摘要:

ANALYST, JANUARY 1984, VOL. 109 97 Indirect Polarographic Determination of Indium(lll) in the Presence of Cadmium(l1) by Utilising the Difference in their Kinetic Effects in an Appropriate Substitution Reaction Lin Sin-ru and Feng Qiang-sheng Shanghai Institute of Metallurgy, Academia Sinica, Shanghai 200050, China Keywords: Indium(///) determination; indirect polarographic determination; cadmium(//); kinetic effect Some elements that do not give a well defined wave at the dropping-mercury electrode in a suitable potential range or even polarographically inactive ions can be indirectly deter- mined by utilising an appropriate reaction1-3- k LY + Nf NY + L z e L(Hg) Let the equilibrium constant of the above substitution reaction be B and the forward rate constant be kf. The replacement of L must be essentially quantitative for the indirect polaro- graphic determination of N.A quantitative treatment of the substitution equilibrium applicable to the polarographic deter- mination of N has been given by Nakagawa and Tanaka.2 The kinetic factor of the substitution reaction was not taken into account in their treatment. During the electrolysis process, the loss of some L in the neighbourhood of the electrode, due to the electrode reaction, is compensated for by a shift in equilibrium according to equation (1). When the value of kf is not very large, it is obvious that the measured limiting current for the reduction of L is dependent on kf. In this work we studied the kinetic effect of the equilibrium shift. On the basis of previous work,4 we considered the Bkf value that will be sufficient to give a quantitative substitution current, i.e., for the recorded limiting current of L to be in agreement with the value obtained from the Ilkovic equation when the concentration of L is equal to the initial concentra- tion of N.The results of the determination of indium(II1) in the presence of cadmium(I1) by utilising the difference in their kinetic parameters (Bk,) in a substitution reaction with the system bismuth(II1) - EDTA chelate are reported. Experimental Apparatus A mechanical square-wave polarograph (Model 895)5,6 was used. The characteristics of the capillary electrode were as follows: flow-rate, 0.47 mg s-1; natural drop time, 6.6 s in 4 M sodium chloride solution (pH 1.1). The counter electrode was a mercury pool.All experiments were performed at 25 k 0.2"C. Reagents All the solutions were prepared with high-purity metals, analytical-reagent grade chemicals and doubly distilled water. The dissolved oxygen was expelled by bubbling argon through the solution before electrolysis. Results and Discussion When kf of process (1) is close to zero, the measured limiting current of L is controlled by the diffusion of L existing in equilibrium with N before electrolysis. When kf is very large, the current is controlled by the diffusion of N from the bulk solution to the neighbourhood of the electrode to participate in the substitution reaction , and it quantitatively represents the concentration of N in the bulk solution (C,). In such an instance, the concentration of L derived from the limiting current represents CN, i.e., CN can be evaluated directly from the limiting current of L.When kf is not very large, the "conversion" rate of N into L is smaller than the rate of loss of L at the electrode. The measured limiting current is controlled by both the diffusion of L existing in equilibrium with N before electrolysis and the kinetic effect of the substitution reaction. Its value is between that in the above two instances and it does not quantitatively represent CN. If the concentration of LY, CLy, is so high in comparison with that of N that it is virtually equal to its concentration in the bulk of the solution even at the electrode surface during the whole electrode reaction, the process described by equation (1) can be regarded as an electrode process preceded by a pseudo-first-order chemical reaction.Also, if B is so small that L, existing in equilibrium with N before electrolysis, can be neglected and the diffusion coefficient of L, DL, is approximately equal to DN, one can calculate the value of Bkf that will be sufficient to give a quantitative polarographic substitution current, on the basis of previous work.4.7 In ordinary polarography, the charge-transfer rate constant of the depolariser at the dropping-mercury electrode is much larger than the material transport rate, v ~ . ~ . , in the potential range of the limiting current. Thus, when CN can be evaluated directly from the recorded limiting current of L, where td is the drop time of the dropping-mercury electrode.In square-wave polarography, the charge-transfer rate of the depolariser at the peak potential must be taken into account. For the reversible square-wave polarographic pro- cess of the indicator ion L, when the substitution current is not dependent on the kinetic effect of the substitution reaction. CN can be evaluated directly from the recorded peak current of L. The kinetics of the polarographic substitution process of the system bismuth(II1) - EDTA chelate with aluminium(II1) were studied. Bismuth(II1) - EDTA exhibits a wave at the dropping-mercury electrode in 4 M sodium chloride solution (pH3). In the presence of aluminium(II1) there is another wave at a more positive potential, which results from the reduction of liberated bismuth(II1). The charge-transfer rate constant, k4,7 of bismuth(II1) at the dropping-mercury elec- trode was measured.The results are given in Table 1. As the peak current in square-wave polarography results from the potential of the dropping-mercury electrode having many small square-wave components, the depolariser transport rate depends on the half-period (T) of the square-wave potential. The transport rate of the depolariser in square-wave polaro- graphy is given by the equation4 where W = 1.4. On the basis of the above equation, when z = 1 x 10-2s and D = (4-9) x 10-6cm2s-1, the transport rate is (1.6-2.4) x 10-2cm s-1. The data in Table 1 are about (3BkfCLytd/7)4 3 350 (2) BkfCLy 2 4kj21DL (3) v ~ , ~ . = 2DV[(xz)$VVl (4)98 ANALYST, JANUARY 1984, VOL. 109 Table 1. k, values of bismuth(II1) Concentration of Bi(III)/M X Supporting electrolyte Dlcm2 s-1 x 10-6 kJcm s-1 0.1 0.1 0.1 0.1 0.1 0.1 KN03 (0.5 M), H2S04 (0.25 M) 6.4 KN03 (0.7 M), HCl(0.3 M) 7.6 KN03 (0.5 M), HCl(0.5 M) 7.6 NaCl(4 M, pH 0.92) 7.2 NaCl(4 M, pH 1.5) 7.2 NaCl(4 M, pH 1.99) 7.2 4.5 x 10-2 >1 (-1.3) >1 (-1.5) 1.5 X 10-l 1.4 X 10-1 1.4 X 10-1 Table 2.Bkf values of the system bismuth(II1) - EDTA chelate with aluminium(II1). Supporting electrolyte: NaCl, 4 M Concentration of electrolyte/M x 10-4 Bi(II1) -EDTA Al(II1) pH Bkf/lmol-'s-l x 106 5 1.6 3.5 7.6 5 1.28 3.6 7.6 5 1.12 3.6 7.6 5 0.96 3.6 7.9 10 3.2 3.3 7.4 I x 1 2 3 4 5 6 36r1 Fig. 1. Graphs of Bi(II1) peak current versus time ( r = r / t , 'c = 1/88 s). X, Bi(II1) (1 X M) and Bi(II1) - EDTA (1 X 10-3 M) with In(II1) (6 x 10-5 M); 0, Bi(II1) - EDTA (1 X 10-3 M) with Cd(I1) (1 X M).Supporting electrolyte, NaCl (4 M, pH 3) 50 - E E CI] 30 $ 20 E 4 0 - . - .- 0, .!= - i! 1 0 - I I I I I 0 1 2 3 4 5 6 Concentration of metal iOnS/M x 10-5 Fig. 2. Calibration graph for A , In(II1) with Bi(II1) - EDTA; and 0, Bi(II1) ten times larger than the transport rate value calculated above, except for those measured in sulphuric acid medium, which shows that the polarographic processes of bismuth(II1) in the media studied, except sulphuric acid, are reversible at the peak potential. The measured Bkf values of the system bismuth(II1) - EDTA chelate with aluminium(II1) are given in Table 2, and indicate that Bkf is independent of the concentration of the substrates under the conditions used.This is characteristic of a first-order reaction. It can be calculated from the data in Tables 1 and 2 that when the concentration of the bismuth(II1) - EDTA chelate is 5 X 1 0 - 4 ~ ~ the BkfCLY value of the system bismuth(II1) - EDTA chelate with aluminium( 111) in sodium chloride medium ( 4 ~ , pH3.5) is 3.8 X 103s-1 and the 4k42lD value of bismuth(II1) in sodium chloride solution (4 M) is 1.2 x 104s-1. I I Potential d Fig. 3. Differential-pulse olarograms of Bi(II1) in Bi(II1) - EDTA (1 x l o - 4 ~ ) with In(II1) p2 x l o - 5 ~ ) in the presence of Cd(II1). Molar ratios of Cd : In: A, 0 : 1; B, 50 : 1; and C , 500 : 1 The former is smaller than the latter, and therefore the substitution peak current of the system bismuth(II1) - EDTA chelate with aluminium(II1) is affected by the kinetic effect.The above result implies that when the concentration of the bismuth(II1) - EDTA chelate is relatively high, the kinetic substitution current, ik, increases linearly with increasing concentration of aluminium(II1). Hence the concentration of aluminium( 111) can be determined from the calibration graph of versus ik. Certainly it is important to keep the experimental conditions constant. By utilising the difference in the kinetic effects between two ions that interfere with each other owing to their half-wave potentials being similar, one of them can be determined indirectly without any previous separation. When cad- mium(I1) and indium(II1) are present at the same time, it is difficult to determine either of them. It can be seen from Figs. 1 and 2 that the substitution current in the system bismuth(II1) - EDTA with indium(II1) is quantitative. However, Fig. 1 shows that the substitution current in the system bismuth(II1) - EDTA chelate with cadmium(I1) is obviously affected by the kinetic effect. There is a greater difference in the kinetic effect between indium(II1) and cadmium(II), so indium(II1) can be determined in the presence of cadmium(I1). Fig. 3 shows that indium(II1) can be determined in the presence of a 500-fold excess of cad- mium(I1) with the system bismuth(II1) - EDTA chelate. Shen Wei and Yin Qi participated in part of this work. References 1. 2. 3. 4. 5. 6. 7. Pribil, R., andvicenova, E., Collect. Czech. Chem. Commun., 1953, 18, 308. Nakagawa, G., and Tanaka, M., Talanta, 1962,9,847 and 917. Sugawara, M., Murayama, Y., and Kambara, T., Fresenius Z. Anal. Chem., 1978, 293, 104. Lin, S. R., and Feng, Q. S . , Anal. Chem., 1982, 54, 1362. Feng, Q. S . , and Liu, G. L., Huaxue Xuebao, 1965, 31, 291. Feng, Q. S., Huaxue Xuebao, 1966, 32, 7. Feng, Q. S., and Lin, S. R., Anal. Chem., 1981, 53, 1006. Paper A3195 Received March 28th, 1983 Accepted July 27th, 1983

ISSN:0003-2654    

DOI:10.1039/AN9840900097

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANALYST, JANUARY 1984, VOL. 109 99 Determination of Silica Surface-confined Monolayer Cobalt by Energy-dispersive X-ray Fluorescence Spectrometry C. Allen Chang* and Chen-Shi Huang Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968, USA Jerry M. Hoffer Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968, USA Keywords: Silica surface-confined monola yer cobalt determination; energ y-dispersive X-ray fluorescence spectrometry Materials in which surfaces are modified with molecular reagents have been used in many processes including stoi- cheiometric and catalytic syntheses, adhesion and other physical surface tailoring, chemical energy conversion and for analysis and separation .I-5 In several instances, monolayer coverage of the surface-confined species is prepared for easy characterisations and controlled applications.We have been using some substitution-inert cobalt(II1) complex bonded silicas in liquid chromatographic separations for the understanding of retention mechanisms, involving strong hydrogen bonding.6.7 Owing to the preparation proce- dures, the metal complex bonded silicas show mixed surface composition, i.e., some of the ligands originally grafted on to the silica did not react with the latter added metal complex. Thus, in order to assess the retention contribution of each surface derivatised reagent, it is necessary to determine the surface concentrations of the metal complexes. The determination of silica surface-confined cobalt by energy-dispersive X-ray fluorescence (XRF) spectrometry is described in this paper.The XRF technique is non- destructive, rapid and has been used for the chemical analyses of stee1,x catalysts9 and geological, biological10 and environ- mental" samples. It should be noted that the determination of surface-confined metals is normally performed with atomic- absorption spectrometry, which is, in general, more time consuming. Experimental Several cobalt(II1) complex bonded-phase compounds were prepared."7 The ethylenediamine and tris(ethy1ene- diamine)cobalt(III) chloride, [ C ~ ( e n ) ~ ] C l ~ , bonded-phase materials were prepared by using Partisil-10 (Whatman), 3-[2-( aminoethyl)amino]propyltrimethoxysilane (Silar Labs.) and cis-[dichlorobis(ethylenediamine)]cobalt(III) chloride, ~is-[Co(en)~Cl~]Cl, according to the methodh Silica (Partisil-10) + (Me0)3Si(CH2)3NH(CH2)zNH2 + I cis-[Co(en),C12]C1 silica-O-Si-(CH2)3NH(CH2)zNH2 > I I silica-0-Si-( CH2)3-[ Co( en)&13 (1) The [Co(edda)(en)]Cl, [ Co(dmedda)( en)]Cl and [Co(deedda)(en)]Cl bonded-phase materials (where edda is ethylenediamine-N,N'-diacetate and dmeeda and deedda are the N,N'-dimethyl and diethyl structural analogues of edda, respectively) were prepared according to the following general equations7: S~~~C~-O-S~-(CH~)~-NH(CH~)~NH~ + H[Co(edda)C12]- I I silica-O-k( I CH2)3-[ Co( edda) (en)]Cl + HCl (2) * To whom correspondence should be addressed. Four different [ Co(edda)(en)]Cl bonded-phase samples (Table 1, samples 3, 4, 5 and 6) were prepared in order to study the reproducibility of the preparation procedure.Samples 3 , 4 and 5 were prepared under the same conditions. Sample 6 was obtained by prolonged acid washing using a pH 1.5 solution after treating as described [equation (2)]. The apparatus used for X-ray fluorescence measurements was an Ortec 6110 TEFA system with a 16K storage computer (PDP-11) system. The unit includes a dual anode X-ray tube source of molybdenum and tungsten, an Si(Li) detector (resolution 150 eV at 5.9 keV) with a liquid nitrogen Dewar. The molybdenum X-ray tube was operated at 40kV and 10 mA and the accumulation time for each sample was 100 s under vacuum. The cobalt concentrations on the silica surface were determined using both Co K a and KP radiations by a linear fit. The excitation and fluorescence beams both made angles of about 45" with the sample plane.Samples were prepared by dispensing the materials on to either polyester thin films or cellulose-filled aluminium specimen caps (as described under Results and Discussion). The atomic-absorption determination of silica surface- confined cobalt was performed by Galbraith Laboratory, Inc. Samples were acid digested, diluted appropriately and analy- sed using a standard procedure. Results and Discussion The silica surface concentrations of cobalt were determined using a set of Spex Mix Time-Saver Standards consisting of 49 common elements, including cobalt, at levels of 1.27,O. 1,0.033 and 0.01% in a silica matrix. Samples were prepared by dispensing the surface derivatised silica on to a 4-pm polyester thin film.In general, the results were unusually high. This may be due to two reasons: firstly, sample preparation using a thin film normally results in loose packing; and secondly, the standards used in the silica matrix do not have monolayer coverage of each element. In order to determine the silica surface-confined cobalt accurately, it is necessary to use standards with the same matrix and to prepare the sample in the same way as the standards. Therefore, samples were prepared by dispensing the material over a cellulose-filled aluminium specimen cap (Spex Inc.) and pelletised under 25 tons pressure. One drop of distilled water was added to aid in binding the solids together. Two internal references (samples 1 and 2) were analysed in duplicate by atomic-absorption spectrometry.The values of the surface concentration (in terms of percentage by mass) of the two references together with another three (samples 3, 4 and 7) were then used to calculate the surface concentrations of other samples determined by XRF spectrometry using a linear-fit equation. The results are presented in Table 1. In general, data obtained using Co K a radiation are similar to those using KP radiation. Also, very good correlations are observed between the values determined by XRF spectro- metry and by atomic-absorption spectrometry, which demon- strates the validity of XRF techniques. The values are also consistent with other published resu1ts.Q An average of lessANALYST, JANUARY 1984. VOL. 109 100 Table 1. Silica surface-confined cobalt concentration (YO mlm) determined by X-ray fluorescence spectrometry (XRFS) and atomic-absorption spectrometry (AAS)".? [Co( edda)(en)]Cl [Co(deedda)(en)]Cl [Co(dmedda)(en)]Cl Sample Sample Sample Sample [C~(en)~]Cl, Method Sample 1 Sample 2 3 4 5 6 Sample 7 XRFS CoKa ., . . . . 0.32 CoKP . . . . . . 0.34 AAS . . . . . , . . 0.35 0.65 1.08 0.98 0.95 0.84 2.22 0.61 1.08 1.01 0.98 0.81 2.21 - 2.22 0.62 1.03 0.98 - * For XRF determination, the linear fit is of the form: Concentration = C1 + C, x intensity t A linear fit between the values determined by XRFS and AAS has the following parameters: Co Ka, slope = 1.004, intercept = 0.006 and where for Co Ka, C1 = -0,053 1, C2 = 0.001 7; and for Co KP, C1 = -0.017 4, C2 = 0.010 6. correlation coefficient = 0.999 1; and KP, slope = 0.9985, intercept = 0.011 and correlation coefficient = 0.999 2.than 10% variation was found from the repeated preparations of [Co(edda)(en)]Cl bonded-phase material. However, pro- longed acid-washing removed some of the anchored com- plexes as indicated by the low cobalt content of sample 6 . Normally, the XRF determination of cobalt does not suffer from severe interference except by Fe KP. However, the concentration of iron, which coexists with cobalt in this type of silica, is too low to cause any detectable interferences. In addition, the size of the silica support, i. e . , 10 pm i.d., requires no additional sample treatment for reproducible results. (Based on our experience, solid samples with particle size greater than 50p.m do not give reproducible results and therefore have to be ground to less than 50 pm in a shatter- box.) In conclusion, it is demonstrated that both selection of standards for calibration and sample preparation are crucial for an accurate determination of surface-confined elements.For the determination of surface-confined monolayer species, standards in the same matrix should be used in order to obtain the best results. The method described is of immediate use for the determination of metals of polymer surface-anchored metal complexes or oxide catalysts. Acknowledgement is made to the Donors of the Petroleum Research Fund Administered by the American Chemical Society for support of this research. The support of the Robert A. Welch Foundation of Houston, Texas, is also gratefully acknowledged. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Murray, R. W., Acc. Chem. Res., 1980, 13, 135. Karger, B. L., and Giese, R. W., Anal. Chem., 1978, 50, 1048A. Grushka, E., and Kikta, E. J . , Anal. Chem., 1977,49, 1004A. Reichel, C. L., and Wrighton, M. S . , J . Am. Chem. SOC., 1981, 103,7180. Collman, J. P., Denisevich, P., Konai, Y., Marrocco, M., Koral, C., and Anson, F. C., J. Am. Chem. Soc., 1980, 102, 602. Chang, C. A., and Tu, Cheng-Fan, Anal. Chem., 1982, 54, 1179. Chang, C. A., Huang, Chen-Shi, and Tu, Cheng-Fan, Anal. Chem., 1983,55, 1390. Blomquist, P. D., X-Ray Spectrom., 1975, 4, 95. Cornelius, C., Anal. Chem., 1983, 53, 2361. Mataumoto, K . , and Fuwa, K., Anal. Chem., 1979, 51,2355. Duzubay, T. G. "X-Ray Fluorescence Analysis of Environ- mental Samples," Ann Arbor Science Publishers, Ann Arbor, MI, 1977. Chow, F. K., and Grushka, E., J. Chromatogr., 1979,185,361. Paper A31151 Received May 25th, 1983 Accepted August 22nd, I983

ISSN:0003-2654    

DOI:10.1039/AN9840900099

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANALYST. JANUARY 1984, VOL. 109 101 Oxidation of Glutamic Acid and its Rare Earth Complexes with Bromamine-T Rangaswamy," B. N. Usha and H. S. Yathirajan Department of Postgraduate Studies and Research in Chemistry, University of Mysore, Manasa Gangotri, Mysore-570006, India Keywords: Glutamic acid; methionine; bromamine-T; rare earth complexes; oxidation Sodium toluene-4-(N-bromosulphonamide) (bromamine-T) has received attention as an oxidimetric reagent. 1-3 Glutamic acid is a non-essential amino acid present in most proteins and its purity can be checked by non-aqueous titration with perchloric acid.4 The monosodium salt, sodium L( +)- glutamate, finds extensive commercial use as a flavour intensifier. Glutamic acid itself is used in medicine and biochemical research and as a salt substitute and dietary supplement.In view of the importance of metal - protein complexes in organic chemistry, a study of metal - amino acid complexes is worthwhile as these are helpful in the separation and identification of amino acids. Experimental and Results Preliminary Studies In the preliminary investigation of the oxidation of glutamic acid by bromamine-T in buffer,5 acidic and alkaline media, glutamic acid solution was added to an excess of bromamine-T in an iodine flask at room temperature. The reaction mixture was set aside for various intervals of time, with occasional shaking, then the excess of bromamine-T was determined by iodimetric back-titration, Typical results are given in Table 1. It can be seen that the oxidation is stoicheiometric in buffer media of pH 1-6, non-stoicheiometric oxidation occurs in acidic media and the reaction is slow in alkaline media.However, the reaction is complete in 1 min in pH4 acetate buffer medium with a four-electron change. The oxidation of rare earth complexes6 having the general formula M(C5H804N)3.3H20 (where M is Y, La, Pr, Nd, Sm, Gd, Tb, Dy and Ho) were also found to be complete within 5 min with a twelve-electron change per complex molecule in pH 4 acetate buffer medium. Results are given in Table 2. Many commercial pharmaceutical preparations contain glutamic acid as a major component together with riboflavin and nicotinamide. The latter (25 mg each) do not interfere in the determination of glutamic acid. Results are given in Table 3. It was found that methionine can be determined accurately by direct titration in the presence of glutamic acid with a visual end-point.Reagents Sodium thiosulphate solution. An approximately 0.1 M solution was prepared and standardised with potassium iodate. Bromamine-T solutions. Approximately 0.05 and 0.005 M solutions of bromamine-T were prepared and standardised by the iodimetric method. Buffer solution. An acetate buffer solution of pH4 was prepared by mixing 41.0ml of 0 . 2 ~ acetic acid and 9.0ml of 0.2 M sodium acetate. * Author to whom correspondence should be addressed. Glutamic acid and its rare earth complexes. Solutions of glutamic acid (about 2 mg ml-1) and rare earth complexes (about 4 mg ml-1) in acetate buffer of pH 4 were prepared. Methionine solution. An approximately 2 mg ml-1 solution was prepared.Indigocarmine solution. A 0.1% solution was used as an indicator. Potassium bromide solution, 10%. Acetic acid, glacial. Table 1. Extent of oxidation of glutamic acid with bromamine-T. GA taken, 0.1 mmol; oxidant taken, 1.25 mmol; time, 5 min Ratio of BAT used (mol) to GA taken (mol) Ratio of BAT used (mol) to Medium GA taken (mol) Medium pH 1.0 pH 2.0 pH 3.0 pH 4.0 pH 5.0 pH 6.0 pH 8.0 pH 9.0 pH 10.0 2.002 0.5 M H2SO4 2.421 1.995 0.005 M H2SO4 1.978 1.995 1 .O M HC104 1.71 1 2.001 0.01 M HC104 2.070 2.009 1 .O M HCI 2.825 1.995 0.01 M HCl 2.058 1.960 0.5 M NaOH 1.870 1.910 1.910 Table 2. Extent of oxidation of trivalent rare earth complexes of glutamic acid with bromamine-T in pH 4 acetate buffer medium. Complex taken, 0.032 mmol; oxidant taken, 1.25 mmol; time, 5 min Ratio of bromamine-T consumed (mol) to complex taken (mol) Rare earth complex Y (C5H804N)3.3HZO La( C5H804N)3.3H20 Pr( CsHs04N)3. 3H20 Sm(C5H804N)3 .3H20 Gd(C5H804N)3.3H20 Nd(CsHs04N)3.3H20 Tb(CSH804N)3. 3H20 DY(C5H804N)3*3H20 HO(C~H~O~N)~. 3H20 . . . . . . 6.01 . . . . . . 6.02 . . . . . . 6.01 . . . . . . 6.02 . . . . . . 6.00 . . . . . . 6.00 . . . . . . 5.99 . . . . . . 5.99 . . . . . . 6.00 Table 3. Determination of glutamic acid with bromamine-T in the presence of riboflavin and nicotinamide Glutamic acid Ta ken/mg Found/mg Error, % 4.00 4.03 +0.75 8.02 8.07 +0.63 16.01 15.92 -0.56 24.01 24.16 +Oh2 36.02 36.30 +0.78102 ANALYST, JANUARY 1984, VOL. 109 Recommended Procedures Back-titration Add an aliquot of a solution containing glutamic acid (440mg) in pH4 acetate buffer to 25ml of 0 .0 5 ~ bromamine-T solution in an iodine flask. Shake the reaction mixture occasionally and, after 5 min, add 15ml of I M sulphuric acid and 15 ml of 10% potassium iodide solution. Titrate the liberated iodine with standard thiosulphate solu- tion ( 0 . 1 ~ ) . Carry out a similar blank experiment with bromamine-T solution alone. The amount of glutamic acid (xmg) is given by x = [MY(V2 - V1)]/4, where M is the relative molecular mass of glutamic acid, Y is the molarity of the thiosulphate solution and V1 and V2 are the volumes of thiosulphate solution required for the sample solution and for the blank experiment, respectively. The same procedure is adopted for the oxidation of trivalent rare earth complexes of glutamic acid with bromamine-T.Direct titration Dissolve the sample containing methionine (4-16 mg) in 20 ml of water in an iodine flask and add 1 ml of glacial acetic acid, 1 ml of 10% potassium bromide solution and 0.2 ml of 0.1% indigo carmine indicator. Shake well and titrate with 0.005 M bromamine-T solution to the appearance of a pale yellow colour. The colour change is distinct. The oxidation corre- sponds to methionine sulphoxide. The amount of methionine (a mg) is given by a = M‘VZ, where M‘ is the relative molecular mass of methionine, V is the volume of bromamine-T solution and Z is the molarity of the bromamine-T solution. Typical results are given in Tables 4 and 5. Discussion Detailed investigation of the system led to the conclusions listed in the opposite column. Table 4.Determination of rare earth complexes of glutamic acid with bromamine-T. Medium, pH 4.0 acetate buffer; time, 5 min Rare earth complex Y(CsH804N)3.3HZO La(CsH804N)3. 3H20 Pr( C5H804N)3. 3H20 Sm(CsH804N)3.3H20 Nd(CSH804N)3.3H20 Gd( CsH804N)3.3H20 T ~ ( C S H ~ O ~ N ) ~ . ~ H ~ O Dy( C S H ~ O ~ N ) ~ . 3H20 Ho( CsH804N)3.3H20 Range studied/mg . . 3-30 . . 4-40 . . 4-40 . . 4-40 . . 4-40 . . 4-40 . . 4-40 . . 4-40 . . 4-40 Maximum error, O h 0.68 0.77 0.77 0.89 0.89 0.50 0.98 0.50 0.50 Table 5. Determination of methionine with bromamine-T in the presence of glutamic acid Methionine Taken/mg Found/mg Error, YO 4.23 4.21 -0.48 8.46 8.50 +0.47 10.30 10.40 +0.98 16.48 16.54 +0.40 1. The stoicheiometry of the oxidation of glutamic acid can be represented by HOOC(CH2)2CH(NH2)C00H + 2RNBrNa + for the complexes: [HOOC(CH2)2CHNH2C00]3M + 6RNBrNa + 3H20+ 6RNH2 + [HOOC(CH2)2CN]3 + 3 c 0 2 + 6NaBr + M(OH)3 and for methionine: 2RNH2 + HOOC(CH2)2CN + C 0 2 + 2NaBr 0 II CH3SR’H + RNBrNa + H20 -+ CH3SR’H + RNH2 + NaBr where R = H3CC6H4S02 and R‘ = H2CCH2CH(NH2)CO0.The presence of toluene-4-sulphonamide among the reac- tion products was detected by paper chromatography7 with benzyl alcohol saturated with water as the solvent and 0.5% vanillin in 1% hydrochloric acid in ethanol as the spray reagent (RF = 0.91). 3-Cyanopropanoic acid was detected by its colour reaction with hydroxylamine and iron( 111) chloride .g A characteristic red - violet colour is formed. Methionine sulphoxide in the reaction products was detec- ted by paper chromatography9 with phenol saturated with water as solvent and ninhydrin as the spray reagent 2.Ions such as K+, Ba2+, Zn2+, NO3-, P043-, S042- and C104- have no influence on the oxidation of glutamic acid. 3. The stoicheiometry is unaffected by the order of addition of the oxidant and glutamic acid. 4. Non-stoicheiometric oxidation occurs in acidic media, whereas rapid and stoicheiometric oxidation takes place in buffer media. 5. Some compounds, such as folic acid, calcium gluconate, pyridoxine hydrochloride and glycine (1 mg each), interfere in the determination of glutamic acid. It can be concluded that the number of ligand molecules present in a rare earth complex can be calculated easily by oxidation with bromamine-T. The proposed method for the determination of glutamic acid is rapid and accurate and is also useful for the analysis of rare earth complexes. (RF = 0.67). One of the authors (B.N.U.) is grateful to the U.G.C., New Delhi, for the award of a Senior Research Fellowship. 1. 2. 3. 4. 5. 6. 7. 8. 9. References Nair, C. G. R., Lalithakumari, R., and Senan, P. I . , Talanta, 1978, 25, 525. Mahadevappa, D. S., Rangappa, K. S., Gowda, B. T., and Gowda, N. M. M., Microchem. J . , 1981,26, 132. Rangappa, K. S . , Mahadevappa, D. S., Gowda, B. T., and Gowda, N. M. M., Microchem. J., 1981, 26, 375. Vogel. A. I . , “Quantitative Organic Analysis,” Part 111, Longmans, London, 1958, p. 708. Findlay, A., “Practical Physical Chemistry,” Longmans, Lon- don, 1954, p. 268. Rangaswamy, Yathirajan, H. S . , and Mahadevappa, D. S., Curr. Sci., 1980, 49, 342. Mahadevappa, D. S . , and Gowda, N. M. M., Talanta, 1975,22, 771. Soloway, S . , and Lipschietz, A., Anal. Chem., 1952, 24, 898. Gowda, N. M. M., and Mahadevappa, D. S . , Talanta, 1977,24, 470. Paper A3133 Received February Ist, I983 Accepted August Ist, 1983

ISSN:0003-2654    

DOI:10.1039/AN9840900101

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANALYST, JANUARY 1984, VOL. 109 103 Titrimetric Determination of Chloride in the Presence of Chlorine Daniel P. Levy* Department of Chemistry, Westfield College, Kidderpore Avenue, London, N W3 7ST, UK Keywords: Chloride determination; chlorine; hydrogen chloride; h ypochlorous acid; titrimetry An investigation into the ring substitution of aromatic compounds by chlorine during their oxidation with ruthenium tetraoxide in carbon tetrachloride1 required a determination for the hydrogen chloride produced in the presence of an excess of chlorine. In the absence of a suitable quantitative chemical determination for this system a method for the analysis of an aqueous solution of the gas mixture was developed. Chlorine in water is in equilibrium with the products of its hydrolysis: Chloride can be determined by titration with aqueous silver nitrate without interference from hypochlorous acid (HOC1) because silver hypochlorite is soluble in water.2 Similarly, hypochlorous acid can be determined iodimetrically3 without interference from chloride.The difference between the two results is therefore a measure of the chloride not originating from chlorine hydrolysis. Even if some chlorine is lost by vaporisation from the aqueous solution or by being incomple- tely dissolved initially, the final result should be the same. However, experiments on an aqueous solution of chlorine alone revealed the following problems: (i) unhydrolysed chlorine interferes with the determination of hypochlorous acid because it also oxidises iodide to iodine; (ii) the chlorine equilibrium (above) can shift during the analyses, especially if acid is added; and (iii) chlorine cannot be extracted from the solution by boiling to enable chloride to be determined by a single analysis because part of the hypochlorous acid is decomposed to hydrochloric acid and ~ x y g e n .~ We found that at temperatures close to 0°C these difficul- ties could be overcome because the equilibrium was effec- tively frozen and unhydrolysed chlorine could be swept out of the cold solutions with nitrogen before the analysis. C12 + H20 HCl + HOCl Experimental Reagents All chemicals used were of analytical-reagent grade. Silver nitrate solution, 0.010 M. Sodium thiosulphate solution, 0.010 M. Sodium chloride solution, approximately 0.01 M. Soluble starch solution, 2%.Concentrated hydrochloric acid. Nitric acid, 5 M. Concentrated sodium hypochlorite solution. Potassium iodide. Determination of Aqueous Chloride All solutions, except those to be added from burettes, are kept in an ice-bath throughout the analysis. Nitrogen is bubbled via a fine bleed or glass frit for 20 min through the cooled sample solution, which contains 0.5-10 mM total chloride, to displace unhydrolysed chlorine. Aliquots (5 ml) are then analysed for chloride by the addition of silver nitrate solution until one * Present address: Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel. drop causes no further precipitation of silver chloride. Near the end-point three drops of nitric acid are added to ensure complete precipitation , and centrifugation enables the end- point to be clearly distinguished.Separate 5-ml aliquots are analysed for hypochlorous acid by the addition of 10mg of potassium iodide and titration with thiosulphate solution. One drop of starch solution is added just before the end-point to clarify when it has been reached. The difference between the two concentrations thus determined gives the concentration of chloride exclusive of that produced by chlorine hydrolysis. Determination of Hydrogen Chloride For the determination of the hydrogen chloride produced in a reaction in the presence of chlorine, the reaction flask is connected to a Drechsel bottle containing 100ml of ice-cold water into which the gas mixture is .passed in a stream of nitrogen at the end of the reaction.The solution is then analysed as described under Determination of Aqueous Chloride. Analysis of Sodium Chloride Test Solutions Five solutions of between 1 and 8 mM of sodium chloride were prepared by dilution of an approximately l O m ~ stock solution. Each of the six solutions was standardised against the standard silver nitrate solution. Chlorine solutions were prepared by the dropwise addition of 3ml of concentrated hydrochloric acid to 5ml of concen- trated sodium hypochlorite solution and the passage of the gas in a stream of air through 50 ml of water cooled in an ice-bath. Volumes of 10 ml of water and of each sodium chloride solution were similarly cooled and made up to 25 ml with ice-cold chlorine solution. The concentration of chlorine was not determined, nor was the same chlorine solution used for all the sodium chloride test solutions. Each mixture was allowed to equilibrate for at least 15 min before analysis, titrations being repeated until three titres consistent to within k0.01 ml were obtained.Results and Discussion A dilute solution of chlorine without extra chloride gave identical concentrations of chloride and hypochlorite (Table l), indicating the validity of the method. After storage for 17 h in an ice-bath a second analysis of the same solution showed 1.6% more chloride than hypochlorite, evidently because of decomposition of 0.8% of the hypochlorous acid. Hence, this decomposition is sufficiently slow at 0 "C not to interfere, but for maximum accuracy solutions should be stored frozen if the analysis cannot be performed within a few hours of the chlorine being present in solution.Another chlorine solution, which was stored for a similar length of time at 4°C after the nitrogen treatment, underwent slightly faster decomposition, as evidenced by a 4% increase in chloride and a corresponding decrease in hypochlorite in the second analysis (without repetition of the nitrogen treatment). Re-attainment of equilibrium by the formation of chlorine,104 ANALYST. JANUARY 1984, VOL. 109 Table 1. Determination of chloride in standardised sodium chloride solutions after the addition of chlorine Total concentration Concentration of Concentration of chloride hypochlorite A-B/ of NaCl*/mM (A)/mM (B)/mM mM Error, % 0 3.71 3.71 0 0.39 4.14 3.73 0.41 5 0.78 4.29 3.54 0.75 4 1.58 5.26 3.67 1.59 0.6 2.39 6.29 3.90 2.39 0 3.16 6.83 3.66 3.17 0.3 3.94 7.23 3.31 3.92 0.5 * Determined before dilution with chlorine solution and corrected - for a dilution factor of 2.5.which would have caused a decrease in chloride concentra- tion, is evidently extremely slow at this temperature and there is ample time to perform the titrations. Other possible reactions of hypochlorous acids do not occur to any significant extent. For example, although its slow disproportionation is accelerated by the presence of silver ions owing to the precipitation of silver chloride ,6 according to the reaction the chloride determination is not affected near 0 “C. Six standardised sodium chloride solutions were each diluted exactly 2.5-fold with a chlorine solution and then analysed.The results are shown in Table 1 and indicate the high accuracy of the method. However, as the result is obtained from the difference of two titres, the percentage error increases as this difference decreases, i.e., when the concentration of chloride due to chlorine is considerably larger than that of the chloride being determined. For each solution three iodimetric titrations gave at least two equal titres, whereas argentimetric titrations were repeated (usually three times after an initial approximate titration) until three titres consistent to within f O . O 1 ml were obtained. Thus a probable maximum error of k0.02 mM is associated with each value of A and of A - B in Table 1, which gives a minimum accuracy for each analysis of approximately double the percentage shown in the final column.An attempt to indicate end-points of the chloride titrations by Mohr’s method with potassium chromate was unsuccessful, the end-points being very indistinct. It has been pointed out that “the sensitivity (of Mohr’s method) varies with the observer and always corresponds to a higher concentration of silver than is theoretically deduced. ”7 Volhard’s method is unsuitable because hypochlorite interferes by reaction with the thiocyanate indicator.* We found that with a little practice, visual judgement of the end-point by the absence of fresh precipitate is easy to perform accurately and is not too tedious. After one titration to obtain an approximate value for the end-point, only one centrifugation near this titre is required in repetitions of the titration. Although a little nitric acid needs to be added to ensure complete precipitation of silver chloride, its effect on the equilibrium is minimised by its addition close to the end-point.However, sample solutions cannot be neutralised to hydrolyse all the chlorine before the 3C10- + 2Ag+ + C103- + 2AgCl titrations because under these conditions re-acidification with nitric acid causes some chlorine to be regenerated, even in cold solutions. Further, in the proposed method no extra acid is required for the oxidation of iodide in the determination of hypochlorous acid. A recent paper,g published since this work was carried out, achieves the analysis of this system by the hydrolysis of all the chlorine at pH8 and the determination of chloride with an ion-selective electrode before and after reduction of the hypochlorous acid with hydrogen per3xide. The authors compare their procedure with “the usual o-tolidine and mercuric thiocyanate method” but give no details or reference for this method.It presumably involves the determination of the total free available chlorine with o-tolidine,“) during which both chlorine and hypochlorous acid are reduced to chloride, and the subsequent determination of total chloride with mercury(I1) thiocyanate. 11 Our method requires no special apparatus and avoids the use of o-tolidine, which is carcino- genic.12 However, if the concentration of chlorine is required as well as that of the additional chloride, one of the alternative methods must be used.Conclusion A simple method has been described for the accurate determination of hydrogen chloride gas or aqueous chloride ions in the presence of chlorine. The support of a studentship from the Science Research Council is acknowledged with gratitude. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Levy, D. P . , “The Oxidation of Organic Compounds with Ruthenium Tetroxide,” PhD Thesis, University of London, 1982, p. 67. Vogel, A. I., “A Textbook of Qualitative Chemical Analysis,’’ Second Edition, Longmans, London, 1941, p. 262. Voge1,’A. I., “A Textbook of Quantitative Inorganic Analy- sis,” Third Edition. Longmans, London, 1961, p. 343. Mellor, J. W., “A Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Supplement 2, Part I, Longmans, London, 1956, p. 547. Kolthoff, I. M., and Belcher, R., “Volumetric Analysis,” Volume 3, Interscience, New York, 1957, p. 573. Charlot, G . , “Qualitative Inorganic Analysis,” Methuen, London, 1954, p. 265. Kolthoff, I. M., and Stenger, V. A., “Volumetric Analysis,” Volume 2, Interscience, New York, 1947, p. 243. Koltoff, I. M., and Stenger, V. A., “Volumetric Analysis,” Volume 2, Interscience, New York, 1947, p. 262. Hori, M., and Kobayashi, Y., Bunseki Kagaku, 1983,32, 75. “Standard Methods for the Examination of Water and Waste- water,” Twelfth Edition, American Public Health Association, New York, 1965, p. 93. Vogel, A. I., “A Textbook of Quantitative Inorganic Analy- sis,” Third Edition, Longmans, London, 1961, p. 809. Searle, C. E., Chem. Brit., 1970,6,5. Paper A31130 Received May l l t h , 1983 Accepted August 19th, 1983

ISSN:0003-2654    

DOI:10.1039/AN9840900103

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANALYST, JANUARY 1984, VOL. 104, 105 BOOK REVIEWS NMR-Spektroskopie. Eiene Einfu hrung in die Pro- tonenresonanz-Spektroskopie und ihre Anwendungen in der Chemie. 2. Verbesserte Auflage Harald Gunther. Pp. xii + 357. Georg Thieme Verlag, Stuttgart. 1983. Price DM59. ISBN 3 13 487502 0. (In German.) ~~ Recent years have seen a steady increase in the chemical uses and in the analytical importance of high-resolution nuclear magnetic resonance (NMR) spectroscopy. In this expanding field, new experimental procedures and fresh developments follow each other in quick succession. Pulsed Fourier trans- form (FT) facilities and superconducting magnet systems, which a decade ago were regarded as exotic technical aids only to be considered in exceptional circumstances, are today in routine use in many analytical laboratories.There was thus a pressing need for revision of the 1973 Edition of this German text-book, written by an experienced spectroscopist at Siegen University. An excellent English translation (“N.M.R. Spec- troscopy,” Wiley , Chichester) of an up-dated and extended version of the original German text appeared in 1980. The first six chapters of the new Edition are virtually the same as those of the 1973 Edition, and provide an informative introduction to the physical basis of continuous-wave proton NMR spectroscopy and to its applications in organic chem- istry; a series of instructional exercises (with answers), selected to help tyros, supplement the text. The three following chapters contain short accounts of, inter a h , relaxation effects, pulsed FT methods, dynamic NMR and lanthanide shift reagent studies, superconducting magnets, double resonance experiments, the nuclear Overhauser effect and NMR imaging.Tables of proton chemical shift and of proton - proton coupling constant values for simple molecules are provided in an Appendix. Unfortunately, the discussion is restricted to proton NMR; the behaviour of other nuclei is, except for comments on heteronuclear coupling and decoupl- ing, not mentioned. This limitation is surprising as the enhanced sensitivity of modern FT methods permits carbon- 13 measurements to be undertaken as freely as those on protons; carbon-13 and proton NMR measurements are complementary and are both of major importance for analytical studies on organic compounds. Such concepts should be presented at an early stage in a course on NMR spectroscopy. In this respect the German Edition differs from the English translation, which contains additional information on practical aspects of FT NMR and has a chapter on carbon-13 and fluorine-19 NMR spectroscopy.The present soft-cover volume is well produced and has clear tables and figures; it offers German-speaking students a sound introduction to basic proton NMR spectroscopy. English-speaking students should, however, opt for the 1980 English translation, which although slightly dated, does have a broader multi-nuclear approach. J . E. Page Soil Analysis. Instrumental Techniques and Related Procedures Edited by Keith A. Smith. Books in Soils and the Environment. Pp. xii + 562.Marcel Dekker. 1983. Price SWFr198. ISBN 0 8247 1844 5. This book is, without doubt, an excellent publication that provides a wealth of information for those concerned with soil analysis. The title of the book is perhaps a little misleading; at first glance it appears to be a general text on soil analysis, but a better title would have been “Instrumental Techniques in Soil Analysis. ” Most of the instrumental techniques that are now in regular use in research institutes, service laboratories and universities are dealt with in the text. A few of them, for example neutron activation and X-ray fluorescence spectrometry, are not so widely used but few laboratories will be without some of the instrumental facilities discussed in the book. The full list of techniques covered, in addition to the two above, includes atomic absorption, flame photometry, automated colori- metry, combustion techniques, radioisotope techniques, gas and high-performance liquid chromatography and ion- selective electrodes.Both optical emission and mass spectro- metry are described for nitrogen isotope measurements. In books of this nature one can generally think of omissions; in this instance inductively coupled plasma spectrometry and ion analysers might have been considered, but the line has to be drawn somewhere. The first half of each chapter presents the theoretical background, which in most instances is easy to digest. This is followed by a section dealing with applications of the technique, occasionally with practical hints. The information on applications gives it added value in comparison with many other instrumental review books, which are often little more than a collection of manufacturers’ notes about particular techniques. The reference lists are in general extensive, although some are more up-to-date than others.Although the standard is uniformly high, some sections stand out as being particularly informative and well written. The ones dealing with continuous-flow and discrete analysis and mass spectrometry appealed to me-this may be because I am interested in these topics at present. One or two chapters appear to be related to specific instruments rather than the subject in general, but this may be due to a lack of competing instruments. Most of the authors involved in this work are well known in their field; indeed, in some instances they are recognised as leading authorities in their subject.This must add weight to the importance of the book. It will find wide acceptance as a reference book and because of the way it is written it will appeal both to students and to experienced soil researchers. It is always difficult to edit a book when one is dealing with prominent contributors. It is therefore to the credit of Keith Smith that he has been able to maintain a reasonably uniform format and presentation. It also appears to be fairly free from mistakes and typing errors. All in all this is a book that must be strongly recommended. S. E. Allen Atomic Absorption Spectrometry Edited by John Edward Cantle. Techniques and Instru- mentation in Analytical Chemistry, Volume 5.Pp. xvi + 448. Elsevier. 1982. Price $97.75; Df1210. ISBN 0 444 42015 0 (Volume 5); 0 444 41744 3 (Series). Atomic-absorption spectrometry text-books have appeared at regular intervals over the past decade as the popularity and widespread applications of the technique have increased. This particular contribution is different from most AAS books in that it is primarily intended as a methods manual. Only essential background information on instrumentation and theory is included. The bulk of the text is devoted to a detailed consideration of the various areas where atomic-absorption spectrometry is currently applied.106 ANALYST, JANUARY 1984, VOL. 109 There are individual chapters on waters and effluents, marine chemistry, airborne particles, foodstuffs, ferrous metals, non-ferrous metals, geochemistry, petrochemicals, glasses and ceramics, clinical chemistry (two chapters), forensic science and chemicals, each compiled by experts on the subject.The format of the chapters is similar. Most authors begin by indicating the significance of AAS in their particular subject area, and then provide details of the elements usually determined, normal concentration ranges, sample preparation requirements and recommended pro- cedures that, in principle, can be directly applied by the reader. A considerable amount of information is presented in tabular form for easy access. Unfortunately, as often happens with multi-author texts, the contributions vary somewhat in standard and detail. The chapters on the analysis of foodstuffs, clinical samples (separate contributions for flame and elec- trothermal applications) and chemicals are excellent. The authors have clearly taken great care to provide texts with as much practical information as possible, and the reference lists in particular are to be commended.Similarly, the chapters on waters and effluents and marine samples are valuable contri- butions, containing pertinent advice on the collection and storage of samples and on pre-concentration procedures. In contrast, the sections on ceramics, non-ferrous metals and applied geology are rather limited, although the last gives useful information on decomposition procedures for rocks and soils. It appears that many of the chapters were prepared 3 or 4 years ago, as the reference lists cover publications only up to 1979/80.Consequently, recent developments on ETA appli- cations are not included, but this does not seriously impair the significance of Dr. Cantle’s book, as most AAS analyses involve flame atomisation. As a reference text, this book should find a place in every technical library. It is clearly aimed at the instrumentalist with interests in a wide range of application areas. However, any specialists considering this text should probably check the contents of the chapters on their subjects before purchase to avoid disappointment. D. Littlejohn Biological Magnetic Resonance. Volume 4. Edited by Lawrence J. Berliner and Jacques Reuben. Pp. xx + 340. Plenum. 1982. Price $42.50. ISBN 0 306 40968 2. This volume continues the valuable tradition of previous volumes in the series and provides authoritative surveys of four areas of biochemistry that emphasise the enormous usefulness of magnetic resonance methods.Although these methods (i.e., NMR and ESR) have led to great advances in our qualitative understanding of form and function in many areas of biochemistry, perhaps of even greater significance is the extent to which they have engendered an analytical approach to problems for which earlier techniques were of little value. An excellent example of this quantitative approach is the use of the NMR active nucleus in the 113Cd ion as a substitute for calcium, magnesium, copper or natural cadmium ions. With this substitution NMR methods can be used to probe directly the role of the metal ion in such enzymes as alkaline phosphatase and metallothionein.This work, and other studies with 113Cd have been surveyed in detail by Armitage and Otvos, pioneers in the development of biochemical applications of this nuclide. Many workers are familiar with the use of spin labelling techniques in physical studies of natural and synthetic membranes. However, they will welcome this timely review by Butterfield of one of the newer areas of application of spin labelling, the investigation of disease. At present the bulk of such work concerns two disorders, Huntington’s disease and muscular dystrophy, where membrane dysfunction is strongly implicated. However, erythrocyte membrane defects may be indicated in other diseases and all recent investigations are critically assessed.It is also emphasised that great care is necessary to evaluate properly ESR studies of this type. Without a properly designed protocol and a valid statistical analysis, spin labelling work can produce results of question- able validity. Chemically induced dynamic nuclear polarisation (CIDNP) has intrigued physical organic chemists for many years. The intensity enhancement of NMR lines by radical recombination provides mechanistic information in organic chemistry, but when combined with laser photochemistry it becomes an elegant new method of probing the surface structure of proteins. Kaptein pioneered this technique and he has given a clear exposition of the theory, practice and results in this new field. Although this technique is only accessible to a few workers and is never likely to be widely available, this chapter is nonetheless essential reading for all interested in protein conformation.The final chapter is an exhaustive examination by Perkins of the application of ring current calculations to the study of proteins. This is a superb article, which highlights the amazing detail that can be deduced about the structure of proteins, such as lysozyme and cytochrome c, from examination of the agreement between experimental shifts and calculated shifts (computer listings are included). This well produced volume is essential reading for bio- chemists who are already convinced of the value of magnetic resonance methods and salutary reading for any who might not be. D. F. Ewing Chemistry John S. Clarke.Teach Yourself Books. Pp. viii + 192. HoddertkStoughton. 1983. Pricef2.50. ISBN 0340275839. This paperback is aimed at those studying chemistry at an elementary level and at those who, in later life, wish to gain some appreciation of the subject as a whole. On the whole the book proves to be rather a disappointment and, despite the publisher’s blurb to the contrary, could easily have been entitled “A Companion to 0-level Chemistry.” It gets nowhere as near achieving its aims as does, say, Hutton’s “Chemistry-The Conquest of Materials” (Pelican, 1969) or Rossotti’s “Introducing Chemistry” (Pelican, 1975). The author avoids any definition of what chemistry is and his opening three chapters concern earth, air and water, giving the vague impression that chemistry is something to do with geology or geography.Also, the firm impression is given that chemicals are nasty materials with which industrialists pollute the environment. The language used is far from simple and will surely discourage the lay reader. On page 8, for example, terms such as “polymorphism” and “enantiotropic” are introduced and on page 9 the mysterious jargon “AH = -2 815 kJ/mole” appears. Atomic theory is introduced within a historical framework, as is the Periodic Table, an approach that seems inappropriate in a book supposedly reflecting “modern trends in theory.” We first hear about analysis in the section on acids and bases; “sodium hydroxide and aqueous ammonia (sometimes called ammonium hydroxide) are often used in analysis.” The coverage of analytical chemistry is at about this level, although there are more mentions of the topic than the index wouldANALYST, JANUARY 1984, VOL.109 107 suggest. Types of reaction are then discussed and it is not until about a third of the way through the book that some everyday chemicals are introduced: coal, coke, photographic emulsion, dyes. Unfortunately, the section on colour, potentially one of the most interesting, contains an error: we are told, “The colour that an object appears to be by reflection, or transmittance, is the colour of the light it absorbs and then emits; light of other colours is absorbed only. Copper sulphate-5-water crystals are blue because they absorb and then emit light of the wavelength blue.’’ Chemical formulae are not discussed, so suddenly coming across the structural formula for hydroquinone on page 83 must be a bit unnerving to the uninitiated.The remaining chapters deal with “metals,” “non-metals,” “some important inorganic compounds,” “fundamental organic chemistry,” “our food” and “building for tomorrow.” The last chapter, consisting of only two pages, would have been much better placed, suitably expanded, right at the beginning of the book. These are by far the best in the book and it just becomes possible to discern the role that chemistry plays in our everyday lives and to get some idea of what some chemists actually do. The book concludes with a short appendix of “units” and an explanation of “accuracy,” which turns out to be “precision.” J . F. Tyson Asbestos. Properties, Applications and Hazards, Volume 2 Edited by S.S. Chissick and R. Derricott. Pp. xiv + 652. Wiley. 1983. Price €39.75. ISBN 0 471 10489 2. This volume continues the style and approach of Volume 1, which was reviewed in 1979 (Chissick was also one of the Editors of that volume). It is a compilation of chapters by various hands, each of which has its own contents page and references, and conveys the general impression of symposium papers rather than the treatise that the over-all title might suggest. Although they figure in the titles of both Volumes 1 and 2, the “applications” of asbestos are not covered systematically in either book. In their Preface the Editors write that a review of Volume 1 criticised their deliberate avoidance of contact with the asbestos industry and its opponents, and they say that in Volume 2 they have gone some way towards meeting this criticism.The book therefore opens with a chapter by W. Penney under the title “Asbestos in Society,” and this is followed by N. Tait on the role of SPAID (The Society for the Prevention of Asbestosis and Industrial Diseases). The following chapter, by W. Simpson, describes the role of the Health and Safety Executive, and this is followed by two that contain rather more on the subject of analytical chemi- stry-J. E. Chisholm on the transmission electron micro- scopy of asbestos and J. Prentice on the monitoring of the atmosphere for respirable asbestos fibres with respect to work on asbestos insulations. D. T. Chambers then gives a review of the development of control of dust, from 1970 to 1980, and, in the first of three chapters by this Editor, S.S. Chissick reviews personal protection in this field (his other chapters cover a “case study” of fire insulation comprising blue asbestos, and a compendium of information about asbestos drawn from various countries- which comprises more than half the volume). There is also a further chapter on asbestos-related disease- “Part 6: The Treatment of Malignant Mesotheliomas,” by K. S. Bragman (the other five parts were covered by various authors in Volume 1). It should perhaps be noted that some of the information given in the compendium is now out of date, and there is a reference in the Editors’ Introduction to the more recent changes in threshold limit values and other possible changes in legislation to come.The subject of the book has become emotive and it would now be difficult if not perhaps impossible to write about it without controversy. However, if one excludes from this volume the lengthy sections dealing with medical matters, legislation, etc., rather little remains that is of direct use to the analytical chemist. The chapter on electron microscopy, in particular, is useful, but for the analyst a few chapters from Volume 1, together with this and some details of monitoring the atmosphere, could have made a single volume that may well have been more helpful-especially in view of the extent to which the analytical chemist may now be occupied in this field. D. Simpson Scheme for the Examination of Foreign Material Con- taminants in Foods P.R. Smith. Pp. iv + 33. Leatherhead Food Research Association. Price €18 (non-members). This book is a slim paperback volume in the format of the well known Technical Reports issued by the Food R.A. The text is clear in definition and is well presented on quality paper. The author has collected together a substantial literature and has succinctly summarised the topic. The context of the title and limitation of the survey to exclude molecular size taints and residues is explained fully. In the introductory section, attention is drawn to the importance of microscopy in screening foods for evidence of contamination. A survey of recent statistics on contamination, types of material found in food and the sources of the material are tabulated. Attention is also drawn to common defects that appear to the uninitiated as evidence.of contamination. The classical examples of “glassy” crystals of calcium phosphate and struvite found in cheese and canned fish, respectively, are two examples of these “natural” defects. The systematic approach to laboratory documentation and examination procedures that is advocated in the book is a model to be followed by students at large. A number of addresses (not an exhaustive list) of relevant advisory services are given together with about 60 references. Space is given for margin annotation and for additional notes. On the whole the book gives good value for money with respect to content, although at El8 it may be regarded by the student as expensive. R. Sawyer Ion Formation from Organic Solids.Proceedings of the Second International Conference, Munster, Fed. Rep. of Germany, September 7-9,1982 Edited by A. Benninghoven. Springer Series in Chemical Physics, Volume 25. Pp. x + 269. Springer-Verlag. 1983. Price DM69; $29.80. ISBN 3 540 12244 3; 0 387 12244 3. The extension of mass spectrometric analysis to the whole range of involatile organic compounds that are otherwise inaccessible using conventional sources is the real theme of this apparently rather specialised conference topic. People outside the field giving a passing glance at the title and summary could miss its significance. The organisers and publishers have done well to bring out the proceedings of such a recent conference in permanent108 ANALYST, JANUARY 1984. VOL. 109 book form in less than a year.The variation in font that is the natural outcome of using photoprocessed typescript is a very small penalty to pay and, unlike some such texts, the general standard of presentation and proof-reading is exceptionally high. The figures are not too wildly variable in style and format, though with some of the detail involved many would have benefitted by suffering somewhat less reduction in scale for reproduction. The fact that this is a rapidly changing field is all too clear when one reads that most of the techniques described have been discovered since 1974 and some as recently as 1981. The questions for the reviewer, then, are how much is this a book for the specialist who will be interested in any case, and how much will it appeal to the general reader? The book contains seven review papers (not six as the introduction claims), which provide a stimulating overview of the surprising range of projectiles that have been hurled at innocent samples with observations and speculation on the mechanisms involved in their disintegration (a contributed paper even looks at dust particles). As reviews for the non-specialist there is a certain lack of elementary information on the system design and basic performance parameters.There is no direct inter-comparison of the different techniques, but the competition between them is probably at too early a stage for such a comparative treatment to be attempted as yet. The reviews are clearly authoritative, but in some of them I was a little uneasy when I observed how many of them seemed to be following a common trend, a reference list quoting the author or his team almost to the exclusion of anyone else.For those with a nose for controversy, the debate on the role of neutral atoms or ions for fast atom bombardment is touched on in both the reviews and the contributed papers. Otherwise, the contributed papers hold more for those directly involved in the technique or biological and medical applications. In conclusion, the book is certainly worth a place on the library shelf for anyone interested in recent developments in organic analysis and is an excellent source book for anyone who may be considering applying these techniques. E. J . Millett Practice of Thin Layer Chromatography. Second Edition Joseph C. Touchstone and Murrell F.Dobbins. Pp. xxiv + 405. Wiley-lnterscience. 1983. Price €38. ISBN 0 471 09766 7. This is a good book, presenting much of that which has appeared in various other books previously. The impact of HPLC on chromatography has reduced the importance of TLC, and whilst there still is an important place for TLC in the battery of techniques that any analyst must possess, much of the published work is “filling in holes,” not really advancing the scope of the technique or its philosophy. There are relatively very few references in the last 5 years. Nonetheless, this book does present some new material in a very useful way; the chapters dealing with high-performance TLC and the combination of TLC and other analytical techniques are refreshingly presented. These chapters make the book a worthwhile purchase.L. S . Bark Wilson and Wilson’s Comprehensive Analytical Chemistry. Volume XVII. Gas and Liquid Analyzers (English translation of Second Czech Edition). J. Vaha. Pp. xxxii + 742. Elsevier. 1982. Price $170.25; Df1400. ISBN 044499691 (VolumeXVII); 044441735 5 (Series). This weighty volume aims to survey automatic gas and liquid analysers. The Czech Edition, of which it is a translation, seems not to have been given a date, but a glance at the references suggests that it is not recent. The chapter on chromatography, for example, has no references later than 1977. The result is that, for this reviewer, the book seems entirely out of date. Most of the instruments described are either from Eastern Europe, or unavailable through sheer antiquity and many familiar techniques are just not described at all. Modern HPLC is hardly touched upon and flow injection analysis, for example, is not mentioned at all. The book also describes many portable analysers for the determi- nation of gases. These chapters include many devices that would hardly be described as automatic, despite the emphasis on automation in the preface. Again, there is a general air of d4h vu, and some obvious omissions-here it is the very sensitive and convenient chemiluminescence systems that have escaped the author’s attention. There are introductory descriptions of the principles of the various physico-chemical techniques employed, but these seem to suffer from the same faults as the applied sections. For example, instruments for measuring gas densities are repeat- edly referred to as densitometers, and the section on fluorescence states that guanine sulphate (presumably it should be quinine!) can be detected at levels of 10-‘) g ml-1, whereas 10-12 g ml-1 would be a better estimate. The book is beautifully produced (over 750 pages of heavy, glossy paper, giving a weight of 1.7 kg), but that is about the only point in its favour. It covers a curious mixture of topics (one chapter is entitled, with more than a hint of desperation, “Various Indicators and Detectors”) and in a rather unsatis- factory way. Perhaps the truth is that the speed of develop- ment of scientific research, and the adoption of new communi- cation techniques, have made the mammoth multi-volume series, of which this book is a part, redundant. At a price of well over &loo, only a sleepy librarian will buy this volume, and that is probably just as well. J . N . Miller

ISSN:0003-2654    

DOI:10.1039/AN9840900105

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

108 ANALYST, JANUARY 1984. VOL. 109 ERRATUM Simultaneous Determination of Choline and Betaine in Some Fish Materials Sara E. Valdes Martinez Analyst, 7983,108, 7 7 7 4 - 7 7 79 The author’s name should be as given above, and not Sana E. Valdes Martinez.

ISSN:0003-2654    

DOI:10.1039/AN9840900108

出版商:RSC    

年代:1984

数据来源: RSC

摘要:

ANALYST. JANUARY 1984, VOL. 109 109 INSTRUCTIONS TO AUTHORS The Analyst publishes papers on all aspects of the theory and practice of analytical chemistry, fundamental and applied, inorganic and organic, including chemical, physical and biological methods. Papers may be submitted for publication by members of The Royal Society of Chemistry or by non-members. There is no page charge for papers published in The Analyst. The following types of papers will be considered. Full papers, describing original work. Short papers, also describing original work, but shorter and of limited breadth of subject matter; there will be no difference in the quality of the work described in full and short papers. Communications, which must be on an urgent matter and be of obvious scientific importance.Rapidity of publication is enhanced if diagrams are omitted, but tables and formulae can be included. Communications should not be simple claims for priority: this facility for rapid publication is intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subsequently, if justified by later work. Reviews, which must be a critical evaluation of the existing state of knowledge on a particular facet of analytical chem- istry. Every paper (except Communications) will be submitted to at least two referees, by whose advice the Editorial Board of The Analyst will be guided as to its acceptance or rejection. Papers that are accepted must not be published elsewhere except by permission.Submission of a manuscript will be regarded as an undertaking that the same material is not being considered for publication by another journal. Copyright. The whole of the literary matter (including tables, figures, diagrams and photographs) in The Analyst is copyright and may not be reproduced without permission from the Society or such other owner of the copyright as may be indicated. Regional Advisory Editors. For the benefit of potential contributors outside the United Kingdom, a Panel of Regional Advisory Editors exists. Requests for help or advice on any matter related to the preparation of papers and their submission for publication in The Analyst can be sent to the nearest member of the Panel. Currently serving Regional Advisory Editors are listed in each issue of The Analyst.Manuscripts. Papers should be typewritten in double spacing on one side only of the paper. Three copies of text and illustrations should be sent to the Editor, The Analyst, The Royal Society of Chemistry, Burlington House, London, W1V OBN, and a further copy retained by the author. Proofs. The address to which proofs are to be sent should accompany the paper. Proofs should be carefully checked and returned immediately (by Air Mail from outside Europe). Reprints. Fifty reprints of each paper are supplied free on request. Additional reprints can be purchased if ordered at the time of publication. Details are sent to authors with the proofs. Notes on the Writing of Papers for The Analyst Manuscripts should be in accordance with the style and usage shown in recent copies of The Analyst.Conciseness of expression should be aimed at: clarity is increased by adopting a logical order of presentation, with suitable paragraph or section headings. To facilitate abstracting and indexing by Chemical Abstracts Service, and other abstracting organisations, it would be helpful if at least one forename could be included with each author's family name. Descriptions of new methods should be supported by ex- perimental results showing accuracy, precision and selectivity. The recommended order of presentation is as indicated below: Title. This should be as brief as is consistent with an adequate indication of the original features of the work. The analytical method used in the work should be mentioned in the title.Synopsis. A synopsis of about 100 words, giving the salient features and drawing attention to the novel aspects, should be provided. Keywords. Up to 5 keywords, indicating the topics of importance in the work described, should be included after the synopsis. Aim of investigation. An introductory statement of the object of the investigation with any essential historical background, followed, if necessary, by a brief account of preliminary experimental work. Description of the experimental procedures. Working details must be given concisely. Analytical procedures should preferably be given in the form of instructions; well known operations should not be described in detail. Results. These are best presented in tabular form, followed by any statistical evaluation, which should be in accordance with accepted practice.Discussion of results. This section will comment on the scope of the method and its validity, followed by a statement of any conclusions drawn from the work. Nomenclature. Current internationally recognised (IUPAC) chemical nomenclature should be used. Common trivial names may be used, but should first be defined in terms of IUPAC nomenclature. SZ units. The SI system of units should be used. These units are summarised in the Appendix. The effect on current style of papers for The Analyst includes the following: dimensions should preferably be given in metres (m) or in millimetres (mm); temperatures should be expressed in K or "C (not O F ) ; wavelengths should be expressed in nanometres (nm) frequency should be expressed in Hz (or kHz, etc.), not in c/s or c.P.s.; rotational frequency can be denoted by use of s-l; radionuclide activity will be expressed in becquerels (Bq) or curies (Ci); 1 Ci = 3.7 x 101° Bq; the micron (p) will not be used; 10-6 m will be 1 pm.(not mv);110 ANALYST, JANUARY 1984, VOL. 109 Abbreviations. SI units should be used. Normality and molarity are generally expressed as decimal fractions (e.g., 0.02 N, 0.375 M). Abbreviational full stops are omitted after the common contractions of metric units (e.g., ml, g, pg, mm) and other units represented by symbols. Abbreviations other than those of recognised units should be avoided in the text. Percentage concentrations of solutions should be stated in internationally recognised terms.Thus the symbols “m” for mass and “V” for volume are to be used instead of “w” for weight and “v” for volume. The following show the manner of expressing these percentages together with an acceptable alternative given in parentheses: YO m/m (g per 100 g); YO m/V (g per 100 ml); YO V/V. Further implications of the use of the term “mass” are that “relative atomic mass” of an element (A,) replaces atomic weight, and “relative molecular mass” of a substance (M,) replaces molecular weight. Concentrations of solutions of the common acids are often conveniently given as dilutions of the concentrated acids, such as “dilute hydrochloric acid (1 + 4) ,” which signifies 1 volume of the concentrated acid mixed with 4 volumes of water. This avoids the ambiguity of 1 : 4, which might represent either 1 + 4 or 1 + 3.Dilutions of other solutions can be expressed in a similar manner. Tables and diagrams. The number of tables should be kept to a minimum. Column headings should be brief. Tables consisting of only two columns can often be arranged horizontally. Tables must be supplied with titles and be so set out as to be understandable without reference to the text. Either tables or graphs may be used but not both for the same set of results, unless important additional information is given by so doing. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation or statement in the text. The style used in headings to tables and in labels on the axes of graphs, where the numbers represent numerical values, is, for example: Volume/ml.The diagonal lines (solidus) will not be used to represent “per.” In accordance with the SI system, units such as grams per millilitre are already expressed in the form g ml-1. For a table (or graph), this would appear as: Concentration of solution/g ml-1. It should be noted that the “combined” unit, g ml-1, must not have any “intrusive” numbers. To express concentration in grams per 100 milli- litres, the word “per” will still be required: Concentratiodg per 100 ml. It may be preferable for an author to express concentrations in grams per litre (g 1-1) rather than grams per 100 ml. Most diagrams will be retraced and lettered in order to achieve uniform line thicknesses and lettering size and style, so it is not essential to prepare specially traced drawings. However, all diagrams should be carefully and clearly drawn on good quality paper and should be clearly lettered.If possible, complicated flow charts, circuit diagrams, etc., should be supplied as artwork for direct reproduction in order to avoid time-consuming and expensive redrawing. Three sets of illustrations should be provided, two sets of which may be made by any convenient copying process for transmission to the referees. All diagrams should be accompanied by a separately typed set of captions. Wherever possible, extensive identifying lettering should be placed in the caption rather than on lines on graphs, etc. Photographs. Photographs should be submitted only if they convey essential information that cannot be shown in any other way.They should be submitted as glossy or matt prints made to give the maximum detail. Colour photographs will be accepted only when a black-and-white photograph fails to show some vital feature and can be supplied either as prints or transparencies. References. References should be numbered serially in the text by means of superscript figures, e.g., Foote and Delves,’ Burns et a1.2 or Hirozawa,3 and collected in numerical order under “References” at the end of the paper. They should be listed, with the authors’ initials, in the following form (double-spaced typing) : 1. 2. 3. Foote, J. W., and Delves, H. T., Analyst, 1983, 108, 492. Burns, D. T., Glocking, F., and Harriott, M., J . Chromatogr., 1980, 200, 305. Hirozawa, S.T., in Kolthoff, I. M., and Elving, P. J., Editors, “Treatise on Analytical Chemistry,’’ Part 11, Volume 14, Wiley, New York, 1971, p. 23. Journal titles should be abbreviated according to the Chemical Abstracts Service Source Index (CASSI). For books, the edition (if not the first), the publisher and the place and date of publication should be given, followed by the page number. Authors must, in their own interest, check their lists of references against the original papers; second-hand references are a frequent source of error. The number of references must be kept to a minimum. Appendix The SI System of Units In the SI system there are seven base units- Physical quantity length mass time electric current thermodynamic temperature amount of substance luminous intensity Name of unit metre kilogram second ampere kelvin mole candela Symbol for unit m kg S A K mol cdANALYST, JANUARY 1984, VOL.109 111 There are two supplementary dimensionless units for plane angle (radian, rad) and solid angle (steradian, sr). Some derived SI units that have special names are as follows- Physical quantity energy force power quantity of electricity electric potential difference electric resistance electric capacitance frequency magnetic flux density radionuclide activity (magnetic induction) Examples of other derived SI units are- Physical quantity Name Symbol of unit for unit joule newton watt coulomb volt ohm farad hertz tesla becquerel J N W C V 52 F Hz SI unit area square metre volume cubic metre density kilogram per cubic metre velocity metre per second angular velocity radian per second acceleration metre per second squared magnetic field strength ampere per metre kg s-2 A-1 S-1 Symbol for unit m2 m3 kg m-3 m s-1 rad 5-1 m s-2 A m-1 Certain units will be allowed in conjunction with the SI system, e.g.- Physical quantity Name Symbol Definition of unit for unit of unit volume litre 1 10-3 m3 = dm3 magnetic flux density radionuclide activity curie Ci 3.7 x 1010Bq energy electronvolt eV 1.6021 x 1O-lYJ (magnetic induction) gauss G 10-4 T temperature, t degree Celsius "C tl"C = TIK - 273.16 The common units of time (e.g., minute, hour, day) and the angular degree (") will continue to be used in appropriate contexts. Decimal multiples and submultiples have the following names and symbols (for use as prefixes)- 10-3 milli m 10-6 micro v 10-9 nano n 10-12 pic0 P 103 kilo k 106 mega M 109 giga G 1012 tera T 1015 peta P 10'8 exa E Compound prefixes (e.g., mpm) should not be used; 10-9 m = 1 nm.

ISSN:0003-2654    

DOI:10.1039/AN9840900109

出版商:RSC    

年代:1984

数据来源: RSC