摘要:

ANALYST JANUARY 1986 VOL. 113 SHORT PAPERS 91 Simple and Precise High-performance Liquid Chromatographic Method for the Investigation of Carbodiimide-mediated Peptide Synthesis Marek Slebioda and Aleksander M. Kolodziejczyk Department of Organic Chemistry Technical University of Gdansk PL 80-952 Gdansk Poland A simple HPLC method for the determination of intermediates products and by-products of peptide synthesis is described. The mean errors of the quantitative determination of all components of the reaction mixture at any stage of peptide synthesis were found to be low (1.3-2.1%). The sensitivity was good enough to detect a 0.05% yield of the products The method was successfully used to determine the effects of the reaction conditions on optical purity and yield of the synthesised peptide and amino acid derivatives.Keywords Peptide synthesis; high-performance liquid chromatography ~ New peptide bond synthesis methods are still being intro- Procedure duced and each carries the risk of racemisation-of the acylating amino acid in the activated form. Moreover, different side products are usually formed that decrease the yield and purity of the main peptide. Even the azide method, formerly considered to be a racemisation-free means of peptide synthesis causes several per cent. racemisation.1 Despite great efforts in many laboratories the mechanisms of many peptide synthesis reactions are still not clear mainly owing to the lack of an appropriate analytical method. Such analyses are also needed in order to evaluate the usefulness of new peptide synthesis methods.Many racemisation tests have been used (for a brief review see reference 2) but all of them were limited to one model reaction and/or had other short-comings so that general conclusions were difficult to obtain. The use of isotopically labelled compounds in connection with high-performance thin-layer chromatography allows detailed studies of peptide synthesis3 but requires unique apparatus and is expensive. In our opinion high-performance liquid chromatography (HPLC) is the best method for such a purpose and should be employed more widely. A normal-phase system has been used to evaluate the racemisation in various coupling methods,' the extent of side reactions4 and the stereoselectivity5 in peptide synthesis. Also the separation of protected peptide dia-stereomers has been achieved by use of a silica gel stationary phase,6 but HPLC has not been used for more precise or kinetic investigations.This HPLC study demonstrates the possibility of resolving all components of peptide synthesis mixtures. Even reactive intermediates such as 5(4H)-oxazolones could be quantitatively determined. Experimental Apparatus A KABID 5101 isocratic chromatograph equipped with a KABID 5301 fixed-wavelength UV detector (254 nm) (Kabid-Zopan Poland) and a home-made column (250 x 4 mm i.d.) packed with LiChrosorb Si-60 5 pm (E. Merck Darmstadt, FRG) was used. The mobile phase was ethanol - propan-2-01 -hexane (2.0 + 2.5 + 95.5 by volume) at a flow-rate of 1.0 cm3 min-1. Reagents All reagents were of analytical-reagent grade.Alcohols (POCh Poland) were dried over molecular sieves and then distilled. Hexane (Reachim USSR) and ethyl acetate (POCh) were used as obtained. Dioxane (POCh) was distilled over K - Na alloy. The dipeptides (Ac-Phe-Leu-OMe and CHO-Phg-Leu-OMe) (Phg = phenylglycyl) were synthesised by the l-hydroxy-benzotriazole (HOBt) - dicyclohexylcarbodiimide (DCC) method with dichloromethane.7 The products were purified on a preparative scale with a home-made liquid chromatograph (300 x 18 mm i.d. column packed with silica gel 60 MN; E. Merck) using the same mobile phase as described above. 4-Benzyl-2-methyl-5(4H)-oxazolone was synthesised according to Chen et aZ.8 and immediately used to determine the relative distribution coefficient Kox.N-(Acetylphenylalany1)dicyclohexylurea was obtained by dropping a solution of acetylphenylalanine (2 mmol) in dimethylformamide (20 cm3) into a solution of dicyclohexyl-carbodiimide (2 mmol) in dimethylformamide (20 cm3) at 50-55 "C within 1.5 h. After cooling to room temperature, ethyl acetate (40 cm3) was added and then a typical work-up procedure as for the dipeptides followed. Standard solutions were prepared and the DCC-mediated peptide synthesis reactions were carried out in dioxane. The kinetics of these reactions were studied by taking small portions (0.3 cm3) of the reaction mixture at suitable intervals. The samples were extracted with ethyl acetate (0.3 cm3) - 0.5 M sodium hydrogen carbonate solution (0.3 cm3) system im-mediately and then 10 mm3 of the supernant were injected on to the HPLC column.With a prolonged reaction time (more than 3 h) extraction of the sample before injection was not necessary. Results and Discussion Preliminary experiments showed that components of the peptide synthesis reaction mixture can be determined by direct HPLC analysis (Fig. 1). With a reaction time shorter than 3 h we observed considerable base-line drift caused by decomposition of the acylating component in the activated form. In order to investigate the kinetics during this very important period of the reaction it was necessary to stop the reaction. This could be achieved by washing a sample removed from the reaction mixture with sodium hydrogen carbonate sblution. We applied the internal standard method to elimi-nate any unforseeable effect of the extraction.Formyl-D-phenylglycyl-D-leucine methyl ester was chosen as a suitable standard because its chromatographic properties were similar to those of both the product and by-products in the studied peptide synthesis (DCU = dicyclohexylurea): dioxane DCC Ac-L-Phe + L-Leu-OMe p) Ac-L-Phe-L-Leu- OMe + Ac-D-Phe-L-Leu-OMe + N-(Ac-Phe)-DC 92 ANALYST JANUARY 1986 VOL. 111 t v) C 0 Q al a LL I I I 0 5 10 15 Ti me/m in Fig. 1. Chromatogram of the reaction mixture of DCC-mediated Synthesis of Ac-Phe-Leu-OMe. Chromatographic conditions as de-scribed in the text. Peaks N N-(acet 1 henylalany1)-N,N'-dicyclohexylurea; Ox 4-benzyl-2-methyl-5(%')-oxazolone; LL, acetyl-L-phenylalanyl-L-leucine methyl ester; IS formyl-D-phenylglycyl-D-leucine methyl ester; and DL acetyl-D-phenylalanyl-L-leucine methyl ester 3 m I E 0 2 -2 2- 0 X 7 4 1 0 0 1 2 Ci,expX 102/mol dm-3 Fig.2. Correlation between determined (Ci exp) and real (Ci real) concentrations of the components of the reaction mixture of Ac-'Phe-Leu-OMe synthesis. For abbreviations see Fig. 1 First a series of experiments were carried out to check if the standard dipeptide undergoes any change during the reaction. The synthesis of acetylphenylalanylleucine methyl ester was carried out in the presence of the internal standard (0.0150 mol dm-3). After 24 h the internal standard concentration was determined by means of HPLC (0.0151 mol dm-3; relative standard deviation 4.1%) and on the basis of a t-test it was concluded that the internal standard is stable in the reaction mixture for at least 24 h.Concentrations \ \ \ Fig. 3. Kinetics of the reaction of the aminolysis of racemic 4-benzyl-2-methyl-5(4H)-oxazolone with racemic leucine methyl ester. Reaction conditions medium dioxane; temperature 298.0 K; and initial concentrations of substrates 0.05 mol dm-3 Relative distribution coefficients (Ki) were determined: where hi hIs and hi,ex hIs,ex represent the peak heights of the products (i) and internal standard (IS) determined directly in the reaction mixture and after extraction respectively. The Ki coefficients were independent of the concentration of the determined compounds and were KN = 1.11 k 0.02 KLL = 1.04 k 0.02 K D L = 1.03 f 0.02 and KO = 1.16 k 0.01 where N LL DL and Ox denote the N-acylurea LL- and DL-dipeptide and the oxazolone respectively.The concentrations of sample components (Ci) were deter-mined on the basis of the Ki coefficients and the relative detector response pi: where pi = CihIs/C&. An excellent correlation between the determined (Ci exp) and the real (Ci real) concentrations of the the components of the reaction mixture was found (Fig. 2). According to the Student's t-test the proposed method appears to be free from any systematic errors (confidence level 0.05). The mean errors of the determination were low The proposed method can serve as a reliable means for investigating DCC-mediated peptide synthesis. It allows the components of the reaction mixture to be easily identified and under the reaction conditions employed (initial concentration of substrates 0.05 mol dm-3) it is sensitive enough to detect down to 0.05% yields of the products.The method has been used successfully to determine the optical purity of synthesised amino acid derivatives9 and to investigate the aminolysis of 4-benzyl-2-methyl-5(4H)-oxazolone (Fig. 3) and the effects of the initial reagent concentrations10 and the amino acid salt and tertiary amine types" on the yield and degree of racemisation in peptide synthesis. (1.3-2.1 Yo) ANALYST JANUARY 1986 VOL. 111 93 This work was supported in part by Research Grant Mr. 1-12 and in part by the Polish Academy of Sciences Committee of Chemistry Science. 6. 7. Goodman M.Koegh P. and Anderson H. Bioorg. Chem., 1977 6 239. Slebioda M. and Kol’odziejczyk A. M. J. Chromatogr., 1985,325 282. 1. 2. 3. 4. 5. References Takuma S . Hamada Y. and Shioiri T. Chem. Pharm. Bull., 1982 30 3153. Benoiton N. L. The Peptides Volume 5 Academic Press, New York 1983 pp. 217-284. Arendt A. Koi’odziejczyk A. M. and Sokdowska T., in “Proceedings of the 15th European Peptide Symposium, Gdansk 1978 Peptides 1978,” Wroctaw University Press, Wrocl’aw 1979 p. 151. Chen F. M. F. Steinauer R. and Benoiton N. L. J. Org. Chem. 1983 48 2939. Benoiton N. L. Kuroda K. and Chen F. M. F. Tetrahedron Lett. 1981 22 3359. 8. 9. 10. Chen F. M. F. Kuroda K. and Benoiton N. L. Synthesis, 1979 230. Kolodziejczyk A. M. and Slebioda M. Synthesis 1984 865. Slebioda M. and Kolodziejczyk A. M. in “Proceedings of the 17th European Peptide Symposium Prague 1982 Peptides 1982,” Walter de Gruyter Berlin 1983 p. 153. Kol’odziejczyk A. M. and Slebioda M. Int. J. Pept. Protein Res. submitted for publication. 11. Paper A5i203 Received June 7th 1985 Accepted July 29th 198

ISSN:0003-2654    

DOI:10.1039/AN9861100091

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST JANUARY 1986 VOL. 111 95 Elimination of Feed Additive Derived Interferences in the Assay for Avoparcin H. L. Hatfield and A. Thomas Product Research and De velo pm en t Laboratories M ed ica I/Ag ricultu ra I Research Divisions C ya na m id o f Great Britain Limited P.O. Box 7 Fareham Road Gosport Hampshire PO13 OAS UK Animal feed additives were screened for their interference in the microbiological assay of the animal growth promoter avoparcin. Positively biased assay results and loss of assay validity were observed with a number of additives. Pre-extraction of samples with dichloromethane was shown to be effective i n eliminating interferences from ionophore antibiotics. The use of a tetracycline-resistant test organism is recommended if chlortetracycline or oxytetracycline is present.Keywords Avoparcin determination; microbiological assay; feed additive interference; ionophore antibiotics Avoparcin,* a glycopeptide antibiotic is used as an animal growth promoter and is incorporated into feeding stuffs at concentrations of 5-40 mg kg-1. Assay methods for avoparcin in feeding stuffs have been examined by the Antibiotics in, Animals Feedingstuffs Sub-committee of the Analytical Methods Committee and a microbiological plate diffusion assay was described.1 This method has been adopted officially by the European Economic Community.2 When the method was published as part of the Medicines Act (Animal Feeding Stuffs Regulations)3 a preliminary statement that ionophore antibiotics interfered in the determination of avoparcin was included.Most broiler feeds produced in Europe include both a growth promoter and a prophylactic anticoccidial compound. As ionophore antibiotics (e.g. monensin salinomycin and lasalocid) are widely used as the anticoccidial compound the inability of the published methods to assay accurately avopar-cin in broiler feeds was of concern. Procedures were therefore investigated that would allow the assay of avoparcin in ionophore-containing feeding stuffs and at the same time other feed additives were examined for their effect on the avoparcin assay. Experimental Preparations of animal feeding stuffs containing various feed additives were obtained by adding solutions of the additives to 50 g of ground (to pass a 1-mm2 sieve) feeding stuffs with or without 10 mg kg-1 of avoparcin.Each 50-g sample was assayed for avoparcin using the method described previously, unless stated otherwise. A Soxhlet extraction apparatus taking 40 X 120 mm cellulose thimbles (Whatman) was employed to pre-extract 50-g samples. Dichloromethane was the solvent of choice. After extraction for 5-7 cycles samples were allowed to air-dry overnight before the whole of the sample and thimble were assayed for avoparcin. The use of assay organism resistant to antibiotics other than avoparcin was not pursued except for the use of a tetracycline-resistant strain of Bacillus cereus. This organism B. cereus K250 TR (NCIB 11183; NCTC 10989) is resistant to at least 200 p.g ml-1 of chlortetracycline and was substituted directly for the normal assay organism B.subtilis (NCIB 8054). * Avoparcin is available in the UK and Europe as AVOTAN the registered trade mark of American Cyanamid Company Wayne NJ, USA. Results An animal feed additive was considered to interfere in the avoparcin assay if when present at normal inclusion levels it caused an increase or decrease in the apparent level of avoparcin of greater than 10%. Additional parameters con-sidered were the quality of inhibition zones and the assay validity (the parallelism of dose - response lines of standard and sample). In practice all three parameters were affected with assay validity an increase in the apparent avoparcin level being frequently associated. No example of an additive causing a negative bias (reduction in apparent avoparcin activity) was found.Table 1 lists the additives tested with their effects on the avoparcin assay. A Soxhlet extraction of feeds with dichloromethane (Table 2) proved useful in removing interfering compounds particul-arly the ionophore antibiotics. Discussion The pre-extraction of animal feeding stuffs with dichloro-methane allowed the assay of avoparcin in broiler feeds that would otherwise have been impossible. However the pre-extraction procedure especially if prolonged may reduce the recovery of avoparcin by 1&15% and it is recommended that a control sample of known avoparcin content is processed with the test samples. The use of therapeutic antibiotics at high concentrations in animal feeds is restricted by the Medicines Act to veterinary prescription only; therefore the presence of antibiotics such as tetracyclines and penicillins should be known before samples are assayed and appropriate measures to allow the assay of such samples can be taken.The presence of small amounts of antibiotics in animal feeding stuffs arising from diverse sources such as cross-contamination during their manufacture or use or improperly taken samples can cause problems particularly if a therapeutic antibiotic is involved. For example a feeding stuff containing chlortetracycline at 2 mg kg-1 will give an apparent assay result of more than 50 mg kg-1 of avoparcin. Therefore when assay results greatly in excess of the theoretical content of avoparcin are obtained, the possibility of contamination by another antibiotic must be considered.Procedures for the detection and identification of animal feed additives have been published and include TLC4 and electrophoresis.5 The use of such procedures can ensure that problems with interference in microbiological assay methods such as that for avoparcin are minimised 96 ANALYST JANUARY 1986 VOL. 111 Table 1. Effect of animal feed additives on avoparcin microbiological assay Level in feed/ Additive mg kg- 1 Arprinocid . . . . 60 Furazolidone . . . . 400 Lasalocid . . . . . . 90 Monensin . . . . . . 100 Narasin . . . . . . 70 Nitrovin . . . . . . 10 Penicillins . . . . . . 80 Salinomycin . . . . 60 Tetracyclines . . . . 100-600 Tylosin . . . . . . 20-500 Flavomycin . . . . 1-10 Purpose Anticoccidial Growth promotion Antibacterial Anticoccidial Anticoccidial Anticoccidial Growth promotion Antibacterial Anticoccidial Antibacterial Antibacterial/ growth promotion Effect* aBc ab aBc aBc aBc aBc aBc aB aBc aB ab Minimised by Pre-extraction Pre-extraction Pre-ex traction Pre-extraction Pre-extraction Pre-extraction Pre-extraction P-Lactamase Pre-extraction Resistant test organism Pre-extraction * a Non-valid assay; b apparent increase in potency; B gross increase in potency; and c indistinct inhibition zone edges.The following feed additives do not interfere amprolium arsenicals bacitracin carbadox copper dimetridazole erythromycin robenidine streptomycin and virginiamycin . Table 2. Assay results following dichloromethane pre-extraction of broiler feeding stuffs The contributions made by our technical staff especially Mrs. Margaret Farrow and Miss Danielle Barrie are gratefully Inclusion level/ Assay? acknowledged. Additive * mg kg-1 avoparcinjmg kg-1 Aprinocid . . . . . . 60 9.0 Lasalocid . . . . . . 75 10.2 Monensin . . . . . . 100 10.3 1. Salinomycin . . . . . . 60 9.9 2. None . . . . . . . . - 10.3$ 3. * Added to feeding stuff containing 10 mg kg-l of avoparcin. -t After pre-extraction with dichloromethane; mean of two $ Not extracted with dichloromethane. 4* 5 . weighings. References Analytical Methods Committee Analyst 1979 104 1075. Off. J. Eur. Commun. 1981 L257 39. “The Fertilisers and Feeding Stuffs Regulations 1985,” SI 1985 No. 273 HM Stationery Office London. Bucher E. and Tischler J. Landwirtsch. Forsch. 1981 34, 166. Smither R. and Vaughan D. R. J. Appl. Bacteriol. 1978,44, 421. Paper A51240 Received July 2nd 1985 Accepted July 31st 198

ISSN:0003-2654    

DOI:10.1039/AN9861100095

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 97 Spectrophotometric Determination of Tetracycline with Sodium Molybdate Salah M. Sultan Chemistry Department, College of Science, King Saud University, Riyadh, Saudi Arabia A spectrophotometric method is described for the determination of tetracycline hydrochloride. The drug is reacted with sodium molybdate at the boiling-point for 15 rnin in hydrochloric acid medium. The absorbance of the colour developed is measured at 430 nm. The method is simple, reproducible and accurate and is easily applied to the determination of the drug in the pure form and in pharmaceutical preparations. Keywords: Tetracycline hydrochloride; sodium molybdate; spectrophotometry Tetracycline derivatives are bacteriostatic an ti bio tics and various methods have been reported for their determination, including titrimetric,lJ fluorimetric,3-5 chromatographic~l5 and spectrophotometriclG22 methods.Spectrophotometric methods based on cornplexation of tetracyclines with some cations have also been reported.2527 This paper describes a spectrophotometric method for the determination of tetra- cycline hydrochloride using sodium molybdate in hydrochloric acid medium. Experimental Apparatus All absorbance measurements were made with a Beckrnan Model 35 spectrophotometer connected to a Beckman Model 24-25 ACC recorder. Matched sets of W 210/UU 10.00-mm cells were used throughout. A Metrohm Model 632 digital pH meter was used for pH measurements. Reagents Quartz-processed high-purity water was used throughout. All chemicals and reagents were of analytical-reagent or phar- maceutical grade.Stock solutions of tetracycline (1 mg ml-1) were freshly prepared. The powder form of the drug was dissolved in water. For capsules, an amount of powder containing the equivalent of 250 mg of tetracycline was accurately weighed and transferred into a 250-ml calibrated flask, shaken with 150 ml of water for 10 min and filtered through a normal filter-paper. The filtrate and washings were placed in another 250-ml calibrated flask and diluted to volume with water. Hydrochloric acid (10 M) and Na2M04.2H20 solution (0.01 M) were prepared in the usual way. Recommended Procedure In a 50-ml calibrated flask place 4 ml of sodium molybdate solution and 5 ml of hydrochloric acid. Dilute near to the mark with water, shake and add 2 ml of tetracycline solution.Place the flask for 15 min in a water-bath at 100 k 5 "C, cool and dilute to the mark with water. Measure the absorbance of the coloured species at 430 nm. Results and Discussion Absorption Spectra The absorption spectra of the reaction products were measured against a reagent blank in the range 300-750 nm. It shows a characteristic A,,,. at 430 nm when the amber colour is fully developed, which could be attributed to the formation of molybdenum(II1). The same colour was previously28>29 attributed to the formation of molybdenum(III), which absorbs at 430 nm. The optimum conditions were established based on the development of maximum colour and stability on variation of parameters such as the concentration of the acid and time of heating on the water-bath, and these optimum conditions are given in the procedure indicated above.The reaction rate and development of the colour were retarded on decreasing the temperature and increasing the concentration of hydrochloric acid. The colour obtained by heating the reactants for 15 min in a water-bath at 100 "C was found to be stable for 4 h at room temperature. The kinetics of the reaction could easily be followed spectrophotometrically when the reactants were maintained at 60 "C. On scanning the spectrum at intervals when the temperature of the reactants was maintained at 60 "C, the absorbance of molybdenum(II1) at 430 nm increased whereas the absorbance of tetracycline hydrochloride at 355 nm decreased, thus giving a characteristic isosbestic point pattern, as illustrated in Fig.1. Fig. 1 clearly indicates that the reaction between tetracycline and molybdenum(V1) is a slow reaction that proceeds to completion and attains maximum absorbance at 430 nm in a few hours. Heating the reactants for 15 min at I A 1.600 1 1.200 a) c (D +? z 2 0.800 0.400 u.uuu ~ 350 400 450 500 W aveleng t hln m Fig. 1. Absorption spectra for reaction mixtures of 40 pg of tetracycline hydrochloride, 200 pg of sodium molybdate and 1 .O M hydrochloric acid against reagent blank at 60 k 5 "C at 5-min intervals for each run (A,B, . . ., J)98 ANALYST, JANUARY 1986, VOL. 111 100 k 5 "C accelerates the reaction and is thus considered to be mandatory for the quantitative determination of the drug. Without the addition of molybdenum(1V) only one maximum at 355 nm was obtained, which verifies that a reaction between tetracycline hydrochloride and molybdenum(V1) takes place and gives the product that appears at 430 nm.The absorbance of tetracycline hydrochloride at 355 nm has previously27 been reported. A kinetic study is in progress in our laboratory in order to eludicate the mechanism of the reaction. Analytical Data Beer's law is valid over the concentration range between 10 and 140 pg ml-1. The molar absorptivity was calculated to be 9.48 x 10-3 1 mol-1 cm-1. The linearity of the graph of concentration versus absorbance was checked by a linear least-squares treatment using a computer; the slope and intercept were obtained with a correlation coefficient of 0.9999. The precision and accuracy of the method were found by analysis of tetracycline hydrochloride in the pure form (A) and in capsule form from two different sources (B1 and B2).Average recoveries of five determinations for each form at different hydrochloric acid concentrations are given in Table 1. At hydrochloric acid concentrations below 0.2 M the determination was not feasible owing to the formation of a brown - yellow precipitate of molybdenum(II1). At hydro- chloric acid concentrations above 4 M, results were not easy to obtain owing to a continuous decrease in absorbance and incompleteness of the reaction. Similarly, poor results were obtained when the reactants were heated for only 5 min at 100 Ifr 5 "C or for 30 min at 60 "C. Comparison with Other Methods The same batch of pure form and capsules of tetracycline hydrochloride were analysed by the proposed, the official3O and the sodium cobaltinitrate22 methods and the results are presented in Table 2.All sets of results were compared statistically by calculation of the t-value using the equation t = (ntlX-fl)/a. At the 95% confidence level, the calculated t-values did not exceed the theoretical t-values, which indi- cates that there is no significant difference between the proposed method and the other two methods. Effect of Excipients The excipients usually added in the preparation of capsules, such as lactose, glucose and starch, did not interfere with the results . Table 1. Precision and accuracy of the determination of tetracycline hydrochloride. Sodium molybdate in an amount of 200 pg taken for source A and 400 pg for sources B1 and B2, with heating for 15 min at 100 k 5 "C Concentration Amount Average Standard of HCUM Source takenlpg foundtpg Recovery,* YO deviation, YO 0.5 A 40 39.65 99.13 0.61 B1 80 79.18 98.98 0.42 B2 80 79.24 99.05 0.21 1 .o A 40 39.95 99.88 0.61 B1 80 79.90 99.88 0.48 B2 80 79.88 99.85 0.31 1.5 A 40 39,98 99.95 0.25 B1 80 79.88 99.85 0.29 B2 80 79.74 99.68 0.37 2.0 A 40 40.11 100.28 0.31 B2 80 79.66 99.58 0.79 B, 80 79.72 99.65 0.81 3.0 A 40 39 * 77 99.43 0.36 B1 80 80.08 100.10 0.76 B2 80 79.84 99.80 0.69 4.0 A 40 39.97 99.93 0.44 B1 80 79.83 99.79 0.96 B2 80 79.76 99.70 0.88 * Average of five determinations. Table 2. Determination of tetracycline hydrochloride by the proposed method compared with the official and the sodium cobaltinitrate methods Recovery* f standard deviation, YO t Source Method I t Method 25 Method 3§ (calcu1ated)l A 99.68 f 0.21 99.61 k 0.45 Bl 99.81 k 0.35 99.25 & 0.61 B2 99.47 k 0.61 100.28 k 0.55 A B1 B2 * Average of five determinations.t Proposed method. 5 Official method.30 0 Sodium cobaltinitrite method.22 7 Theoretical value = 2.78 (p = 0.05). 0.89 0.61 0.94 99.14 f 0.48 0.45 100.29 k 0.54 0.97 100.88 2 0.49 1.25ANALYST, JANUARY 1986, VOL. 111 99 Application to Other Derivatives Trials were made of the application of the method to the determination of other derivatives of tetracycline, such as oxytetracycline hydrochloride and doxycycline hyclate, but no reaction seemed to occur and no colour developed at any acid concentration at elevated temperature.Conclusion It may be concluded that this method could be applied as a general analytical procedure for the determination of tetra- cycline hydrochloride in its pure form and in pharmaceutical preparations in the hydrochloric acid concentration range 0.2-4.0 M with heating for 15 min at 100 +_ 5 “C. The author thanks Lederle Laboratories, A Division of American Cyanamid Co., Pearl River, NY, USA, for supplying the materials. 1. 2. 3. 4. 5. 6. 7. 8. 9. References Haroun, I . , and Khattab, F., Zndian J. Pharm., 1978,40, 12. Yokoyama, F., and Chatten, L. G., J. Am. Chem. Pharm. ASSOC., Sci. Ed., 1958, 47, 548. Poiger, H., and Schlatter, C., Analyst, 1976, 101, 808. Regosz, A., Pharmazie, 1977,32, 681. Ragazzi, E., and Veronese, G., J.Chromatogr., 1977,132,105. Selzer, G. B., and Wright, W. W.,Antibiot. Chemother., 1957, 7, 292. Addison, G. W., and Clark, R. G., J. Pharm. Pharmacol., 1963, 15, 268. Kelley, G. G., J. Pharm. Sci., 1964, 53, 1551. Simmsons, D. L., Woo, H. S. L., Koorengevel, C. M., and Seers, P., J. Pharm. Sci., 1966, 55, 1313. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22 * 23. 24. 25. 26. 27. 28. 29. 30. Griffiths, B. W., J. Pharm. Sci., 1966, 55, 353, Ascoione, P. P., Zagar, J. B . , and Chrekian, G. B., J. Pharm. Sci., 1967, 56, 1393. Dijkhuis, 1. C., and Brommet, M. R., J. Pharm. Sci., 1970,59, 558. Fike, W. W., and Brake, N. W., J. Pharm. Sci., 1972,61,615. Tsuji, K., and Robertson, J., J. Pharm. Sci., 1976, 65, 400. Ragazzi, E., and Veronese, J. Chromatogr., 1977, 134, 223. Ciccarelli, F. S., Woolford, M. H., and Avery, M. E., J. Am. Pharm. Assoc., Sci. Ed., 1959, 48, 263. Kohn, W . K., Anal. Chem., 1961, 33, 862. Mazor, L., and Papay, M., Fresenius Z. Anal. Chem., 1960, 175, 355. Hayes, J. E., and Du Bey, H. G., Anal. Biochem., 1964,7,322. Agrawal, K. C., and Dutta, B. N., Sci. Cult., 1961, 27, 450. Abdel-Khalek, M. M., and Mahrous, M. S., Talanta, 1983,30, 792. Mahrous, M. S., and Abdel-Khalek, M. M., Talanta, 1984,31, 289. Amer, M. M., Ahmad, A. K. S., and Tawakkol, M. S., Bull. Fac. Pharm. Cairo Univ., 1969, 8, 87. Sakaguchi, T., Toma, M., Yoshida, T., and Takasu, H., Pharm. Bull., 1958, 6, 1. Sakaguchi, T., and Takaguchi, K., Pharm. Bull., 1955,3,303. “US Pharmacopeia, XV Revision,” Mack, Easton, PA, 1955. Schumacher, G. E., Am. J. Hosp. Pharm., 1975, 32, 625. Lewis, J., Nyholm, R. S., and Smith, P. W., J. Chem. SOC., 1961, 4590. Burns, D. T., Townshend, A., and Carter, A. H., “Inorganic Reaction Chemistry,” Volume 2, Ellis Horwood, Chichester, 1981, p. 253. “US Pharmacopeia, XX Revision,” Mack, Easton, PA, 1980. Paper A51202 Received June 6th, 1985 Accepted July 30th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100097

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 101 Determination of Alkylnaphthalenes in Petroleum Fractions by Second-derivative Ultraviolet Spectrophotometry Lalji Dixit," Siya Ram, R. 6. Gupta, H. C. Chandola and Pradeep Kumar Instrumental Analysis Section, Indian Institute of Petroleum, Dehradun-248005, India The determination of naphthalene and its alkyl derivatives in aviation turbine fuels (ATF) and other petroleum products is important not only with respect to their performance but also for establishing heart cuts for producing intermediate chemicals for the manufacture of dyes, pesticides and agrochemicals. Normal and second-derivative UV spectra of naphthalenes, biphenyls and other interfering aromatics have been studied with a view to developing a method for determining naphthalene and a- and /3-methyl-, dimethyl- and trimethylnaphthalenes.The characteristic signals due to the substituted naphthalenes were identified in terms of second-derivative signals in a number of straight-run and cracked products of varying nature. Working relationships were derived for each of the naphthalenes in terms of their signal amplitudes. The method was tested on a number of straight-run and cracked petroleum products and it was found that the results calculated by the proposed method are in close agreement with those given by the zero-order UV spectrophotometric method. Keywords; Alkylnaphthalene determination; petroleum; derivative UV spectrophotometry Systematic studies on the determination of alkylnaphthalenes in straight-run and cracked petroleum products boiling in the kerosene range are in progress in this laboratory using molecular spectroscopic methods.l-3 Although a method exists for the determination of all the alkylnaphthalenes found in the kerosene range by UV absorption spectrophotometry using the average absorptivities at a wavelength of 285 nm,4 the method suffers owing to its limitations and is strictly applicable to aviation turbine fuels containing not more than 5% of alkylnaphthalenes.In addition, it does not provide any information about the distribution of the alkyl derivatives of naphthalene. There are also other methods in the literatures7 that can be applied in conjunction with mass spectral measurements and calculation of carbon number distributions to determine accurately alkylnaphthalenes in such fractions.It is obvious that the aforementioned methods are either laborious or have limited applicability, and there seems to be no rapid and direct method that can be applied to individual alkylnaphthalenes, particularly because of their random distribution in petroleum fractions, kerosenes and cracked petroleum products. The purpose of this work was to develop a derivative UV method that can be applied effectively to the quantitation of alkylnaphthalenes in fractions boiling in the kerosene range, Table 1. Analysis of typical petroleum fractions boiling in the kerosene range for their content of naphthalenes using normal absorbance and the second-derivative signals Concentration of naphthalenes, % m/mt a-Methyl- P-Methyl- Dimethyl- Trimethyl- Sample Naphthalene naphthalene naphthalene naphthalene naphthalene No.Sample * (311 nm) (314 nm) (319 nm) (322 nm) (324 nm) - - 1 Iomex 1.2 0.1 0.2 0.5 2 Iomex 12.5 0.6 3 Iomex 2.3 0.6 4.3 4 Light cycle oil 2.6 1.1 2.9 3.0 3.0 5 Light cycle oil 7.7 0.4 0.5 6 Light cycle oil - 1.2 3.7 17.0 14.9 7 Light cycle oil 2.2 1 .o 2.8 2.5 2.5 - - (5.7) (IBP-205 "C) (23.8) ( 4 4 (205-220 "C) (242.4) (28.6) (16.7) (220-230 "C) (43.9) (32.2) (147.5) - - (IBP-280 "C) (50.3) (53.3) (99.7) (34.5) (43.4) - - (205-220 "C) (148.5) (21.8) (17.8) (60.0) (128.0) (200.0) (2 16.0) (hydrogenated, I) (42.5) (48.5) (95.0) (29.7) (35.6) (245+ "C?.) - (IBP-280 "C) 8 Light cycle oil 2.8 1.1 3.1 4.0 3.5 (hydrogenated, 11) (53.2) (54.2) (106.4) (46.3) (50.2) (IBP-280 "C) - - 9 Aviation turbine fuel 2.8 0.6 1.5 (54.2) (29.4) (54.2) 10 Aromatic extract 23.5 9.8 23.0 23.0 - from kerosene (452.1) (488.5) (794.8) (269.8) * Values in parentheses are boiling ranges; IBP = initial boiling point.7 Values in parentheses are second-derivative signals A nm-2 per unit concentration). Total naphthalenes, % mlm ASTM D-1840 This work method4 1.5 1.4 13.6 11.6 7.2 9.8 12.6 14.9 8.6 7.7 36.8 34.3 11.0 12.8 14.5 14.9 4.9 4.8 79.3 77.7 * To whom correspondence should be addressed.102 ANALYST, JANUARY 1986, VOL. 111 either straight-run or cracked products. For a full description of the theory of derivative UV spectrophotometry, instrumen- tation and practical uses of derivative signals, the reader is referrred to papers by Fell and Smith,8 Talsky et al.,9 O'HaverlO and Dixit and Ram.' In developing this method based on second-derivative UV absorbance signals and the concentrations of different com- ponents of interest, we were partly guided by our earlier infrared studies on the determination of total aromatics in kerosenes and total naphthalenes in Iomex and aromatic extracts prepared from straight-run and cracked petroleum products, and partly by studies made by Michelot and Buzonll and other investigators57 on such petroleum fractions using normal UV absorbances. Experimental All the measurements were made on a Cary 210 UV - visible spectrophotometer, equipped with the facility for recording normal and first- and second-derivative absorbance spectra.The petroleum products examined were those boiling in the kerosene range, either straight-run or cracked, and aromatic extracts such as Iomex.The spectra were recorded in BDH Specpure 2,2,4- trimethylpentane solutions and measurements were made in both the normal and second-derivative mode between 200 and 400 nm. The measurement conditions when working in the normal UV absorbance mode were band width 1 nm, scan rate 0.5 nm s-1, chart speed 5 nm cm-1, absorbance range 2 and period 1 s; in the derivative mode the conditions were recorder time base 5 s cm-1 and scan rate 0.5 nm s-1, which gave a wavelength display on the chart paper of 2.5 nm cm-I, and other conditions as in the normal UV absorbance mode. It should be noted that if the reference spectra in the derivative mode are recorded under different experimental conditions, then all the derivative signals should be translated to a common scale after the entire scanning is completed.In other words, for a compound yielding an analyte derivative signal at a particular wavelength, if two scans are made using different experimental conditions then in order to generate a working relationship between the concentration of the compound of interest and its derivative signal, the correlation between the signal amplitude under the two sets of conditions must be established a priori, in order to be able to carry out routine determinations of that compound using a general equation. Results and Discussion Not all the spectra recorded for the samples under study are shown here in order to save space and only a few normal and second-derivative spectra (Fig.1) and final results (Table 1) are included. For more details of the experimental procedure and methods of measuring peak heights, see reference 1. Table 1 summarises the second-derivative signal amplitudes in units of absorbance per nm2 per unit concentration. The concentrations of naphthalene, a- and P-methylnaphthalene and dimethyl- and trimethylnaphthalenes in several straight- run and cracked products with varying initial and final boiling-points (all boiling in the kerosene range) are also given. The positions of the signals utilised for quantitation (in nm) are indicated against each component. The columns for the individual alkylnaphthalenes give concentrations found from the variation of the signal with concentration and the general equation d2Aldh2 (d%/dh2)1 Naphthalenes (YO m/m) = K - where K is the instrumental constant, d2Aldh2 is the second- derivative absorbance, d2ddh2 is the second-derivative molar absorptivity of each component at appropriate wavelengths and I is the cell thickness.For details of the procedure and 0.; 0.5 0.3 0.1 0.8 0.6 a C ln 0.4 2 2 0.2 0 0.7 0.5 0.3 0.1 'd) o 280 300 320 300 310 320 330 Wavelengthlnm Fig. 1. Normal and second-derivative spectra of light cycle oils in 2,2,4-trimethylpentane. (a) Normal spectrum of light cycle oil (245+"C), concentration 0.0500 g 1-1; (b) and ( c ) normal and second-derivative spectra of the same sample, concentration 0.2500 g 1-1. (d) normal spectrum of light cycle oil (205-220 "C), concentration 0.2020 g 1-1; (e) and U, normal and second-derivative spectra of the same sample, concentration 1.0098 g 1-1.(g) Normal spectrum of light cycle oil (IBP-280°C), concentration 0.0507 g 1-l; (h) and (i) normal and second-derivative spectra of the same sample, concentration 1.0135 g 1-1 empirical equations the reader is referred to references 1 and 12. In the last two columns, the total of the individual naphthalenes in each fraction is compared with the values obtained by measurement of the normal absorbance at 285 nm according to the ASTM proced~re.~ The results indicate that instead of being able to calculate only the total naphthalenes using the normal absorbance at 285 nm and the ASTM procedure,4 it is now feasible to determine individual alkylnaphthalenes by selecting analyte second-derivative signals at 311, 314,319,322 and 324 nm for naphthalene, a-methylnaphthalene, P-methylnaphthalene, dimethylnaphthalene and trimethylnaphthalene, respectively.When the individual concentrations are added, the totals are consistent with those obtained by the ASTM method.4 The present method should be useful in preparing suitable heart cuts from cracked petroleum products for the produc- tion of naphthalene.13ANALYST, JANUARY 1986, VOL. 111 103 The authors express their gratitude to Dr. G. C. Joshi, Head, Synthetic and Structural Chemistry Division, for his critical comments and encouragement during the development of this work. References 1. Dixit, L., and Ram, S., Appl. Spectrosc. Rev., 1985, 21, 311. 2. Dixit, L., Kumar, P., Gupta, R. B., and Chandola, H. C., Indian J. Technol., 1985, in the press. 3. Dixit, L., and Siya, R., “Normal and Second Derivative Ultraviolet Spectroscopy of Petroleum. Part 1. On the Use of Derivative Ultraviolet Signals for the Distribution of Alkyl Naphthalenes in Petroleum Stocks Boiling in the Kerosene Range,” IIP Report No. 9.12, Indian Institute of Petroleum, Dehradun, 1985. “ASTM Annual Book of Standards,” Part 17, ASTM Method D1840-64, American Society for Testing and Materials, Philidelphia, 1968, p. 656. 4. 5. 6 . 7. 8. 9. 10. 11. 12. 13. Mayer, M. J., Oil Gas J . , 1964, 62, 130. Kasematsu, K., Bull. Jpn. Pet. Inst., 1975, 17, 28. Cogshell, N. D., and Glessner, A. S., Anal. Chem., 1949,21, 550-3. Fell, A. F., and Smith, G., Anal. Proc. 1982, 19, 28. Talsky, G., Mayring, L., and Kreuzer, H., Angew. Chem., Int. Ed. Engl., 1978, 17, 785. O’Haver, T. C., Anal. Chem., 1979, 91, 51. Michelot, S., and Buzon, J., IFP Report No. 12368, Institut Fransais du PCtrole, Paris, 1965. Dixit, L., to be published. Dixit, L., and Ram, S., in preparation. Paper A51193 Received May 30th, 1985 Accepted August 12th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100101

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 105 Critical Comparison of X-ray Fluorescence and Combustion - Infrared Methods for the Determination of Sulphur in Biological Matrices Nathan W. Bower Chemistry Department, Colorado College, Colorado Springs, CO 80903, USA Ernest S. Gladney Health and Environmental Chemistry, USE-9, MS K-484, Los Alamos National Laboratory, Los Alamos, NM 87545, USA and Roger W. Ferenbaugh Environmental Surveillance Group, USE-8, MS K-490, Los Alamos National Laboratory, Los Alamos, NM 87545, USA Eleven NBS SRMs were used to evaluate XRF and combustion - IR as methods for the rapid, routine determination of sulphur and biological matrices. Relative standard deviations of 2.8 and 3.8% and analysis times of 1 and 3 min were obtained for the two methods, respectively, on dry, powdered material.Good agreement with the literature was obtained for plant tissues, but both methods produced higher results (14%) on animal tissues compared with NBS values. Keywords: Sulphur determination; X-ray fluorescence spectrometry; sulphur combustion analyser; biological Standard Reference Materials The importance of measuring the sulphur content of coal and other fuel sources to evaluate the impact of their use on the environment is widely recognised. It is also important to be able to measure the accumulated sulphur in biological materials for the same reason. In particular, techniques that are capable of measuring routinely trace levels of sulphur in large numbers of samples are needed to provide base line information for environmental impact studies.An investiga- tion of the relative merits of the LECO SC-132 combustion sulphur analyser and X-ray fluorescence (XRF) spectrometry was therefore undertaken. A number of methods for analysing the total sulphur in biological or coal matrices have been reported ,1-7 including the use of the LECO SC-132g-10 sulphur combustion analyser and XRF spectrometry.11-14 Using National Bureau of Stan- dards (NBS) Standard Reference Materials (SRMs) the precision and accuracy of each method was evaluated, and values for the sulphur content of SRM 1569 (brewer's yeast) are reported. Experimental The LECO SC-132 (LECO Corp., St. Joseph, MI, USA) sulphur combustion analyser with an optional insulation block (No. 776-797) and a honeycomb boat stop (No. 529-028) was used for these analyses.The principle of operation is based on the high-temperature combusion (1370 'C) of the sample in a stream of oxygen, which is then passed through a magnesium perchlorate drier to an IR cell where the SO2 produced is measured. Replacement of the drier after 30-40 samples is necessary to prevent water entering the IR cell, giving high sulphur readings. Various NBS SRMs were weighed on the balance integral to the analyser. The accuracy and range of this balance were investigated with Class-S weights and they were found to be within _+ 1 mg for masses as low as 25 mg. An improvement in the instrument balance performance was obtained by simply inverting a 100 x 50 mm glass dish over the balance pan during weighings. This minimised fluctuations due to ambient air currents.The instrument's response over a variety of sample masses and sulphur contents was also investigated. Different sulphur compounds (sodium salts of sulphate, sulphite, thiosulphate, peroxydisulphate and L-cysteine) in standard solutions pipetted on to sulphur-free filter-paper were investi- gated to determine the SO2 conversion efficiency. The instrument was recalibrated each day by analysing LECO and NBS coal standards with the samples. The XRF measurements were made with a wavelength- dispersive Rigaku 3064 Dataflex spectrometer at the sulphur Ka line using an EDDT (PET) crystal and a Rh end-window tube operated at 40 kV and 50 mA. The peak wavelength was counted for 20 s and the background was calculated from the average of the 10 s counts obtained at 28 angles of 74.00 and 77.85'.Ratioing the peak to the Rh Compton peaks did not improve the analysis, so no matrix correction was applied. No overlap corrections were made for other elements, as the C1 and P peaks were completely resolved and the Mo overlap was not thought to be significant for these samples, although in a routine analysis it should be measured. The SRM samples and standards were analysed under vacuum for 40 s each after hand packing the powder in a 3 cm diameter, vented Spex cell covered with Mylar film. These covered cells prevented organic materials from contaminating the spectrometer, a potential problem with uncovered pressed pellets. (Smaller diameter cells without vents sometimes burst the Mylar film and their use is not recommended.) It is important to make the analysis surface flat by packing the material tightly so that the surface remains flat under vacuum.Variability in this parameter is the limiting error when it is not controlled. No special equipment was needed for this packing, but a press would be advantageous. Count rates of about 1 count s-1 (p.p.m.)-' of sulphur were obtained for all of the samples presented in Table 1. Calibration was achieved using sulphur-free cellulose powder for a blank and NBS certified citrus leaves in conjunction with certified coals and reagent standards to determine linearity and dynamic ranges. The coal standards could not be used directly as standards because their matrix gave a much lower calibration slope than the biological samples, and because there was a particle size effect that created large blanks for the coal samples.These blanks were not present in the biological samples. With the automatic sample changer available as an option with this instrument, sample analysis times averaged about 1 min per sample compared with about 3 min per sample for the LECO sulphur analyser.106 ANALYST, JANUARY 1986, VOL. 111 Table 1. Sulphur content of NBS biological Standard Reference Materials. Results are means k standard deviations XRF LECO Sample Oyster tissue (SRM 1566) . . . . Wheat flour (SRM 1567) . . . . Rice flour (SRM 1568) . . . . Brewer’s yeast (SRM 1569) . . Spinach(SRM1570) . . . . . . Orchard leaves (SRM 1571) . . Citrus leaves (SRM 1572) . . Tomato leaves (SRM 1573) . . Pine needles (SRM 1575) .. . . Bovine liver (SRM 1577) . . . . Bovine liver (SRM 1577a) . . . . No. of Sulphur No. of Sulphur Literature determinations content, p.p. m. determinations content, p.p. m. value Reference 7 8 8 3 8 7 9 9 7 3 5 8700 f 200 1780 f 60 1320 f 30 4140 f 120 4500 k 270 2140 t 60 4070 k 90t 5960 f 150 1490 2 40 8550 k 150 8860 f 170 8 13 10 10 3 33 72 13 34 4 2 8700 t 200 1830 f 140 1360 f 50 4100 f 90 4400 k 400 1920 k 90 3990 k 90 5860 k 270 1250 f 40 8150 2 80 8550 t 70 7600 1790 k 100 1400 k 30 4440 k 60 1900 2040 f 60 2100 f 300 4070 k 90 4140 k 100 6260 k 100 1290 k 50 7100 k 100 8000 k 1300 7800 k 100 15 10* 10 10 15 10 16 15 10 10 10 15 16 15 * The method reported in reference 10 used a LECO SC-132 calibrated with citrus leaves using a V205 accelerator for the values reported t All values for XRF were calibrated against citrus leaves, assuming it to be equal to 4070 p.p.m.here. Results and Discussion Table 1 presents the means and standard deviations (la) for sulphur in 11 NBS SRMs. The XRF method gave significantly higher results (p = 0.05) than the combustion - IR analyser for orchard leaves (SRM 1571) and pine needles (SRM 1575). Both the XRF and combustion - IR methods produced significantly higher concentrations than those reported by the NBS for the animal standards (oyster tissue, SRM 1566, and bovine liver, SRM 1577 and 1577a). This would appear to be a matrix effect as these methods were in good agreement with the literature values for plant materials. However, it seems unlikely that these two disparate methods would suffer from the same instrumental matrix effects so further study of the NBS animal matrix standards by other laboratories is neces- sary to resolve this difference.NBS brewer’s yeast (SRM 1569) has a matrix that is neither strictly animal nor plant, and sulphur data for this standard are presented here for the first time. Further study of this standard should also prove useful. The combusion method appears to have a poorer precision than XRF, although this was not significant at the 95% level in this study (p = 0.2). This may be due to the smaller sample size analysed by the combustion method, as those samples (spinach, tomato leaves and wheat flour) which were the least homogeneous by either method are the ones that have the greatest difference in precision.The LECO SC-132 gives consistently low results when the total sulphur content is below 0.5 mg. For low sulphur-containing samples appro- priately larger samples should be used, although the sample boat size limits the analysis to concentrations greater than about 300 p.p.m. Non-linearity in the upper portion of the graph for the LECO sulphur combustion analyser makes extrapolation to high sulphur concentrations inaccurate, and smaller sample sizes or additional calibration standards should be used in this region. Experiments for the conversion efficiency of the LECO instrument for the various sulphur- containing compounds showed 100% conversion into S02, implying that the form of the sulphur in the sample is not important for this instrumental arrangement and that the use of an accelerant such as V205 is unnecessary.This observation agrees with the conclusions drawn by Jackson et al.1° The advantages of these methods clearly lie in the speed and precision of analysis as well as the minimal sample preparation required. The accuracy of the method is also good, although more investigation is required for the animal matrices. Analysis times are of the order of a few minutes and loading of the sample cups is the only sample preparation necessary. XRF, especially, can be readily automated, is non- destructive, allows other elements to be measured on the same sample readily and has detection limits (2a) for sulphur of ca. 30 p.p.m. On the other hand, the LECO SC-132 instrument can be readily operated with the minimum amount of training and it is significantly less expensive than the wavelength- dispersive XRF spectrometer.Less expensive dedicated energy-dispersive systems could be used,l4 but at the cost of inter-element interferences and detection limits in some applications, especially those with significant concentrations of P and C1. This work was supported by a grant from Colorado College, by the US Department of Energy and by the USDI National Park Service, Air Quality Division, through Interagency Agreement No. 0475-4-8009. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. References Khan, S. U., and Morris, G. F., Microchem. J., 1979,24,291. Smith, G. R., Anal. Lett., 1980, 13(A6), 465. Killham, K., and Wainwright, M., Environ. Pollut. (Ser. B), 1981, 2, 81. Busman, L. M., Dick, R. P., and Tabatakai, M. A., Soil Sci. SOC. Am. J . , 1983, 47, 1167. Watanabe, K., Anal. Chim. Acta, 1983, 147, 417. Farroha, S. M., Habboush, A. E., Michael, M. N., Anal. Chem., 1984,56, 1182. Prichard, M. W., and Lee, J., Anal. Chim. Acta, 1984, 157, 313. Hern, J. L., Commun. Soil Sci. Plant Anal., 1984, 15, 99. Gladney, E. S., Raymond, R., and Bower, N. W., Am. Lab., 1985, 17, 34. Jackson, L. L., Engleman, E. E., and Peard, J. L., Environ. Sci. Technol., 1985, 19, 437. Evans, C. C., Analyst, 1970, 95, 919. Bolton, J., Brown, G., Pruden, G., and Williams, C., J. Sci. Food Agric., 1973, 24, 557. Norrish, K., and Hutton, J. T., X-ray Spectrom., 1977, 6, 6. Takahashi, Y., and Rey, M., Am. Lab., 1983, 15,27. NBS Certificates of Analysis, National Bureau of Standards, Washington, DC. Gladney, E. S., Burns, C. E., Perrin, D. R., Roelandes, I . , and Gills, T. E., “1982 Compilation of Elemental Concentrations for NBS Biological, Geological, and Environmental SRMs,” NBS Special Publication No. 260-88, National Bureau of Standards, Washington, DC, 1984. Paper A5/218 Received June 19th, 1985 Accepted August 16th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100105

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 107 Determination of 28 Elements in American Cigarette Tobacco by Neutron-activation Analysis Felib Y. Iskander, Thomas L. Bauer and Dale E. Klein Nuclear Engineering Teaching Laboratory, Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA The concentrations of 28 toxic and other elements in cigarette tobacco of twelve brands commercially manufactured in the USA were determined using instrumental neutron-activation analysis. The elements determined were Al, As, Ba, Br, Ca, Ce, CI, Co, Cr, Cs, Eu, Fe, Hf, K, La, Mg, Mn, Na, Ni, Rb, Sb, Sc, Se, Sr, Th, Ti, V and Zn. The concentrations of the determined elements in the American cigarettes were compared with the elemental concentrations reported for Iranian, Pakistani and Japanese brands.It was concluded that the concentrations of As, Br, Ca, Eu, K and Zn in the samples under investigation are lower than those reported for the analysis of University of Kentucky reference cigarettes, whereas the concentrations of M n and Na are higher. The contents of Al, CI, Co, Cr, Cs, Fe, La, Sb, Sc and Se are similar to those i n the reference cigarettes. Keywords: Cigarette tobacco; trace elements; neutron-activation analysis; toxic elements It has been documented that as many as 60 elements are known to be present in biological matter, of which 22-26 are found in human tissue.l The uptake of certain elements or their compounds by a living organism may, under certain conditions, induce undesirable toxicological effects.The importance of trace elements has directed the attention of researchers worldwide to study these elements in human uptakes (food, drinks, etc.2-5). The sources of trace elements in human tissue are numer- ous; however, cigarette and other tobacco products represent a unique source for these elements to smokers. The concentra- tions of toxic and other elements in tobacco products have been determined in different parts of the world using instrumental neutron-activation analysis.614 It was shown that the concentrations of several elements in cigarette filters are increased dramatically after the smoking process; there- fore, subsequent inhalation of these elements to the smoker's lungs may occur.15 The concentrations of trace and minor elements in tobacco leaves vary not only from one year to another, but also from top leaves to middle or lower leaves.10 Also, a variation in the element concentration between tobacco leaves and stalks has been reported.11 As a result, it is not uncommon between researchers to analyse a particular commercial cigarette brand at a different period of time.For example the Iranian brand Zarrin was analysed in 19738 and 1977,7 and it was observed that the elemental concentration changed significantly. Another example is the analysis of University of Kentucky reference cigarettes (IRI) in 197013 and 1971.14 One of the common trends in studying elemental concentra- tions in cigarette tobacco is to compare local and imported brands (e.g., comparison between Japanese and imported brands,lO Egyptian and imported brands,16 Jordanian and imported brands17 and UK and international brandslg) or to compare local brands themselves (e.g., Iranian,8 Japanese,lo Jordanian17 and American brandsll).Another trend involves the comparison between commercial brands and the reference cigarettes introduced by the University of Kentucky. l2 The transfer of toxic and other elements from cigarette tobacco to smoke and smoke condensate has been considered in several studies.7~9J4Jg. It was concluded that the total content of As, Br and Co and more than 50% of the Se, Sb, Sc and Zn in tobacco were transferred to the smoke.9 In another study,7 the percentage transfer of Na, K, Mn, Fe, Co, Rb, As, Ba, La, Ce, Sm, Eu, Tb, Hf, Au and Th was <1% and that of Sc, Cr, Zn, Se, Br, Sb and Cs was 4%.The concentrations of Co, Ni and, to a lesser extent, Fe in cigarette tobacco are of special importance as it has been shown that these elements tend to form toxic metal carbonyls.19720 Thus, treatment of tobacco with CO results in the removal of approximately 80% of Ni and Co and 60% of Fe. Experimental Samples and Standards The samples examined in this study represent twelve different cigarette brands commercially manufactured in the USA. For each brand, the tobacco content of a cigarette was well mixed and about 500 mg were thermally sealed inside a high-purity polyethylene vial, which in turn was encapsulated in a secondary vial. All vials were cleaned before use by soaking in 10% HN03, distilled water and acetone, each for a 24-h period.The standards used were carefully chosen to contain all the elements of interest and,included National Bureau of Standards Standard Reference Materials and 'US Geological Survey Standard Rocks. All standards used were prepared by double encapsulation in the same way as the samples. Irradiation and Counting Procedures Samples and standards were irradiated at The University of Texas at Austin in the Nuclear Engineering Teaching Labora- tory TRIGA Mark I research reactor at an average thermal neutron flux of 2 x 1012 neutrons cm-2 s-1. Two irradiation periods were used, the first for 3 min and the second for 8 h. The irradiation and counting procedures used and the elements determined are presented in Table 1. After irradia- tion, the primary vials containing the samples and standards were inserted into non-irradiated secondary vials.Gamma-ray Table 1. Irradiation and counting procedures for instrumental neutron-activation analysis Irradiation time Decay time Counting time determined 1 min 180 s Al, Ca, Mg, Ti, V 8h 36h 4000s As, Br, K, La, Na Elements 3 min 30 min 1000s C1,Mn 21 d 40000 s Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Ni, Rb, Sb, Sc, Se, Sr, Th, Zn108 ANALYST, JANUARY 1986, VOL. 111 spectroscopy was performed utilising an EG&G ORTEC 7010 multi-channel analyser connected to a high-purity germanium coaxial detector and an EG&G ORTEC 1150 computer system. A typical detector specification was a 1.9 keV full width at half-maximum at the 1.33-MeV 6OCo line, a peak to Compton ratio of 55 : 1 and a 20% relative efficiency.Results and Discussion The concentrations of the 28 elements determined in cigarette tobacco used in manufacturing the twelve brands examined are shown in Table 2. The values reported are the minimum and maximum concentrations detected. Each value represents the average of two independent measurements. The accuracy of the method was checked by analysing NBS Standard Reference Material No. 1632 (coal). Reasonable agreement Table 2. Concentration range for 28 trace and other elements in cigarette tobacco of 12 American brands* Concentration rangelpg g-1 Element This work Other studiest A1 699-1200 707(9) Ba 40.7-56.6 1.15(2), 5.78 and 4.68(3) Br 61.4-90.1 137(2), 108 and206(3), 73-173(4), 36-154(6), Ca(%)$ 1.39-1.96 1.96-2.73(5), 1.74(9) Ce 1.12-1.59 1.19(2), 0.978and 1.54(3) Co <0.01-0.94 0.21(2), 0.349 and 0.606(3), 0.41-1.8(4), Cr cO.1-3.45 3.14(2), 4.26 and 6.21(3), 2.9-6.2(4) Cs 0.053-0.12 0.17(2), 0.140and0.179(3), 0.075(7), Eu Fe 325-520 649(2), 621 and 1031(3), 712-2668(4), Hf <0.002-0.21 0.09(2), 0.124and0.146(3) K(%) 1.73-2.98 0.22(2), 0.24 and0.28(3), 0.13-0.37(4), La 1.31-1.89 0.62(2), 0.394 and 0.668(3), 0.14-0.82(6), Mn 155-400 99(2), 74.3 and 102(3), 93-165(4), Na 198-1180 347(2), 341 and 376(3), 243-840(4), Ni <2-4.00 0.5-10(13), 1.91(14), 6.21(15), 1.1(16), Rb 8.72-13.3 22.6(2), 21.8 and 16.7(3), 17-30(5) Sb <0.01-0.12 0.68(2), 0.063 and0.117(3), 0.03-0.22(4), <0.3-0.9(5), 0.3-38(6), 0.29(7), 0.04-0.15(8) Sc 0.085-0.12 0.43(2), 0.192and0.311(3), 0.15-9.1(4), 0.53-2.5(6),0.19(7),0.03-0.11(8),0.32(9) Se <0.007-0.091 2.28(2), 1.23 and0.907(3), 0.11-3.15(4), Sr 29.7-49.5 66-106(5) Th 0.11-0.16 0.177(2), 0.183 and0.194(3) Ti 63.1-149 188(15) V 1.06-1.65 Zn 16.8-30.5 12.6(2), 51.0 and55.8(3), 8.1-21.5(4), As <1 0.25-2.7(4), 0.4-0.9(5), 3.26(7), 1.79-3.52(8) 172.3(7), 123-277(8), 191(9) Cl(Y0) 0.29-0.69 0.95-1.45(5), 0.64(9) 0.01-2.3(6), 0.50( 7), 0.32-1.06( 8) 0.24-6.3(6) , 2.23(7), 0.39-2.05( 8) 0.03-0.1 1 (8) <0.003-0.023 0.045(2), 0.0191 and 0.0363(3), 0.04-0.08(8) 330-610(5), 398(7), 260-715(8) 3.25-4.04(5), 3.11 (9) 2.68(7), 1.01-2.88(8), 1.2(9) Mg(Yo) 0.13-0.54 0.40-0.64(5) 144-227( 5 ) , 190( 9) 207-396(5), 379(9) 5.62-9.4 1 (18) 0.14-5.8(6), 0.21(7), <1-1.29(8) 16-130(5), 4.1-54(6) 73.9(7), 34-69(8) * Concentrations are in pg g-1 except where YO is indicated in the t References cited are given in parentheses.$. Calcium was determined in 2 brands only. first column. with the certified values was obtained. All twelve samples examined show positive evidence for Al, Ba, Br, Ce, C1, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sc, Sr, Th, Ti, V and Zn, eleven samples for Co, Cr, Eu and Hf, nine samples for Sb and eight samples for Ni and Se. Calcium was determined in two samples. Arsenic was not detected in any of the twelve samples. For the purpose of comparison, Table 2 lists the concentra- tions or the range of concentrations for the elements of interest in other independent trace and other element determinations in cigarette tobacco.7-1s The Iranian cigarette brands7J3show higher concentrations of Br, Cs, Eu, Fe, Rb, Sc and Se.However, the examined brands show higher concen- trations of Ba, K, La, Mn and Th. The concentrations of Ce, Co, Cr, Hf, Na, Sb, and Zn overlap. The data reported on the analysis of twelve elements in eleven different commercial Pakistani brands9 indicate that the concentrations of Fe, Sc and Se are higher than in the American brands under investigation, and that the concentration ranges of As, Br, Co, Cr, K, Mn, Na, Sb and Zn overlap. The concentration ranges of C1, K, Rb and Sr in Japanese cigarettes10 are higher than those determined for the brands under investigation; however, the As, Ca, Fe, Mg, Mn, Na, Sb and Zn concentra- tions overlap. The analysis of cigarette tobacco used to manufacture 19 commercial American brands was reported in 1969.l’ Although there is no assurance that the brands under investigation are the same as those examined before, it can be concluded that the concentrations of Sb, Sc and Se decreased whereas that of La increased.The tobacco used to manufacture the University of Ken- tucky reference cigarettes was analysed for trace and minor elements.12-14 The concentrations of Al, Ca, C1, Co, Cr, Cs, Fe, La, Mn, Na, Sb, Sc and Se in the reference cigarettes are comparable to those in the brands under investigation, whereas the concentrations of As, Br, Eu, K and Zn are higher in the reference cigarettes. Conclusion The results indicate that the concentrations of toxic elements in American cigarettes are much lower than in other interna- tional brands. Also, the concentrations of some toxic elements in the tobacco used to manufacture American cigarettes are lower than those used in 1969.Lower element concentrations in tobacco result in a reduction in their levels in smoke. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Orten, J. M., and Neuhaus, 0. W. “Human Biochemistry,” Tenth Edition, C. V. Mosby Co., St. Louis, MO, 1982, p. 5. Rao, D. S . , and Deosthale, Y. G., J . Plant Foods, 1981,3,251. Tork, S . , and Szokefalvi-Nagy, Z., J . Radioanal. Chem., 1983, 78, 117. Lomachinskii, V. A., Nakhmedov, F. G., and Andreeva, E. V., Konservn. Ovoshchesush. Promst., 1980, No. 2, 28. Bertrand, D., Aliment. Vie, 1979, 59, 91. Iskander, F. Y., J. Radioanal. Nucl. Chem., 1985, 89, 511. Abedinzadeh, Z . , Razenghi, M., and Parsa, B., J . Radioanal. Chem., 1977, 35, 373. Abedinzadeh, Z . , and Parsa, B., J. Radioanal. Chem., 1973, 14, 139. Ahmed, S . , Chaudhry, M. S., and Qureshi, I. H., J. Radioanal. Chem., 1979,54, 331. Sato, N., Kato, T., and Suzuki, N., J . Radioanal. Chem., 1977, 36, 221. Nadkarni, R. A., and Ehmann, W. D., Nat. Bur. Stand. ( U . S . ) Spec. Publ., 1969, No. 312, 190.ANALYST, JANUARY 1986, VOL. 111 109 12. Nadkarni, R. A . , andEhmann, W. D . , Radiochem. Radioanal. Lett., 1969, 2 , 161. 217. 13. Nadkarni, R. A . , and Ehmann, W. D., Radiochem. Radioanal. Lett., 1970, 4, 325. 14. Williamson, T. G., Jenkins, R. W . , Jr., Mewrnan, R. H., and Carpenter, R. D., Trans. Am. Nucl. SOC., 1971, 14, 110. 15. Iskander, F. Y., J. Radioanal. Nucl. Chem., 1985, 91, 191. 16. Iskander, F. Y., J. Radioanal. Nucl. Chem., 1986, 97, 107. 17. Hallak, A . B., J. Radioanal. Chem., 1981, 67, 549. 18. 19. 20. Westcott, D. T., andspincer, D., Beitr. Tabakforsch., 1974,7, StahlY, E. E., Chem. Ind. (London), 1973, 620. Stahly, E. E . , and Lard, E. W., Chem. Znd. (London), 1977, 85. Paper A41267 Received August 6th, 1984 Accepted July 26th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100107

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 111 Releasing Effect of Iron(ll1) and Other Oxidants on the Interference from Nickel in the Determination of Selenium by Hydride Generation Atomic Absorption Spectrometry Ragnar Bye Department of Chemistry, University of Oslo, Box 1033, Blindern, Oslo 3, Norway The releasing effect of iron(ll1) on the interference from nickel(l1) in the determination of selenium has been extended to nickel concentrations commonly found in solutions of real nickel samples. In solutions containing 10 yg 1-1 of selenium(1V) and 1600 mg 1-1 of nickel(l1) almost 80% of the sensitivityfor selenium was retained if the solutions were made 1000 mg I-' in iron(ll1) and 2.5 M in hydrochloric acid. Alternative oxidants such as chromium(Vl), thallium(lll) and nitric acid were investigated, but were found to be far less effective than iron(ll1) in reducing the nickel interference.Keywords: Selenium determination; hydride generation atomic absorption spectrometry; nickel interfer- ence; iron releasing effect; oxidant releasing effect Many papers have been published on the interferences from metal ions in the determination of selenium by hydride generation atomic absorption spectrometry and of those studied the most serious interferents were found to be Au, Ag, Pt, Cu, Ni and Co. Copper and nickel are of particular interest because they are often present in high concentrations in various matrices. When the above-mentioned elements were present as aqueous ions, it was observed that a metallic precipitate was formed immediately on the addition of sodium tetrahydroborate solution, which is used for the generation of the selenium hydride gas.It is thought that this interference is caused by the decomposition or the absorption of selenium hydride by the metallic precipitate. Some workers have considered the mechanisms involved when the formation of selenium hydride is depressed by other elements. Of the papers published on this matter those of Welz and Melcher are the most comprehensive.1J These workers found that the presence of iron(II1) in the sample solution extended the interference-free range of selenium when nickel ions were present. It was observed that iron(II1) and possibly nitrate, which was also present in their sample solutions, depressed the reduction of nickel ions by the added hydroborate ions, owing to the preferential reduction of iron(II1) and nitrate, as both possess a high oxidation potential.As the reduction product of iron(1II) is primarily iron(I1) and not the metal, the decomposition or absorption effect on selenium hydride is thus avoided. However, the results of Welz and Melcher are not entirely clear. For instance, nitric acid seems to have much less effect than iron(II1) in depressing the interference from nickel(I1). In view of the proposed explanation, this is surprising because the standard oxidation potential of nitric acid is even higher than that of iron(II1). Moreover, the concentration of nitric acid was about 1000 times higher than that of iron(II1). However, these workers employed nitric acid solutions containing hydrochloric acid, which changes the oxidation potential of the solutions, making interpretation of the results more difficult.From their results it can be seen that relative to the sensitivity obtained from solutions of selenium(1V) in 0.5 M HC1, only 10% of the sensitivity for selenium was retained in a 2.0 M HN03 - 0.5 M HC1 medium containing 1000 mg 1-1 of nickel(I1) and 200 mg 1-1 of iron(II1). As this is a low sensitivity for the determination of selenium in real nickel samples, in which nickel concentrations higher than 1000 mg 1-1 can be expected, it was decided to optimise the conditions that could extend the tolerable concentration of nickel(I1) in solutions taken for the determination of selenium using iron(II1) as a releasing agent. This paper also describes attempts to elucidate the possible mechanisms involved when selenium hydride is released by oxidating agents.The effect of oxidising ions other than iron(II1) has therefore also been investigated. Experimental Apparatus A Perkin-Elmer Model 300 atomic absorption spectrometer, equipped with a discharge lamp for selenium and operated at 6 W was used. The selenium signals were measured at the 196.0-nm resonance line and recorded on a Radiometer Servograph REC 51 recorder. The Perkin-Elmer MHS-10 hydride generation system was operated as recommended by the manufacturer. Reagents Sample solutions. The following salts, all of analytical- reagent grade, were used: nickel(I1) chloride hexahydrate, iron(II1) chloride hexahydrate, potassium dichromate(V1) and thallium(II1) nitrate.Nitric, hydrochloric and sulphuric acids. All of analytical- reagent grade. Sodium tetrahydroborate(III) solution, 3% ml V. Prepared by dissolving the salt of purum pro analysi grade (Fluka) in 1% mlV sodium hydroxide solution. The solution was filtered before use. Selenium(IV) standard solution, 5 mg 1-1. Prepared by diluting a 1000 mg 1-1 solution made from sodium selenite of puriss. pro analysi grade (Fluka). Procedure Aliquots of 10 ml of each solution and three aliquots of each concentration were taken for analysis. The results presented in Figs. 1-4 are hence the means of three determinations. Results and Discussion Initially it was thought that other ions, with a high oxidation potential that could be reduced to a lower oxidation state (not being the metal), could be used instead of iron(II1).This possibility was investigated using Cr(V1) and Tl(II1). The oxidation potentials for Cr(V1) - Cr(II1) and Tl(II1) - Tl(1) are + 1.33 and + 1.26 V, respectively i.e., considerably higher than112 0.4 ANALYST, JANUARY 1986, VOL. 111 - A I I C Y 0 500 1000 Concentration of oxidising ion/mg 1-1 Fig. 1. Effect of the concentrations of oxidising ions on 100 ng of Se(1V) in 1.0 M HC1 - 100 mg I-' Ni(I1) solutions. A, Fe(II1); B, TI(II1); and C, Cr(V1) 0.06 1 X 0.1 1 I - I I 1 I I I 0 1 2 3 4 5 Concentration of acid/mol 1-1 A/ I Fig. 3. Effect of the concentrations of acids on the determination of 100 ng of Se(1V) in 100 m 1-1 Ni(I1) - 1000 m 1-1 Fe(II1) solutions. A, HCl; B, HN03 - HCl t4 + 1); and C, HN& 0 1 2 3 4 5 Concentration of acid/mol I-' Fig.2. Effect of the concentrations of acids on 100 ng of Se(1V) in 100 mg 1-1 Ni(I1) solutions. A, HCl; B, H,SO,; and C, HN03 that of Fe(II1) - Fe(I1) (+0.77 V). The solutions examined were all 1 M in HC1 and contained 10 pg 1-1 of Se(1V) and 100 mg 1-1 of Ni(I1). The signals were compared with those obtained for a solution containing the same concentrations of Se(1V) and HCl only. However, despite the high oxidation potentials of Cr(V1) and Tl(III), these ions had much less effect than Fe(III), as revealed in Fig. 1. Further work with Cr(V1) and Tl(II1) was therefore neglected. Welz and Melcher obtained the best results, for both Se and As, when HN03 and HC1 were present simultaneously in iron(II1) solutions.The most probable explanation for this is that nitric acid, or possibly chlorine formed by the reaction of the acids, has a similar effect to Fe(III), i.e., is reduced before Ni(I1). However, the effect from HN03 appeared to be low, and any releasing effect from HN03 was therefore investi- gated. Solutions containing the same concentrations of Se(1V) and Ni(I1) as above, but with variable concentrations of HN03, HCl and H2S04, were examined. From Fig. 2 it is apparent that HN03 has no advantageous effect compared with HC1 when Ni(I1) is present. Moreover, it has less effect on the selenium signals than H2SO4, which has no oxidising properties. As expected, high concentrations of hydrochloric acid were more effective than H2S04 owing to complexation of the nickel ions.Any combined effects of Fe(II1) and HN03, HCl or HN03 - HCl mixtures were also studied using solutions containing the same concentrations of Se(1V) and Ni(I1) as above and 1000 mg 1-1 of Fe(II1). All HN03 - HCI mixtures were prepared in 4 : 1 molar ratios (as employed by Welz and Melcher); a 3 M concentration of this mixture is 2.4 M in HN03 and 0.6 M in I Abs. 0.441 for A .$ I Abs. 0.26 \ B -1 A / I I I I I J 0 400 800 1200 1600 Ni concentrationimg I-' Fig. 4. Effect of the concentration of Ni(I1) on the determination of 100 ng of Se(1V) in 2.5 M HCI containing A, 1000 mg 1-I of Fe(II1); and B, 10 OOO mg 1-1 of Fe(II1) HCl. The sensitivity for Se(1V) was highest for the HCl solution with a maximum at 2-3 M (Fig. 3). For the HN03 - HCl solutions the sensitivity increased continuously with increasing molarity of the acid and reched a maximum at 4-5 M; however, this was still less sensitive than the solutions containing HC1.Fig. 3 also demonstrates that the combination of Fe(II1) and HN03 gave a considerably lower sensitivity, and is obviously of no advantage compared with the other acids. In the last series of experiments, solutions that were 10 pgl-1 in Se(IV), 2.5 M in HCl and 1000 or 10000 mg 1-1 in Fe(II1) were examined. The concentration of Ni(I1) was varied up to 1600 mg 1-l. A 2.5 M concentration of hydrochloric acid was chosen because this concentration was within the range giving the greatest sensitivity (Fig. 3). The sensitivities for Se(1V) at various concentrations of nickel(I1) were calculated relative to the signals obtained from the solutions [containing 1000 or 10000 mg 1-1 of Fe(III)] without Ni(I1) (Fig.4). It was observed that a concentration of Fe(II1) of 10 000 mg 1-1 was of no advantage as a 1000 mg 1-l solution produced the same results. Most importantly it was found that almost 80% of the Se(1V) signals were retained when 1600 mg 1-1 of Ni(I1) were present in solutions that were 2.5 M in HC1 and 1000 mg 1-1 in Fe(II1). The reason for the favourable effect of Fe(II1) on the nickel interference is probably the reduction of Fe(II1) to Fe(I1) by tetrahydroborate ions before reduction of the nickel ions, as proposed by Welz and Melcher. This effect was much lower for other strong oxidants such as Cr(VI), Tl(I1I) and HN03, probably for kinetic reasons.There are few other oxidants thatANALYST, JANUARY 1986, VOL. 111 113 are suitable as releasing agents, because it is required that the oxidants must be reduced to the respective ions in a lower oxidation state, rather than being reduced to a precipitate or gas. Therefore, Fe(II1) seems to be the most suitable agent. The mechanisms of the precipitate formation when Ni(I1) (and other interfering ions) and tetrahydroborate ions react, and the character of the metallic precipitate, are discussed elsewhere.3 In this work the combination of Fe(II1) and HCI has been found to reduce the interference from large amounts (1600 mg 1-1) of Ni(I1) to such a degree that the determination of selenium in nickel metal samples by the hydride generation technique should be feasible using the proposed concentra- tions of Fe(II1) and HCI. This method is more suitable for masking the nickel interference than the one proposed recently,4 in which citric acid was capable of masking up to 1600 mg 1-1 of Ni(I1). This is sufficient but the major drawback is the large amount of citric acid required (250 g 1-1). However, although Fe(II1) can be used successfully as a releasing agent it may be still be necessary to use the standard additions method for real nickel samples. This is to be investigated. References 1. 2. 3. 4. Welz, B., and Melcher, M., Analyst, 1984, 109, 569. Welz, B . , and Melcher, M., Analyst, 1984, 109, 577. Bye, R., Talanta, in the press. Bye, R., Analyst, 1985, 110, 85. Paper A51263 Received July 18th, 1985 Accepted August 19th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100111

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 115 Rapid Determination of Tungsten in Alloys, Ores and Concentrates by Atomic Absorption Spectrometry Sarala Raoot, S. V. Athavale and T. H. Rao Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad-500258, India Tungsten has been determined by atomic absorption spectrometry at 400.9 nm using a dinitrogen oxide - acetylene flame in an alkaline medium with potassium persulphate as releasing agent, which causes an enhancement of around 75% in the tungsten signals. The medium being alkaline, the cations generally associated with tungsten, such as chromium(lll), iron(lll), vanadium(lV), manganese(ll), cobalt( II), nickel(ll), titanium(lV), calcium(l1) and magnesium(ll), are separated as hydroxides and hence have no effect. Aluminium(lll), vanadium(\/), molybdenum(Vl) and chromium(Vl), which remain in solution along with tungsten, do not interfere.The method has been applied to the analysis of a variety of alloys, ferrotungsten, cobalt- and nickel-base alloys, tungsten ores and concentrates. Keywords : Tungsten determination; atomic absorption spectrometry; alloys; ores; concentrates Classical gravimetric methods for the determination of tung- sten are not only tedious and time consuming, but also demand a high degree of operational skill, particularly when molybdenum, silicon, titanium and chromium are also present. 172 Spectrophotometric procedures are suitable only for low percentage concentrations of tungsten and invariably involve either solvent extraction or elaborate separations of the associated cations.374 Although atomic absorption spec- trometry offers a much quicker rates of analysis compared with gravimetry and spectrophotometry, it has limitations such as poor sensitivity6 and serious interferences caused by a large number of associated cations.2.7 To overcome these limitations, techniques such as solvent extraction ,8,9 standard additions,2 matrix matchinglOJ1 and addition of bases are generally incorporated into methods dealing with the determi- nation of tungsten by atomic absorption spectrometry.Edger7 improved the sensitivity of the method and minimised the interfering effects from other metal ions by using sodium sulphate as a releasing agent. Sprenz and Pragerl2 later used this approach for determining tungsten in ores and concen- trates. In this paper a simple and more sensitive atomic absorption spectrometric method for the determination of tungsten in alloys, ores and concentrates is described. The method is based on the separation of contaminants such as hydroxides and the determination of tungsten in alkaline solution by atomic absorption spectrometry at a wavelength of 400.9 nm with a dinitrogen oxide - acetylene flame using potassium persulphate as a releasing agent.Experimental Apparatus A Varian Techtron AA6 atomic absorption spectrometer with a 5-cm dinitrogen oxide - acetylene burner, a fixed tantalum throat nebuliser and a Varian Techtron HCN-W hollow- cathode lamp were used under the following operating conditions: dinitrogen oxide fuel flow meter reading, 9.0; acetylene flow meter reading, 6.5; lamp current, 20 mA; wavelength, 400.9 nm; spectral band pass, 0.5 nm; and burner height, 10 mm.Reagents All chemicals used were of analytical-reagent grade, unless stated otherwise. Tungsten standard solution, 2 mg ml-1. Dissolve 3.590 g of sodium tungstate in 1 1 of distilled water containing 10 ml of 10% sodium hydroxide solution. Potassium persulphate, solid. Cali brat ion Graph A 5-50-ml volume of stock solution was transferred into a series of 100-ml beakers, the pH adjusted to between 10 and 12 with dilute sodium hydroxide solution and, after adding about 100 mg of potassium persulphate, was diluted to 100 ml in calibrated flasks. These solutions were aspirated under the conditions mentioned. Procedure Determination of tungsten in the presence of foreign metal ions A volume of solution equivalent to 40 mg of tungsten was transferred into a 100-ml beaker containing various amounts of foreign metal ions.The pH was adjusted to between 10 and 12 with dilute sodium hydroxide solution. The contents were heated at 60-70 "C for 5 min for the complete dissolution of tungsten and the quantitative precipitation of other cations. The solution, together with the precipitate, was transferred into 100-ml calibrated flasks and diluted to the mark. The precipitated hydroxides were filtered through a dry filter- paper. To the filtrate 100 mg of potassium persulphate were added and the absorbance was measured under the conditions described earlier. Determination of tungsten in alloys, ores and concentrates A 0.5-1.0-g amount of the alloy was digested in the minimum volume of aqua regia by heating slowly, evaporated to a syrupy consistency and diluted to 10-15 ml with distilled water.(For ores and concentrates 0.2-0.5 g of finely ground sample was fused with 2-4 g of sodium carbonate in a platinum crucible at 900 "C. The fused mass was leached with distilled water and digested on a hot-plate for 10-15 min. A 50-100-mg mass of ascorbic acid was added whenever manganese was present. The pH of the solution was adjusted to between 10 and 12 with dilute sodium hydroxide solution. After heating at 60-70 "C for 5 min, the contents were diluted appropriately in the calibrated flask and the absorption was measured under the conditions described. Results and Discussion Mixtures containing hydrofluoric acid are preferred for the dissolution of tungs t en-cont aining materials ,13-15 a1 though combinations of sulphuric acid with phosphoric acid and perchloric acid have also been used.llJ6 However, the loss of small amounts of tungsten as tungstic acid is possible using mixtures of these solutions.In this method, the use of hazardous hydrofluoric acid, and the special requirements and116 ANALYST, JANUARY 1986, VOL. 111 Table 1. Recovery of 400 pg ml-1 of tungsten from mixtures containing contaminants at pH 10-12 Contaminant Tungsten recovered, ‘/o Concentration/ Present pg ml-1 None . . . . . . Fe(II1) . . . . . . Mn(I1) . . . . . . Cr(V1) . . . . . . Cu(I1) . . . . . . Ni(I1) . . . . . . AI(II1) . . . . . . V(V) . . . . .. CO(1I) . . * . . . Ti(1V) . . . . . . Mo(V1) . . . . . . Mg(I1) . . . . . . Ca(1I) . . . . . . - 5000 2000 2000 2000 2000 2000 2000 2000 lo00 3000 2000 2000 Without K2S208 57.6 57.6 57.6 100.0 56.7 38.0 100.0 100.0 57.6 58.7 100.0 56.7 58.4 With K2S208 100.0 100.0 100.0 100.0 101.5 72.6 100.0 100.0 101.5 100.0 100.0 100.0 100.0 0.30 I 1 0) 0.20 . 0 c a ,- Q 0.10 ’ /’ 0.04 / / 200 400 600 800 1000 Concentration of tungsten/pg ml-1 Fig. 1. Effect of potassium persulphate on the absorbance signal of tungsten at 255.1 and 400.9 nm. A, With S208*- at 255.1 nm; B, with S208*- at 400.9 nm; C, without S2082- at 255.1 nm; and D, without S20& at 400.9 nm. precautions associated with it, are avoided. After digesting the sample with aqua regia it is made alkaline, which converts tungsten ions into highly soluble sodium tungstate, eliminat- ing any possible losses.These observations are in agreement with those of Quin and Brooke5 made during their work on ores and concentrates. using potassium hydroxide for the separation of contaminants. As a separation technique, the proposed method is simpler than the standard additions and matrix matching techniques, which pose problems when analysing samples of unknown compositions. Under these experimental conditions, the calibration graph obtained at 255.1 nm, a more generally suggested wavelength,l7 had a strong tendency to curve towards the concentration axis, whereas at 400.9 nm a linear graph for 100-1000 pg ml-l solutions was obtained and so this wavelength was chosen for this work (Fig.1). The effect of alkalinity was studied separately in a series of experiments and it was found that at a pH between 8 and 12, there were no variations; however, beyond pH 12, there was a decline in the absorption. In order to bring tungsten quantitatively into solution and for complete precipitation of the contaminants as hydroxides, it was necessary for the minimum alkalinity to be maintained at pH 10. Hence a medium of pH between 10 and 12 was the most suitable for this study. Potassium persulphate yielded an improvement of the order of 75% in tungsten signals compared with the alkaline solution without the releasing agent, as can be seen from the results in Table 1. According to Edger,7 sodium sulphate yields about a 45% enhancement in tungsten signals in acidic medium at 255.1 nm.Under the proposed experimental conditions, it was observed to be 60%; however, this was much less than the Table 2. Determination of tungsten in alloys, ores and concentrates Tungsten, % Sample No. Sample 1 2 3 4 5 6 7 8 9 10 11 Low tungsten steel BCS No. 422 Low tungsten steel BCS No. 423 Low tungsten steel BCS No. 424 High speed tool steel BCS No. 22012 High speed tool steel BCS No. 483 High speed tool steel BCS No. 482 High speed tool steel BCS No. 484 Ferrotungsten BCS No. 242/2 Waspalloy (Ni-base) NBS No. 349 S t ellite (Co- base) DMRL alloy Scheelite 12 Wolframite 13 Tungsten concentrate 14 Tungsten concentrate NBS No. 277 * Gravimetric value. Present 1.28 2.06 3.02 6.97 10.80 18.10 22.40 79.90 3.85 4.15* 51.80* 41.75* 53.44 53.24* Found 1.25 1.28 2.02 2.04 3.01 2.99 7.03 6.93 10.89 10.75 18.25 18.16 22.52 22.31 79.36 79.24 3.85 3.88 4.12 4.19 51.38 52.15 41.38 42.05 53.05 52.93 52.75 53.68 Relative error, Yo -2.34 0 -1.94 -0.97 -0.33 -0.99 -0.57 -0.46 +0.86 +0.83 +0.83 +0.54 -0.33 -0.41 -0.68 -0.83 0 +0.78 -0.73 +0.96 -0.81 +0.68 -0.89 +0.72 -0.73 -0.95 -0.92 +0.68 enhancement found with the present releasing reagent.From repeated experiments, 100 mg of potassium persulphate were found to be sufficient for 1000 pg ml-1 tungsten solution and higher amounts did not have any adverse effect on the signals. A plausible explanation for the enhancing effect of potassium persulphate could be that the reagent oxidises certain non- volatile compounds of tungsten to the more volatile and more easily dissociable oxides, resulting in the enhancement of the absorbance signal. It can be seen from Table 2 that manganese(II), copper(II), cobalt(II), calcium(II), magnesium(II), iron(II1) and titan- ium(1V) separate as their hydroxides with no adverse effects.For aluminium(II1) , vanadium(V) , chromium(V1) and molyb- denum(V1) , which remained in solution together with the tungsten , it was observed that optimum signals were obtained even without potassium persulphate. The possibility of using some of these cations as releasing agents for tungsten is being examined in a separate investigation. Nickel(I1) when present alone, even in small amounts, interfered seriously; however, it did not have any effect when cobalt(I1) or iron(II1) was also present. The most plausible explanation for this could be that tungstate ions are adsorbed by the nickel hydroxide and are carried away during filtration, whereas cobalt or iron inhibits this adsorption.This is corroborated by the observation of Pashchenko and Maltsev18 during a photometric determina- tion in which they recorded a similar loss of tungsten and successfully overcame it by the addition of iron. The coefficients of variation for 100, 400 and 1000 l g ml-1 of tungsten were calculated from a set of ten readings each at both the wavelengths. Whereas at 255.1 nm the coefficients of variations were found to be 6.40, 2.66 and 1.67%, the corresponding results at 400.9 nm were 3.70,0.93 and 0.73%. Hence, in spite of the low sensitivity (20 pg ml-I), linearity of the graph was achieved over a wide range of concentration, as can be seen from Fig.1, leading to improved practical applicability.ANALYST, JANUARY 1986, VOL. 111 117 The results in Table 2 show that the relative percentage error for low-tungsten steels containing 1.28 and 2.06% of tungsten, the lowest percentages analysed, were 2.34 and 1.94%, respectively. However, in no other samples did it exceed 1 YO. A set of five samples can conveniently be analysed in 4-5 h. Thus the method is rapid, in addition to being simple and accurate. We thank Dr. P. Rama Rao, Director, Defence Metallurgical Research Laboratory, Hyderabad, for his permission to publish this paper. 1. 2. 3. References Westwood, W., and Mayer, A., “Chemical Analysis of Cast Iron and Foundry Material,” Second Edition, Allen and Unwin, London, 1960, p.271. Rooney, R. C., and Pratt, D. F., Analyst, 1972, 97, 401. Elwell, W. T., and Wood, D. F., “Analytical Chemistry of Molybdenum and Tungsten,” Pergamon Press, Oxford, 1971, p. 103. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Snell, F. D., “Photometric and Fluorometric Methods of Analysis of Metals, Part 2,” Wiley, Chichester, 1978, p. 1265. Quin, B. E., and Brooks, R. R., Anal. Chim. Acta, 1973, 65, 206. Manning, D. C., At. Absorpt. Newsl., 1966, 5 , 127. Edger, R. M., Anal. Chem., 1976, 48, 1643. Rao, P. D., At. Absorpt. Newsl., 1970, 9, 131. Yudelevich, I. G., and Shabrova, N. P., Chem. Anal., 1974,19, 941. Welcher, G. G., and Kriege, 0. H., At. Absorpt. Newsl., 1969, 8,97. Husler, J., At. Absorpt. Newsl., 1971, 10, 60. Sprenz, E. C., and Prager, M. J., Analyst, 1981, 106, 1210. Ghandehari, M. H., Pope, L. E., and Pierce, F. D., Znt. J . Powder Metall. Powder Technol., 1979, 55, 61. Stanislaw, G., and Wycislik, A., Przegl. Odlew., 1980, 30, 21. Pant, E. Y., Zavod. Lab., 1980,46, 1008. Seco, J. L. J., and Coedo, A. G., Rev. Metal. (Madrid), 1971, 6,64. Price, W. J., “Analytical Atomic Absorption Spectrometry,” Heyden, London, 1972, p. 215. Pashchenko, E. N., and Maltsev, V. F., Zavod. Lab., 1975,41, 800. Paper A51145 Received April 22nd, 1985 Accepted August Sth, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100115

出版商:RSC    

年代:1986

数据来源: RSC

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ANALYST, JANUARY 1986, VOL. 111 119 Titrimetric Determination of A2-Pyrazol-5-ones and A3-Pyrazol-Ei-ones via Bromination Darwish Amin and Redha 1. Al-Bayati Department of Chemistry, College of Science, University of MOSU~, MOSU~, Iraq A novel titrimetric method for the determination of 0.1-10 mg of An-pyrazol- or A3-pyrazol-5-ones is described. It is based on their reaction with an excess of bromine water to form the corresponding N-bromo derivatives, which liberate equivalent amounts of iodine when treated with iodide. The liberated iodine is determined titrimetrically with thiosulphate. The method is simple, rapid and accurate; the complete procedure requires about 5 min. Keywords: A2-Pyrazol-5-one determination; A3-pyrazol-5-one determination; bromination; titrimetry To our knowledge, the literature contains no suitable method for determining A2-pyrazol-5-ones and A3-pyrazol-5-ones.The purpose of the present investigation was to develop a simple, rapid and accurate assay for the determination of such compounds using bromine water to form the corresponding N-bromo derivatives. These derivatives then oxidise equi- valent amounts of iodide to iodine, which is determined titrimetrically using thiosulphate. The method is applicable to the determination of the following compounds: 3-methyl-A2- p yrazol-5-one ; 3,6dime thyl-A2-pyrazol-5-one ; 4,4-dibromo- 3-methyLA2-pyrazol-5-one; 3-methyl-A3-pyrazol-5-one; l-phenyl-3-methyl-A3-pyrazol-5-one; and 4-ethoxycarbonyl- A3-pyrazol-5-one. Experimental Reagents All chemicals used were of analytical-reagent grade.Standard A2-pyrazol-5-one and A3-pyrazol-5-one solutions. Solutions of the pyrazolone compounds, synthesised in our laboratory,lJ were prepared in distilled water. The solutions were diluted with water as required. Sodium thiosulphate solutions. Solutions of 0.01 and 0.001 N sodium thiosulphate were prepared and standardised against potassium iodate solutions of similar normality. Bromine water, saturated. Formic acid solution, 80%. Sodium acetate solution, 1 M. Starch solution, 1 % . Potassium iodide. Procedure Into a 100-ml Erlenmeyer flask, introduce a suitable volume (1-5 ml) of sample solution containing 0.1-10 mg of the pyrazolone compound. Add 1 ml of 1 M sodium acetate solution and dilute with water to about 20 ml. Add 2 ml of bromine water, stopper the flask for 2 min, then destroy the excess of bromine by the addition of 2 ml of formic acid solution.Add ca. 0.5 g of potassium iodide, and after 1 min titrate the liberated iodine with 0.01 N thiosulphate solution in the usual way, using starch as an indicator. For low concentra- tions (less than 1 mg of the determinant) use 0.001 N thiosulphate solution. Run a blank determination under identical conditions but with no active ingredient present. In the thiosulphate titrations ot the ioaine liberated by the different pyrazolone derivatives 1 ml of 0.01 N thiosulphate solution is equivalent to: 0.49 mg of 3-methyl-A2-pyrazol-5- one; 1.28 mg of 4,4-dibromo-3-methyl-A2-pyrazol-5-one; 0.56 mg of 3,4-dimethyl-A*-pyrazol-5-one; 0.49 mg of 3-methyl- A3-pyrazol-5-one; 0.87 mg of 1-phenyl-3-methyl-A3- pyrazol-5-one; and 0.78 mg of ethoxycarbonyl-A3-pyrazol-5- one.Results and Discussion A2-Pyrazol-5-ones and A3-pyrazol-5-ones readily and quanti- tatively undergo bromine substitution on the NH group to form the corresponding N-bromo derivatives. Effect of Amount of Bromine Experimental results showed that 2 ml of saturated bromine water were sufficient for a rapid and quantitative reaction of up to 10 mg of the pyrazolone compounds. Complete removal of the excess of bromine was achieved using 2 ml of 80% formic acid solution. Table 1. Accuracy and precision of the method Amount Coefficient taken/ Recovery, of variation, Compound mg Yo O/O 3-Methyl-A2-pyrazol-5-one . . 0.1 98.7 0.8 1 .o 100.0 0.0 10.0 99.2 0.1 4,4-Dibromo-3-methyl-A2- pyrazol-5-one .. . . . . 0.1 97.0 1.1 1.0 99.6 0.5 10.0 98.9 0.3 o n e . . . . . . . . . . 0.1 98.1 0.6 1 .o 100.1 0.2 10.0 99.0 0.5 3-Methyl-A3-pyrazol-5-one . . 0.1 99.0 0.5 1.0 100.0 0.1 10.0 99.5 0.0 3,4-Dimethyl-A*-pyrazol-5- l-Phenyl-3-methyl-A3- pyrazol-5-one . . . . . . 0.1 98.3 1 .o 1 .o 100.1 0.1 10.0 98.8 0.3 pyrazol-5-one . . . . . . 0.1 98.6 1.3 1 .o 99.2 0.2 10.0 98.9 0.4 4-Ethoxycarbonyl-A3-120 ANALYST, JANUARY 1983, VOL. 111 Table 2. Effect of organic compounds on the determination of 1 mg of A2- and A3-pyrazol-5-ones Permissible concentration*/ Compound added mg Semicarbazide . . . . Thiosemicarbazide . . 1-Phenylthiosemicarbazide 4-Phenylthiosemicarbazide 1-Acetylthiosemicarbazide Hydrazine hydrate . . Phenylhydrazine .. . . Pyrrolidine . . . . . . Indole . . . . . . Thiourea . . . . . . Allylthiourea . . . . Phenylthiourea . . . . Isoniazid . . . . . . . . 20 . . Interferes seriously . . 10 . . 5 . . Interferes seriously . . 10 . . 10 . . 10 . . 1 . . 10 . . 5 . . 15 . . 15 * Amount of foreign organic compound causing an error of more than +2% in the determination. Reaction Time It was found that the reaction of the pyrazolones with bromine goes to completion within 2 min, and a reaction time of up to 30 min has no significant effect on the results. Effect of Reaction Medium If the reaction of the pyrazolones with bromine was performed in a neutral medium (water), inconsistent results were obtained. However, consistent results were obtained if 1 ml of 1 M sodium acetate solution was added, and the end-point remained stable for more than 5 min.Addition of more than 1 ml of sodium acetate solution gave low results; low results were also obtained in acidic media. Effect of Sample Volume The present method was applied to the determination of 0.1-10 mg of the title compounds in a total volume of about 20 ml. However, low results were obtained for amounts of less than 0.1 mg of the compounds in such a volume, which may be attributed to the incomplete reaction in dilute solutions. Iodine Liberation Time One addition of iodide to the N-bromo compounds, the iodine liberated quantitatively within 1 min and a liberation time of up to 10 min had no effect on the results. It should be noted that the average blank value was obtained with 0.05 ml of 0.01 N thiosulphate solution.Accuracy and Precision Under the optimised conditions used, the accuracy and precision of the method were checked. The results (ten replicates) are compiled in Table 1, and indicate a reliable method. Proposed Reactions The proposed reactions via the formation of N-bromo derivatives are as follows: A 6 r 3-Methyl-A2-pyrazol-5-one N, ,C=O+Br, - N, ,C=O+HBr / N / N H I H I H 3-Methyl-A3-pyrazol-5-one Br I Br I H Interferences The interference of some organic compounds that may accompany A2- or A3-pyrazol-5-ones was examined by carry- ing out determinations of 1 mg of the pyrazol-5-one in the presence of each of these compounds. The results are summarised in Table 2. It was found that the organic compounds have the same effect on both A2- and A3- pyrazol-5-ones.The method is inapplicable when more than one A2- or A3-pyrazol-5-one is present, and when the samples contained more than one A2- or A3-pyrazol-5-one, the method was applied to pure synthetic compounds, which were prepared in our 1aboratories.lJ It should be noted that the matrices from which these compounds need to be extracted are not available in our laboratories. Pyrazoles can be used as antioxidants in fuels and their major practical applications have been in drugs, anaes- thetics, dyes and agricultural formulations. Recently there have been applications of reduced pyrazoles as chemical bleaching agents, as luminescent and fluorescent compounds and in the cinematographic film industry.3 1. 2. 3. References Taylor, E. C., Robey, R. L., and Mckillop, A., J . Org. Chern., 1972,37, 2797. Vogel, A. I., “Textbook of Practical Organic Chemistry,” Fourth Edition, Longman, London, 1978, p. 594. Barton, S . D., and Ollis, W. D., “Comprehensive Organic Chemistry,” Volume 4, Pergamon Press, Oxford and New York, 1979, p. 357. Paper A51152 Received April 25th, 1985 Accepted July 18th, 1985

ISSN:0003-2654    

DOI:10.1039/AN9861100119

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, JANUARY 1986, VOL. 111 BOOK REVIEWS 121 Methods of Biochemical Analysis. Volume 31 Edited by David Glick. Pp. x + 541. Wiley-lnterscience. 1985. ISBN 0 471 82177 2. This reference work of 514 pages is followed by cumulative author and subject indexes covering Volumes 1-31 and the supplement, and these are very welcome in bringing to the reader’s attention all related work. This volume maintains the high standard of the prede- cessors and presents a lucid treatment of the present instrumental techniques available. The range of chapter topics covers the use of rapid flow quenching, circular dichroism, measurement of dissolved gases, platelet factor isolation, use of high-performance liquid chromatography, NMR, chemilu- minescence and use of computers in biochemical analysis, which serves to illustrate the present preoccupation with non-destructive analysis, carried out rapidly, at the limits of sensitivity and the use of computers to direct or control the experiments and to digest the data produced. Throughout, the use of varied print faces makes for clarity and ease of reading with ease of access to the quoted references.Comments appropriate to each chapter are as follows. In the chapter by Barman and Travers (pp. 1-59) the use of two Fig. 6s and three lonely data points in Fig. 9 could be misleading. Otherwise, the chapter is authoritative, lucid and up to date with key references up to mid-1983 and most post-1975. Johnson (pp. 61-163) covers a difficult field in an admirable fashion, with the slight criticism that owing to compression many of the diagrams are small, and the appropriate data curves, for example, Fig.43, are crowded. However, reference to the original publication is always given. The chapter by Degn, Cos and Lloyd (pp. 165-194) explains both the advantages and limitations of the quadrupole mass spectrometer, the associated cells and measuring equipment and most important the biochemical applications of the method. The applications naturally concentrate on the range of fermentation studies where continuous monitoring, espe- cially on a laboratory and pilot-plant scale, is vital. The dominance of high-resolution instrumental methods even within the traditional biochemical field of platelet activating factors is shown in the chapters by Hanahan and Weintraub (pp.195-219) and Mefford (pp. 221-258). Some of the reaction pathways in [he latter chapter, for example, Fig. 7, are so reduced in size that clarity is lost. The section on biochemical NMR by Bock (pp. 259-315) attempts to cover too much, with the result that Figs. 9 and 10 convey little to the non-specialist. In spite of this, the text is very clear and descriptive. The role of chemiluminescence is reviewed by Campbell, Hallett and Weeks (pp. 317-416), and this chapter suffers from undue compression; for example, details of bonds and names in Fig. 2 are difficult to discern. There is the occasional quirk such as a “black” photograph in Fig. lb. This surely could have been described more concisely than as given. Finally, the input of computers is reviewed by Crabbe (pp.417-514) and noteworthy is the correlation of computer language and selected applications, presented very clearly. The difficult areas of interfacing of computers to equipment such as spectrophotometers and chromatographs, advanced methodology of DNA sequencing and protein structure have not been forgotten and are clearly covered. One may be forgiven for thinking that some of the diagrams, such as Fig. 15, are more appropriate to the Bayeux tapestry rather than computer graphics, such are the limits of two-dimensional representation. Overall a fine book, hard to read in places owing to compression and perhaps, given the breadth of topics covered in depth, approaching the limit of a single-volume work, but nevertheless highly recommended for its intended readership.R. J. Washington Spot Test Analysis. Clinical, Environmental, Forensic and Geochemical Applications Ervin Jungreis. Chemical Analysis, Volume 75. Pp. xiv + 315. Wiley-lnterscience. 1985. Price f76. ISBN 0 471 86524 9. It is a great pleasure to welcome a new volume in continuation of the tradition set by the classic texts of Fritz Feigl. The author clearly demonstrates that, despite the over-all sophisti- cation of chemical analysis via increasingly complex and expensive instrumentation, there remains a significant role for simple, rapid and inexpensive spot and screening tests in many areas such as those indicated in the title. This well referenced text provides detailed chemical and procedural information on a great variety of spot and screening tests; usefully this includes the chemical basis of operation of a range of commercial kits, papers and tubes of both American and European origin.The introduction (5pp.) briefly surveys the subject and indicates the historical origins dating back at least to Pliny the Elder. Aspects of techniques (8pp.) common to the various application areas and simple instrumental evaluations are summarised in a way that will be most helpful to those who have not had the benefit of a basic training in classical semi-micro inorganic and also in organic qualitative analysis. The chapter on clinical analysis (32pp.) deals mainly with the screening of urine and of blood for key components but includes a few miscellaneous tests such as those for occult blood in faeces, urinary calculi, urinary lactic acid and for the detection of cystic fibrosis.Forensic applications (59pp.) include residues of firearm discharge, explosives and their residues, drugs and poisons and the detection of certain biological materials, namely blood, semen, saliva and urine. A variety of geochemical spot tests (51pp.) suitable for field use by relatively unskilled operators are described together with some semi-quantitative applications. The environmental sec- tion consists of chapters on air pollution control (15pp.), water quality screening (29pp.) and soils and plant tissues (13pp.), dealing with common industrially important air pollutants, inorganic and organic content of potable and polluted waters and main nutrient elements, respectively. Strangely omitted from the sub-title is a large and interesting section (55pp.) concerned with food adulteration and food composition; typical examples are the tests for antioxidants, chelates in beer, differentiation between butter and margarine (not the usual TV non-differentiation organoleptic test), adulteration of crabmeat with cod, and mammalian faeces and urine in food.A very adequate index is provided. Overall this is a well written and scholarly text and one I wish to commend to academics and industrialists. However, the price for a book of its size is likely to make any commendation somewhat theoretical. In view of the great potential value and use in less well developed countries it is regretted that it will be priced out of this market and, indeed, even for private purchase in the more affluent areas of the world.As the book is likely to have a substantial useful lifetime the excessive price cannot be justified. D. Thorburn Burns122 ANALYST, JANUARY 1986, VOL. 111 Annual Reports on NMR Spectroscopy. Volume 15 Edited by G. A. Webb. Pp. x + 370. Academic Press. 1984. Price $100. ISBN 0 12 505315 0. ISSN 0066 4103. Handbook of Laboratory Health and Safety Measures Edited by S. B. Pal. Pp. xviii + 391. MTP Press. 1985. Price f59.95. ISBN 0 85200 766 3. This further volume in a well known series continues to cover various aspects of NMR with different chapters by different authors. An important element is the thoroughness of the coverage of the topics chosen so that the volumes are partly bibliographic in nature. This volume has 391,361,256 and 182 references, respectively, to its four chapters, almost all to publications in the last ten years.The first chapter, “Substituent Effects on Nuclear Shield- ing” by D. J. Craik, relies strongly on Hammett parameters and related constants to indicate the trends for aromatic rings with substituents. A wide range of good correlations between chemical shifts and the substituent parameters and position for different series are given and predictions for new cases should be good. Care must be taken, however, if the geometry is not nearly planar as ring currents have a large differential effect between peripheral atoms and those sitting over the central parts of the ring system. The account is particularly strong on 13C shifts, which have been the most studied; 1H shifts on substitution are often too small for very accurate measure- ment.Their range seldom exceeds 0.4 p.p.m. whereas ring 13C shifts, including the ips0 position, exceed 60 p.p.m. and for second substituents to -199HgC1 the Hg shift ranges from +81 p.p.m. forpuru-OCH3 to -88 p.p.m. forpara -CF3, although these shifts are strongly solvent dependent. B, N, 0, F, P, S, Se and Mo shifts are also covered. The second chapter, “Isotope Effects on Nuclear Shielding” by P. E. Hansen, makes a good companion. Here aromatic compounds are no longer dominant and the relationship is to the hybridisation of the carbon atoms, both those being studied and those carrying the changed isotope. By far the largest section concerns change of 13C shifts on replacing -H by -D.This is not surprising since other mass changes have far less effect on zero point averaged bond lengths and 13C can be studied without enrichment and is sensitive to the exact chemical structure. The correlation between compounds is good and can be useful for identifying the site of deuterium substitution. These differences in 13C seldom exceed 0.5 p.p.m. for an H - D switch, but 1H shifts need careful measurement as they are a factor of 10-100 smaller. All nuclei are included where measurements have been made, 1 6 0 - 1 8 0 substitution pairs being the most common after H - D. Recent technical advances have made experiments on the above topics more readily available and this is equally true for 29Si resonances, which are reviewed by E. A. Williams. Here polarisation transfer is especially useful.With a range of 600 p.p.m. many nice structural elucidations are possible and especially the elucidation of siloxane chains and rings based on -Si-04-0- structures. I I I 1 Finally Chapter 4, “NMR of Organic Compounds Absorbed on Porous Solids” by Pfeifer, Meiler and Deininger from Leipzig, shows the help given by NMR to extending the classic work of R. M. Barrer on zeolites and related materials. Studies on flat surfaces seem beyond the range of present sensitivity. This field has benefited from Overhauser factors and from magic angle spinning. The results are impressive as is the general understanding. Inclusion of paramagnetic impuri- ties, generally or at special sites, is also useful because of the large associated shifts.The sections in this volume are more varied and interesting to the general reader than some of the earlier tabulations and show that improvements in NMR experimentation have opened up many new applications. D. H . Whiffen If a handbook is a concise work of reference, then this really should be classed as a demi-handbook-concise enough but lacking the depth necessary for continuing reference. It is in fact a series of short articles (average 21 pp.) with the usual curate’s egg effect that a large number of contributors (22) can produce relative to the taste of the individual reader. The book is distinctly biased towards hospitals, and from an industrial chemist’s point of view the contributions on laboratory design and responsibilities of the Chief (sic) for health and safety are somewhat lightweight, and there is little that is new in those on electrical and mechanical equipment.Safety aspects of radiation are well covered by individual articles on X-rays, radionuclides, UV, ultra-sound, NMR and lasers. However, the most interesting are the contributions about the various types of laboratory, chemical, haematolog- ical, microbiological and clinical chemistry, chemical cytogenetics and animal handling. Some overlap and repeti- tion are inevitable, but the juxtaposition of information on the different approaches to health and safety is both useful and thought provoking. On the whole the book is remarkably easy to read and it is probably this as much as anything that makes the reviewer uneasy about its use as a handbook.A series of well written press articles would probably have produced the same effect. G . E. Penketh Methods of Protein Analysis Edited by lstvan Kerese. Ellis Horwood Series in Analy- tical Chemistry. Pp. 371, Ellis Howood and Akademiai Kiado. 1984. Price €39.50. ISBN 0 85312 176 1 (Ellis Horwood); 0 470 27497 2 (Halsted Press). This book, with five contributors, has the practical purpose of describing and discussing methods that can be performed in an average laboratory. It contains generous experimental detail throughout and includes separations of samples from plant, animal, tissue, food and fermentation sources. After a short introduction, laboratory methods are described for the preparation and characterisation of samples. The latter includes general procedures, such as the Kjeldahl method, and those for measuring proteins.However, the section on fluorimetry does not discuss use of o-phthalaldehyde. Only one general reference book is dated after 1969. All common methods, with many illustrations, are covered in the chapter on electrophoresis with emphasis on polyacrylamide gel (with tables of gel compositions and staining methods) and isoelec- tric focusing. Combined methods, such as the Andersons’ work on plasma proteins, and the technique of high-sensitivity silver staining are mentioned only briefly. Three chapters on chromatography comprise about half the book. Adsorption, partition, ion-exchange, affinity and hydrophobic interaction chromatography are examined and amino acid analysis is discussed. However, the book would have benefited from inclusion of relevant information on HPLC rather than by its deliberate omission. Thin-layer chromatography is discussed thoroughly with 255 references.Examples cover separations of proteins, peptides and amino acids and R, values are quoted extensively. Types of layers and reagents for specific detection are discussed. There is an informative section on sequence analysis. The additional resolution achieved by combining electrophoresis and chro- matography on thin layers is illustrated. The chapter on gel chromatography covers both analytical and preparative sep- arations and includes a section on size-exclusion HPLC. In the final chapter, one sample, egg-white, is examined by techniques described in the other chapters and the FiguresANALYST, JANUARY 1986, VOL. 111 123 well illustrate the relative power of each procedure.This chapter is a useful guide to enable someone with limited experience of protein analysis to select a method. It is, however, marred by incorrect numbering of the last six Figures through omission of reference to Fig. 7.23 in the correct section. The layout and the standard of presentation of this volume are high, although the proof-reader’s concentration has lapsed occasionally. The translation is generally lucid but “through- flow” is not a term in common use. The idiosyncratic layout of tables and Figures is more disconcerting, as some lack headings and some are placed apart from the relevant text. The contents list is very detailed and the index is adequate.An author index and a list of abbreviations would have been helpful. Although the publication date is 1984, references cited suggest that the Hungarian original appeared during 1982. Because of the lack of recent references, this book will be of limited value to research groups. However, it surveys critically methods for protein separation and analysis and collects in one volume much practical information that is otherwise difficult to assemble. It should, therefore, appeal particularly to students and to analysts faced with unfamiliar material. D. H. Calam Inorganic Chromatographic Analysis Edited by John C. MacDonald. Chemical Analysis, Vol- ume. 78. Pp. xiv + 450. Wiley-lnterscience. 1985. Price f75.20. ISBN 0 471 86263 0. This book contains chapters by eleven contributors: R.J. Laub, J. C. MacDonald, H. M. McNair, J. W. Mitchell, J. T. Overfield, C . A. Pohl, J. M. Riviello, J. Sherma, E. R. Savitzky, P. C. Uden and R. A. Wetzel. The text opens with an Introduction and the history and theory of chromato- graphy, and these are followed by discussion of instrumenta- tion for gas and high-performance liquid chromatography, with descriptions of columns, packings, and so forth, for various techniques including size exclusion, reversed-phase HPLC and ion-pair chromatography. Thin-layer chromato- graphy is described, and also the use of ion exchange in radiochemistry. Then follows a chapter devoted to ion chromatography and the concluding chapter on the subject of searching literature data bases on-line by computer tech- niques.Overall the text gives a favourable impression as an introduction to the subject of inorganic chromatographic analysis. By far the longest chapter is on the theoretical aspects of this topic and this is expressed clearly and should be capable of being understood readily. The chapter is concluded by a description of the use of window diagrams for chromato- graphic optimisation and it includes the author’s computer programs. As examples of applications that are covered thoroughly one would mention organometallic compounds and metal complexes. Among other applications given are thin-layer chromatographic conditions for detecting a wide range of cations and anions, together with some inorganic compounds, complexes and derivatives. The volume contains ten chapters, around 800 references, and a good index.If it has a fault it is that it provides (apart from those given under thin-layer chromatography) compara- tively few of the practical details that would enable a student to carry out the necessary manipulations; as the book is intended as an introduction to inorganic chromatographic analysis it could well have been helpful to have included these. The price will put it out of the reach of most students but it will no doubt be purchased by libraries of both academic and industrial research establishments. D. Simpson Gradient Elution in Column Liquid Chromatography. Theory and Practice P. Jandera and J. ChuraEek. Journal of Chromatography Library, Volume 37. Pp. xix + 510. Elsevier. 1985. Price $90.75; Dfl245. ISBN 0 444 42124 6.The authors of this volume are in the Department of Analytical Chemistry at the University of Chemical Technol- ogy, Pardubice, Czechoslavakia, and in a Preface give their reasons for not wishing to write just another book about column liquid chromatography and for selecting the topic of gradient elution in HPLC (they refer readers to some of the outstanding books dealing with HPLC in general). Gel chromatography is not considered specifically in this text, and the applications of gels are classified among other reversed- or normal-phase chromatographic systems, according to the nature of the predominating interactions. The book is composed of four parts-isocratic elution chromatography, theory of chromatography with pro- grammed composition of the mobile phase, instrumental and other practical aspects and applications.It contains 33 chapters, 4 appendices, 510 pages (including a good subject index) and over 1400 references. References are given at the end of each of the first three parts of the book and then at the end of each chapter on applications. The first three parts of the volume of necessity include much theory, but some examples are given of actual separations, together with useful tables with optimum conditions for various components. A summary is provided of some com- mercial gradient elution instruments. Applications mentioned (albeit briefly in some instances) include environmental samples, foods and beverages, clinical diagnostics, technical products such as polymers, surfactants, fossil fuels, pesticides, heterocyclic biochemicals, antibiotics, dyes and intermediates, drugs, vitamins, nucleic and amino acids, amines, steroids, proteins, lipids, sugars, carboxylic acids, hydrocarbons and carbonyls.Such a lengthy list of applications means that there is little room for many figures showing actual chromatograms and, in fact, the applications are presented in the form of a review, with numerous references. Some of the chapters in the applications section could well have benefited from being a little longer, but the volume as a whole is a well planned specialist text that can be recommended to experienced chromatographers and to research libraries. D. Simpson A Manual of Fluorometric and Spectrophotometric Experiments ’ Allesia M. Gillespie, Jr. Pp.x + 151. Gordon and Breach. 1985. Price $25. ISBN 2 88124 005 4. This book is a major disappointment, the more so because there is a need for an up-to-date text describing student experiments on absorption and fluorescence spectrometry. The book’s title is seriously misleading-it is basically about fluorescence, with experiments in absorption spectrometry appearing only as adjuncts to the fluorescence methods. There are 16 experiments, many with several related sections, and the range of topics covered is ambitious, from fundamental photochemistry through experimental techniques to fluores- cence analysis in pharmaceutical chemistry. Descriptions of procedures are detailed, almost excessively so (“1. Obtain a fluorescence spectrometer . , .”), and each experiment is followed by tutorial questions. The latter are sometimes vague (e.g., at the end of Chapter 13-“What are fluorophors?”).The book has two crucial drawbacks. Firstly, it has a very dated air about it. While it is understandable that modern techniques such as synchronous scanning, contour mapping,124 ANALYST, JANUARY 1986, VOL. 111 multi-channel detectors, room temperature phosphorescence, etc., receive scant attention, the omission of any serious mention of fluorescence as an HPLC detection method is ludicrous; perhaps 80% of all fluorescence spectrometers are sold as HPLC detectors! The commercial instruments des- cribed are also dated, and the references are mostly from the 1960s or earlier. Recent developments in the use of quinine as a primary fluorescence standard are ignored, as are modern attempts to rationalise the nomenclature and symbols in this area of spectrometry.While I was reminded of old friends when reading that the velocity of light is 3 X 1010 cm s-1, and that the unit of energy is the erg, SI units must really be regarded as mandatory, especially in student texts! Overall, this book could easily have been written at least 7 years ago. Its second drawback is that it is full of errors, Some are trivial (e.g., “Browian” motion, “inelestic” scattering, “wavelengths,” etc.) , but inevitably many are more serious, such as “pyrolle”( !) and “anilonapthalene.” Several chemical structures are incorrect. The format of the references is not uniform, and although Dr. Udenfriend, a pioneer of fluores- cence spectrometry, might be delighted to see his work cited many times, his pleasure would be diminished by the fact that his name is misspelt (in various ways!) on every occasion.The author seems at times unaware that “spectrum” is a singular noun and that “spectra” is the plural (“What is the excitation spectra?”). Some of these mistakes might be trivial if the intended readership was at an expert level, but in a student text they are simply unacceptable. The index is poor- monochromators, discussed in Chapter 1, do not even get a mention. Finally, if any of my students presented spectra of the quality of those on page 126, they would get a well deserved flea in the ear-this book deserves no better. James N. Miller ~~ -~ Analytical Solution Calorimetry Edited by J.Keith Grime. Chemical Analysis, Volume 79. Pp. xviii + 401. Wiley-lnterscience. 1985. Price f69.40. ISBN 0 471 86942 2. The title of the book may not indicate to some readers what to expect from the contents. Whilst in a wide context the term “analytical solution calorimetry” denotes a study of a wide range of instrumental techniques used to determine the rate of, or the extent of, a reaction by measuring the rate of temperature change or the amount of heat change, within a closed system, in this book the Editor has restricted the term to describe a distinct group of thermochemical techniques in which temperature or the rate of change of temperature is the measured dependent variable of the experiment. This may be a point for future debate, as it is the reviewer’s experience that a generic description of what is discussed in this volume has occupied the attention of international workers in this area for many hours.The problems associated with the terminology of the techniques described in this volume do not, however, diminish their importance and the necessity to have up-to-date and critical reviews of the techniques and their applications. The seven chapters have been composed by authors whose names are well known in this field and the book is a cohesive whole. The chapter that deals with the theoretical aspects of analytical solution calorimetry and reviews the ins and outs of the various experimental parameters that have to be con- sidered leads naturally into that dealing with instrumentation and data reduction.This latter chapter is very good and certainly will help solve some of the problems that confront workers wanting to apply these techniques to their own problems. A large proportion of the volume is devoted to analytical applications and to biochemical and clinical analysis. These are well referenced sections; in the section dealing with general applications there are over 230 references and it may come as a surprise to some that so many industrial problems of analysis can be solved by the use of these techniques. The importance of these techniques to quality control applications in selected areas in the pharmaceutical industry, in general organic analysis and in environmental analysis is well illus- trated in this chapter, which should provide food for thought to many readers.With the increasing importance of biochemical and clinical analysis , including the use of immobilised enzyme technology, the chapter dealing with applications of solution calorimetry in these areas is timely. The volume is well presented, free from irritating errors and should form an integral part of any well balanced library dealing with modern analytical chemistry. L. S . Bark Inductively Coupled Plasma - Atomic Emission Spectro- scopy. An Atlas of Spectral Information R. K. Winge, V. A. Fassel, V. J. Peterson and M. A. Floyd. Physical Sciences Data, Volume 20. Pp. x + 584. Elsevier. 1985. Price $192.25 (USA & Canada); Dfl 500 (Rest of the World). ISBN 0 444 42358 3. The attractive feature of this atlas is that it has been prepared from actual spectra emitted by ICPs operated under the optimised conditions usually employed for sample analysis. This means that this compilation includes lines that are not to be found in tables intended for use with conventional emission sources, or in ICP atlases that have been based on them, even though many of these ICP lines are analytically useful. Part I of the atlas is a brief and rather sketchy account of the historical aspects of compilation of spectral information. Part I1 describes the experimental procedure and interpretation of wavelength scans and reference blank scans together with the interpretation of prominent lines. These scans are contained in Appendix A and amount to 232 wavelength scans of 70 elements. Reference blank spectra are included and a second set of reference blank spectra, in the form of transparencies, is located in a pocket in the rear cover. These may be superimposed on a spectrum and element lines distinguished from the background. Appendix B contains listings by element and by wavelength of prominent lines emitted by the ICP. Part I11 is concerned with experimental procedures and interpreta- tion of coincidence profiles and Appendix C contains scans of spectral coincidence profiles, each with profiles of ten of the most prevalent concomitants superimposed. The book is nicely produced, possibly on the expensive side, but probably worth it in terms of usefulness. S. Greenfield

ISSN:0003-2654    

DOI:10.1039/AN9861100121

出版商:RSC    

年代:1986

数据来源: RSC