-3 rnol 1-1 stock standard solution with a final hydrochloric acid concentration of 0.008 rnol 1-1. Working standard solu- tions were obtained by appropriate dilution of the stock standard solution.Buffer solution was prepared by mixing 0.5 rnol I-' monochloroacetic acid and 0.5 moll- 1 sodium hydroxide solutions in a suitable ratio (pH 2.75). Procedure Into each of a series of 25 ml calibrated flasks, transfer a known volume of iron(m) solution, a known volume of ECR solution, 5 ml of buffer solution and a suitable volume of 1 rnol 1-1 potassium nitrate solution (keep the ionic strength at 0.70 0.60 0.50 0.40 (0 e s n q 0.30 0.20 0.10 0 E 520 560 600 640 Wavelengthlnm Fig. 1 Absorption spectra for Fe'Il-ECR system. pH, 2.77; 2 cm cells; reagent blanks as reference. A-E, cFe = 3.20 X 10-5 rnol 1-1; cECR (xl0-6 rnol 1-1): A, 2.00; B, 4.00; C, 6.00; D, 8.00; and E, 10.00.A'-F', cECR = 4.00 x 10-5 moll-1; cFe (x10-6 mollp1): A', 2.00; B', 4.00; C', 6.00; D', 8.00; E', 10.00; and F', 12.00. CECR > C F ~ , solid lines; cECR < cFe, broken lines O . l ) , dilute to the mark with distilled water and mix. After allowing the flask to stand for 15 min, measure the absorption spectra or absorbances of the solution. Maintain the tempera- ture of the solutions at 20 ? 1 "C throughout. Results and Discussion Langmyhr and Stumpes studied the complexing reaction between iron(ir1) and ECR in detail. They found Fe(ECR) and Fe2(ECR) complexes around pH 2.7 and that the formation of the two species depended on the mole ratio between the reactants. In the presence of a large excess of iron over the ligand, the formation of 2 : 1 complexes predominated; with a large excess of the ligand, the formation of 1 : 1 complexes predominated.We obtained similar results. However, in the pH range 3.9-4.2, they reported the existence of 2 : 2 complexes, but we could not obtain the same results, because the colour of the solutions was unstable under these conditions and turbidity occurred soon after the solutions had been mixed and set aside. Therefore, in this work, the equilibria among 1 : 1 and 2 : 1 complexes and the reactants were studied at pH ==: 2.7. 0.35 m 0.30 - 0.25 - yJ 0.20 - +? s n a 0.15 - c m 0.10 - 0.05 - 0 Wavelengthlnm Fig. 2 Absorption spectra for Fe-ECR system. CECR = 5.00 X 10-6 mol 1-1; cFe (X10-5 moll-1): A, 0.40; B, 0.80; C, 1.20; D, 1.60; E, 2.40; F, 3.20; and G, 4.00. Other conditions are the same as for Fig.1 Table 1 Conditions measured and results obtained by the Asmus method (pH 2.77). Subscripts 0 and i represent the fixed and increased concentration, respectively Measuring wave- length/ No. cFe,o/mol 1-l cEcRJmol 1- nm 4MtnR;z) 1 2.00x 10-6 (0.50-2.so) x 10-5 573 1 2 3 . 2 0 ~ 10-5 (2.00-10.00) x lo-" 586 1 3 (2.00-12.00) x 10-6 4.00 x 10-5 573 1 4 (2.0W.80) X 10-5 5.00 x 10-6 586 2 cFe,l/mol 1-1 cEcR,o/mol I-' m ( M m R,,)ANALYST, JANUARY 1993, VOL. 118 99 Table 2 Values of E ( X 10-5 1 mol-1) for five series of solutions. Measuring wavelength, 586 nm; for other conditions, see Fig. 1 Curve in Fig. 3 1 0.50 1 .oo 0.109 0.201 0.280 0.345 0.400 0.456 0.498 0.538 0.574 0.589 - 2 1.50 0.083 0.161 0.230 0.294 0.343 0.401 0.445 0.486 0.514 0.545 - 3 2.00 0.071 0.136 0.194 0.248 0.293 0.338 0.378 0.415 0.446 0.474 0.496 4 2.50 0.060 0.118 0.171 0.217 0.261 0.305 0.344 0.381 0.412 0.436 0.464 5 c ~ , / ~ O - ~ mol I-' cEcR/10-5 moll-L 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60 4.00 4.40 0.134 0.248 0.336 0.414 0.474 0.530 0.576 0.618 - - - Table 3 Values of rn and [MI for four sets of anti-corresponding solutions Corresponding By substituting [Fe] and 6 into eqn. (7a): No. of - equation solutions [Fe]/10-5 moll-' rn (2 - G)K21[M]2 + (1 - G)K1I[M] = G a1-1 1.06 0.9879 1.137 x 10-'OK21+ 0.0128 X 10-5KIl = 0.9879 7a-1 a2-e2 0.84 0.8430 0.8164 x lO-l"K21 + 0.1319 X 10-5K11 = 0.8430 7a-2 a4-e4 0.50 0.5920 0.3520 x 10-1"K21 + 0.2040 X 10-5Kll = 0.5920 7a-4 are3 0.67 0.6954 0.5856 x 10-1"KZl + 0.2041 X lO-'KIl= 0.6954 7a-3 Table 4 Values of K2, and K1, obtained by the method of anti-corresponding solutions No.of simultaneous equations 7a-1. 7a-2, 7a-1, 7a-2, 7a-1, Parameter 7a-2 7a-3 7a-4 7a-4 7a-3 Average Kll(x 10-5) 1.090 0.830 1.431 1.554 0.945 1.17 K2,(x10-l") 0.856 0.899 0.853 0.782 0.858 0.85 Absorption Spectra Three series of solutions were prepared: (1) cECR fixed and cFe gradually increased (cEcK > CFcj; (2) cFC fixed and C ~ C K gradually increased (cECR < cFe); ( 3 ) cECR fixed and cFe gradually increased to an excess. Their absorption spectra are shown in Figs. 1 and 2. The solid and broken lines in Fig. 1 represent the absorption spectra of solution series (1) and (2), respectively, and it can be seen that the wavelengths of maximum absorption differ. This shows that there may be two different complexes in the system.When cECR < cFe, complexes with a maximum at 586 nm are mainly formed; when cECK > cFe, complexes with a maximum at 573 nm are mainly formed. The regular pattern of the series of curves in Fig. 2 is identical with that in Fig. 1. The above conclusion of the existence of two complexes at pH 2.77 agrees with that reported by Langmyhr and Stumpe.5 Determination of the Compositions of the Complexes The compositions of the two complexes were determined under different experimental conditions. At pH 2.77, in the presence of a large excess of iron(iir), the composition of complexes with a maximum at 586 nm was found to be Fe2(ECR); in the presence of a large excess of ECR the composition of the complexes with a maximum at 573 nm was Fe(ECR).The calculation method used was the Asmus method" and extended by Klausen and Langmyhr.13 The conditions and the results are shown in Table 1. Determination of Stability Constants The determination of the stability constants of Fe-ECR complexes as reported5 requires the preparation of solutions under specified conditions in advance, such that only one complex actually exists and the other is neglected. It includes approximate treatments in the equilibrium calculation. It is considered that the method published previously5 is not suitable for anti-stepwise complexes where K21 approaches KI1. However, the method proposed here is not restricted by these conditions and can allow the complexes to co-exist during the determination of their stability constants.0.60 0.50 7 0.40 - E - 8 0.30 ;5 0.20 0.10 I 0.80 1.60 2.40 3.20 4.00 0 cF,/10-5 mol 1-1 Fig. 3 conditions see Table 2. Graphs of T. versus C F ~ for five series of solutions. For 3.60 1 ";p 1 3.20 2.80 7 2.40 0 - - E 2.00 LD I 0 7 1.60 1.20 W 0" 0.80 0.40 t cEcR/10-5 mol 1-1 Graphs of cFe versus cECR for four sets of anti-corresponding Fig. 4 solutions100 ANALYST, JANUARY 1993, VOL. 118 Five series of solutions were prepared as shown in Fig. 2. The AA value of each solution prepared was measured, then E was evaluated from eqn. (6). The results are given in Table 2. A series of graphs of E versus cFe are plotted in Fig. 3. As described above, several lines were drawn parallel with the abscissa, intersecting the curves at points a-e, e.g., al-el at E = 0.40 x 10s 1 mol-1 .The solutions corresponding to the points of intersection are anti-corresponding solutions, with the following compositions: a1 bl c1 dl el cECK/10-s moll-1 0.50 1.00 1.50 2.00 2.50 cF,/lO-~mol 1-1 1.53 2.00 2.44 3.05 3.49 and correspondingly for a2-e2, etc. After the anti-corresponding solutions had been obtained, graphs of cFe versus cECR were plotted according to eqn. (7b) (Fig. 4). In Fig. 4, each line represents a set of anti-corre- sponding solutions, and therefore each pair of values (6, [MI) can be obtained from its slope and intercept. The results are given in Table 3. These values were substituted into eqn. (7a) and on rearrangement yielded the linear equations given in the fourth column. Further, by taking arbitrarily two of the equations to form simultaneous equations, we obtained the values of KI1 and K2] (Table 4). The results are basically the same as those reported (at pH 2.70, K Z 1 = 2.00 x 1010 and K I 1 = 3.16 X 10s).5 The advantage of this method is that it can be applied to any situation where complexes are formed. 1 2 3 4 5 6 7 8 9 10 11 12 13 References Sato, H., Koyama, Y., and Momoki, K . , Anal. Chim. Acta, 1978, 99, 167. DoLsa, L., Saabo. A., and Beck. M. T., Acta Chim. Hung., 1971. 67, 189. Murakami, S., and Yoshino, T., Bull. Chem. Soc. Jpn., 1981, 54, 619. Semb, A . , and Langmyhr, F. J., Anal. Chim. Acta, 1966, 35, 286. Langmyhr, F. J., and Stumpe, T., Anal. Chim. Acra, 1965,32, 535. Langmyhr, F. J., and Klausen. K. S . , Anal. Chim. Acta, 1963, 29, 149. Zou, S. F., Chao, W., and Wen, S . Q., Gaodeng Xuexiao Huaxue Xuehao, 1990, 11. 240. Bjerrum, J . , Metul Ammine Formation in Aqueous Solution, Haase, Copenhagen, 1941. Orszagh, I., and Beck, M. T., Acta Chem. Scand., 1979,33,63. Dixon. E. J., Grislcy, L. M.. and Sawycr, K., Analyst, 1970,95. 945. King, H. G. C., and Pruden, G., Analyst, 1967. 92, 83. Asmus, E., FreJenius’ 2. Anal. Chem., 1960, 178, 104. Klausen, K. S., and Langmyhr, F. J., Anal. Chim. Acta, 1963, 28. 501. Paper 21037673 Received July 15, I992 Accepted August 6, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800097

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 101 Spectrophotometric Titration of Some Thiazine Dyes With Iron(ii) in Buffer Medium in the Presence of Oxalate K. Vijaya Raju and G. Bangar Raju Department of Engineering Chemistry, Andhra University, Visakhapatnam 530 003, India An accurate and convenient spectrophotometric titration method was developed for the determination of microgram amounts of seven thiazine dyes employing iron(l1) as a reductant in buffer medium (optimum pH 3.7-4.7) in the presence of sodium oxalate (optimum concentration 0.06-0.12 moll-1). All the dyes are rapidly and quantitatively reduced to their colourless leuco-bases in a two-electron reduction with iron(l1). The redox potentials of the iron(lll)-iron(ll) couple in buffer media of different pH and oxalate ion concentrations were measured.The function of pH and oxalate ion in the reaction medium is discussed. Keywords: Spectrophotometric titration; thiazine dye; iron(//) reductant; buffer medium; oxalate Thiazine dyes find numerous applications such as in textile technology,' medicine and biology2 and as redox indicators.34 Surprisingly, only a few titrimetric methods, involving the use of titanium(ni) chloride2.7 and iron(ii)8+9 in the presence of phosphoric acid as reductants, have so far been reported for the assay of these dyes. For the determination of a few dyes (Methylene Bluelo-17 and Thionine14-17) among the group, however, some other reductants [tin(ii) ,lo vanadium(1r) ,I1 chromium(i1) ,I2 molybdenum(iii)13 and ascorbic acid141 and a few oxidants [cerium(iv)15,16 and chloramine-T17] have also been used.All these methods suffer from one disadvantage or another. For example, the preparation and preservation of some of the reductant solutions2~7~10--'3 is tedious and the titrations using them need be carried out at elevated tempera- tures. The high concentration of orthophosphoric acid required in the iron(i1) method makes the medium viscous and the method expensive; in addition, a correction factor is necessary for calculating the dye content. In the oxidimetric methods reported it is difficult to ascertain the end-product of a dye and hence the stoichiometry of the reaction. This paper describes a spectrophotometric titration method for the determination of thiazine dyes in which the dye solutions are taken in a buffer medium containing oxalate and titrated with iron(i1).The method obviates all the disadvan- tages of the earlier methods. Further, the reagents of the reaction medium are relatively inexpensive and available in high purity. As most of the commercial dyes are generally found impure, assay methods for dye samples are of great importance. Even the manufacturers of the dyes (except a few) do not furnish the percentage dye contents of the samples. Experimental Reagents All solutions were prepared with distilled water and all chemicals were of analytical-reagent grade unless stated otherwise. Zron(rr) solution , 0.01 rnol 1 - 1. Prepared from ammonium iron(1i) sulfate hexahydrate in 0.01 mol 1-1 sulfuric acid and standardized18 against a standard solution of potassium dichromate. A portion was diluted further to 5.0 X 10-4 rnol 1-1 (in 5.0 x 10-4 rnol 1-1 sulfuric acid).Iron(ir1) solution, 0.01 rnol 1-1. Prepared from ammonium iron(i1i) sulfate dodecahydrate in 0.01 moll-' sulfuric acid and standardized18 by reduction with tin(1r) and then titration with a standard solution of dichromate. Titanium (111) chloride solution , 0.01 mol I- 1. Prepared from 15% m/v titanium chloride in 2 moll-' hydrochloric acid and standardized19 with a standard solution of dichromate. Sodium oxalate sohtion, 0.02 rnol 1-1. Prepared from disodium oxalate in distilled water. Buffer solutions. Various buffers of the desired pH (1-5) were obtained20 by mixing suitable volumes of 1 rnol 1-1 hydrochloric acid and 1 rnol 1-1 sodium acetate in a total volume of 50 ml.Purification and solutions of the dyes. The purity of the dye samples was tested qualitatively by thin-layer chromatography with acetic acid-water (1 + 1) as the mobile phase. The dyes, Azure-A (AZA), Azure-B (AZB) and Azure-C (AZC) (Gurr) were found to be associated with some coloured impurities. These dyes were rendered free from such impuri- ties by silica gel column chromatography as follows. The coloured impurities were first removed by elution with chloroform. The dye was then eluted with chloroform- methanol (with a gradual increase in the concentration of the former) and finally with methanol (the dye being highly polar) to minimize the recovery loss. The purified dyes were used for analysis. The other dyes, Thionine (THN) (Riedel-de Haen), Methy- lene Blue (MB), New Methylene Blue (NMB) (both from Merck) and Toludine Blue (TLB) (Gurr) were found to be free from coloured or visible impurities.The colourless impurities are generally due to additives1 such as sodium chloride and sodium sulfate used in the preparation of the dyes1 and do not interfere in the proposed method. Aqueous 0.05% solutions of all the dyes (50 mg in 100 ml) were prepared and standardized against titanium(iI1) chloride.2-7 From these standard dye solutions 5.0 X 10-5 moll-' solutions were prepared by suitable solution. Leuco-dye solutions. Solutions of the leuco-dyes were prepared in 50 ml calibrated flasks by taking a known aliquot (5.0 ml) of the dye solution (5.0 x 10-4 rnol 1-1) in a buffer (pH =4.20) medium containing 0.06 rnol 1-1 sodium oxalate and adding a 50-fold excess of iron(n) (5.0 ml of 0.03 moll-' solution) and finally diluting to the mark.Apparatus A Shimadzu (UV 140.02) double-beam spectrophotometer with optically matched glass cells of 1 cm pathlength was used to record the absorption spectra. An optical glass cell of 3 cm pathlength (3 x 5 x 6 cm) was employed for the spectro- photometric titrations. As the cell holder for such a glass cell to fit on to the cell compartment is not provided with the spectrophotometer, a102 ANALYST, JANUARY 1993. VOL. 118 Table 1 Spectrophotometric titration of some thiazine dyes with iron( 11) Dye* AZA AZB AZC MB NMB THN TLB Referencc met hodz-7 73.0 116.7 145.9 218.9 87.6 140.0 175.1 262.6 69.4 111.0 138.8 208.2 93.5 149.5 186.9 280.3 104.0 166.4 208.0 312.0 71.8 114.9 143.6 215.4 76.4 122.3 152.9 220.3 Proposed method 73.5 116.1 146.5 219.5 88.2 139.4 175.8 263.4 70.0 110.5 139.3 208.8 94.1 148.8 187.6 281 .0 103.1 167.6 208.7 311.1 71.2 115.7 143.0 214.8 77.0 121.7 153.5 229.9 Found/pgl Relative standard deviation 0.5 0.4 0.4 0.3 0.6 0.4 0.3 0.2 0.5 0.4 0.3 0.2 0.4 0.3 0.3 0.2 0.4 0.3 0.2 0.2 0.6 0.5 0.4 0.3 0.5 0.4 0.3 0.3 (%) Conditional redox pot enti al/ Assay mV (%)$ ( k 5 m V ) 88.9-t-0.4 411 87.5 -1-0.3 407 81.3 k 0.3 403 X8.4f0.5 425 90.5 -1-0.3 401 92.5 k0.3 398 90.0 k 0.3 418 contents were not labelled on the samples * Percentage dye - - supplied.t Average of six determinations. $ Confidence interval for the mean of six determinations (95% probability). few modifications to the cell compartment were made as described earlier21 in order to carry out the titrations.A digital potentiometer and a digital pH meter were used for potential and pH measurements, respectively. Procedure To a known aliquot (5-15 ml) of the dye solution ( 5 x 10-5 rnol 1-1) placed in the titration cell, 10.0 ml of sodium acetate (1 rnol I - l ) , 8.0 ml of hydrochloric acid (1 moll-1) and about 15 ml of sodium oxalate (0.2 rnol 1-1) solutions were added and diluted to SO ml (observed pH 4.20 k 0.01). The titration cell was then placed in position in the spectrophotometer, which was initially set to the desired wavelength (see Absorption Spectra of the Dyes) and at zero absorbance with respect to a blank. Purified nitrogen was bubbled through the reaction mixture for about 2 min to homogenize the solution and to expel any dissolved oxygen present and the absorbance was noted.The iron(i1) solution (5.0 X 10-4 rnol 1-1) was added in increments. After adding each portion of the titrant, the solution in the cell was stirred for about 30 s by passing nitrogen, which incidentally served as the inert atmosphere needed in the titration (to prevent the aerial oxidation of the Zeuco-dye or reduced product). The stirring was then stopped and the absorbance noted. The titration was continued in this way until the absorbance became almost constant. A plot of absorbance (corrected to dilution) versus volume of titrant added consists of two straight lines and their point of intersection corresponds to the equivalence point.Some typical results and assay values obtained are given in Table 1. 1.4 1 .o u m 5 s 2 0.6 0.2 n 400 480 560 640 720 800 Wavelengthlnm H '-/% 2H+ + 2e- f i Thiazine dye leuco-Base Dye CINo. R1 R2 AZA 52005 NH2 N(CH3)Z AZB 52010 NHCH3 N(CH3)2 MB 52015 N(CHS)zN(CH3)2 THN 52000 NH2 NH2 Fig. 1 Absorption spectra of A, AZA; B, AZB; C, MB; and D, THN in buffer medium (pH ~ 4 . 2 ) in the presence of 0.06 mol 1-I sodium oxalate. Concentration of each dye = 3.5 x mol I-' Results and Discussion Absorption Spectra of the Dyes In order to select a suitable wavelength for the spectropho- tometric titration of each dye, the absorption spectra of the dyes, their feuco-bases, iron(I1) and iron(II1) in media of various pH (range 4-5) and oxalate ion concentrations were recorded over the range 400-800 nm.The iron solutions and the leuco-bases have negligible absorbance in the visible region. The spectra of all the dyes (Figs. 1 and 2) were found to be independent of the pH of the medium (4-5) and the concentration of sodium oxalate (0.01-0.12 rnol 1-1). The optimum wavelengths for the spectrophotometric titrations are (Figs. 1 and 2) 600 nm for THN, 620 nm for TLB and NMB, 640 nm for AZA and AZC, 660 nm for AZB and 680 nm for MB. Beer's Law and Stability of the Dye Solutions Beer's law was found to be obeyed from about 1.5 to 4.5 pg ml-1 (3 cm pathlength) for THN, AZA, AZC and TLB. and from 2.0 to 6.0 pg ml-1 for AZB, MB and NMB. A spectrophotometric study of the stability of the dye solutions and leuco-bases under the titration conditions of the proce- dure (pH -4.2 in the presence of 0.06 moll-' sodium oxalate) revealed that all the dye solutions were stable for 3 d.However, the Zeuco-dye solutions were found to be stable towards oxygen in air for only 3 h even in the presence of a 50-fold excess of iron(r1). Effect of pH and Oxalate Ion Concentrations and Stoichiometry of the Reaction Preliminary investigations of these titrations revealed that of various buffers tried, the hydrochloric acid-sodium acetate buffer appears to be the best. Further, the pH of the buffer must be in the range 3.7-4.7 and the concentration of oxalateANALYST, JANUARY 1993. VOL. 118 103 Wavelengthhm H Thiazine dye leuco- Ba se Dye CINo. R' R2 R3 R4 TLB 52040 NH2 CH3 H N(CHd2 NMB 52030 NHC2H5 CH3 CH3 NHC2H5 AZC 52002 NH2 H H NHCH3 Fig.2 Absorption spectra of A, AZA; B, TLB; and C, NMB in buffer medium (pH -4.2) in the prcscnce of 0.06 mol 1-1 sodium oxalatc. Concentration of each dyc = 3.5 x 10-5 mol 1-1 500 400 W I z v, $ 300 > > E 1 (D .- c 5 200 * n 50 I I I I 0 0.04 0.08 0.12 Concentration of sodium oxalate/mol I-' Fig. 3 Formal redox potentials of the iron(ii)-iron(iii) couple in a buffer medium ( H =4.0-4.3) at different concentrations of sodium oxalate. lrron(ii,P = [iron(iii)l= 0.001 moll-1; temperature = 28 * 0.1 "C 0.06 mol 1-1 or above for rapid reduction and satisfactory titration of the dyes with iron(ii). All these dyes are reduced by iron(I1) to their corresponding leuco-bases in a two-electron reduction.2.7 Redox Potentials As early as in 1931, Michaelis and Friedheirn2' reported that the potential of the iron system decreases in a buffer medium containing oxalate.However, the use of iron(i1) as a useful reductimetric titrant in such a medium has recently been introduced in our laboratories.23J4 The redox potentials of the iron(rr1)-iron(ii) system at different pH and oxalate ion concentrations have not pre- viously been measured. Hence these potential values were 400 W $ 320 v, $ > 240 E 1 .- c 160 n 80 0.5 1.5 2.5 3.5 4.5 5.5 PH Fig. 4 Formal redox potentials of the iron(ii)-iron(iii) couple in buffer mcdia of various H (0.8-5.3) in the prescncc of 0.06 mol 1-1 sodium oxalate. [Iron(ir)r= [iron(iii)] = 0.001 moll-1; temperature = 28 k 0.1"C Table 2 pH of the buffer (3.95 k 0.01)* containing equimolar amounts of iron(iii) and iron(ir) at different concentrations of sodium oxalatc.[Fe"] = [Fe"'] = 0.001 mol 1-I. temperaturc = 29 C O.l"C, total dilution = 50 ml concentration of pH Concentration o f pH 0.0 3.95 0.06 4.20 0.01 4.02 0.08 4.27 0.02 4.07 0.10 4.32 0.04 4.13 0.12 4.33 oxalate/mol1-1 f 0.01 oxalate/mol1-~ Zk 0.01 * pH of the buffer under titration conditions of the procedure in the absence of oxalatc. determined adopting the method of Rao and Dikshitulu25 to explain the redox reaction between the dyes and iron(ii). The results for fixed pH and varied sodium oxalate are shown in Fig. 3 and those for fixed sodium oxalate and varied pH in Fig. 4. The acid contribution from the iron salt solution was taken into account when adjusting the pH of the solution.The pH of the buffer was found to increase to a small extent with increase in oxalate ion concentration (Table 2). The potentials are reproducible to within k5 mV and the pH of the medium was checked experimentally before each potential measurement. The redox potentials of the dye couple (ox.dye)-(red.dye) could not be determined in the same way because of the difficulties in the preparation of the leuco-dyes, which are highly sensitive to atmospheric oxygen. However, the condi- tional redox potentials of the dye couples were determined by measuring the potential of the dye solution that had been exactly 50% titrated with iron(r1) under a nitrogen atmosphere and are given in Table 1 . From a comparison of the conditional redox potentials of the dye couples (Table 1) and the redox potentials of the iron system (Figs.3 and 4), it can be seen that at a pH of about 4.20 (pH observed under the titration conditions) in the presence of 0.06 mol I-' sodium oxalate there is sufficient difference (290-320 mV) between the redox potential of the iron system (105 mV) and the dye systems (398425 mV) to bring about rapid reduction of the dyes with iron(ir). The amount of sulfuric acid present in the titrant, iron(Ii), is small (overall acidity 5.0 x 10-4 mol 1-1) and was found to have almost no effect on the buffer (pH 4.2 2 0.01) during the titration. It is well known that the redox potential of the iron(irr)- iron(1r) system decreases in the presence of certain complexing ions ( e . g . , fluoride, pyrophosphate, phosphoric acid, ethyl- enediaminetetraacetic acid) that bind iron(1Ii) in the form of a complex much more strongly than they do iron(1r) and enhance the reducing ability of iron(1r).In the present instance also, the decrease in potential of the iron system by oxalate is104 no doubt due to the formation of a stronger complex between iron(m) and oxalate (log p1 = 7.53, log 8 2 = 13.64 and log p3 = 18.49)26 than that between iron(ii) and oxalate (log p1 = 3.05, log p2 = 5.15).26 However, the effect of pH on the oxalato complex of iron(rr1) has to be taken into account, as the oxalate anion is readily protonated (pKl = 1.3, pK2 = 4.3).27 This mainly accounts for the change in the iron(iii)-iron(rI) potential as a function of pH and of the overall oxalate ion concentration of the medium.At a fixed pH, the potential will decrease (Fig. 3) with increase in oxalate ion concentration, because of the greater extent of complexation, and at fixed oxalate ion concentration the potential will increase (Fig. 4) with decrease in pH, because of the greater protonation of oxalate ion. Nature of the Complex Expected to be Formed Between Iron(m) and Oxalate In a medium of pH ==4.20 (observed pH under the titration conditions of the procedure), about half (0.028 moll-1) of the total oxalate (0.06 mol 1-1) is expected to be present in the form of C2042- ions according to the equation28 K,’ K,” [OX], [C2042-] = (1) [H+]2 + K,’ [H+] + K,’ K,” where K,‘ (5.6 x 10-2) and K,” (5.4 X 10-5) are the first and second dissociation constants27 of oxalic acid and [OX], represents the total oxalate (0.06 mol 1-1) in the medium.Iron(ii1) is tightly and more strongly bound by C2O42- ion (log = 7.53, log p2 = 13.64 and log p3 = 18.49)26 than by HC204- ion (log K = 4.3926 and is capable of forming 1 : 1 (mono) [Fe(C204)]+, 1 : 2 (bis) [Fe(C204)2]- and 1 : 3 (tris) [Fe(C204)3]3- complexes with oxalate ion .29-31 The fraction of the complexes present in the system can be calculated from the equations.32 Ki K2 K3 [c2042- l3 N [MOX~] = where M represents Fell1 and N = 1 + K1[C204~-] + KlK2 [C2042-]2 + KiK2K3 [C2042-]3. K1, K2 and K3 are stepwise stability constants of the complexes (K1 = 3.4 X 107, K2 = 1.3 x 106 and K3 = 7.1 x 104).26 From eqns. (2), only the 1 : 3 complex or trisoxalatoferrate(II1) , [Fe( C204)3]3- , must be predominant at pH 4.20 (on calculation, the fractions of the MOx, MOx2 and MOx3 complexes present in the system are found to be 0.14 x lO-7,0.50 x 10-3 and 0.98, respectively).Attempts to detect the end-point of these titrations using a potentiometric technique did not succeed because of the lack of a clear break in potential at the equivalence point. ANALYST, JANUARY 1993, VOL. 118 Interferences Chloride, sulfate, acetate, perchlorate and nitrate ions do not interfere. However, the nitrite ion interferes. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 References Venkataraman, K., The Chemistry of Synthetic Dyes, Academic Press, New York, 1952, vol. 2, p. 780. Conn, H. J., Biological Strains, Williams and Wilkins, Balti- more, 9th edn., 1977, pp.415430 and 602-605. Bishop, E., Indicators, Pergamon Press, Oxford, 1972, pp. 506-509. Krishna Murthy, N., and Satyanarayan, V., Acta Cienc. Indica. 1977,3, 201. Krishna Murthy, N., Dakshina Murthy, P. M., and Krishna Rao, P. V., Acta Cienc. Indica, 1985, 11, 181. Vijaya Raju, K., Bangarraju, G., and Madhu Gautam, G., J. Znst. Chem. (India), in the press. Knecht, E., and Hibbert, E., New Reduction Methods in Volumetric Analysis, Longmans, London, 1925, p. 101. Rukmini, N., Ph.D. Thesis, Andhra University, 1964. Ramanadham, G. V., Ph.D. Thesis, Andhra University, 1976. Leutweim, F., Fresenius’ 2. Anal. Chem., 1940, 120,233. Banerjee, P. C., J . Indian Chem. SOC., 1942, 19, 35. Tandon, J. P. , and Mehrotra, R. C., Fresenius’ 2. Anal. Chem., 1957,158, 189.Sagi, S. R., and Bosu Babu, T., Talanta, 1976, 23,465. RfiiiEka, E., and Kotoucek, M., Fresenius’ Z. Anal. Chem., 1961, 180, 429. Murali Krishna, U., and Ramanatham, G. V., J. Indian Chem. SOC., 1976, 58, 95. Murali Krishna, U., Ramanatham, G. V., and Kanna Rao, P., Acta Cienc. Indica, 1976, 2, 344. Chermavina, M. S., Tr. Sverdl. Skh. Znst., 1960, 7, 363. Vogel, A. I., A Text Book of Quantitative Inorganic Analysis, Longmans, London, 4th edn., 1978, pp. 360 and 399. Breit, J. E., J. Assoc. Off. Agric. Chem., 1949, 32, 589. Vogel, A. I., A Text Book of Quantitative Inorganic Analysis, Theory and Practice, Longmans, London, 2nd edn., 1951, p. 869. Vijaya Raju, K., Madhu Gautam, G., and Bangarraju, G., Mikrochim. Acta, in the press. Michaelis, L., and Fricdheim, E . , J. Biol. Chem., 1931,91,343. Murthy, N. K., Pulla Rao, Y., and Satyanarayana, V., J. Indian Chem. SOC., 1978, 55,686. Pulla Rao, Y ., Prasad, G. V., and Murthy, N. K., Analyst, 1987, 112, 1777. Rao, G. G.. and Dikshitulu, L. S. A., Talanta, 1962, 9, 715. Smith, R. M., and Martell, A. E., Critical Stability Constants, Plenum Press, New York, 1977, vol. 3, pp. 93 and 94. Haight, G. P., Jr.. and Huber, C. F., J. Am. Chem. SOC., 1976, 98, 14. Day, R. A., Jr., and Underwood, A. L.. Quantitative Analysis, Prentice-Hall, Englewood Cliffs, NJ, 5th edn., 1986, p. 213. Lambling, J . , Bull. SOC. Chim. Fr., 1949, 16, 495. Lingane, J. J . , J. Am. Chem. SOC., 1946, 68, 2448. Bobtelsky, M., Chasson, D., and Klein, S. F., Anal. Chim. Acta, 1953,8,460. Subba Rao, P. V., Krishna Rao, G. S. R., Rama Krishna, K., and Murthy, P. S. N., Indian J . Chem., Sect. A , 1991,30,239. Paper 2104.5736 Received June 11, 1992 Accepted August 26, 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800101

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 105 Simultaneous Determination of Iodide and Nitrite by Catalytic Kinetics Zhong-liang Zhu and Zhi-cheng Gu* Department of Chemistry, Tongji University, Shanghai 200092, People's Republic of China Nitrite and iodide can be determined simultaneously by a single experiment using their kinetic effect on the colour fading of the iron(i1)-thiocyanate complex in nitric acid solution. The rate of the colour-fading reaction is in proportion to the concentration of iodide and is independent of the concentration of nitrite. The length of the induction period of the indicator reaction is in inverse proportion to the logarithm of the concentration of nitrite and is independent of the concentration of iodide. Under conditions of 1.3 rnol 1-1 HN03, 0.067 moll-' Fe3+ and 2.7 x 10-4 rnol 1-1 SCN-, concentrations of 4.0 x 10-5-1.6 x 10-4 rnol I-' iodide and 4.1 x 10-7-6.6 x 10-6 rnol 1-1 NO2- were determined with mean relative errors of 1.5 and 3.9%, respectively.Keywords: Kinetic catalytic method; simultaneous determination; iodide and nitrite determination Although some methods for the simultaneous determination of two or more catalysts by catalytic kinetics without prior separation have been described, most need two or more kinetic runs under different conditions, such as pH,' tem- perature,2 concentration of reagents,3 etc. Weiser and Pardue4 have developed a method for the simultaneous kinetic determination of catalysts based on differences in the rates of inhibition. A method for the simultaneous determination of Br- and I-, based on their different catalytic behaviours, was carried out recently with a single kinetic run.5 The catalytic action of iodide on the colour-fading reaction of the iron(rr1)-thiocyanate complex was used to determine iodine .b This indicator reaction was characterized by an induction period, the length of which depended on the concentration of nitrite.This kinetic effect has been utilized to determine the concentration of nitrite.7 It has been found that in a certain range, the length of the induction period only depended on the concentration of nitrite. Changes in the NO?_- concentration had no influence on the rate of colour- fading. Only changes in the I- concentration influenced the rate of the indicator reaction, although they did not cause changes in the induction period.Hence it could be used for the simultaneous determination of I- and NOz- in a single kinetic run. So far there has been no report about the simultaneous determination in just one kinetic run using induction periods and reaction rates. This work concentrates on the simul- taneous determination of a mixture using only one kinetic run. Experimental Apparatus and Reagents A Model F7230 spectrophotometer was used to record the changes in absorbance over time. The reaction was performed at 24.0 "C using a Model 501-type thermostatically controlled bath. The data was handled using an IBM PC computer. All of the chemicals used were of analytical-reagent grade, except p-aminobenzene sulfonic acid, which was of primary-standard grade.Sub-boiling distilled water was used. Ammonium iron( 111) sulfate-nitric acid mixture solution. A 0.10 rnol I-' ammonium iron(ii1) sulfate solution was prepared in 2 moll-' nitric acid. Before use urea was added to the nitric acid, in order to remove the nitrous acid, and the acid boiled t o hydrolyse the excess of urea remaining. Potassium thiocyanate solution. A 0.10 rnol 1-1 solution of KSCN was prepared. It was diluted to 0.0050 rnol 1-1 prior to use. * To whom correspondence should be addressed. Potassium iodide standard solution. A 0.10 rnol 1-1 solution of KI was prepared and stored in a brown bottle. The solution was standardized against AgN03 by potentiometric titration and diluted to 5 x 10-4 rnol 1-1 prior to use. Standard nitrite solution. A 0.02 moll-' solution of NaN02 was prepared and stored in a brown bottle.The concentration was standardized against p-aminobenzene sulfonic acid as follows. About 0.5 g of acid was dried at 120 "C to constant mass, which was determined to an accuracy of +0.0002 g, then the acid was dissolved in 20 ml of NH3-H20, and about 20 ml of HCI and 150 ml of H20 was added, the mixture was titrated with NaN02 by potentiometry.8 The solution was diluted to 4.3 x 10-4 rnol 1-1 prior to use. Procedure A sample solution containing I- and NO2- was placed in a 25 ml standard calibrated flask, 2.0 ml potassium thiocyanate solution was added and diluted to exactly 25 ml (solution A). Both solution A and 0.10 rnol 1-1 ammonium iron(i1i) sulfate-2 moll-' HN03 solution (solution B) were placed in a thermostatically controlled water-bath at 24.0 "C until the temperature remained stable.A 1.0 ml aliquot of solution A was transferred into a cuvette and 2.0 ml of solution B added rapidly. The absorbance change with time at 458 nm, measured against water, was recorded synchronously. A typical pattern for the reaction curve is shown as Fig. 1. Data Processing The linear part of the colour-fading, shown in Fig. 1, was prolonged and intersected the extrapolation of the line at the initiation of the curve, shown as point P. The time correspond- ti Time - Fig. 1 present of I- and NOz- (A-t relation curve) Change in absorbance of FeSCN2+ complex with time in the106 ANALYST, JANUARY 1993, VOL. 118 1.5 1.2 g 0.9 g m 2 0.6 a 0.3 0 1 I 1 I 180 360 540 720 Time/s 1 900 Fig.2 Dependence of A-t relation on [Fe"]. Conditions: HN03, 1.3 moll-1; SCN-, 3.3 x 10-4 moll-I; I-, 1.1 X moll-l; NOz-, 2.3 x 10-6 rnol 1-1; and temperature 25.0 "C. [Fe"]: A, 0.033; B. 0.067; C, 0.100; and D. 0.133 rnol 1-1 1.5 1.2 ! 0.9 e 2 0.6 a 0.3 1.5 I I I 1.2 a, ; 0.9 g 2 0.6 a 0.3 0 180 360 540 720 900 Time/s Fig. 4 3.3 x 3. [HNOs]: A, 1.3; B, 2.0; and C, 2.7 rnol I-1 Dependence of A-t relation on [HN03]. Conditions: SCN-, mol 1-1; temperature, 25.0 "C; others are the same as Fig. 1.2 a, E 0.9 g 2 0.6 a 0.3 I I I I 0 180 360 540 720 900 Time/s Fig. 3 Dependence of A-f relation on [SCN-1. Conditions: HNO?, 1.3 rnol I - I ; Fe3+, 0.067 rnol I-'; I - , 1.6 x 10-3 moll-1; NO2-, 4.6 x 10-"mol I-'; and temperature 20.0 "C. [SCN 1: A , I .3 x 10-4; B, 2.0 x 10F; C, 2.7 x and D, 3.3 x 10-d rnol 1-1 0 180 360 540 720 900 Time/s Fig.5 Dependence of A-t relation on temperature. Conditions: Fe3+, 0.067 mol 1-1; others are the same as Fig. 2. Temperature: A , 21.7; B, 24.6; and C, 27.5 "C ing to point P was defined as the induction period ti. The rate of the colour-fading reaction (Y) was characterized by the slope of the linear part of the curve. Results and Discussion Effect of the Concentration of Fe3+ Ion The initial absorbance and the length of induction period increased with increasing Fe3+ concentration, while the reaction rate decreased (see Fig. 2). Lower concentrations of Fe3+ gave higher sensitivities for iodide determination. Very low concentrations of Fe3+ caused difficulties in the recording of the reaction stage because the coordinated reaction of Fe3+ with SCN- was very incomplete.An excess of Fe3+ ensured that the indicator of the reaction was only FeSCN2+. Hence 6.7 x 10-2 rnol 1-1 Fe3+ was specified in the procedure. Effect of the SCN- Concentration The effect of SCN- concentration on the reaction rate was marked, but the length of induction period remained almost unchanged (Fig. 3). The initial absorbance increased linearly with increasing SCN- concentration. Over the range 1.3 x 10-4-3.3 x rnol 1-1 SCN-, the sensitivity for the determination of I- increased with increasing SCN- concen- tration. A concentration of 2.7 x 10-4 rnol 1 - I SCN- was specified in the procedure. Effect of HN03 Acidity It was found that the higher the concentration of HN03 the shorter the induction period and the more rapid the reaction rate.When the concentration of HN03 was more than 6 mol 1-1, the fading reaction of the Fe3+-SCN- complex was completed in about 1 min without any catalyst. When the concentration of HN03 was lower, the time of the reaction was too long. The effect of different HN03 concentrations are shown in Fig. 4. The effect of HN03 concentration on both the reaction rate and the induction period was marked. The sensitivity for the determination of I- was increased with increasing HN03 concentration, but the sensitivity for NO2- determination was markedly decreased. Moreover, the rate of the blank reaction also increased with the increase of HN03 concentration. So as a compromise between sensitivity and time, the concentration of HN03 had to be between 1.0 and 2.0 rnol 1-1.Hence 1.3 rnol 1 - 1 HN03 was specified in the procedure. Effect of Temperature It can be seen from Fig. 5 that the reaction was accelerated and the induction period shortened with an increase in tempera- ture. Also the sensitivity for the determination of 1- was increased and the sensitivity for the determination of NO2- reduced. So different temperatures would have to be used when I- and NOz- are present in different proportions. The 24 "C temperature selected is restricted by the conditions of the experiment. According to the Arrhenius equation, the -Inv-T-1 plot (as shown in Fig. 6) was a straight line between 19.5 and 29.5 "C. The regression equation was obtained by least-squares fitting: -Inv = bl/T + a l (1) where bl = 4.54 x 103 and a l = 0.12.The activation energies can be calculated from the slope of the regression curve of '-lnv-l/T. In this work it was 3.77 x l o 4 J mol-1.ANALYST, JANUARY 1993, VOL. 118 ;_350/ 250 150 107 I I I I I -6.2 5.2 3.30 3.32 3.34 3.36. 3.38 3.40 3.42 1/T x 103 K Fig. 6 Effect of thc tempcraturc on reaction rate (v) and induction period (t,). A. -Inv-l/C and B. -lnt,-l/T. All conditions are the same as Fig. 5 +\ \ - I I I 1.2, 1 0 180 360 540 720 900 Time/s Fig. 7 De endence of A-t relation on [I-]. Conditions. HN03, 1.3 10-6 moll-1; and temperature, 24.0 "C. [I-]: A, 0; B, 8.00 x 10-5; C, 1.07 x and D, 1.33 x rnol 1-1 moll-1; Fe-+, P 0.067 rnol l - l ; SCN-, 2.7 x 10-4 moll-1; NO2-, 4.6 x 1.2, 0 0.3 - I I 1 I I 0 180 360 540 720 900 Time/s Fig.8 Dependence of A-t rclation on [NOz-]. Conditions: I-, 1.1 x 10-4 moll-1; others are the samc as Fig. 7. [NOz- 1: A, 5.8 x 10-7; B , 1.2 x 10-6; C, 2.3 x 10-6; D, 4.6 x 10-6; and E, 9.3 x 10-6 rnol I-' The -Intl-T-l plot over the same temperature range was also linear (Fig. 6). The regression equation is -Inti = b2/T + a2 (2) where bz = -6.82 x 103 and a2 = 0.86. Effect of I- and NO2- on Each Other When the NO2- concentration was kept constant changing the I- concentration only caused a change in the slope of the curve, it caused no change in ti (Fig. 7). On the other hand, changing the NO2- concentration gave rise to the changes in the length of induction period, and not to changes in the slope (Fig. 8). So it was possible to determine these two ions simultaneously.Calibration Graphs The calibration graph for the determination of the I- is shown in Fig. 9. The regression equation was v = sIcI- + kl (3) where s1 = 15.05 and k l = 8.07 x 10-4. I I I I 0 0.5 1 .o 1.5 2.0 [l-]/lO4 mol I-' 1.0 I Fig. 9 Calibration graph (v-[I-]). Conditions: HN03, 1.3 rnol 1-1; Fe3+, 0.067 mol 1-1; SCN-, 2.7 X 10-4 rnol I-'; and temperature, 24.0 "C 550 ', 1 Ln[ NO2-] Fig. 10 Calibration graph (4-ln[NOz-]). HN03, 1.3 rnol 1-1; Fe3+ 0.067 mol 1-1; SCN-, 2.7 x 10-4 mol 1-1; and temperature, 24.0 "C Table 1 Analysis of mixtures of I- and NO2- I-/lOs rnol 1-l N02/107 moll-l Added 16.00 14.67 13.33 12.00 10.67 9.33 8.00 6.67 5.33 4.00 Found 15.9 14.3 13.3 11.8 10.6 9.52 8.06 6.82 5.40 3.90 Relative error (%) -0.6 -2.5 -1.0 -1.7 -0.6 2.0 0.7 2.3 1.2 -2.5 Added 4.10 5.79 8.19 11.58 16.38 23.17 32.76 46.33 65.53 32.76 Found 3.95 5.31 7.93 11.6 17.0 24.9 33.4 50.1 64.1 32.7 Relative error (YO) -3.5 -8.3 -3.2 0.1 3.8 7.5 1.9 8.1 -2.2 -0.2 The calibration graph was rectilinear over the range 4 X 10-5-2 x 10-4 rnol 1-1.The length of induction period was inversely proportional to the logarithm of the NOz- concen- tration by experiment. The relationship between ti and In[N02-] is shown in Fig. 10. The regression equation was ti = s21ncNo2- + k2 (4) where s2 = -95.3 and kz = -875. The calibration graph was rectilinear over the range 5 x 10-7-9 x 10-6 rnol 1 - 1 . The correlation coefficient (Y) for both of the regression equations was 0.9998. Determination of I- and NO2- in Mixtures Several synthetic sample solutions containing 4.0 x 10-5-1.6 x 10-4 rnol 1-1 I- and 4.1 x 10-7-6.6 x 10-6 moll-1 NOz- were determined.The results are listed in Table 1. The maximum relative errors for T- and NO2- were 2.5 and 8.3%,108 ANALYST, JANUARY 1993, VOL. 118 respectively. The values for the mean relative standard deviation were 1.5 and 3.9% , respectively. The precision for the determination of N02- was less than for I-. One of the important reasons for this was that the effect of fluctuations in temperature on the sensitivity of the determination of NO2- and I- was different. For the determination of I- [From eqn. (l)], the following equation is obtained: dlnv/dT = b l / P or dv/dT = blv/T2 ( 5 ) dci-ldv = l / ~ l (6) From eqn. (3), we get Combining eqns.( 5 ) and (6), we have dci-/dT = blV/(SI P ) If cI- = 1.1 x 10-4moll-1, T = 297.2 K and v = 3.64 x 10-3, then we get dcl- = 1.2 X 10-5 dT. If the fluctuation in the temperature (AT) = 0.1 "C then Ac- = 1.2 x 10-6 mol 1-1. So the relative error is 1.1%. Similarly, for the determination of NO2-, the precision can be obtained from eqn. (2) dlnti/dT = b 2 / P or dti/dT = b2ti/72 (7) dlncNo2-/dti = 1/s2 (8) From eqn. (4), we get Combining eqns. (7) and (8), we have dhcNo2-/dT = b2ti/s2T2 or dcNO2-/cNo2- = b2ti/s2T2dT. When T = 297.2 K, ti = 318.7 s and AT = 0.1 "C, then AcNO2-/cNo2- = 2.6%. So the error in the results for the determination of NO2- would be larger than those for the determination of I- with the same temperature fluctuation. Mechanism of the Reaction The I- does not act as a catalyst on the decomposition of the thiocyanate-iron(ir1) complex.Although it accelerates the reaction in the presence of NO2-, the true catalyst is an oxidation product of I-. It has been found that iodine cannot significantly accelerate the reaction without the presence of N02-. The true catalyst may be iodine(1). The oxidation of I- to iodine(1) is a slow reaction, NO2- can accelerate this reaction, which is why there is an induction period in the catalytic reaction and the length of the induction period depends on the N02- concentration. Owing to the complexity of the mechanism, some steps of the reaction are still unclear. This work was supported in part by National Science Foundation of the People's Republic of China. References Yatsimirskii, K. B., and Raizmann, L. P., Zh. Anal. Khim., 1963, 18, 829. Wolff, C. M., and Schwing, J . P., Buff. SOC. Chim. Fr., 1976, 679. Worthington, J . B.. and Pardue, H. L., Anal. Chem., 1970,42, 1157. Weiser, W. E., and Pardue, H. L., Anal. Chem., 1986,58,2523. Yonehara, N., Yamane, T., Tomiyasu, T., and Sakamoto, H., Anal. Sci.. 1989, 5 , 175. Iwasaki, I . , Utsumi. S., and Ozawa, T., Buff. Chem. SOC. Jpn., 1953, 26, 108. Utsumi, S . , Okutani, T., Sakuragawa, A., and Kenmotsu, A . , Buff. Chem. SOC. Jpn., 1978, 51, 3496. Chinese Standard for Chemical Reagents 1984 (GB 1261-77), Chinese Standard Press, Beijing, 1986, p. 34. Paper 2/01549H Received March 24, 1992 Accepted October 8, I992

ISSN:0003-2654    

DOI:10.1039/AN9931800105

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 109 Bangar Raju, G., 101 Barjat, HervC. 73 Barnard Howie, Judith A., 35 Belton, Peter S., 73 Bhaskar, Nilam, 1 Birmingham, John. J., 1 Brinkman, Udo A. Th., 11 Cai, Xiaohua, 53 Cermak, Josef, 79 Chadima, Radko, 79 Cummins, Diane, 1 Cummins, Phillip G., 1 de la Guardia, Miguel, 23 Diewald, Wolfgang, 53 Dowle, Chris J., 17 Economou, Anastasios, 47 Espinosa-Mansilla, Anunciacion, 89 CUMULATIVE AUTHOR INDEX JANUARY 1993 Fielden, Peter R., 47 Frutos, G., 59 Ghijsen, Rudy T., 11 Goodfellow, Brian J., 73 Greenway, Gillian, 17 Gregory, Donald P.. 1 Grob, Robert, 11 Gu, Zhi-cheng, 105 Hawkins, Peter, 35 Howard, Vyvyan C., 1 Hunt, Terence P., 17 Jones, Carol L., 1 Kalcher, Kurt, 53 Kotrly, Stanislav, 79 Krishan Puri, Bal, 85 Liang, Wei-An, 97 Lopez Ruiz, B., 59 Magee, Robert J., 53 Martin, J. P., 59 Mathieu, Jacques, 11 Midgley, Derek, 41 Miller, Richard M., 1 Moriyama, Youichi, 29 Moss, Martin C., 1 Nagahiro, Tohru, 85 Nakamura, Kayoko, 29 Neuhold, Christian, 53 Peris Cardells, Empar, 23 Pitre, Krishna S., 65 Pramauro, Edmondo, 23 Prevot, Alessandra Bianco, 23 Reckhow, David A., 71 Rubio Leal, Amparo, 89 Salinas, Francisco, 89 Sanz Pedrero, P., 59 Satake, Masatada, 85 Savarino, Piero, 23 Sheppard, Robert C., 1 $ingleton, Scott, 1 Sramkova, Jitka, 79 Taniguchi, Hirokazu, 29 Veiro, Jeffrey A., 1 Verma, Neerja, 65 Vijaya Raju, K., 101 Viscardi, Guido, 23 Wuchner, Klaus. 11 Xie, Yuefeng, 71 Yoshida, Tomohiko, 29 Zhou, Jie, 97 Zhu, Zhong-Iiang, 105 Zou, Shi-Fu, 97

ISSN:0003-2654    

DOI:10.1039/AN9931800109

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993, VOL. 118 Analyst 111 INSTRUCTIONS TO AUTHORS The Analyst publishes original research papers on all aspects of the theory and practice of analytical chemistry, fundamental and applied, inorganic and organic, including chemical, physical, biochemical, clinical. pharmaceutical, biological, automatic and computer-based methods. Papers on new techniques and instrumentation, detectors and sensors, and new areas of application with due attention to overcoming limitations and to underlying principles are all equally welcome. All contributions should represent a significant develop- ment in the particular field of analysis and are judged on the criteria of (i) originality and quality of scientific content and (ii) appropriateness of the length to content of new science.Thus, papers reporting results which would be routinely predicted or result from application of standard procedures or techniques are unlikely to prove acceptable in the absence of other attributes which themselves make publication desirable. Applications papers (particularly, those dealing with spectrophotometry or chelating reagents for high-performance liquid chromatography) must contain a comparison with existing methods and demonstrate advantages over accepted methods before publica- tion can be considered. Descriptions of methods should be supportcd by experimental results showing accuracy, precision and selectivity. Although short articles are acceptable, the Society strongly discourages fragmentation of a substantial body of work into a number of short publications.Unnecessary fragmentation will be a valid reason for rejection of manuscripts. There is no page charge for papers published in The Analyst. The following types of papers will be considered. Original researcli papers. Communications. which must be on an urgent matter and be of obvious scientific importance. Rapidity of publication is enhanced if diagrams are omitted, but tables and formulae can be included. Communications receive priority and are usually published within 5-8 weeks of receipt. They are intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subse- quently, if justified by later work. Although publication is at the discretion of the Editor, communications will be examined by at least one referee. Reviews, which must be a critical evaluation of the existing state of knowledge on a particular facet of analytical chemistry.However, original work may be included. Simple literature surveys will not be accepted for publication. It is desirable that potential review writers should contact the Editor before embarking on their work. Copyright. The whole of the literary matter (including tables, figures, diagrams and photographs) in The Analyst is Royal Society of Chemistry copyright and may not be reproduced without permission from the Society or such other owner of the copyright as may be indicated. Papers that are accepted must not be published elsewhere except by permission.Submission of a manuscript will be regarded as an undertaking that the same material is not being considered for publication by another journal in any language. US Associate Editor. Papers from North America can be submitted to Dr. J . F. Tyson, Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA. To enhance the speed of processing of manuscripts, these papers will usually be refereed in the United States or Canada. Regional Advisory Editors. For the benefit of potential contributors outside the United Kingdom and North America, a Group of Regional Advisory Editors exists. Requests for help or advice on any matter related to the preparation of papers and their submission for publication in The Analyst can be sent to the nearest member of the Group.Currently serving Regional Advisory Editors are listed in each issue of The Analyst. Manuscripts. Papcrs should be typewritten in double spacing on one side only of the paper. Copies of any related, relevant, unpublished material and raw data should be made available on request. Each table and illustration should be on a separate sheet at the end of the text; three copies of text and illustrations should be sent to the Editor, The Analyst, The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, or directly to the US Associate Editor, and a further copy retained by the author. Administration and Publication Procedure. Receipt of a contribu- tion for consideration will be acknowledged immediately by the Editorial Office.The acknowledgement will indicate the paper reference number assigned to the contribution. Authors are particu- larly asked to quote this number on all subsequent correspondence. All papers (including conference presentations submitted for special issues) are sent simultaneously to at least two referees, whose names are not disclosed to the authors. On the basis of the referees’ reports, the Editor decides whether the paper is suitable for publication. either unchanged or after appropriate revision. This decision and relevant comments of the referees are communicated to the author. Differences of opinion are mediated by the Editor, possibly after consultation with further referees, or, in the last resort, by the Editorial Board. When rejection of a paper is recommended, the Editor informs the author, and returns the top copy of the manuscript.Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. Authors will receive formal notification when papers are accepted for publication. Proofs. The address to which proofs are to be sent should accompany the paper. Proofs should be carefully checked and returned immediately (by first class mail, air mail or fax). Particular attention should be paid to numerical data both in the tables and text. Reprints. Fifty reprints of each paper are supplied free on request. Additional reprints can be purchased if ordered at the time of publication. Details are sent to authors with the proofs. Notes on the Writing of Papers for The Analyst Manuscripts should be in accordance with the style and usage shown in recent copies of The Analyst.Conciseness of expression is expected: clarity is increased by adopting a logical order of presentation, with suitable paragraph or section headings. Spellings should be in accordance with the Oxford English Dictionary. To facilitate abstracting and indexing by Chemical Abstracts Service, and other abstracting organizations, it would be helpful if at least one forename could be included with each author’s family name. The corresponding author should be clearly indicated. Descriptions of methods should be supported by experimental results showing accuracy, precision and selectivity. The recommended order of presentation is as indicated below: Title. This should be as brief as is consistent with an adequate indication of the original features of the work.The title should usually include the analyte being determined or identified, the matrix and the analytical method used. Summary. A summary of about 250 words, giving the salient features and drawing attention to the novel aspects, should be provided for all papers. It should be essentially independent of the main text and include relevant quantitative information such as detection limits, precision and accuracy data. Keywords. Up to 5 keywords or key phrases, indicating the topics of importance in the work described, should be included after the summary.112 ANALYST, JANUARY 1993, VOL. 118 ( d ) A i m of investigation. A concise introductory statement of the novel fcaturcs of the work and the object of the investigation with any essential historical background, followed, if neces- sary, by a brief account of preliminary experimental work with relevant references.(e) Description of the experimental procedures. Working details must be given concisely. Analytical procedures should pre- ferably be given in the form of instructions; well known operations should not be described in detail. Suppliers of equipment and materials and their locations should be men- tioned. (f) ReJults and Discussion. Results are best presented in tabular or diagrammatic form (but not both for the same results), followed by an appropriatc statistical evaluation, which should be in accordance with accepted practice. For example, a new procedure for multi-element determinations which produced results for which the concentrations of 8 out of 10 of the elements determined in a standard reference material were statistically indistinguishable from the certificate values should be dcscribed in those terms and not refcrred to as ‘excellent agreement’. This is particularly important in the summary.Any discussion should comment on thc scope of thc method and its validity, followed by a statement of any conclusions drawn from the work. A separate conclusions section is not encouraged but, if included, it should not simply duplicate statements in the discussion. (8) Acknowledgements. Contributors other than co-authors, com- panies or sponsors may be acknowledged in a separate paragraph at the end of the paper. Titles may be given but not degrees.( h ) References. References should be numbered serially in the text by means of superscript figures, e.g., Foote and Delves,l Burns et a1.2 or . . . in a recent paper3 . . ., and collected in numerical order under ‘References’ at the end of the paper. They should be listed, with all the authors’ names and initials, in the following form (double-spaced typing): Yerian, T. D., Christian, G . D., and RfiiiCka, J., Analyst, 1986, 111,865. Sharp, B. L., Barnctt, N. W., Burridgc, J. C., Littlejohn, D., and Tyson, J. F., J. Anal. At. Specnom., 1988, 3, 133R. Committcc for Analytical Methods for Residues of Pesticides and Veterinary Products in Foodstuffs and the Working Party on Pesticide Residues of the Ministry of Agriculture, Fisheries and Food, Analyst, 1985, 110.765. Hara, H.. Horvai, G., and Pungor, E.. Analyst, 1988,113, 1817; Anal. Abstr., 1989, 51, 6H57. Norwitz. G., and Keliher, P. N., Analyst. 1987, 112, 903 (and references cited therein). L’vov. B. V., Polzik, L. K., Romanova. N. P.. and Yuzeforskii, A. I.. J . Anal. A/. Spectrom., in the press. O’Connor. A., Sigma, St. Louis. MO, personal communication, 1989. Appelqvist, R., Ph.D. Thesis, University of Lund, Sweden, 1987. 7 Official Methods of Analysis of the Association of Official Analytical Chemists, ed. Horwitz, W., Association of Official Analytical Chemists, Arlington, VA, 13th edn., 1980, sect. 20. 104. Authors must, in their own interest, check the lists of refcrcnces against the original papers; second-hand references are a frequent source of error.References to conference abstracts which have not been published in the open literature are not acceptable. The number of references must be kept to a minimum. Nomenclature. Current internationally recognized (IUPAC) chem- ical nomenclature should be used. Common trivial names may be used, but should first be defined in terms of IUPAC nomenclature. A listing of all relevant IUPAC nomenclature publications appears in the January issue. Symbols and units. The SI syster , of units, as recommended by IUPAC, should be followed. Their t isis is the ‘Systeme Internation- ale d’Unit6s’ (SI). A detailed treatmc it is given in the ‘Green Book’: Quantities, Units and Symbols in hysical Chemistry (Blackwell, Oxford, 1988 edn.). The following will be the guidelines used: ( a ) A metric system will always bc used in prcfcrcnce to a ( b ) SI will be the standard usage.( c ) The units used to record the definitive values of ‘critical data’ or quantities measured to a high degree of accuracy will be SI. These units are summarized in the Appendix. non-metric one. The effect on current style of papers for The Analyst includes the following: ( a ) dimcnsions should preferably be given in metres (m) or in ( b ) temperatures should be expressed in K or “C (not OF); ( c ) wavelengths should be expressed in nanometres (nm) (not mp); ( d ) frequency should be expressed in Hz (or kHz, etc.), not in c/s or c.P.s.; rotational frequency can be denoted by use of s-l; in mass spectrometry. signal intensity should be expressed in counts s-1 and not in Hz; millimetres (mm); ( e ) radionuclide activity should be cxpressed in becquerels (Bq); (f) the micron (p) will not be used; 10-6 m will be 1 pm. When non-SI units are used they must be adequately explained unless their definition is obvious (e.g., “C and A).The derivation of derived non-SI units should be indicated. Abbreviations. Abbreviational full stops arc omitted after the common contractions of metric units (e.g., ml, g, pg, mm) and other units represcnted by symbols. Abbreviations other than those of Journal titles should be abbreviated according to the Chemical For books, the edition (if not the first), the publisher and the place recogniz‘ed Units shouldbe avoided in the tCXt except after definition. Upper case letters without points should be used for abbreviations for techniques and associated terms, subsequent to definition, e.g., HPLC, AAS, XRF, uv, NMR, SCE, Other abbreviations Abstracts Service Source Index (CASSI).and Of publication be given, by the page number. and contractions require full points, e.g., eqn,, m.p., Dr., except Harrison, W. W., and Donohuc, D. L., in Treatise on Analytical Chemistry. eds. Kolthoff. I. M., and Winefordner, J. D., Wiley. New York. 2nd edn., 1989, pt. 1, vol. 11, ch. 3 , pp. 189-235. Gutscht. C. D., Calixarenes. The Royal Society of Chemistry, Cambridge. 1989. British Pharmacopoeia 1988. HM Stationery Office, London, 1988, vol. 1 , p. 140. RfiiiEka, J . , and Hansen, E. H., Flow Injection Analysis, 2nd edn., Wiley. New York, 1988, pp.299-304. Moody, G. J . , and Thomas, J . I). R., in Ion Selective Electrodes in Analytical Chemistry, ed. Freiser, H., Plenum, New York, 1978, ch. 4. Beauchemin, D., and Craig, J. M., in Plasma Source Mass Spectrometry. The Proceedings of the Third Surrey Conference on Plasma Source Mass Spectrometry, University of Surrey, July 16th-l9th, 1989, eds. Jarvis. K. E., Gray. A. L., Jarvis, I.. and Williams, J . G., The Royal Society of Chemistry, Cambridge, 1990, pp. 25-42. I _ when sub- or supersciipt, A,,, fbr example. The abbrcGiations Me, Et, Prn, Bun, Bu’, Bu’, But, Ph, Ac, Alk, Ar and Hal can be used; others should be defined. Carboxy groups are written C02R, not COOR. Substituents should be indicated by R (one) or by R’, R2, R3 . . . (more than one). Percentage concentrations of solutions should be stated in inter- nationally recognized terms.Thus the symbols ‘m’ instead of ‘w’ for mass and ‘v’ for volume are to be used. The following show the manner of expressing these percentages together with a n acccptable alternative given in parentheses: % m/m (g per 100 6); % m/v (g per 100 ml); % v/v. Further implications of the use of the term ‘mass’ are that ‘rclative atomic mass’ of an element (A,.) replaces atomic weight, and ‘relative molecular mass’ of a substance (M,) replaces molecular weight. Concentrations of solutions of the common acids are often conveniently given as dilutions of the concentrated acids, such asANALYST, JANUARY 1993, VOL. 118 113 ‘dilute hydrochloric acid (1 + 4)’, which signifies 1 volume of the concentrated acid mixed with 4 volumes of water. This avoids the ambiguity of 1 : 4, which might represent either 1 + 4 or 1 + 3.Dilutions of other solutions can be expressed in a similar manner. Molarity is generally expressed as a decimal fraction (e.g., 0.375 mol dm-3)). Tables and diagrams. Table column headings should be brief. Tables consisting of only two columns can often be arranged horizontally. Tables must be supplied with titles and be so set out as to be understandable without reference to the text. Either tables or graphs may be used but not both for the same set of results, unless important additional information is given by so doing. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation or statement in the text.Column headings and graph axis labels should be in accord with SI conventions. Thus, the expression of numerical values of a physical quantity should be dimensionless, i.e., the quotient of the symbol for the physical quantity and the symbol for the unit used, e.g., dmol dm-?, or some mathematical function of a number, e.g., ln(clmo1 dm-?). Further examples are vlcm-1, Ucm, mass of substance/g and flowrate/ml min-1. For units which are already dimensionless, i.e., ratios such as % or ppm, the type of ratio is indicated in parentheses, e.g., c (%) or c (ppm). The diagonal line (solidus) will not be used t o represent ‘per’. In accordance with the SI system, units such as grams per millilitre are already expressed in the form g ml-l. It should be noted that the ‘combined’ unit, g ml-’, must not have any ‘intrusive’ numbers.To express concentration in grams per 100 millilitres, the word ‘per’ will still be required: Concentration/g per 100 ml. It may be preferable for an author t o express concentrations in grams per litre (g 1-l) rather than grams per 100 ml. Most diagrams will be retraced and lettered in order to achieve uniform line thicknesses and lettering size and style. However, all diagrams should be carefully and clearly drawn on good quality paper and should be carefully and clearly lettered. If possible, chromato- grams and spectra, complicated flow charts, circuit diagrams, efc., should be supplied as artwork for direct reproduction in order to avoid time-consuming and expensive redrawing.The clearest copy should be without lettering. Three complete sets of illustrations should be provided, two sets of which may be made by any convenient copying process for trans- mission to the referees. All diagrams should be accompanied by a separately typed set of captions. Wherever possible, extensive identifying lettering should be placed in the caption rather than on lines on graphs, efc. Photogruphs. Photographs can be submitted if they convey essential information that cannot be shown in any other way. They should be submitted as glossy or matt prints made to give the maximum detail. Colour photographs will be accepted only when a black-and-white photograph fails to show some vital feature and can be supplied either as prints or transparencies. Appendix The SI System of Units In the SI system there are seven base units- Physical quantity length mass time electric current thermodynamic temperature amount of substance luminous intensity Name of unit metre kilogram second ampere kelvin mole candela Symbol for unit m kg S A K mol cd There are two supplementary dimensionless units for plane angle (radian, rad) and solid angle (steradian, sr).Some derived SI units that have special names are as follows- Physical quantity energy force power electric charge electric conductance electric potential difference electric resistance electric capacitance frequency magnetic flux density radionuclide activity pressure, stress energy, work, heat inductance (magnetic induction) Name of unit joule newton watt coulomb siemens volt ohm farad hertz tesla becquerel pascal joule henry Symbol Definition for unit of unit J N W C S V 52 F Hz T kg s-2 A-1 = V s m-2 Bq s-1 Pa m-1 kg s-2 (= N m-2) J m2kgs-z(=Nm=Pam3) H m2 kg s-2 A-2 (= VA--l s)114 ANALYST.JANUARY 1993, VOL. 118 Examples of other derived ST units are- Physical quantity SI unit area square metre volume cubic metre density kilogram per cubic metre velocity metre per second angular velocity radian per second acceleration metre per second squared magnetic field strength ampere per metre Certain units will be allowed in conjunction with the S1 system, e.g.- Physical quantity time plane angle volume magnetic flux density temperature, t energy mass (magnetic induction) Name Symbol of unit for unit minute degree litre min 1 0 gauss G degree Celsius "C electronvolt eV unified atomic U mass unit Symbol for unit m2 m3 kg m-3 m s-1 rad s-1 m s-2 A m-1 Definition of unit 60 s (~11180) rad 10-3 m3 = dm-7 10-4 T 1.6021 x 10-1"J 1.66054 x 10-27 kg tl"C = T/K - 273.16 The other common units of time (e.g., hour and day) will continue to be used in appropriate contexts. Decimal multiples and submultiples have the following names and symbols (for use as prefixes)- milli micro nano pico femto atto zepto yocto m P n P f a Y Z Compound prefixes (e.g., mpm) should not be used; 10-9 m = 1 nm. The Royal Society of Chemistry, Thomas Gruhum House, Science Park, Milton Road, Cambridge, UK CB4 4WF kilo mega tera peta exa zetta yotta gigs k M G T P E Z Y Telephone +44 (0) 223 420066; Fax 4-44 (0) 223 420427; E-mail RSC09QUK.AC. RL.GB (JANET)

ISSN:0003-2654    

DOI:10.1039/AN9931800111

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST. JANUARY 1993, VOL. 118 115 Refereeing Procedure and Policy (1993) 1.0 Contributions to Dalton, Perkin and Faraday Transactions, J. Mater. Chem., The Analyst, J. Anal. At. Spectrom. and J. Chem. Research 1.1 Introduction This document summarises. the procedure used for assessing papers submitted to the four Transuctions, J. Mater. Clwn., The Antcljlst, J. A t i d . A t . Sprctrom., and J . Ciiem. Resc~arch, and provides guidelines for referees engaged in this assessment. 1.2 Subject matter Papers are submitted to the various journals according to subject matter. If it is felt that a paper would be published more appropriately in an RSC journal other than the one suggested by the author, the referee should inform the Editor. The topics covered by the various journals are as follows.Dulton Trtrnsuctiom (Inorganic Chemistry). All aspects of the chemistry of inorganic and organometallic compounds, including bioinorganic chemistry and solid-state inorganic chemistry; the applications of physicochemical techniques to the study of their structures, properties, and reactions, including kinetics and mechanism; new or improved experimental techniques and syntheses. F m h j y Trntasccrtions (Phj~sical Cherziistrj, and Chtwiical Phj*sic~). Cas-phase kinetics and dynamics; molecular beam kinetics and spectroscopy, photochemistry and photophysics; energy transfer and relaxation processes: laser-induced chemistry; spectroscopies of molecules, molecular and gas- phase complexes: quantum chemistry and molecular structure, statistical mechanics of gaseous molecules and complexes; spectroscopies, statistical mechanics and quantum theory of the condensed phase, computational chemistry and molecular dynamics; colloid and interface science, surface science, physisorption and chromatographic science, chemisorption and heterogeneous catalysis, zeolites and ion-exchange phenomena; electrode processes, liquids and solutions; solid-state chemistry (microstructures and dynamics); reactions in condensed phases; physical chemistry of macromolecules and polymers; materials science; thermodynamics; biophysical chemistry and radiation chemistry .Porkin Trcrnscictions I (Orgmic Chetitistrj,). All aspects of organic and bio-organic chemistry. These include synthetic organic chemistry of all types, organometallic chemistry, Chemistry and biosynthesis of natural products, the relationship between molecular structure and biological activity, the chemistry of polymers and biological macromolecules, and medicinal and agricultural chemistry where there is originality in the science.Perk it? Ti~tinsuc~tiom 2 ( Phj~sical Organic Chemistrj,). Physicochemical aspects of organic, organometallic, and bio- organic chemistry, including kinetic, mechanistic, structural, spectroscopic, and theoretical studies. Such topics include structure- activity relationships and physical aspects of biological processes and of the study of polymers and biological macromolecules. Journal of Materiuls Chemistry. The chemistry of materials, particularly those associated with advanced technology; modelling of materials; synthesis and structural characteris- ation; physicochemical aspects of fabrication; chemical, structural, electrical, magnetic and optical properties; applic- ations.The Analyst (Analytical Chemistry). Theory and practice of all aspects of analytical chemistry, fundamental and applied, inorganic and organic, including chemical, physical, and biological methods. Journal of’ Analytical Atomic Spectrometry. The develop- ment and analytical application of atomic spectrometric techniques. Jotirnul of’ Chemical Research. All areas of chemistry. The format of this journal (one- or two-page printed synopsis in Part S, plus microform version of authors’ full text typescript in Part M) makes it particularly suitable for papers containing lengthy experimental sections or extensive data tabiilations.1.3 Procedure Each manuscript is considered independently by two referees. The referees’ reports constitute recommendations to the appropriate Editorial Board, which is empowered to take final action on manuscripts submitted. The Editor, acting for the Editorial Board, is responsible for all administrative and executive actions, and is empowered to accept or reject papers. It is the Editor’s duty to see that. as far as possible, agreement is reached between authors and referees; although the referees may need to be consulted again concerning an author’s reply to comments, further refereeing will be avoided as far as possible. 1.3.1 A4udicution of’ disagreements. If there is a notable discrepancy between the reports of the two referees, or if the difference between authors and referees cannot be resolved readily, a third referee may be appointed as adjudicator.In extreme cases, differences may be reported to the appropriate Editorial Board for resolution. When a paper is recommended for rejection by referees, the Editor will inform the authors and return the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. The Editor may refer to the Editorial Boards any papers which have been recommended for acceptance by the referees, but about which the Editor is doubtful. 1.3.2 Anonyrnitj-. The anonymity of referees is strictly preserved, and reports should be couched in terms which do not disclose the identity of the writer.A referee should never communicate directly with an author, unless and until such action has been sanctioned by the Society, through the Editor. 1.3.3 Confidentiality. A referee should treat a paper received for assessment as confidential material. Information acquired116 ANALYST, JANUARY 1993, VOL. 118 by a referee from such a paper is not available for citation until the paper is published. 1.4 Policy The primary criterion for acceptance of a contribution for publication is that it should advance scientific knowledge significantly. Papers that do not contain new experimental results may be considered for publication only if they either reinterpret or summarise known facts or results in a manner presenting an advance in chemical knowledge.Papers in interdisciplinary areas are acceptable if the chemical content is considered satisfactory. Papers reporting results regarded as routine or trivial are not acceptable in the absence of other, desirable attributes. Although short papers are acceptable, the Society strongly discourages the fragmentation of a substantial body of work into a number of short publications; such fragmentation is likely to be grounds for rejection. The length of an article should be commensurate with its scientific content; however, authors are allowed every latitude (consistent with reasonable brevity) in the form in which their work is presented. Figures and flow-charts can often save space as well as clarify complicated arguments, and should not be excised unless they are unhelpful or really extrava- gant.If a paper as a whole is judged suitable for the Journal, minor criticisms should not be unduly emphasised. It is the responsibility of the Editor to ensure the use of reasonably brief phraseology, and to assist the author to present his work in the most appropriate format. However, referees should not hesitate to recommend rejection of papers which appear incurably badly composed. It should be clearly understood that referees’ reports are made in confidence to the Editor, at whose discretion comments will be transmitted to the author. To assist the Editor, referees are requested to indicate which comments are designed only for consideration, as distinct from those which, in the referee’s view, require specific action or an adequate answer before the paper is accepted.Referees may ask for sight of supporting data not submitted for publication, or for sight of a previous paper which has been submitted but not yet published. Such requests must be made to the Editor, not directly to the author. 1.4.1 Authentication of’ new compounds. Referees are asked to assess, as a whole, the evidence in support of the homogeneity and structure of all new compounds. No hard and fast rules can be laid down to cover all types of compounds, but the Society’s policy is that evidence for the unequivocal identification of new compounds should wherever possible include good elemental analytical data; for example, an accurate mass measurement of a molecular ion does not provide evidence of purity of a compound and must be accompanied by independent evidence of homogeneity. Low-resolution mass spectrometry must be treated with even more reserve in the absence of firm evidence to distinguish between alternative molecular formulae. Where elemental analytical data are not available, appropriate evidence which is convincing to an expert in the field may be acceptable.Spectroscopic information necessary to the assignment of structure should normally be given. Just how complete this information should be must depend upon the circumstances; the structure of a compound obtained from an unusual reaction or isolated from a natural source needs much stronger supporting evidence than one derived by a standard reaction from a precursor of undisputed structure. Referees are reminded of the need to be exacting in their standards but at the same time flexible in their admission of evidence.It remains the Society’s policy to accept work only of high quality and to permit no iowering of stand- ards. 1.5 Titles and summaries Referees should comment on titles and summaries with the following points in mind. Titles of papers are used out of context by several organisations for current awareness purposes. To enable such systems to serve chemists adequately, titles must be written around a sufficient number of scientific words carefully chosen to cover the important aspects of the paper. Summaries should preferably be self-contained, so that they can be understood without reference to the main text. 1.6 Speed of Refereeing The Editorial Boards are anxious to maintain and to reduce further if possible the publication times now being achieved.In this connection, referees should submit their reports with the minimum of delay, or return manuscripts immediately to the Editor if long delay seems inevitable. 1.7 Suggestion of Alternative Referees The Editor welcomes suggestions of alternative referees competent to deal with particular subject areas. Such suggestions are particularly helpful in cases where referees consider themselves ill-equipped (in terms of specialist knowledge) to deal with a specific paper, and in highly specialized or new areas of research where only a limited number of experts may be available. If, in such a case, the alternative and the original referee work in the same institution, the manuscript may be passed on directly after informing the Editor.1.8 Short Papers and Letters ‘Short Papers’ are published in J. Chem. Reseurch. They are intended for the description of essentially complete pieces of work which can be described in two printed pages or less. They are NOT preliminary communications, nor in any way an alternative to Chemical Communications, for which there are additional criteria of novelty and urgency. The quality of material contained in a short paper should be the same as that in a full paper. Investigations arising out of some larger project but not prosecuted to the same degree are particularly appropriate for this format. A short paper should not normally exceed in length about 8 pages of typescript, including figures, tables, etc.It should comprise a one-sentence abstract and discussion, but adequate experimental details are required. As a consequence of its length, it appears in full in Part S with no microform version in Part M. ‘Letters’, published only in Dalton Transactions, are a medium for the expression of scientific opinions and views normally concerning material published in that journal; it is intended that contributions in this format should be published rapidly. The letters section is for scientific discussion, and is not intended to compete with media for the publication of more general matters such as Chemistry in Britain. Only rarely should a Letter exceed one printed column in length (about 1-2 pages of typescript). Where a letter is polemical in nature, and if it is accepted, a reply will be solicited from other parties implicated, for consideration for publication alongside the original letter.1.9 Relationship with Communications Journals In cases where a preliminary report of the work described has appeared (for example in Chemical Communications), refereesANALYST, JANUARY 1993, VOL. 118 117 should alert the editor to any excessive and unnecessary repetition of material; this can arise in connection with communications journals in which the restrictions on length and the reporting of experimental data are less severe than those of Chemicul Communications. Furthermore, the acceptability of the full paper must be judged on the basis of the significance of the additional information provided, as well as on the criteria outlined in the foregoing sections.2.0 Contributions to Chemical Communic- ations Chemicul Communiwtions is intended as a forum for preliminary accounts of original and significant work, in any area of chemistry that is likely to prove of wide general appeal or exceptional specialist interest. Such preliminary reports should be followed up in most cases by full papers in other journals, providing detailed accounts of the work. It is Society policy that only a fraction of research work warrants publication in Cheniicul Coruzmunications, and strict refereeing standards should be applied. The benefit to the reader from the rapid publication of a particular piece of work before it appears as a full paper must be balanced against the desirability of avoiding duplicate publication.The needs of the reader, not the author, must be considered, and priority in publication should not be allowed to determine acceptability. Acceptance should be recommended only if, in the opinion of the referee, the content of the paper is of such urgency that rapid publication will be advantageous to the progress of chemical research. The length of Communications is strictly limited; only in exceptional circumstances should it exceed one printed page (two-and-a-half to three A4 pages of typescript) and referees should be particularly critical of manuscripts longer than this. Communications do not contain extensive spectroscopic or other experimental data, but referees may ask for sight of such data before reaching a decision. The refereeing procedure for Communications is the same as that for full papers, except that rapidity of reporting is crucial in order to maintain rapid publication.The Journals Committee functions as the Editorial Board of Chemical Conznzunications and as such acts as final arbiter in cases of dispute. 3.0 Communications submitted to The Analyst and J. Anal. At. Spectrom. Criteria for acceptance of communications submitted to The Analjist and J . Anal. At. Spectrom. are similar to those for contributions to Chenzical Communications, except that they should be concerned specifically with analytical chemistry. However communications to The Analj3st and J. And. At. Spoctroni. are not subjected to refereeing in the usual way; a decision whether or not to publish rests with the Editor, who may or may not obtain advice from a referee. 4.0 Communications submitted t o Perkin, Dalton or Faraday Transactions or J.Mater. Chem. Criteria for acceptance of Communications submitted to Prrkin, Dalton or Fcrrudcij~ Trunsuctions or J. Mater. Chem. are similar to those for contributions to Chemicul Communications, except that the work will be of more specialist interest. For Perkin and Dulton Conzniunications inclusion of key experi- mental data is expected. Assessment is carried out by a small nucleus of referees, consisting largely of members of the appropriate Editorial Boards. 5.0 Contributions t o Mendeleev Communic- ations Mendeleeu Communications, published jointly by the Royal Society of Chemistry and the Russian Academy of Sciences, is a sister publication to Chemical Communications, containing preliminary reports of the same type, in any area of chemistry.The majority of contributions are from Russian authors. Assessment involves two stages of refereeing. Manuscripts submitted to the Moscow Editorial Office are refereed initially by a Soviet scientist. If found acceptable they are then reviewed by Western scientists chosen by the Royal Society of Chemistry. Manuscripts submitted to the UK Editorial Office undergo this two-stage refereeing process in reverse. 6.0 X-Ray Crystallographic Work 6.1 (A) The majority, which contain definitive data on completely refined determinations. (B) A minority which include brief accounts of structures containing feature(s) of unusual interest and where the structure solutions are clear but where (for any of a variety of reasons) the full refinement has not been completed.These are then regarded as preliminary publications, at least so far as the X-ray results are concerned. Both types of publication are appropriate for Communic- ations; only those of type (A) should normally appear as full papers. Crystallographic papers are of two types: 6.2 It is often appropriate (but not obligatory) for papers of type (A) to contain the information in their titles that an X-ray structure determination has been carried out. Papers of type (B) need not do so if the X-ray determination forms only a minor part. Summaries should always contain this information unless the paper is of type (B) and the structure determination is not a main point of the communication.6.3 All papers containing crystallographic determinations will be refereed by two referees, one a structural chemist. If the editor considers it advisable, the paper may also be sent to a crystallographer for comment. Referees will not normally be expected to check values of structural parameters for publication (eg. bond lengths and angles against atomic co- ordinates; this will be done after publication by CCDC or Bonn), but should still pay attention to the quality of the experimental crystallographic work. However their primary concern should be such new chemistry as is involved in the structure. 6.4 O n occasions Communications will contain preliminary accounts [type (B)] of crystal structures of unusual chemicul interest. By ‘preliminary’ is meant that the data have not yet been fully refined.Sufficient supplementary data must be provided for the referee to judge whether the ’not-fully-refined’ structure does indeed prove the desired point, and care should be taken by the referees to ensure that the authors do not overstate the case they have-for example by reporting bond lengths to very high degrees of apparent precision when they have poor R-factors. Such papers will always be refereed by a professional crystallographer. Authors must indicate in the paper or the supplementary data the justification for publishing without full refinement and referees should comment on whether the case for publication is convincing. 6.5 In many cases the structure referred to in a Communication will be fully refined. The Communication can then be considered to fulfil the archival function, and the structure determination may not require further detailed118 ANALYST, JANUARY 1993, VOL, 118 refereeing when presented as part of a full paper. In the full paper, the author’s purpose will then be served by a simple reference back to the original communication. However, if the crystallography is discussed again at any length in the full paper, the data should be re-presented to the referees in full, and re- published if considered necessary. 6.6 There may be other cases when an author wishes to publish a full paper in which the result of a crystal structure determination is discussed, but in which details or extensive discussion are considered unnecessary. The crystallographer may even be omitted as a co-author (for example when the determination is carried out by a commercial company). If the author is able to show the referees that this procedure is appropriate, it will be allowed provided that it does not lead to unnecessary fragmentation. However, the author must provide, as supplementary information, sufficient data relating to the crystal structure determination to allow a referee to make sure that the point made is correct, and co-ordinates etc. will be deposited with CCDC (or Bonn). The brief published description of the determination should be supplemented by appropriate reference to ‘unpublished work’.

ISSN:0003-2654    

DOI:10.1039/AN9931800115

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, JANUARY 1993. VOL. I18 119 IUPAC Publications on Nomenclature and Symbolism 1 .O Compilations 1.1 Nomenclature of Organic Chemistry, a 550-page hardcover volume published in 1979, available from Pergamon, Oxford. Section A: Hydrocarbons Section B: Fundamental heterocyclic systems Section C: Characteristic groups containing carbon, hy- drogen, oxygen, nitrogen, halogen, sulphur, selenium, and tellurium Section D: Organic compounds containing elements not exclusively those referred to in the title of Section C Section E: Stereochemistry Section F: General principles for the naming of natural products and related compounds Section H: Isotopically modified compounds 1.2 Nomenclature of Inorganic Chemistry, a 278-page hardcover volume published in 1990, available from Blackwell Scientific Publications, Oxford.Chapter I : General aims, functions and methods Chapter 2: Grammar Chapter 3: Elements, atoms, and groups Chapter 4: Formulae Chapter 5: Names based on stoichiometry Chapter 6: Neutral molecular compounds Chapter 7: Names for ions, substituent groups and radicals, and salts Chapter 8: Oxoacids and derived anions Chapter 9: Co-ordination compounds Chapter 10: Boron hydrides and related compounds 1.3 Biochemical Nomenclature and Related Documents, a 348-page softcover manual published in 1992 by Portland Press Ltd. for IUBMB, and available from the publisher (59 Portland Place, London W 1 N 3AJ, UK). The contents are as follows: Nomenclature of organic chemistry. Section E: Stereo- chemistry (1974) Nomenclature of organic chemistry. Section F: Natural products and related compounds (1976) Isotopically modified compounds Recommendations for the presentation of thermodynamic and related data in biology (1985) Citation of bibliographic references in biochemical journals (1971) Nomenclature and symbolism for amino acids and peptides (1 983) Abbreviated nomenclature of synthetic polypeptides or polymerized amino acids (1971) Abbreviations and symbols for the description of the conformation of polypeptide chains ( 1 969) Nomenclature of peptide hormones (1974) Nomenclature of glycoproteins, glycopeptides and peptidoglycans (1985) Nomenclature of initiation, elongation and termination factors for translation in eukaryotes (1988) Nomenclature of multiple forms of enzymes (1976) Symbolism and terminology in enzyme kinetics (1 98 1) Nomenclature for multienzymes (1989) Abbreviations and symbols for nucleic acids, poly- nucleotides and their constituents (1970) Abbreviations and symbols for the description of the conformations of pol ynucleotide chains (1 982) Nomenclature for incompletely specified bases in nucleic acid sequences (1984) Carbohydrate nomenclature.Part I (1969) Nomenclature of cyclitols (1 973) Numbering of atoms in myo-inositol (1 988) Conformational nomenclature for five- and six-membered ring forms of monosaccharides and their derivatives (1980) Nomenclature of unsaturated monosaccharides (1980) Nomenclature of branched-chain monosaccharides (1 980) Abbreviated terminology of oligosaccharide chains (1 980) Polysaccharide nomenclature ( I 980) Symbols for specifying the conformation of polysaccharide chains (1981) Nomenclature of lipids (1976) Nomenclature of steroids (1989) Nomenclature of quinones with isoprenoid side chains (1 973) Nomenclature of carotenoids (1 970) and amendments (1 974) Nomenclature of tocopherols and related compounds (1981) Nomenclature of vitamin D (1981) Nomenclature of retinoids (1 98 1 ) Prenol nomenclature (1986) Nomenclature of phosphorus-containing compounds of biochemical importance (1976) Nomenclature and symbols for folic acids and related compounds (1 986) Nomenclature for vitamins B-6 and related compounds (1973) Nomenclature of corrinoids (1 973) Nomenclature of tetrapyrroles (1 986) 1.4 Compendium of Analytical Nomenclature, a 280-page hardcover volume published in 1987, available from Blackwell Scientific Publications, Oxford.The contents are as follows: Presentation of the Results of Chemical Analysis Solution Thermodynamics (activity coefficients, equilibria, Recommendations for Terminology to be used with Precision Balances Recommendations for Nomenclature of Thermal Analysis Recommendations for Nomenclature of Titrimetric Analysis Electrochemical Analysis Analytical Separation Processes (precipitation, liquid- liquid distribution, zone melting and fractional crystallis- ation, chromatography, ion exchange) Spectrochemical Analysis (radiation sources, general atomic emission spectroscopy, flame spectroscopy, X-ray emission spectroscopy, molecular methods) Recommendations for Nomenclature of Mass Spec- t rome try Recommendations for Nomenclature of Radiochemical Methods Surface Analysis (including photoelectron spectroscopy) PH)120 ANALYST, JANUARY 1993, VOL.118 1.5 Compendium of Macromolecular Nomenclature, a 172- page hardcover volume published in 1991, available from Blackwell Scientific Publications, Oxford. The contents are as follows: Basic Definitions of Terms Relating to Polymers Stereochemical Definitions and Notations Relating to Polymers Definitions of Terms Relating to Individual Macro- molecules, their Assemblies, and Dilute Polymer Solutions Definitions of Terms Relating to Crystalline Polymers Nomenclature of Regular Single-strand Organic Polymers Nomenclature for Regular Single-strand and Quasi-single- strand Inorganic and Coordination Polymers Source-based Nomenclature for Copolymers A Classification of Linear Single-strand Polymers Use of Abbreviations for Names of Polymeric Substances 1.6 Compendium of Chemical Terminology: IUPAC Recommendations, a 456-page volume published in 1987, available in hardcover and softcover from Blackwell Scientific Publications, Oxford.1.7 Quantities, Units, and Symbols in Physical Chemistry, a 134-page hardcover volume published in 1988 by Black- well Scientific Publications, Oxford (new edition to appear 1993). 2.0 Documents not included in the compil- ations 2.1 Boron Cornpoiindb Nomenclature of inorganic boron compounds (Pure Appl. Chenz., 1972, 30, 68 1). Del ta Concen tion Nomenclature for cyclic organic compounds with contiguous formal double bonds (Pure Appl.Chem., 1988,60, 1395). Recommendations for the names of elements of atomic number greater than 100 (Pure Appl. Chem., 1979,51,381). Enzyme Nomenclature (1 992), published by Academic- Press in hardcover and softcover editions. Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles (Pure Appl. Cizem., 1983, 55,409). Names for hydrogen atoms, ions, and groups, and for reactions involving them (Pure Appl. Chenz., 1988,60, 1 1 15). Nomenclature of inorganic chemistry. Part 11. 1. Isotopically modified compounds (Pure Appl. Chem., 198 1,53, 1887). Treatment of variable valence in organic nomenclature (Pure Appl. Chem., 1984,56,769). Nomenclature of hydrides of nitrogen and derived cations, anions, and ligands (Pure Appl. Chem., 1982, 54, 2545).Extension of Rules A- 1.1 and A-2.5 concerning numerical terms used in organic chemical nomenclature (Pure Appl. Chern., 1986, 58, 1693). Nomenclature of Elements and Compounds Elements En :j vn es Heteroc~dic. Compounds Hydrogen Isotopicully Modijed Compound Lambda Conuention Nitrogen Hjdrrdes Numcvical Terms Polyanions Zeolites Nomenclature of polyanions (Pure Appl. Chem., 1987,59, 1529). Chemical nomenclature and formulation of compositions of synthetic and natural zeolites (Pure Appl. Chern., 1979, 51, 109 1). 2.2 Presentation of Results Glossary of terms used in physical organic chemistry (Pure Appl. Chem., 1983,55,1281). Glossary of atmospheric chemistry terms (Pure Appl. Chem., 1990,62, 2167). English-derived abbreviations for experimental techniques in surface science and chemical spectroscopy (Pure Appl. Chem., 1991,63, 887).Analytical Recommendations for publication of papers on a new analytical method based on ion exchange or ion-exchange chromato- graphy (Pure Appl. Chem., 1980,52,2555). Recommendations for presentation of data on compleximetric indicators. 1. General (Pure Appl. Chem., 1979,51, 1357). Recommendations for publishing manuscripts on ion-selective electrodes (Pure Appl. Chern., 1981,53, 1907). Recommendations on use of the term amplification reactions (Pure Appl. Chem., 1982,54,2553). Recommendations for the usage of selective, selectivity, and related terms in analytical chemistry (Pure Appl. Cheulz., 1983, Nomenclature for automated and mechanised analysis (Pure Appl. Chem., 1989,61, 1657).Nomenclature for sampling in analytical chemistry (Pure Appl. Chem., 1990,62, 1 193). Glossary for chemists of terms used in biotechnology (Pure Appl. Clzeni., 1992, 64, 143). Selection of terms, symbols and units related to microbial processes (Pure Appl. Chem. 1992,64, 1047). Physicochemical quantities and units in clinical chemistry with special emphasis on activities and activity coefficients (Pure Appl. Chem., 1984,56, 567). Quantities and units in clinical chemistry (Pure Appl. Chem., 1979,51, 2451). Quantities and units in clinical chemistry: nebulizer and flame properties in flame emission and absorption spectrometry (Pure Appl. Chern., 1986, 58, 1737). List of quantities in clinical chemistry (Pure Appl. Clzem., 1979, 51,2481). Proposals for the description and measurement of carry-over effects in clinical chemistry (Pure Appl.Chem., 1991,63, 301). Colloicls and Surface Chenzistry Definitions, terminology, and symbols in colloid and surface chemistry. I (Pure Appl. Clzeuli., 1972, 31, 577). 11, Hetero- geneous catalysis (Pure Appl. Chem., 1976, 46, 71). Part 1.14: Light scattering (provisional) (Pure Appl. Chem., 1983, 55, 93 1). Reporting experimental pressure-area data with film balances (Pure Appl. Chenz., 1985,57, 621). Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Pure Appl. Chem., 1985,57, 603). Reporting data on adsorption from solution at the solid/ solution interface (Pure Appl. Chem., 1986,523,967). Manual on catalyst characterization (Pure Appl.Chem., 199 1, 63, 1227). Terminology, Symbols, and Units, and tienerul 55, 553). Bio techno logy ClinicalANALYST, JANUARY 1993, VOL. 118 Electrochcmistrjt Nomenclature for transfer phenomena in electrolytic systems (Pure Appl. Cliem., 198 1,53, 1827). Electrode reaction orders, transfer coefficients, and rate constants-amplification of definitions and recommendations for publication of parameters (Pure Appl. Chem., 1980,52,233). Classification and nomenclature of electroanalytical techniques (Pure Appl. Chem., 1976,45, 8 1). Recommendations for sign conventions and plotting of electrochemical data (Pure Appl. Chem., 1976,45, 13 1). Electrochemical nomenclature (Pure Appl. Chem., 1974,37,499). Recommendations on reporting electrode potentials in non-aqueous solvents (Pure Appl.Chem., 1984,56,461). Definition of pH scales, standard reference values, measurement of pH and related terminology (Pure Appl. Chem., 1985,57,53 1). Interphases in systems of conducting phases (Pure Appl. Chem., 1986,58,437). The absolute electrode potential: an explanatory note (Pure Appl. Chem., 1986,58,955). Electrochemical corrosion nomenclature (Pure Appl. Chem., 1989,61, 19). Terminology in semiconductor electrochemistry and photo- electrochemical energy conversion (Pure Appl. Chem., 1991, 63, 569). Nomenclature, symbols, definitions and measurements for electrified interfaces in aqueous dispersions of solids (Pure Appl. Chem., 199 1,63,895). Symbolism and terminology in chemical kinetics (provisional) (Pure Appl.Chem., 1981,53, 753). Recommended standards for reporting photochemical data (Pure Appl. Chem., 1984,56,939). Glossary of terms used in photochemistry (Pure Appl. Chem., 1988,60, 1055). Expression of results in quantum chemistry (Pure Appl. Chem., 1978,50, 75). Reactions Nomenclature for organic chemical transformations (Pure Appl. Cliem., 1989, 61, 725). System for symbolic representation of reaction mechanisms (Pure Appl. Chem., 1989,61,23). Detailed linear representation of reaction mechanisms (Pure Appl. Cliem., 1989,61, 57). Rlzeological Properties Selected definitions, terminology, and symbols for rheological properties (Pure Appl. Chem., 1979,51, 121 5). Kinetics Plio t oc hem is t ry Q uan t um Chemistry 121 Spectroscopy Recommendations for publication of papers on methods of molecular absorption spectrophotometry in solution (Pure Appl.Chem., 1978,50, 237). Recommendations for the presentation of infrared absorption spectra in data collections. A, Condensed phases (Pure Appl. Chem., 1978,50,23 1). Definition and symbolism of molecular force constants (Pure Appl. Chem., 1978,50, 1709). Nomenclature and conventions for reporting Mossbauer spectroscopic data (Pure Appl. Chem., 1976,45,211). Recommendations for the presentation of NMR data for publication in chemical journals. A, Proton spectra (Pure Appl. Chem., 1972,29,625). B, Spectra from nuclei other than protons (Pure Appl. Chem., 1976,45,217). Presentation of Raman spectra in data collections (Pure Appl. Chem., 1981,53, 1879). Names, symbols, definitions and units of quantities in optical spectroscopy (Pure Appl.Chem., 1985,57, 105). A descriptive classification of the electron spectroscopies (Pure Appl. Chem., 1987,59, 1343). Presentation of molecular parameter values for TR and Raman intensity (Pure Appl. Chem., 1988,60, 1385). Recommendations for EPR/ESR nomenclature and conven- tions for presenting experimental data in publications (Pure Appl. Chem., 1989,61,2195). Nomenclature, symbols, units and their usage in spectro- chemical analysis. VIT. Molecular absorption spectroscopy, UV and visible (Pure Appl. Chem., 1988, 60, 1449); VTII. Nomenclature system for X-ray spectroscopy (Pure Appl. Chem., 1991,63, 735); X. Preparation of materials for analytical atomic spectroscopy (Pure Appl. Clzem., 1988, 60, 1461); XIT. Terms related to electrothermal atomization (Pure Appl. Chem., 1992, 64, 253); XITI. Terms related to chemical vapour generation (Pure Appl. Chem., 1992,64,261). Recommendations for nomenclature and symbolism for mass spectroscopy (Pure Appl. Chem., 1991,63, 1541). A guide to procedures for the publication of thermodynamic data (Pure Appl. Chem., 1972,39, 395). Assignment and presentation of uncertainties of the numerical results of thermodynamic measurements (Pure Appl. Chem., 1981,53, 1805). Notation for states and processes; significance of the word ‘standard’ in chemical thermodynamics and remarks on commonly tabulated forms of thermodynamic functions (Pure Appl. Chem., 1982,54, 1239). Tlzermodynamics

ISSN:0003-2654    

DOI:10.1039/AN9931800119

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

V What is FACSS? FACSS is the Federation of Analytical Chemistry and Spectroscopy Societies. FACSS is governed by a board with representatives from 7 member organizations including: American Chemical Society Analytical Division, Analysis Division of the Instrument Society of America, Association of Analytical Chemists, Society for Applied Spectroscopy, Chromatography Forum of the Delaware Valley, Coblentz Society, and the Royal Society of Chemistry. FACSS is a cooperative of these nonprofit chemical and spectroscopic organizations. The intent of FACSS is to bring together scientists interested in analytical problem solving at an annual national conference. The FACSS conference is a premier technical analytical meeting consisting of invited and contributed papers, workshops and short courses, and a technical instrumentation exhibit.A total of 16 FACSS conferences have been held to date. Diverse analytical interests are represented in the technical program which typically includes papers in the areas of: atomic spectroscopy, biotechnology and clinical chemistry, chemometrics, chromatography, electrochemistry, environmental analysis, infrared spectroscopy, lasers, mass spectrometry, nuclear magnetic resonance spectrometry, process analysis, raman spectroscopy, x-ray spectroscopy and surface analysis. Speakers include leaders in the field of these areas of research. Domestic and foreign speakers include scientists from academia, industry, and government. Workshops and short courses provide attendees with the opportunity to gain specialized technical skills in various areas of analytical chemistry.The exhibition allows conferees the opportunity to talk to the various vendors of analytical equipment and specialty items. Attendance at the annual meeting is approximately 2500. Approximately 1000 papers and posters are presented through out the week in parallel sessions. FACSS is often referred to as being "just the right size meeting" because it is small enough that conferees run into the people they want to talk to, yet large enough to cover the full range of analytical sciences. Who Should Attend? Individuals actively involved in analytical research often consider this to be the one meeting each year that they can't afford to miss. Any individual working in the field of analytical chemistry as a researcher, analyst, or technician will benefit from the exchange of information at FACSS.where is FACSS held? FACSS has been held in a variety of locations including: Philadelphia, St. Louis, Detroit, Cleveland, and Chicago. In 1993 the FACSS conference will be held in Detroit (Oct. 17-22) and in 1994 it will be held in St. Louis (Oct. 2-7). How do you get more information? To get on the FACSS mailing list please send a note to: FACSS, P.O. Box 278, Manhattan, KS 66502-0003, This will ensure that you receive a call for papers and a preliminary program containing registration materials for the next conference.V What is FACSS? FACSS is the Federation of Analytical Chemistry and Spectroscopy Societies. FACSS is governed by a board with representatives from 7 member organizations including: American Chemical Society Analytical Division, Analysis Division of the Instrument Society of America, Association of Analytical Chemists, Society for Applied Spectroscopy, Chromatography Forum of the Delaware Valley, Coblentz Society, and the Royal Society of Chemistry.FACSS is a cooperative of these nonprofit chemical and spectroscopic organizations. The intent of FACSS is to bring together scientists interested in analytical problem solving at an annual national conference. The FACSS conference is a premier technical analytical meeting consisting of invited and contributed papers, workshops and short courses, and a technical instrumentation exhibit. A total of 16 FACSS conferences have been held to date. Diverse analytical interests are represented in the technical program which typically includes papers in the areas of: atomic spectroscopy, biotechnology and clinical chemistry, chemometrics, chromatography, electrochemistry, environmental analysis, infrared spectroscopy, lasers, mass spectrometry, nuclear magnetic resonance spectrometry, process analysis, raman spectroscopy, x-ray spectroscopy and surface analysis.Speakers include leaders in the field of these areas of research. Domestic and foreign speakers include scientists from academia, industry, and government. Workshops and short courses provide attendees with the opportunity to gain specialized technical skills in various areas of analytical chemistry. The exhibition allows conferees the opportunity to talk to the various vendors of analytical equipment and specialty items.Attendance at the annual meeting is approximately 2500. Approximately 1000 papers and posters are presented through out the week in parallel sessions. FACSS is often referred to as being "just the right size meeting" because it is small enough that conferees run into the people they want to talk to, yet large enough to cover the full range of analytical sciences. Who Should Attend? Individuals actively involved in analytical research often consider this to be the one meeting each year that they can't afford to miss. Any individual working in the field of analytical chemistry as a researcher, analyst, or technician will benefit from the exchange of information at FACSS. where is FACSS held? FACSS has been held in a variety of locations including: Philadelphia, St.Louis, Detroit, Cleveland, and Chicago. In 1993 the FACSS conference will be held in Detroit (Oct. 17-22) and in 1994 it will be held in St. Louis (Oct. 2-7). How do you get more information? To get on the FACSS mailing list please send a note to: FACSS, P.O. Box 278, Manhattan, KS 66502-0003, This will ensure that you receive a call for papers and a preliminary program containing registration materials for the next conference.V What is FACSS? FACSS is the Federation of Analytical Chemistry and Spectroscopy Societies. FACSS is governed by a board with representatives from 7 member organizations including: American Chemical Society Analytical Division, Analysis Division of the Instrument Society of America, Association of Analytical Chemists, Society for Applied Spectroscopy, Chromatography Forum of the Delaware Valley, Coblentz Society, and the Royal Society of Chemistry.FACSS is a cooperative of these nonprofit chemical and spectroscopic organizations. The intent of FACSS is to bring together scientists interested in analytical problem solving at an annual national conference. The FACSS conference is a premier technical analytical meeting consisting of invited and contributed papers, workshops and short courses, and a technical instrumentation exhibit. A total of 16 FACSS conferences have been held to date. Diverse analytical interests are represented in the technical program which typically includes papers in the areas of: atomic spectroscopy, biotechnology and clinical chemistry, chemometrics, chromatography, electrochemistry, environmental analysis, infrared spectroscopy, lasers, mass spectrometry, nuclear magnetic resonance spectrometry, process analysis, raman spectroscopy, x-ray spectroscopy and surface analysis.Speakers include leaders in the field of these areas of research. Domestic and foreign speakers include scientists from academia, industry, and government. Workshops and short courses provide attendees with the opportunity to gain specialized technical skills in various areas of analytical chemistry. The exhibition allows conferees the opportunity to talk to the various vendors of analytical equipment and specialty items. Attendance at the annual meeting is approximately 2500. Approximately 1000 papers and posters are presented through out the week in parallel sessions.FACSS is often referred to as being "just the right size meeting" because it is small enough that conferees run into the people they want to talk to, yet large enough to cover the full range of analytical sciences. Who Should Attend? Individuals actively involved in analytical research often consider this to be the one meeting each year that they can't afford to miss. Any individual working in the field of analytical chemistry as a researcher, analyst, or technician will benefit from the exchange of information at FACSS. where is FACSS held? FACSS has been held in a variety of locations including: Philadelphia, St. Louis, Detroit, Cleveland, and Chicago. In 1993 the FACSS conference will be held in Detroit (Oct.17-22) and in 1994 it will be held in St. Louis (Oct. 2-7). How do you get more information? To get on the FACSS mailing list please send a note to: FACSS, P.O. Box 278, Manhattan, KS 66502-0003, This will ensure that you receive a call for papers and a preliminary program containing registration materials for the next conference.V What is FACSS? FACSS is the Federation of Analytical Chemistry and Spectroscopy Societies. FACSS is governed by a board with representatives from 7 member organizations including: American Chemical Society Analytical Division, Analysis Division of the Instrument Society of America, Association of Analytical Chemists, Society for Applied Spectroscopy, Chromatography Forum of the Delaware Valley, Coblentz Society, and the Royal Society of Chemistry.FACSS is a cooperative of these nonprofit chemical and spectroscopic organizations. The intent of FACSS is to bring together scientists interested in analytical problem solving at an annual national conference. The FACSS conference is a premier technical analytical meeting consisting of invited and contributed papers, workshops and short courses, and a technical instrumentation exhibit. A total of 16 FACSS conferences have been held to date. Diverse analytical interests are represented in the technical program which typically includes papers in the areas of: atomic spectroscopy, biotechnology and clinical chemistry, chemometrics, chromatography, electrochemistry, environmental analysis, infrared spectroscopy, lasers, mass spectrometry, nuclear magnetic resonance spectrometry, process analysis, raman spectroscopy, x-ray spectroscopy and surface analysis.Speakers include leaders in the field of these areas of research. Domestic and foreign speakers include scientists from academia, industry, and government. Workshops and short courses provide attendees with the opportunity to gain specialized technical skills in various areas of analytical chemistry. The exhibition allows conferees the opportunity to talk to the various vendors of analytical equipment and specialty items. Attendance at the annual meeting is approximately 2500. Approximately 1000 papers and posters are presented through out the week in parallel sessions. FACSS is often referred to as being "just the right size meeting" because it is small enough that conferees run into the people they want to talk to, yet large enough to cover the full range of analytical sciences. Who Should Attend? Individuals actively involved in analytical research often consider this to be the one meeting each year that they can't afford to miss. Any individual working in the field of analytical chemistry as a researcher, analyst, or technician will benefit from the exchange of information at FACSS. where is FACSS held? FACSS has been held in a variety of locations including: Philadelphia, St. Louis, Detroit, Cleveland, and Chicago. In 1993 the FACSS conference will be held in Detroit (Oct. 17-22) and in 1994 it will be held in St. Louis (Oct. 2-7). How do you get more information? To get on the FACSS mailing list please send a note to: FACSS, P.O. Box 278, Manhattan, KS 66502-0003, This will ensure that you receive a call for papers and a preliminary program containing registration materials for the next conference.

ISSN:0003-2654    

DOI:10.1039/AN993180000v

出版商:RSC    

年代:1993

数据来源: RSC