摘要:

ANALYST, JUNE 1991, VOL. 116 653 Kinetic Determination of Iodide in Pharmaceutical and Food Samples Ma. Soledad Garcia, Concepcion Sanchez-Pedreiio," Ma. Isabel Albero and Catalina Sanchez Department of Analytical Chemistry, Faculty of Sciences, University of Murcia, Murcia, Spain A kinetic method for the determination of iodide based on its inhibitory effect on the Pd" catalysed reaction between ethylenediaminetetraacetic acid (EDTA)-Co"' and the hypophosphite ion is described. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance at 540 nm. Under the optimum experimental conditions of 2.6 x 10-3 rnol dm-3 Co"'-EDTA, 0.4 rnol dm-3 H2P02-, pH 3.2 (adjusted with Britton-Robinson buffer), 0.57 pg ml-1 Pd" and 20 k 0.2 "C, iodide was determined in the range 2-28 ng ml-1.The method was applied to the determination of iodide in pharmaceutical products, iodinated salts, cow's milk and infants' powdered milk. Keywords: Kinetic determination; iodide; palladium (Ir)-eth ylenediaminetetraacetic acid-cobaIt(iix)-h ypo- phosphite; pharmaceutical and food samples In an earlier paper,' the Pd" catalysed reduction of the ColIt- ethylenediaminetetraacetic acid (EDTA) complex by hypo- phosphite was reported and this led to the proposal of a new kinetic method for the determination of palladium. It was also found that some species exert a strong inhibitory effect on this catalysed system. As a result, sensitive kinetic methods for the determination of Hg", cysteine, N-acetylcysteine and cystine were developed.2.3 The present paper reports on the modifying effect of iodide on the Pd" catalysed reaction between Co"'-EDTA and the hypophosphite ion.Iodide, which does not act by itself on the reduction of Co"'-EDTA by H2P02-, does inhibit the catalysed reaction, the rate of which was observed to decrease in proportion to the concentration of iodide present. The principal uses of iodide are in photography, and in pharmaceuticals because of its effectiveness as an expector- ant. In trace amounts, iodide is important to animal and plant life. In recent years, there has been an increase in interest in the determination of iodide in foods because of the advantages of including iodide in the human diet. The use of iodinated salt in the diet is the most frequent way of obtaining an additional supply of iodide, which is metabolized in the thyroid for the synthesis of hormones.An absence of iodide in the diet produces several diseases with known clinical symptoms. Current techniques used for the determination of trace amounts of iodide include activation and catalytic methods. Most catalytic methods use the CetV-Asl'' reaction.614 Other reactions catalysed and inhibited by iodide have also been described. 15-26 In this paper a kinetic method for the determination of iodide based on its inhibitory effect on the H2P02--(Co1"- EDTA)-Pd" system is presented. The procedure has been successfully applied to the determination of iodide in phar- maceutical preparations, iodinated salts and milks. Experimental Apparatus Absorbance versus time (A-t) graphs were recorded on a Perkin-Elmer 550 SE dual-beam spectrophotometer with 1 cm cells, kept at constant temperature by means of a Colora Minicryostat M2 111.A Radiometer pH M63 pH meter was used for measurements. A Hanam muffle furnace (W. C. Heraeus) and an ultrasonic bath (Bransonic B5, 55KHz, 14 W), were also used. * To whom correspondence should be addressed. Reagents All chemicals were of analytical-reagent grade. Doubly distilled water was used throughout. Cobalt"'-EDTA, 0.04 mol dm-3. Exactly 50ml of 0.1 mol dm-3 cobalt(I1) nitrate (Merck) and 50 ml of 0.1 mol dm-3 Na2H2EDTA (Merck) were pipetted into a 250 ml beaker. Dipotassium peroxodisulphate (3 g, Merck) was then added and the solution adjusted to pH 6 with ammonia solution (1 + 1, v/v, d = 0.88) and boiled gently for about 20 min in order to decompose the excess of peroxodisulphate .27 The solution was made up to volume with doubly distilled water in a 125 ml calibrated flask.Sodium hypophosphite (Probus), 3 mol dm-3. Prepared each week and stored in a dark bottle. Palladium dichloride (Merck), 5 X 10-3 rnol dm-3. Pre- pared in 0.2 mol dm-3 HCI. Standard iodide solution, 1 g 1 - 1 . Prepared by dissolving 0.1308 g of potassium iodide (Merck) (dried at 105 "C for 2 h) in doubly distilled water and diluted to 100 ml in a calibrated flask. Working solutions were prepared daily by suitable dilution with doubly distilled water. Britton-Robinson buffer, p H 3.2. Working solutions of lower concentrations were prepared by appropriate dilution prior to use.General Procedure A 0.2 ml volume of 0.04 mol dm-3 Co"'-EDTA, 1.0 ml of Britton-Robinson buffer and 0.3 ml of 5 X 10-5 mol dm-3 PdC12, in that order, were placed in the spectrophotometric cells and appropriate volumes of the iodide standard solution were added to give a final iodide concentration of between 2 and 28 ng ml-1. The solutions were then diluted to 2.6 ml with distilled water and the cells placed in a thermostated bath at 20 -+_ 0.2 "C for 10 min. A 0.4 ml volume of 3 mol dm-3 sodium hypophosphite was then added to the test cell and the spectrophotometer recorder was started. The solution was shaken, the cell placed in the spectrophotometer and the A-t curve recorded at 540nm in order to obtain the slope (tg a) from the initial linear portions of these graphs, and to obtain the calibration graph by plotting tg a versus iodide concentra- tion.The cells were cleaned after use by immersion in 1 + 1 nitric acid for 15 min in order to remove any traces of Pd adsorbed on their walls. Determination of Iodide in Authentic Samples Pharmaceutical samples No sample pre-treatment was needed for these analyses apart from an appropriate dilution of the sample to obtain a654 ANALYST, JUNE 1991, VOL. 116 concentration level that was within the linear working range of the calibration graph. Diluted samples were treated as described under General Procedure. Common iodinated salt Iodinated salt (0.2 g) was accurately weighed, dissolved in doubly distilled water and diluted to volume in a 100 ml calibrated flask. Iodide was determined in a 0.4 ml or 0.2 ml aliquot, according to the General Procedure, but using a calibration graph constructed for iodide in the presence of the same amount of chloride as in the sample.The chloride was added in the form of sodium chloride solution prepared by the reaction of iodide-free hydrochloric acid and sodium hydroxide. Cow's milk The samples required alkaline ashin@-28 prior to the final determination of iodide. This treatment was performed in a Pyrex tube (160 x 25 mm) as follows. Approximately 1 g of milk was accurately weighed and mixed with 1 ml of 4 mol dm-3 potassium hydroxide solution. After drying at 105 "C for 20 h, the sample was heated at 150 "C for 30 min and at 600°C for a further 1 h. The ash was dissolved in 10 ml of boiling water by means of an ultrasonic bath and the solution was centrifuged at 2500g for 15min.An aliquot of the supernatant liquid (2 ml) was taken, the pH was adjusted to between 4 and 5 with nitric acid (1 + 5) and the mixture was diluted in a 10 ml calibrated flask with doubly distilled water. A 1 ml aliquot was used for the determination of iodide as described under General Procedure. Infants' powdered milk Approximately 5 g of powdered milk were accurately weighed, mixed with 10 g of doubly distilled water and shaken until totally homogenized. Approximately 1 g of the previ- ously prepared mixture was accurately weighed and mixed with 1 ml of 4 mol dm-3 potassium hydroxide solution. The same procedure as described for cow's milk was followed. Results and Discussion Previous work demonstrated that over a wide pH range hypophosphite does not reduce CoIII-EDTA at an appreciable rate, but that Pd" is a sensitive catalyst for this process.It was found that iodide had no effect on the H2P02--(Co111-EDTA) system. On the other hand, it has a strong inhibitory effect on the PdlI catalysed reaction. For a given fixed amount of Pd" present in the medium, the rate of the inhibited process is proportional to the concentration of iodide. The process is monitored spectrophotometrically at 540 nm by measuring the decrease in the absorbance of the ColI1- 0.4 - I 0 1 2 Time/min Fig. 1 Absorbance-time curves. Conditions: Co"'-EDTA, 2.6 x 10-3 mol dm-3; H2P02-, 0.4 rnol dm-3; pH, 3.2; Pd", 0.57 pg ml-1; and temperature, 20 k 0.2 "C. Iodide concentration: 1,O; 2,2; 3,6; 4, 11; 5 , 16; 6, 21; 7, 25; and 8, 29 ng ml-1 EDTA.The slope of the A-t graph was used as a measure of the reaction rate. Fig. 1 shows A-t graphs corresponding to mixtures at pH 3.2 with concentrations of 2.6 X 10-3 mol dm-3 Co"'-EDTA; 0.4 mol dm-3 H,POZ-; 0.57 pg ml-1 of PdlI and up to 29 ng ml-1 of iodide. As can be seen the rate of the process decreases with an increase in the concentration of iodide even at very low concentrations of this ion. Effect of Reaction Variables This study was carried out by altering each variable in turn while keeping the others constant. The optimum reaction conditions chosen were those which yielded a maximum and constant percentage inhibition and which resulted in a reaction order of zero or near to zero in the variables concerned.All concentrations described here are the initial concentrations in the reaction mixtures at time zero after mixing them. Each kinetic result is the average of three determinations. The effect of pH on the inhibited reaction was studied over the pH range 2.04.5 with the concentrations of the reactants similar to those described above, both in the absence and in the presence of 13ngml-1 of iodide. Fig. 2(a) shows the percentage inhibition calculated as % inhibition = (tg (x)pd" - (tg (x)pd" + I-/(tg versus pH, the inhibitor effect of the iodide is maximum and constant over the pH range 3.0-3.7. The partial inhibition reaction order in the hydrogen ion is zero in the pH range 3.0-3.7. All subsequent investigations were performed at pH 3.2.The influence of the concentration of CoIII-EDTA was studied in the range 1.4 x 10-34.0 x 10-3 rnol dm-3. The experiments were carried out at pH 3.2, 0.4 mol dm-3 H2P02-, 0.57 pg ml-1 of Pd" and no inhibitor or 13 ng ml-1 of iodide. The rate of both the catalysed and the inhibited reaction increases with an increase in the concentration of Co"'-EDTA, showing a partial kinetic order of +1 in the range 2.5 x 10-3-4.0 x 10-3 rnol dm-3. Fig. 2(b) shows the percentage inhibition of iodide versus Co"'-EDTA concentra- tion. A concentration of 2.6 X rnol dm-3 ColI1-EDTA, at which the inhibitory effect of iodide is maximum and constant, was selected. The influence of the concentration of hypophosphite was studied similarly over the range 0.1-1.0 rnol dm-3. The rates of the catalysed and inhibited processes increased with increasing concentrations of hypophosphite up to 0.4 30 .30 .- 0 2 3 4 2 3 rr PH [Co~~l-EDTA]/10-3 mol dm-3 +J .- 0.2 0.4 0.6 0.8 1.0 20 30 40 [H2PO2-1/mo1 d m 3 Tern peratu re/"C Fig. 2 Influence of reaction variables on the inhibitory effect of iodide: (a) pH; ( 6 ) Co'II-EDTA concentration; (c) H2PO2- concen- tration; and (d) temperatureANALYST, JUNE 1991, VOL. 116 655 rnol dm-3, above which they remained virtually constant. The partial kinetic order in the hypophosphite ion was zero in the range 0.44.7 rnol dm-3. As can be seen in Fig. 2(c) the inhibitory effect of iodide is appreciable and constant in the concentration range 0.3-0.7 rnol dm-3 of H2P02-; a concen- tration of 0.4 rnol dm-3 was chosen for further experiments.Fig. 2 ( d ) shows the influence of temperature on the percentage inhibition of iodide, determined at the concentra- tions of reactants stated above and with 21 ng ml-1 of iodide. A temperature of 20 f 0.2 "C was chosen. An important variable is the concentration of palladium. It was observed that when the concentration of iodide is constant the rate of the process increases considerably with the concentration of Pd" showing a kinetic order of +1 in the range 0.2-0.8 pg ml-1 of Pd". The inhibitory effect of iodide decreases when the Pd" concentration increases, as can be seen in Fig. 3, which shows the results obtained in the presence of 13 ng ml-1 of iodide and increasing amounts of Pd". It has been shown that the range of concentrations used for the determination of iodide and the slopes of the graphs obtained with the mentioned concentrations of Co"'-EDTA, H2P02- and pH in the presence of 0.37, 0.57 or 0.75 pg ml- of Pd" and variable amounts of iodide, depends on the concentration of the catalyst.A concentration of 0.57 pg ml-L of Pd" was selected as being the most suitable, as the linear range for the determination of iodide is wide. Mechanisms of the Inhibited Reaction In earlier work' it was found that the catalytic effect of Pd" on the reduction of Co"'-EDTA by hypophosphite seems to be due to heterogeneous catalysis attributable to elemental Pd formed in the fast reduction of Pd" by hypophosphite. This palladium catalytically decomposes the excess of hypophos- phite, yielding active hydrogen (H"), which rapidly reduces the Co"l-EDTA, as occurs in some processes involving hypophosphite and dyes and catalysed by Pdi1.*'9,30 The inhibitory effect of the iodide can be explained because this anion, acts as a complexing or precipitating agent for Pd'l thus decreasing the amount of catalyst available for the Co"l-EDTA reaction. Features of the Analytical Method By the use of the tangent method and under the optimum experimental conditions previously established (2.6 x 10-3 rnol dm-3 CoIIl-EDTA; 0.4 rnol dm-3 H2P02-; pH 3.2; 0.57 pg ml-1 of Pd" and 20 k 0.2"C) a calibration graph, linear between 2 and 28 ng ml-1 of iodide, was obtained. The slope of the calibration graph was 5.8 x 10-3 min-1 ng-1 ml with a correlation coefficient of 0.996.The limit of detection and quantification calculated according to the recommendations of the International Union of Pure and Applied Chemistry I 0.3 0.4 0.5 0.6 0.7 IPdl~l/pg ml-1 Fig.3 iodide Influence of Pd" concentration on the inhibitory effect of (IUPAC)3* was 1.2 and 1.5 ng ml-1 of iodide. The precision [relative standard deviation (RSD)] of the method (p = 0.05, n = 10) for 12.1 ng ml-1 of iodide was +2.2%. The selectivity of the method was determined by adding different amounts of potentially interfering species to samples containing 13 ng ml-1 of iodide. The tolerance limit was taken as the concentration causing an error of no more than +5% in the determination of iodide. The limiting molar ratio was obtained in the presence of EDTA for Pb", Hg" and Ag' and by prior heating of the samples in acetic acid medium for S032- and S2-.The results obtained are summarized in Table 1. Applications In order to demonstrate the applicability of the proposed method to the determination of iodide, the method was applied to the analysis of iodide in various samples, viz., pharmaceutical preparations, iodinated salts, cow's milk and infants' powdered milk. The results obtained for anti-asthmatic pharmaceutical preparations that contain iodide, in addition to the data from the recovery study, are summarized in Table 2. Recovery data were obtained by adding different amounts of iodide standard to the samples and subtracting the results obtained from samples prepared in a similar way but with no iodide added. No sample pre-treatment was required for the determina- tion of iodide in iodinated salts; however, in order to compensate for the effect of the chloride ions present in the samples, the standard iodide samples used when constructing the calibration graph must contain the same amount of chloride as the salt samples. The effect of this modification was that the calibration graph obtained showed a slope smaller than that obtained in the absence of chloride.The main problem lies in finding an iodide-free chloride for preparing Table 1 Interferences in the determination of 13 ng ml-L of iodide Species assayed SO4'- ~ NO3- , NH4+, HP04Z-, F- , Na+, K+, Mg*+, Ca'+, Co?+, Ni'+, Zn?+, Mn'+. Al", citrate Fe3+ , glycine, tartrate Br-, Cl- Pb2+i HzEDTA*-, caffeine Saccharin CU' + Hg'+t, SO3*-, S'- Ag+t NO?-, 1 0 3 * Maximum ratio tested.t In the presence of EDTA. Limiting molar ratio [species] : [I-] 10000* 2 so0 800 so0 300 2s 20 10 2 <0.S Table 2 Determination of iodide in pharmaceutical preparations Iodide content*/ Iodide mg ml-1 Added/ Foundtl Recovery Sample Stated Found? ngml-1 ngml-' (YO) 1% 8.66 8.75 3.46 3.40 98.3 6.93 6.85 98.8 10.40 10.14 97.5 3.60 104.0 6.93 6.80 98.1 10.40 10.39 99.9 29 1O.(K) 10.04 3.46 * Expressed as potassium iodide. t Average of three determinations. $ Elixifilin (Morrith): theophylline (0.533 g) and potassium iodide 5 Lasa antiasmatico (Lasa); aminophylline (10 mg), potassium (0.866 g), excipient up to 100 ml. iodide (10 mg) and sodium saccharin (3 mg). exeipient up to 10 ml.656 ANALYST, JUNE 1991, VOL. 116 Table 3 Determination of iodide in iodinated salt Iodide Iodide content*/ Added/ Found*/ Recovery Sample pgg-1 ngml-1 ngml-1 (%.) 1 64.44 3.36 3.20 95.4 6.72 6.96 103.4 2 59.25 3.36 3.16 94.1 6.72 6.60 98.2 * Average of three determinations.Table 4 Determination of iodide in milk Iodide content*/ Sample pgg-1 Cow's milk- Sterilized 1.59 Skimmed 1.13 Infants' powdered milk- 1 3.35 2 3.93 Iodide Added/ ng ml-1 2.76 5.52 2.76 5.52 2.76 5.52 2.76 5.52 * Average of three determinations. Found ng ml-1 2.68 5.50 2.74 5.48 2.69 5.38 2.79 5.52 Recovery (%I 97.1 99.77 99.3 99.3 97.5 97.5 101.1 100.0 the calibration graph; most of the usual analytical reagent- grade chloride salts were unsuitable. The use of a sodium chloride solution prepared from analytical reagent-grade hydrochloric acid and sodium hydroxide was adopted .32 Table 3 shows the results obtained for the determination of iodide in two iodinated salts and for the recovery study.The corresponding results obtained for various cow's milk and infants' powdered milk samples are summarized in Table 4. Conclusions The proposed method allows the determination of 1.5 ng ml-1 of iodide and its sensitivity is similar to that obtained by the Ce1"-Asr1' method.4-14 The method is selective and the procedure is widely applicable to different natural samples. 1 2 References Sanchez-Pedrefio, C., Garcia, M. S., and Albero, M. I., An. Quim. Ser. B . , 1987,83, 78. Sanchez-Pedreiio, C., Albero, M. I., and Garcia, M. S., Talanta, 1988, 35, 337. 3 Garcia, M. S., Sanchez-Pedreiio, C., and Albero, M.I., Analyst, 1990, 115, 989. 4 Sandell, E. B., and Kolthoff, I. M., 1. Am. Chem. Soc., 1934, 56, 1426. 5 Sandell, E. B., and Kolthoff, I. M., Mikrochirn. Acta, 1937, 1, 6. 6 Rodriguez, P. A. and Pardue, H. L., Anal. Chem., 1969, 41, 1369. 7 Elvecrog, J. M., and Carr, P. W., Anal. Chim. Acta. 1980,121, 135. 8 Aumont, G., and Tressol, J. C., Analyst, 1986, 111, 841. 9 Garcia, M. C., Ramis, G., Pineda, V.. and Villanueva, R., Microchem. J . . 1987, 36, 222. 10 O'Kennedy, R., Bator, J., and Reading, C., Anal. Biochem., 1989, 179, 138. 11 Carmen Gutierrez, M., Gomez-Hens, A., and Perez-Bendito, D., Analyst, 1989, 114, 89. 12 Wang, Z., Zheng, Z., and Gong, G., Fenxi Huaxue, 1989,17, 83. 13 Rubio, S., and Perez-Bendito, D., Anal. Chim. Acta, 1989,224, 185. 14 Toledano, M., Carmen, M., Gomez-Hens, A., and Perez- Bendito, D., Analusis, 1989, 17, 514.15 Bognar, J., and Nagy, L., Mikrochim. Acta, 1969, I, 109. 16 Sierra, F., Sanchez-Pedreiio, C., Perez, T., Martinez, C., and Hernandez, M., Anal. Chim. Acta, 1975, 78,277. 17 Jasinskiene, E., and Umbraziunaite, O., Zh. Anal. Khim., 1975,30, 1590. 18 Sierra, F., Sanchez-Pedreiio, C., PCrez, T., Martinez, C., and Hernandez, M., An. Quim., 1977, 73, 67. 19 Kreingol'd, S., Sosenkova, L., Panteleimonova, A., and Lavrelashvili, L., Zh. Anal. Khim., 1978, 33, 2168. 20 Igov, R., Jaredic, D., and Pecev, T., Mikrochim. Acta, Part I I , 2979, 171. 21 Sriramam, K . , Saama, B., Prasad, A., and Kalidas, K.. Analyst, 1983, 108, 543. 22 Tanaka, A., Miyazaki, M., and Deguchi, T., Anal. Lett., 1985, 18, 695. 23 Sanchez-Pedreiio, C., Albero, M. I., and Garcia, M. S., Quim. Anal.. 1985,4. 168. 24 Viiias, P., Hernandez, M., and SAnchez-Pedreiio, C., Talanta, 1987,34, 351. 25 Sriramam, K., Ravidranath, P., Sastry, B . , and Rao, R., Analusis, 1987, 15, 248. 26 Yonehara, N., Yamane, T., Tomiyasu, T.. and Sakamoto, H., Anal. Sci., 1989, 5, 175. 27 Chang, F. Ch., and Cheng, K. L., Mikrochim. Acta Part ZI, 1979, 219. 28 Belling, G. B., Analyst, 1983, 108, 763. 29 Eswara Dutt, V. S., and Mottola, H., Anal. Chem., 1976, 48, 80. 30 Sanchez-Pedreiio, C., Hernandez Cordoba, M., and Martinez, G., An. Quim., 1979, 75, 536. 31 Long, G. L., and Winefordner, J. D., Anal. Chem., 1983, 55, 712A. 32 Malvano, R., Buzzigoli, G., Scarlattini, M., Cenderelli, G., Gandolfi, C., and Grosso, P., Anal. Chim. Acta, 1972,61,201. Paper Ol04947F Received November 5th, I990 Accepted February 12th, 1991

ISSN:0003-2654    

DOI:10.1039/AN9911600653

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST, JUNE 1991, VOL. 116 657 Use of Lissamine Green B as a Spectrophotometric Reagent for the Determination of Low Residuals of Chlorine Dioxide Barry Chiswell and Kelvin R. O'Halloran Department of Chemistry, University of Queensland, St. Lucia, Queensland 4072, Australia A method for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz., free chlorine, chlorite, chloramine and chlorate, has been developed. The method overcomes the major problem found with the commonly used N,N'-diethyl-p-phenylenediamine method for determining chlorine dioxide, namely interference from free and combined chlorine. The detection limit of the proposed method is 0.03 k 0.01 ppm of chlorine dioxide; the calibration graph is linear over the range 0-0.5 ppm of chlorine dioxide.Cyclic voltammetric studies of the chlorine species were used t o verify the findings of the spectrophotometric work. Keywords; Chlorine dioxide; aqueous solutions; spectrophotometry; Lissamine Green B In the last 20 years there has been increased interest in the use of disinfectants other than the widely used free chlorine. This interest has been largely generated by the concern over trihalomethane (THM) production, linked to the use of free chlorine in water treatment.' One of the most attractive alternatives to the use of free chlorine has been chlorine dioxide, which has been shown not to produce THMs.2 A major disadvantage of the use of chlorine dioxide is that little or no residual disinfectant is produced; this necessitates the addition of free or combined chlorine to the finished water to provide an effective residual.This situation complicates the determination of all the chlorine species, as throughout the treatment plant and the reticulation system any of the chlorine species, viz., chlorine dioxide, free chlorine, chlorite, chlorate and combined chlorine, can exist either as residuals or by-products from the use of a mixed chlorine dioxide-free chlorine treatment regime. Any reagent used for the deter- mination of a particular chlorine species must be both sensitive and selective. Numerous spectrophotometric reagents have been de- scribed for the determination of chlorine, and most of these including tyrosine,3 o-tolidine,4 Indigo Blue,5 disodium 5,5'- dimethyl-2,2'-[ (9,10-dihydro-9,10-dioxoanthracene-1,5-diyl)- diimino] bisbenzenesulphonate (ACVK) ,6 Chlorophenol Red7 and N,N'-diethyl-p-phenylenediamine (DPD)s are claimed to be selective for chlorine dioxide.However, some of these reagents, such as tyrosine and ACVK, although selective, do not possess the necessary sensitivity to determine low levels of chlorine dioxide, and only the DPD reagent is recommended by standard references.9.10 This paper describes a spectrophotometric reagent which is both selective and sensitive for the determination of low levels of chlorine dioxide in the presence of free chlorine, chlorite, chloramine and chlorate. The advantages of the proposed method over the use of the DPD reagent are also discussed. Experimental Preparation and Standardization of Stock Solutions of Chlorine Species All water used, unless specified otherwise, was obtained from a Milli-Q Reagent Water System (Millipore), resistivity 18 MQ cm.This water is referred to as 'reagent water'. All chemicals used were of analytical-reagent grade unless speci- fied otherwise. All spectrophotometric reagent solutions were stored in amber-coloured, high-density , polypropylene bottles (Nalgene). All glassware used was cleaned using the following regime: the glassware was first soaked for 24 h in 2% Extran cleaning agent (BDH), followed by rinsing and soaking in 5% nitric acid for 48 h. The glassware was then rinsed thrice with distilled water and once with reagent water. All buffers used were prepared according to the procedures given by Perrin and Dempsey.11 Ultraviolet (UV)/visible spectra were obtained using a Hewlett-Packard HP8450A spectrophotometer unless speci- fied otherwise.Stock chlorine solution, 1000 ppm. High-purity chlorine gas (CIG) was passed first through a water trap and then into a collection vessel containing 1 mol dm-3 NaOH solution for 10 min. The concentration of this solution was determined by iodimetric titration; the solution was then diluted with water to provide a 1000 ppm (as OCl-) solution. This solution, if stored in a polyethylene bottle under refrigeration, main- tained its titre for at least six months. Stock chlorine dioxide solution, 100-300 ppm. Chlorine dioxide was prepared as required by the method described in reference 12. The solution thus generated was manipulated by means of a floating piston delivery apparatus described elsewhere.13,14 Standard solutions were prepared fresh as required. Stock chlorite solution, 1000 ppm. Sodium chlorite (80%) (Ajax) was recrystallized thrice from water and its purity tested by iodimetric titration. A 1.34085 g amount of the purified chlorite (> 98%) was dissolved in 1 1 of reagent water. Standard solutions were prepared fresh as required. Stock chlorate solution, 1000 ppm. Potassium chlorate (99.5% minimum) (Ajax) was used without further purifica- tion. A 1.46852 g amount was dissolved in 1 1 of reagent water. Stock monochloramine solution, 50 ppm. Prepared as described in reference 15. A 0.26745 g amount of ammonium chloride (Merck) was dissolved in 500 ml of water. Sufficient borate buffer (pH 8.0) was added to bring the pH to 7.5, and 50 ml of the 1000 pprn OCI- solution (prepared as described above) were added slowly with gentle stirring.The ratio of ammonium : hypochlorite ion is 5 : 1. The solution was made up to 1 1 and stored under refrigeration in a polyethylene bottle. Standardization. All stock solutions of the chlorine species, except the chlorate stock solution, which was prepared from an analytical-reagent grade solid and was therefore not standardized, were standardized by iodimetric titration. 16 The monochloramine stock solution, which was prepared from analytical-reagent grade ammonium chloride and standard- ized hypochlorite, had its concentration confirmed by com- parison of its maximum UV absorbance with the reported UV molar absorptivity for monochloramine. 17658 ANALYST, JUNE 1991, VOL.116 Cyclic Voltammetry All cyclic voltammograms were recorded on a Metrohm Herisau E 506 Polarecord, with voltages being controlled by a Metrohm Herisau E 612 VA-Scanner. Analyses were per- formed at platinum electrodes against a saturated silver-silver chloride reference electrode, at scan rates of 100 mV s-l. All reagent or analyte solutions for cyclic voltammetric studies were approximately 0.001 rnol dm-3, with 0.1 rnol dm-3 sodium sulphate supporting electrolyte added; the buffers used have been described above. Spectrophotometric Analyses The procedure for the determination of chlorine dioxide by the DPD method was that given in reference 10. Lissamine Green B Procedure An approximately 0.001 rnol dm-3 Lissamine Green B (LGB) solution was prepared by dissolving 0.1922 g of LGB (dye content, about 60%; Aldrich) in 200 ml of water.A sufficient amount of this solution was added to a 100 ml calibrated flask so that the absorbance of a reagent blank was C1.0 at 616 nm. Five millilitres of pH 9.0 buffer were added, followed by various amounts of the chlorine dioxide stock solution. The volume was made up to the mark and the absorbance at 616 nm measured. Results and Discussion The most frequently used spectrophotometric reagent for the determination of chlorine dioxide is undoubtedly DPD. The colour stability of this reagent was investigated in the presence of chlorine dioxide, free chlorine, chloramine, chlorite and chlorate as these species represent the likely chlorine-contain- ing oxidants found in a water treatment process using a mixed regime of chlorine dioxide and free chlorine.Fig. 1 shows the results obtained using the reagents and methodology outlined in reference 9. Chlorine dioxide rapidly oxidizes DPD to produce a relatively stable, coloured product. Free chlorine , although rapidly oxidizing DPD, fails to produce a stable colour. Monochloramine has a similar oxidation behaviour to free chlorine, whereas chlorite slowly oxidizes the reagent; chlorate was found to be unreactive 'towards DPD. The procedure described in reference 9 utilizes the masking reagent glycine to bind free chlorine as chloroaminoacetic acid, which supposedly has a much reduced oxidation poten- tial compared with free chlorine and is therefore expected not to oxidize DPD. 0.5 I, - x - ~ n I .,, x - x-x E 0.4 C 0 In m 0.3 al 0 0- 20 40 60 Time/m in Fig. 1 Colour stability of the DPD reagent after oxidation by the various chlorine species, using the procedure described in reference 9.A, C102 (0.5 ppm); B, C102 ( 5 pprn); C, HOCl (2.5 pprn); and D, NH2Cl(5 P P 4 Fig. 2 shows the oxidation profile (shown by colour change) of both chlorine dioxide and free chlorine, with glycine added to the reagent solutions according to the method described in reference 9. The presence of glycine would appear merely to slow the oxidation of DPD by free chlorine, similar to the effect of monochloramine, thus not effectively masking the interference from this analyte. Electrochemistry was used in an attempt to evaluate the effects that the individual chlorine species have towards the D P b reagent.Cyclic Voltammetry of DPD and the Chlorine Species Standard potentials give little indication of the true relative redox potentials between the chlorine species and DPD under conditions such as those found in a spectrophotometric analysis, as the concentration of the analytes is 1 rnol dm-3 and the pH either 1 or 14. Although the conditions employed during typical voltammetric studies, i.e., 0.1 rnol dm-3 supporting electrolyte and an analyte concentration of 0.001 mol dm-3, are not those experienced during a spectrophoto- metric analysis, there can be little argument that the results obtained are more representative of the relative redox potentials than are the standard potentials which are quoted by most workers.Cyclic voltammograms, at platinum elec- trodes, were obtained for chlorine dioxide and chlorite , chloramine, free chlorine and DPD; the results are sum- marized in Table 1. The cyclic voltammograms can be used to explain the behaviour of the various chlorine species towards the DPD reagent. Both chlorine dioxide and free chlorine are shown to be powerful oxidants with reduction potentials (E,) of +0.88 and +0.94 V, respectively, and consequently oxidize the DPD reagent, which has an oxidation potential (E,) of +0.49 V. Chlorite, on the other hand, is a substantially weaker oxidant (E, = +0.08 V, first electron) and only slowly oxidizes the DPD reagent. The important point to note is that chloramine is a relatively strong oxidant at pH 6.4, with a reduction potential (E,) of +0.40 V. [Although two reduction potentials 0.6 E 0 m c m 0.4 0) C CU -e x 0.2 a 0 20 40 60 Time/min Fig.2 Oxidation profile of both free chlorine and chlorine dioxide in the presence of glycine, using the procedure described in reference 9. A, C10,; and B, HOCl ~~~ ~ Table 1 Redox potentials of the chlorine species obtained by cyclic voltammetry at platinum electrodes at pH 6.4. All potentials are adjusted to voltages relative to the standard hydrogen electrode Species E 6 v ErN E f l AEN HOCVOCI - + 1 .OO +0.94 +0.97 0.06 NH2CI +0.97 +0.94 +0.96 0.03 - - - +0.40 c10* +0.99 +0.88 +0.94 0.11 c102- +0.33 +0.08 +0.20 0.25 +0.11 0.00 +0.06 0.11 DPD +0.49 +0.40 +0.45 0.09ANALYST, JUNE 1991, VOL.116 659 were observed for chloramine, the first ( E , = +0.94 V) is attributed to the break-back of free chlorine under the experimental conditions. It is free chlorine that is being reduced at this potential.] The result is the extensive oxidation of the DPD reagent, albeit at a slower rate than the oxidation of DPD by free chlorine. A cyclic voltammogram of a solution of free chlorine and glycine was obtained, thus supposedly containing chloraminoacetic acid, but no reduc- tion or oxidation potentials could be observed for this combined chlorine species. It is reasonable to assume that the reduction potential for chloraminoacetic acid is similar to chloramine, and that the results observed for chloramine explain the extensive oxidation of the DPD reagent in the presence of chloraminoacetic acid.The use of DPD as a spectrophotometric reagent for the determination of chlorine dioxide has three major disadvan- tages; these are: (1) the combined chlorine species monochlor- amine and chloraminoacetic acid both oxidize the DPD reagent; (2) as different problems have been recognized in Palin's original DPD method,s i.e. , interference from oxidized manganese and colour drift-back in the presence of high concentrations of chlorite, more reagents and steps have been added to the procedure, resulting in the DPD method becoming cumbersome; and (3) when free chlorine is present, the masking step involving the combination of glycine with the analyte solution results in additional manipulation of the analyte solution causing loss of the highly volatile chlorine dioxide.The first two of these problems are a direct consequence of the relatively low oxidation potential of the DPD reagent compared with the chlorine species. A method was therefore needed which overcomes the major problems of the DPD method. Investigation of the LGB Reagent Several spectrophotometric reagents, which have been re- ported as having a much higher redox potential than DPD, were evaluated in an attempt to find a suitable reagent with which to develop a selective, sensitive and rapid method for the determination of chlorine dioxide. These included ferroin, erioglaucine, N-phenylanthranilic acid and LGB; the most suitable reagent was found to be LGB, which is a triphenyl- methane dye with the structure given in Fig.3. Such dyes are particularly suited to the determination of the chlorine species as most have standard redox potentials greater than or equal to + 1.0 V; the standard redox potential of LGB is reported to be + 1 .O V. 18 By using a reagent that has a redox potential of + 1.0 V, the likelihood of interference from combined chlorine and chlorite is greatly reduced; however, interference from free chlorine, as hypochlorous acid, is still likely as it has a reduction potential greater than chlorine dioxide at a pH of 6.4. On the other hand, hypochlorite is a less powerful oxidant under standard conditions (El = +0.95 V)*9 than is hypo- S03Na Fig. 3 Structure of LGB chlorous acid (E; = +1.49 V). It follows that by raising the pH to a value that ensures free chlorine will exist almost entirely as hypochlorite , greater separation between the reduction potentials of free chlorine and chlorine dioxide will be achieved.When raising the pH, consideration must be given to the reported tendency of chlorine dioxide to disproportionate to chlorite and chlorate.20 Therefore, a pH of 9.0 is a com- promise between having 99.9% hypochlorite (pH 10.5) and a pH at which the disproportionation of chlorine dioxide would be expected to be negligible. Cyclic voltammograms were obtained for hypochlorite, chlorite and chlorine dioxide, chloramine and LGB at pH 9.0; the results are summarized in Table 2. The results shown in Table 2 suggest that there is a significant difference in the oxidizing power of free chlorine at pH 9.0 compared with pH 6.4.The oxidizing potentials of chlorite and chloramine have also been significantly reduced from their values at pH 6.4. In contrast, the oxidation potential of chlorine dioxide has been largely unaffected by the change in pH. The behaviour of free chlorine and chlorine dioxide towards LGB was studied at pH 9.0, using a borate buffer; the results are shown in Fig. 4. Chloramine, chlorite and chlorate produced no measurable effect at pH 9.0. The difference in methodology when using the LGB reagent is that the method is a colour-loss technique in contrast to the colour-forming DPD method. The oxidation of LGB by free chlorine, now as hypochlorite, is significantly slower than the rate of oxidation by chlorine dioxide, reflecting the lower oxidizing power of hypochlorite compared with chlorine dioxide.The results presented above suggest that, although the oxidizing power of free chlorine has been markedly affected by the change in pH used to achieve selectivity between chlorine and chlorine dioxide, using this dye, a masking agent will still be required. Results from work with other spectrophotometric reagents for the determination of chlorine dioxide, in the presence of free chlorine,z' indicated that ammonia is the most successful Table 2 Redox potentials of the chlorine species obtained by cyclic voltammetry at platinum electrodes at pH 9.0. All potentials are adjusted to voltages relative to the standard hydrogen electrode Species ErN EJV EtN A EIV oc1- +0.49 +0.76 +0.62 0.27 c10* +0.87 +0.96 +0.91 0.09 c102- -0.07 +0.53 +0.23 0.61 LGB - - - - NH2Cl +0.09 - +0.96 - . x.x. ' X . 0.9 ' . l ~ 0 20 40 60 Time/m i n Fig. 4 Time dependency of the oxidation of LGB by chlorine dioxide (0.5 ppm) and free chlorine (5 ppm) at pH 9.0 (borate buffer). A, C10,; and B, OC1-660 ANALYST, JUNE 1991, VOL. 116 masking agent for free chlorine; the oxidants were again added to a solution of LGB in the presence of an ammonia- ammonium chloride buffer at pH 9.0. The results are shown in Fig. 5. Chlorine dioxide oxidizes LGB rapidly and completely, whereas oxidation of the dye by hypochlorite is much less than that observed in the absence of ammonia. A measurable loss of colour is observed however, but this is attributed to the slight instability of LGB at this pH. In order to confirm that free chlorine is not even partly responsible for the slight colour loss observed, the absorbance (at 616 nm) of two reagent solutions, one containing 5 pprn of free chlorine and the other a blank solution with no oxidant added, was recorded over a period of 60 min.The colour loss in the solution containing free chlorine is not significantly different, at a confidence interval of 95%, to the blank solution. A calibration graph for chlorine dioxide over the range 0-0.5 ppm was obtained in the presence and absence of 5 ppm of free chlorine; the results are shown graphically in Fig. 6 and the statistical analysis is given in Table 3. This analysis suggests that, over a (1-0.5 ppm chlorine dioxide concentra- tion, there is no significant difference in either the presence or absence of 5 pprn of added chlorine; texp < tcrit, indicating that selectivity can be achieved using an ammonia buffer.Clearly, selectivity can be achieved between chlorine dioxide and free chlorine by using an ammonia buffer to bind the free chlorine as chloramine, which the cyclic voltammetric results have shown to be a significantly weaker oxidant than free chlorine. Repetitive construction of calibration graphs over the chlorine dioxide concentration range 0-0.5 ppm suggests that the detection limit of the LGB method is reproducible at a level of 0.03 k 0.01 pprn of chlorine dioxide in the presence or absence of added free chlorine. 2.0 , 1 1 . 5 8 E A n u I I L 0 20 40 60 Time/min Fig. 5 Time deDendencv of the oxidation of LGB bv chlorine dioxide (0:s ppm) and f k e chlohne ( 5 ppm) at pH 9.0 (ammonia buffer).A, C102; and B, OCI- 0 0.1 0.2 0.3 0.4 0.5 IC1021 (ppm) Fig. 6 Comparison of the oxidation of LGB by chlorine dioxide (04.5 p m) in the presence and absence of 5 ppm of free chlorine at pH 9.0 gmmonia buffer). 0, C10 ; and 0, CI02-OCI- The LGB method for the determination of chlorine dioxide is selective, sensitive and rapid. In addition, no interference was found from manganese dioxide or oxidized forms of iron. Hence the LGB method overcomes all of the disadvantages of the DPD method in that: (1) other chlorine species do not interfere; (2) only two reagents are necessary, making the LGB method much simpler; (3) the resulting colour produced after addition of the sample is stable, making the method an excellent prospect for analyses in the field, where rapid analyses are impracticable; and (4) no manipulation of the analyte solution is necessary.A sample containing chlorine dioxide and other chlorine species can be added directly to a calibrated flask containing the LGB reagent and the ammonia buffer, as the reaction between ammonia and free chlorine is more rapid than that with the LGB reagent. Table 3 Regression analysis data for the determination of chlorine dioxide over the range 0-0.5 pprn in the presence and absence of 5 ppm of free chlorine, using the reagent LGB PO21 (PPm) 0 0.05 0.10 0.15 0.20 0.25 0.31 0.35 0.40 0.45 0.50 Absorbanceof Absorbanceof LGB with LGB with 5 ppm of OC1- no OC1- 0.9259 0.9205 0.8690 0.8687 0.8091 0.8005 0.7354 0.7351 0.6837 0.6770 0.6320 0.6194 0.5394 0.5538 0.5076 0.5028 0.4518 0.4633 0.3910 0.4249 0.3562 0.3612 - 0.0029 12 x d * s d t 0.01261 texpl 0.7652 tcrit(o.os)§ 2.26 Regression data Constant Standard error of Y estimate Correlation coefficient X coefficient (sensitivity) Standard error of Xcoefficient Limit of detection Absorbance difference 0.0054 0.0003 0.0086 0.0003 0.0067 - 0.0126 0.0144 -0.0048 -0.0115 - 0.0339 - 0.0050 With OCI- Without OC1- 0.9219 0.9133 0.0093 0.0143 0.9990 0.9974 -1.173 -1.128 0.0178 0.0273 0.0238 0.0380 * Average deviation from mean. t Standard deviation.I Calculated r-value. 9 Critical t-value for 95% probability level. Table 4 Percentage recovery of chlorine dioxide from filtered and clear water samples C102 added C102 recovered Recovery (PPm) (PPm) (Yo 1 Filtered water samples- 0 0 0.10 0.103 103 0.20 0.205 102.5 0.30 0.309 103 0.40 0.398 99.5 0.50 0.516 103.2 0 0 0.10 0.095 95 0.20 0.208 104 0.30 0.309 103 0.40 0.407 101.8 0.50 0.498 99.6 c Clear water samples*- - * 1.0 ppm of OCI- added.ANALYST, JUNE 1991, VOL.116 661 The proposed method was tested at the Molendinar Water Purification Plant at the Gold Coast, South-east Queensland, Australia. The water treatment process employed at this plant can be summarized as follows: raw water flows into the plant and is initially dosed with lime in order to adjust the pH prior to the addition of alum to initiate flocculation before the water enters the clarifiers. Flocculation is accelerated in the clarifiers by the addition of polyelectrolyte.Water is then taken from the top of the clarifiers and dosed with chlorine dioxide on admission to the filter basins. Filtration is accomplished by passage of the water through a bed of sand approximately 75 cm deep; on passage through the sand filter the water is termed ‘filtered water’. After filtration, chlorine is added at a level of between 1 and 2 ppm in order to provide a residual disinfectant level, while the pH is adjusted to between 7.5 and 8.5. ‘The water is now termed ‘clear water’. The water is then stored in above-ground reservoirs prior to distribution through the reticulation system. Both the filtered and clear water were sampled; the level of chlorine dioxide was determined by the LGB method and was found to be below the detection limit of the method, i.e., <0.03 ppm.Samples of the filtered water and clear water matrices were taken back to the laboratory and percentage recovery experiments were conducted. The results are pre- sented in Table 4. The results suggest that the LGB method gives excellent results on chlorine dioxide recovery experiments using sample matrices from a water treatment process employing a mixed oxidant regime of chlorine and chlorine dioxide. Chlorine dioxide residual measurements on unspiked water treatment samples are more difficult as the reactivity of the oxidant is such that unless the analyte samples are taken very near to the source of chlorine dioxide addition, no residuals will be found. 3 8 9 10 11 12 13 14 15 16 17 18 19 20 21 References 1 2 Industrial Pollution of the Lower Mississippi River in Louisiana, US Environmental Protection Agency, Cincinnati, OH, 1972.Miltner. R. J.. MSc Thesis. University of Cincinnati, 1976. Hodgden, H. W.. and Ingols, R. S . , Anal. Chem., 1954, 26, 1224. Aston, R. N., J . Am. Water Works Assoc., 1950,42, 151. Hoignd, J . , and Bader, H . , Vom Wasser, 1980, 55, 261. Masschelein, W., Anal. Chem., 1966, 38, 1839. Wheeler, G. L., Lott, P. F., and Yau, F. W., Microchem. J . , 1978, 23, 160. Palin, A. T., Water Sewage Works, 1960, 107, 457. Standard Methods for the Examination of Water and Wastewater, American Public Health Association, American Water Works Association, Water Pollution Control Federation, Washington, DC, 16th edn., 1985, p. 323. Methods for the Examination of Waters and Associated Materials. Department of the Environment/National Water Council, HM Stationery Office, London, 1980. Perrin, D. D., and Dempsey, B.. Buffers for p H and Metal ton Control, Chapman and Hall, London, 1974. Standard Methods for the Examination of Water and Wastewater, American Public Health Association, American Water Works Association, Water Pollution Control Federation, Washington, DC, 16th edn., 1985, pp. 320 and 321. Rauchle, G. P., MSc Thesis, University of Queensland, 1989. Chiswell, B., O’Halloran. K. R., and Rauchle, G. P . , Australian Water and Wastewater Association, 13th Federal Canberra Convention, 1989, p. 465. White, G. C., Handbook of Chlorination, Van Nostrand Reinhold, New York, 2nd edn., 1986, p. 182. Standard Methods for the Examination of Water and Wastewater, American Public Health Association, American Water Works Association. Water Pollution Control Federation. Washington, DC, 16th edn., 1985, pp. 298, 299 and 320. Yiin, B. S . , and Margerum, D. W., tnorg. Chem., 1990, 29. 2135. ‘AnalaR’, Handbook and Green Pages, BDH, Poole, Dorset. 1984, p. 55. CRC Handbook of Chemistry and Physics, ed. Weast, R. C.. CRC Press, Boca Raton, FL, 63rd edn., 1982, pp. D-162-D- 164. Feuss, J. F.. J . Am. Water Works Assoc., 1964, 56, 607. O’Halloran, K. R., PhD Thesis, University of Queensland, 1990. Paper 0103901 B Received August 29th, 1990 Accepted February l l t h , 1991

ISSN:0003-2654    

DOI:10.1039/AN9911600657

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST. JUNE 1991, VOL. 116 663 Determination of Trace Amounts of Gallium, Indium and Thallium by Successive Titrations Using Semi-xylenol Orange With Spectrophotometric and/or Visual End-point Indication Medhat Abd El-Hamied Hafez, Amin M. A. Abdallah and Tarek M. Abd El-Fatah Wahdan Chemistry Department, Faculty of Science, El-Mansoura University, El-Mansoura, Egypt The precision and accuracy attainable in successive titrations of Ga3+, ln3+ and TP+ with a 0.001 mol dm-3 solution of disodium ethylenediaminetetraacetate (Na2EDTA) using Semi-xylenol Orange (SXO) as a metallochromic indicator with spectrophotometric and/or visual end-point indication were studied. Indium(lll) was initially titrated directly at pH 5.4-5.8 (490 nm) by using hexamethylenetetramine (hexamine) buffer in the presence of ascorbic acid t o reduce TP+ t o TI+.At the indium end-point, an excess of Na2EDTA was added, and Ga3+ was determined by back-titration with a standard PbCI2 solution. Gallium(lil), ln3+ and Tl3+ in another aliquot were determined by indirect titration of an excess of Na2EDTA with a standard PbCI2 solution at pH 5.4-5.8 (490 nm). The interference of various anions, cations and organic acids in the determination of Ga3+, In3+ and TP+ was studied. A comparison of the indicators SXO and Xylenol Orange for successive titrations of the metal ions studied was carried out. Keywords: Gallium, indium and thallium determination; Semi-xylenol Orange; spectrophotometric and visual titration Many direct and indirect complexometric methods for the individual determination of Ga3+, I++ and TP+ ions using different metallochromic indicators at various pH values have been described.1-16 However, only a comparatively small number of papers have dealt with the quantitative approach to the determination of two of these three ions. The selection of specific physical conditions for carrying out such an analysis complicates the determination by the use of a group of reagents for separating mixtures and for the determination of individual ions. It has previously been shown17-22 that the spectrophotometric indication of chelatometric titrations using Semi-xylenol Orange (SXO) as indicator gives very accurate results at the microgram level. The aim of this work was to determine Tn3+ and Ga3+ successively in a single solution with high precision and accuracy with the minimum number of operational steps, foflowed by back-titration of another aliquot containing Ga3+, In3+ and TP+, in which TI3+ can be determined by difference, with both spectrophotometric and visual end-point indication using SXO as a metallochromic indicator.Different synthetic mixtures containing different compositions of Ga3+, In3+ and TP+ were analysed. A comparison of the detection limit, accuracy and precision of successive titrations of Ga3+, In3+ and TF+ using SXO and Xylenol Orange (XO) as indicator19 was also carried out. Experimental The reagents and solutions, apparatus and procedure were as described previously. 1923 Computation of Experimental Data and Evaluation of Statistical Data In each series of experiments the number of determinations ( n ) was 10.The standard deviation, s, and relative standard deviation, s,, were calculated from the equations and where x is the mean concentration found and Xi is the concentration found for each number (i) of repetitive exper- iments. If necessary, Lord’s test was used to eliminate values showing a statistically significant deviation.24 Results and Discussion Successive Microtitrations of Ga3+, W* and T13+ by Spectrophotometric and/or Visual End-point Indication using sxo Few methods for the determination of two of the three ions Ga3+, In3+ and Tl3+ have been described in the literature. The determination of Ga3+, In3+ and TP+ in an individual aliquot with high precision and accuracy by spectrophotometric and/or visual titration using SXO as indicator is important.In this work, I$+ was first determined in a sample of the three ions by titration in hexamine buffer (3 ml of a 1 mol dm-3 solution), of pH 5.4-5.8 either spectrophotometrically (A = 490nm) or visually in the presence of ascorbic acid (1 mol dm-3) to reduce TI3+ to Tl+. The latter ion does not react with SXO and disodium ethylenediaminetetraacetate (Na2EDTA). The Ga3+ ion does not react directly with Na2EDTA. At the indium end-point, an excess of a known volume of standard Na2EDTA solution was added and the whole solution was transferred into a 50 ml beaker, covered, heated gently until boiling occurred and then boiled for a further 5 min. The mixture was cooled to room temperature and quantitatively transferred into the titration cell which contained the necessary concentration of SXO.A further 2 ml of hexamine buffer were added and the whole mixture was made up to a constant volume of 1.5 ml for spectrophotometric titration. In the visual titration the whole mixture was transferred into a 2.50 ml conical flask containing 20-25 ml of re-distilled water together with a suitable amount of SXO to allow the end-point to be easily detected by the human eye. The mixture was titrated against a standard PbC12 solution of the same concentration as the Na,EDTA solution. This step664 ANALYST, JUNE 1991. VOL. 116 gives the amount of Ga3+ present. It was found that Ga3+, In3+ and T13+ could be determined together in another aliquot, spectrophotometrically (490 nm) or visually, by back-titration of the excess of Na2EDTA with the standard PbC12 solution using SXO as indicator in the presence of hexamine buffer of pH 5.4-5.8, whcrc TP+ can be determined by difference from the first titration (In3+ and Ga3+).For the spectrophotometric titration the feasibility of this successive determination was studied for trace amounts of metals. Seven series of successive microtitrations were performed with molar ratios of G a : I n : TI ranging from 10: 1: 1 to 1 : 10: 1 to 1 : 1 : 10, respectively. Fig. 1 shows a typical spectrophoto- metric titration curve for one of such a series for the determination of In3+ (curve 1) and Ga3+ (curve 2). For the back-titration of the three metal ions a titration curve similar 0 100 200 300 400 500 600 700 Volume of Na,EDTA/pl (1 1 0 100 200 300 400 500 600 700 Volume of PbCI2/pI (2) Fig.1 Successive microtitrations of 1, In3+; and 2, Ga3+ with 1 x 10-3 rnol dm-3 Na2EDTA. Conditions: cIn = 1.33 x 10-5 mol dm-3; cGa = 1.33 x 10-5 rnol dm-3; csxo = 6 X 10-5 mol dm-3; pH = 5.4-5.8; h = 490 nm for all metals; 1 = 18 mm. Ga3+ (curve 2) was determined by adding 0.5ml of Na2EDTA solution after the In3+ end-point had been reached to that shown in Fig. 1 (2) was obtained. No difficulties were encountered in the end-point evaluation for all the three metals studies.17-19 The results of seven series of parallel determinations of the three ions using the spectrophotometric titration method are given in Table 1. A wavelength of 490 nm was found to be suitable for the direct microtitration of In3+ and the back-titration procedure.For the visual method six series of successive titrations were carried out in which the molar ratios of Ga3+ : In3+ : TP+ were 1 : 1 : 1, 1 : 3 : 2, 1 : 2 : 3, 1 : 4 : 1, 1 : 1 : 4 and 4 : 1 : 1. The titration procedures were the same as for the spectrophotometric techniques. The results of six series of parallel determinations of the three ions using the visual titration method are shown in Table 2. The statistical evaluation shows that the determinations of all the metal ions studied are of the same precision in spite of the difference in the determination procedures. It is necessary to determine the value of the blank by titrating the same volume of a solution containing all the constituents with the exception of the metal ions at the appropriate pH value.Interference of Foreign Species This study was divided into two parts: (1) the interference in the direct titration of In3+; and (2) the interference in the back-titration procedures for Ga3+, In3+ and TP+. For the first type of interference, it was found that S042-, NO3-, C104-, C1-, I- and F- at a concentration of up to 1000 times that of In3+ did not interfere. Phosphate started to interfere when present at a concentration of at least ten times that of In3+. Higher concentrations of P043- led to the formation of a precipitate (most probably InP04), which disrupted the titration completely. Further, citric, oxalic, tartaric and acetic acids at a concentration of up to 1000 times that of In3+ did not interfere. The cations Mg2+, Ca2+, Sr2+ and Ba2+ did not interfere.Chromium(r1I) did not interfere; this might be due to the slow reaction between this ion and Na2EDTA. Alu- minium(m) did not interfere when present at a concentration equal to that of In3+, although it caused a positive deviation when present at higher concentrations. However, AP+ forms a stable complex with fluoride and tartrate ions while In3+ does not; hence In3+ can be titrated safely in the presence of Table 1 Statistical evaluation of seven series of successive microtitrations of Ga3-+, In3+ and Tl3+ with 0.001 mol dm-3 Na2EDTA and 0.001 mol dm-3 PbC12 solutions using SXO as indicator. Conditions: csxo = 6 X 10-6 mol dm-3; pH = 5.4-5.8; h = 490 nm; ionic strength of titrated solution (Z) = 0.2 mol dm-3; pathlength of cuvette (I) = 18mm; and number of titrations in a series ( n ) = 10.The blank was determined by titrating 15 ml of a solution containing all the components with the exception of the metals against 0.001 mol dm-3 Na2EDTA solution. In each series of titrations the blank values were either negligible or zero Titrated concentration of metal (cM)/ Metal taken/ Mead Series Metal ion pmol per 15 ml pg per 15 ml pg per 15 ml s/Pg sr (Yo 1 Recovery (%) 1 Ga3+ 1n3+ 1n3+ 1n3+ ~ 1 3 + 1n3+ TP + 1n3+ 1n3+ 1n3+ n3+ 2 Ga3+ T13 + 3 Ga3+ 4 Ga3+ 5 Ga3+ n3+ 6 Ga3+ Tl3+ 7 Ga3+ Tl3+ 0.30 0.10 0.20 0.30 0.20 0.10 0.10 0.20 0.30 0.2 0.2 0.2 0.50 0.05 0.05 0.05 0.50 0.05 0.05 0.05 0.50 20.92 11.48 40.87 20.92 22.96 20.44 6.97 22.96 61.31 13.94 22.96 40.87 34.86 5.74 10.22 3.49 57.41 10.22 3.49 5.74 102.18 20.74 11.46 40.65 20.66 22.75 20.64 7.12 22.84 61.45 13.92 22.65 40.95 34.96 5.68 10.28 3.38 57.66 10.36 3.45 5.65 102.34 0.12 0.05 0.22 0.15 0.12 0.15 0.04 0.12 0.25 0.05 0.14 0.24 0.16 0.02 0.06 0.02 0.22 0.05 0.05 0.06 0.18 0.58 0.44 0.54 0.73 0.53 0.73 0.56 0.53 0.41 0.48 0.62 0.59 0.46 0.35 0.58 0.59 0.38 0.48 1.45 1.06 0.18 99.14 99.83 99.46 98.76 99.09 100.98 102.15 99.48 100.23 99.86 101.37 100.20 100.29 98.95 100.59 96.85 100.44 101.37 98.85 98.43 100.16ANALYST, JUNE 1991, VOL.116 665 Table 2 Statistical evaluation of six series of successive microtitrations of Ga3+, In3+ and TP+ with visual detection of the end-point using SXO as indicator (pH 5.4-5.8) Titrated concentration of metal (cM)/ Metal taken Series Metal ion 10-3 mol dm-3 (PPm) Mean (PPm) s (PPm) s r (% ) Recovery (%) 1 Ga"+ In3+ TI'+ In3+ 'rp+ 3 Ga3+ In3i TF+ 4 Ga7+ In3+ T13+ I d + T13+ In3+ Tl3+ 2 Ga3+ 5 Ga3+ 6 Ga3+ 5.0 5.0 5.0 2.5 7.5 5.0 2.5 5.0 7.5 2.5 2.5 2.5 2.5 10 10 10 2.5 2.5 * End-point from lemon yellow to brilliant red.End-point from deep orange to lemon yellow. 348.60" 574. lot 102 1.85" 174.30 861.15 1021.85 174.30 574.10 1532.77 174.30 1148.20 510.92 174.30 287.05 2043.70 697.20 287.05 5 10.92 348.40 574.30 1021.60 174.00 860.00 102 1.71 174.80 574.2 1533.0 174.50 1147.30 511.00 173.80 287.20 2042.4 696.10 288.10 5 10.00 0.40 0.50 0.30 0.50 0.50 0.50 0.30 0.30 0.40 0.30 0.40 0.40 0.50 0.40 0.30 0.35 0.35 0.40 0.11 0.09 0.03 0.29 0.06 0.05 0.17 0.05 0.03 0.17 0.03 0.08 0.29 0.14 0.02 0.50 0.12 0.08 99.94 100.03 99.98 99.83 99.87 99.99 100.29 100.02 100.02 loo.12 99.98 1 00.02 99.71 100.05 99.94 99.84 100.37 99. 82 Table 3 Statistical evaluation of seven series of successive spectrophotometric microtitrations of Ga3+, 0.001 mol dm-3 solutions of Na,EDTA and PbCl? using XO as indicator. Conditions as in Table 1 Series 1 2 3 4 5 6 7 Metal ion Ga3+ In3+ TP+ Ga3+ In3+ T13+ Gas+ TI3 + Ga3+ I d + Ga3+ In3+ TI'+ Ga3+ ln3+ Ga3+ I d + Tl'+ 1n3+ T13-t ~ 1 3 + Titrated concentration of metal (cM)/ pmol per 15 ml 0.30 0.10 0.20 0.30 0.20 0.10 0.10 0.20 0.30 0.20 0.20 0.20 0.50 0.05 0.05 0.05 0.50 0.05 0.05 0.05 0.50 Metal takenf pg per 15 ml 20.92 11.48 40.87 20.92 22.96 20.44 6.97 22.96 61.31 13.94 22.96 40.87 34.86 5.74 10.22 3.49 57.41 10.22 3.49 5.74 102.18 Mead pg per 15 ml 20.72 11.32 40.52 20.56 22.86 20.62 6.75 22.65 61.25 14.05 22.60 40.76 34.65 5.95 10.35 3.65 57.25 10.12 3.40 5.60 102.45 s/Pg 0.26 0.15 0.42 0.35 0.25 0.32 0.12 0.24 0.32 0.28 0.30 0.46 0.34 0.08 0.12 0.06 0.36 0.15 0.12 0.15 0.24 s r (Yo) 1.25 1.33 1.04 1.70 1.09 1 .55 1.78 1.06 0.52 1.23 1.33 1.99 0.98 1.34 1.16 1.64 0.63 I .48 3.53 2.68 0.23 In3+ and TF+ with Recovery (% ) 99.04 98.61 99.14 98.28 99.56 100.88 96.84 98.65 99.90 100.79 98.43 99.73 99.40 103.66 101.27 104.58 99.72 99.02 97.42 97.56 100.26 AP+ by adding an excess of fluoride to the titration mixture.Iron(iii), Nil+, Th", Zn?+, Cd2+, Pb2+, Mn2+, Bi3+, Cu2+ and the lanthanides interfered seriously even when present at trace concentrations in the solution. The interfering effect of Cu2+ can be removed by ascorbic acid in the presence of KCN solution.The interference from Ni2+, Th4+, Zn2+ and Cd*+ can be eliminated by adding KCN solution prior to titration with Na2EDTA. Indium(in) does not react with KCN. For the second type of interference in the back-titration of Ga3+, In3+ and TP+, it was found that S042-, NO3-, P043-, Clod-, F- and C1- at a concentration of up to 1000 times that of Ga3+, I++ and T13+ did not interfere. The use of I- even at trace concentrations led to the complete reduction of TP+ to TI+. Tartaric, acetic and citric acids at a concentration of up to 1000 times that of Gas+, In3+ and TP+ did not interfere. Oxalic acid at a concentration of up to ten times that of Ga3+, I++ and Tl3+ appeared not to interfere; however, a 100-fold excess of oxalic acid interfered seriously.Aluminium(~i~), Cr3+, Fe3+, Zn2+, Pb2+, Co2+, Mn2+, C$+, N?+, Bi3+, Th4+ and the lanthanides interfered seriously when added to the titration mixture at any concentration. The interference due to Fe3+, Zn2+, Co2+, Cu2+, Ni2+, Th4+ and the lanthanides can be removed by KCN in the presence of ascorbic acid. The KCN solution does not react with either Ga3+ or In3+, but unfortunately completely masks TP+, a problem which could not be resolved in this work. Successive Microtitrations of Ga3+, I d + and T13+ by Spectrophotometric and/or Visual End-point Indication Using xo As for the SXO, seven series of successive spectrophotornetric microtitrations were performed with molar ratios of Ga3+:In3+:TP+ of l O : l : l , 1:lO:l and l:l:lO(andother ratios) in order to obtain a meaningful comparison of the666 ANALYST, JUNE 1991, VOL.116 Table 4 Statistical evaluation of six series of successive microtitrations of Ga3+, In3+ and T13+ with visual determination of the end- point using XO as indicator (pH 5.4-5.8) Series Metal Ion 1 Ga3+ 1n3+ n3+ In"+ 2 Ga3+ ~ 1 3 + 1n3+ 1n3+ 1n3+ 1n3 + 3 Ga3+ T13+ 4 Ga3+ n3+ 5 Ga3+ T13 + 6 Ga3+ m3 + Ti trated concentration of metal (cM)l 10-3 mol dm-3 5 .0 5 .O 5.0 2.5 7.5 5.0 2.5 5.0 7.5 2.5 10.0 2.5 2.5 2.5 10.0 10.0 2.5 2.5 * End-point from lemon yellow to brilliant red. 7 End-point from deep orange to lemon yellow. Metal taken 348.60* 574. 10t 102 1.85 * 174.30 861.15 1021.85 174.30 574.10 1532.77 174.30 1148.20 510.92 174.30 287.05 2043.70 697.20 287.05 510.92 ( P P 4 Mean (ppm) 348.10 574.70 1021.40 174.80 860.50 1022.10 174.90 573.70 1533.20 173.80 1148.60 510.50 173.70 287.30 696.20 288.20 510.10 2042.4 s (ppm) 0.60 0.75 0.50 0.80 0.60 0.70 0.50 0.40 0.60 0.50 0.50 0.60 0.70 0.50 0.40 0.60 0.40 0.70 s r (Yo 1 0.17 0.13 0.05 0.46 0.07 0.07 0.29 0.07 0.04 0.29 0.04 0.12 0.40 0.17 0.02 0.09 0.14 0.14 Recovery (% ) 99.86 100.10 99.96 100.29 99.92 100.02 100.34 99.93 100.03 99.71 100.03 99.92 99.66 100.09 99.94 99.86 100.40 99.84 accuracy, precision and detection limit of both indicators. The experimental procedure was the same for both indicators. The results of seven series of parallel determination of the three ions are given in Table 3. The statistical evaluation shows that the detection limit of the spectrophotometric titration is approximately the same for both indicators.The detection limit was 3.4-9.0 pg per 15 ml(0.23 ppm) for Ga3+, 5.74 pg per 15 ml (0.38 ppm) for In3+ and 10.22 pg per 15 ml (0.68 ppm) for TP+. The detection limit is defined here as the concentration below which no reasonable titration curve can be obtained. For the visual titration, six series of successive titrations (as for SXO) were carried out with molar ratios of Ga3+ : In3+ :TP+ of 1 : 1 : 1 , l : 3 : 2 , l : 2 : 3 , l : 4 : 1 , l : 1 : 4 and 4 : 1 : 1, in order to obtain a true comparison of the statistical values of the two indicators. The procedure was again the same for both indicators. The results of six series of parallel determinations of the three ions are given in Table 4.The statistical calculation shows that the detection limit of the visual titration is approximately the same for both indicators. The detetion limit was 2610 pg per 15 ml(l74 ppm) for Ga3+, 4305 yg per 15 ml (287 ppm) for In3+ and 7665 pg per 15 ml(511 ppm) for TP+. The detection limit in this instance is defined as the concentra- tion below which the colour of the metal-indicator complex cannot be easily detected by the human eye. It is clear from Tables 1-4 that SXO gives a lower standard deviation than XO, i.e., the range of values for successive determinations is smaller for SXO than for XO. References Milner, G. W. C . , Analyst, 1955, 80, 77. Suk, V., and MalBt, M., Chemist-Analyst, 1956, 45, 30. Busev, A. I., Skrebkova, L. M., andTalipova, L. L., Zh.Anal. Khim., 1962,17, 831. Busev, A. I., Talipova, L. L., and Skrebkova, L. M., Zh, Anal. Khim., 1962, 17, 180. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Busev, A. I . , and Tiptsova. V. G., Zh. Anal. Khim., 1960, 15, 698. Yamada, M., Takiguchi, I.. and Fujimoto, M.. Chem. Lett., 1980, 567. Flaschka, H., and Amin. A. M., Fresenius 2. Anal. Chem.. 1953, 140, 6. Dolezal, J., Sir, Z . , and JanaEek, K., Collect. Czech. Chem. Commun., 1952.21, 1300. Cheng, K. L., Anal. Chem., 1955,27, 1582. Kinnunen, J., and Wennerstrad, B . , Chemist-Analyst, 1957,46, 92. Belcher, R., Leonard, M. A., and West, T. S., J. Chem. SOC.. 1958, 2390. Patrovsky, V., Chem. Listy, 1953, 47, 1338. Belcher, R., Ress, D. I., and Stephen, W. I., Talanta, 1960,4, 78. Flaschka, H., Mikrochim. Acta, 1952,39. 38. Flaschka, H., Mikrochim. Acta, 1952, 40, 42. Foley, W. T., and Pottie, R. F., Anal. Chem.. 1956,28, 1101. Hafez, M. A. H., Kenawy, 1. M. M.. and Kabil, M. A., Anal. Lett., 1985, 18,2043. Hafez, M. A. H., and Emam, M. E. M., Analyst, 1986, 111, 1435. Hafez, M. A. H., Abdallah, A. M. A., and Abd El-Gany, N. E. S . , Analyst, 1990, 115, 221. Olson, D. C., and Margeram, D. W., Anal. Chem., 1962, 34, 1299. Sato, H., Yokoyama, Y.. and Momoki, K., Anal. Chim. Acta, 1978, 99, 167. Pijpers, C. J. C., Denop-Weever, L. G., den Boef, G., and van der Linden, W. E., Mikrochim. Acta, 1976, 667. Britton, H. T. S., Hydrogen Zons, Chapman and Hall, London, 1955, vol. 1, p. 365. Echshlager, K., Errors, Measurement and Results in Chemical Analysis. Van Nostrand Reinhold, London, New York, Toronto and Melbourne, 1969. Paper 0/04946H Received November 5th, 1990 Accepted January 1 Oth, 1991

ISSN:0003-2654    

DOI:10.1039/AN9911600663

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST, JUNE 1991, VOL. 116 667 Extraction-Spectrophotometric Determination of Nitrite Using 1 -Aminonaphthalene=2=suIphonic Acid Rachana Kaveeshwar, Lata Cherian and V. K. Gupta* Department of Chemistry, Ravishankar University, Raipur-492 070, India A simple and highly sensitive extraction-spectrophotometric method for the determination of nitrite is described. The method is based on diazotization of o-nitroaniline with nitrite and subsequent coupling with I-aminonaphthalene-2-sulphonic acid in acidic medium to yield a red dye with an absorption maximum at 545 nm. The dye could be extracted into isopentyl alcohol, whereupon its absorption maximum shifted to 530 nm. Beer's law is obeyed in the range 0.08-0.68 and 0.01-0.08 ppm of nitrite in the aqueous and extraction systems, respectively.The molar absorptivity and Sandell's sensitivity were found to be 5.46 x lo4 dm3 mol-1 cm-1 and 0.0008 pg cm-2/ and 4.83 x lO5dm3 mol-1 cm-1 and 0.00009 pg cm-2 in the aqueous and extraction systems, respectively. The method is free from the interferences of Cu and Fe which are the normal interferents in other methods. The method was applied successfully to the determination of nitrite in polluted water. Keywords: Nitrite determination; extraction-spectrophotometry; I-aminonaphthalene-2-suiphonic acid; polluted water Nitrite is an important water pollutant; it is also an important intermediate formed during the biodegradation of nitrogen- ous organic matter.1 The use of nitrites in food preservation, fertilizers, detergents and in the gas, coke, fertilizer, wood pulp, dye and synthetic fibre industries has caused serious pollution problems.'J Nitrites are regarded as hazardous compounds.4 They react readily with secondary and tertiary amines and amides to form carcinogenic N-nitroso com- pounds.5-6 They also induce methemoglobinaemia, in which haemoglobin becomes incapable of transporting oxygen owing to oxidation of the iron(I1) form of haem to the iron(rr1) form.7 The maximum permissible limit, as fixed by the US Public Health Association, is 0.06 pprn of nitrite in potable water.8.9 Apart from the various instrumental methods, such as polarography,'O flow injectionll and voltammetry,I2~l3 nitrites are normally determined by the Griess reaction14 using various reagents.15.16 Many of these reaction systems suffer from the interference of Cu and Fe and have low sensitiv- A number of other spectrophotometric methods have also been reported for the determination of nitrite using different reagents, viz., pararosaniline and N-l-naphthylethylene- diamine dihydrochloride (NEDA) ,Iy p-nitroaniline (PNA) and o-methoxyphenol,20 4-nitroaniline and l-naphthol,21 p-aminophenyimercaptoacetic acid,22 4-aminobenzoic acid23 and p-aminoacetophenone and NEDA.24 In this paper, a reagent system based on the Greiss reaction is described.o-Nitroaniline is diazotized with nitrite and the diazonium ion obtained is coupled with l-aminonaphthalene- 2-sulphonic acid in acidic medium to give a red dye. The dye is then extractable into isopentyl alcohol. The method was applied to the determination of nitrite in polluted water.ity. X. 17.18 Experimental Apparatus A Carl Zeiss Spekol spectrophotometer with matched 1 cm silica cells was used for absorbance measurements. A short- stemmed, pear-shaped 250 ml separating funnel was used for extraction purposes. Calibrated glassware was used for volumetric measurements. * To whom correspondence should be addressed. Reagents Analytical-reagent grade chemicals were used where avail- able, and demineralized water was used for preparing the solutions. Standard sodium nitrite solution (Merck). A 1 mg ml-1 stock solution of nitrite was prepared by dissolving 150 mg of pre-dried analytical-reagent grade sodium nitrite in 100 ml of demineralized water. A small amount of chloroform was added as a stabilizer.5 Working standards were prepared by appropriate dilution of the stock solution.o-Nitroaniline (ONA) solution (Johnson). A 0.2% solution in 20% ethanol was prepared from recrystallized ONA. 1-Aminonaphthalene-2-sulphonic acid solution (Eastman). A 1% solution in 50% ethanol was used. Hydrochloric acid, 6 mol dm-3 (BDH). Isopentyl alcohol (BDH). Procedure for Aqueous Systems An aliquot (0.5-4.25 ml) of a sample solution containing 2-17 pg (0.08-0.68 ppm) of nitrite was placed in a 25 ml calibrated flask. To this solution was added 1 ml of ONA and the acidity was adjusted to 1-2.5 mol dm-3 with hydrochloric acid. The solution was shaken thoroughly for 2 min to allow the diazotization reaction to go to completion. Then, 1.5 ml of 1-aminonaphthalene-2-sulphonic acid were added and the acidity was maintained at 2.5 mol dm-3 by the addition of hydrochloric acid.The absorbance of the red-violet dye obtained was measured at 545 nm against a reagent blank. Procedure for Solvent Extraction A 100 ml volume of a sample solution containing 1-7 pg (0.01-0.08 ppm) of nitrite was placed in a 250 ml separating funnel. To this solution was added 1 ml of the ONA reagent and the acidity was adjusted to 1-2.5 mol dm-3 with hydrochloric acid. After shaking for 2 min, 1.5 ml of 1-aminonaphthalene-2-sulphonic acid solution were added and the acidity was adjusted to 2.5 rnol dm-3 by the addition of hydrochloric acid. The dye formed was extracted with two 5 ml portions of isopentyl alcohol. The combined extracts were dried over 1 g of anhydrous sodium sulphate and the absorbance of the coloured solution was measured at 530 nm against isopentyl alcohol as a reference. The de facto molar668 ANALYST, JUNE 1991, VOL.116 absorptivity of the dye in the aqueous system, 5.46 x 104 dm3 mol-1 cm-1, was found to increase considerably in the extraction system, making the method highly sensitive. Results and Discussion The absorption spectrum of the coloured dye shows maximum absorption at 545 and 530 nm in the aqueous and extraction systems, respectively. As the reagent blanks have negligible absorption at these wavelengths, all absorbance measure- ments were carried out against water and isopentyl alcohol, respectively. Effects of Various Reaction Conditions Effect of acidity and time It was found that constant absorbance values were obtained in the acidity range 1-2.5 mol dm-3 (hydrochloric acid) for Table 1 Effect of foreign ions. Concentration of nitrite, 4 pg per 100 ml (0.04 PPm) Tolerance Pod3-, Sr2+, Sb3+, K+, Pb2+ 2000 Ni2+, SO& 1000 NO3-, Cd*+, Zn2+, Hg2+ 400 Cu2+, Fe3+ 300 As3+, Be2+ 100 Vv, F- 50 Se4+ 15 Foreign ion limit* (ppm) * Amount can vary by +2%.diazotization. Above this range, a decrease in the absorbance was observed. The minimum time required for diazotization was 2 min; there was a decrease in the absorbance after this time. The acidity necessary for full colour development was also studied and it was found that the colour started to develop at an acidity of about 1 mol dm-3. Constant absorbance values were observed in the acidity range 1-2.5 mol dm-3 (hydro- chloric acid).Effect of temperature and stability of the dye No significant changes were observed in the absorbance values within the temperature range 5-60 "C. The dye was stable for about 24 h in the aqueous system and for about 30 min in the extraction system. Effect of reagent concentrations o-Nitroaniline. It was observed that 1 ml of a 0.2% solution of ONA was required for complete diazotization. There was no change in the absorbance at higher concentrations, whereas at lower concentrations there was a decrease in the absorbance. l-Aminonaphthalene-2-sulphonic acid. It was found that 1.5 ml of a 1% solution of the reagent were required for completion of the coupling reaction. There was a decrease in the absorbance at lower concentrations, whereas at higher concentrations no change in the absorbance was observed.Table 2 Application of the proposed method to various water samples. Amount of sample taken, 1 ml Nitrite found*/pg Recovery (YO ) Nitrite Sample added/ Proposed Reported Proposed Reported No. Sample V8 method method? method method 1. 2. Polluted - - water$ - 1.0 0.96 - 1.5 1.53 - 1.9 2.05 Tap water 2.0 1.94 1.96 97.0 98.0 4.0 3.92 3.96 98.0 99.0 6.0 5.91 5.90 98.5 98.33 8.0 7.92 7.93 99.0 99.10 - - - - * Mean of three replicate analyses. t Reference 21. $ Samples were collected from different regions from the Kharoon river, which receives effluents from various industries. Table 3 Comparison of the proposed method with other spectrophotometric methods Reagents Pararosaniline + NEDA PNA + o-methoxyphenol 4-Nitroaniline + l-naphthol p-Aminophenylmercaptoacetic 4-Aminobenzoic acid acid p-Aminoacetophenone + NEDA o-Nitroaniline + l-aminonaph- thalene-2-sulphonic acid Reference Range (ppm) 19 0.08-0.72 20 0.03-0.15 21 0.02-0.14 22 0.1-1.6 23 0.1-1.3 24 0.1-0.8 This 0.08-0.68 work 0.01-0.08 Llax/nm 565 540 610 495 519 545 545 530 ddm3 mol-1 cm-1 5.75 x 104 6.2 x 104" 5.24 x 104* 3.4 x lo4 3.5 x 1w 4 . 6 ~ lo4 5.46 x 1041- 4.83 x 105* Remarks Fe2+, Crvi and sulphide seriously interfere AP+, etc. interfere Many interferences, less sensitive than the proposed method NH4+, S042-, N03-, Sulphide and tin interfere Less sensitive than the proposed method Less sensitive than the proposed method - Most sensitive, less inter- ference, dye is stable up to 60 "C * In the extraction system.t In the aqueous system.ANALYST, JUNE 1991, VOL. 116 669 Beer’s Law, Molar Absorptivity, Sandell’s Sensitivity and Reproducibility Beer’s law was obeyed in the range 0.08-0.68 ppm of nitrite for the aqueous system, and from 0.01 to 0.08 ppm of nitrite for the extraction system. The molar absorptivity (E) and Sandell’s sensitivity for the aqueous and extraction systems were found to be 5.46 x 104 dm3 mol-1 cm-1 and 0.0008 pg cm-2, and 4.83 x 105 dm3 mol-1 cm-1 and 0.00009 pg cm-2, respectively. The repeatability of the method was tested by replicate analyses of a standard nitrite solution over a period of 7 d. The standard deviation and relative standard deviation for the aqueous and extraction systems were found to be kO.01 A and 2.32%, and k0.035 A and 8.43%, respectively.Effect of Foreign Ions As the system was developed for the analysis of polluted waters, the interference from foreign ions commonly present in water was studied by adding known amounts of foreign ions to a solution containing 4 pg of nitrite per 100 ml of water. The tolerance limits for the ions studied are given in Table 1, which shows that most of the cations and anions tested do not interfere. Copper(i1) and iron(n), which are the most common interferents, were found not to interfere with the proposed method. Application The method was applied to the determination of nitrite in river water, effluent water and tap water. The water samples were collected from different sources and were filtered before analysis.As the samples that were available contained no nitrite, synthetic samples were pre- pared by the addition of known amounts of nitrite, and then analysed by the proposed method. The recoveries are shown in Table 2. Conclusion The proposed method is simple and rapid, and more sensitive than other reported spectrophotometric methods (Table 3). Solvent extraction of the dye into isopentyl alcohol accounts for the higher sensitivity of the proposed method. Most of the ions normally present in polluted waters do not interfere. The authors are grateful to the Head, Department of Chemistry, Ravishankar University, for providing laboratory facilities. One of the authors (L. C.) thanks the Council of Scientific and Industrial Research, New Delhi, for the award of a Senior Research Fellowship. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 References Black, J.A., Water Pollution Technology, Reston Publishing Co., Reston, VA, 1977, p. 189. Paul. M., J. Assoc. Off. Anal. Chem., 1980, 63, 937. Zafiriov, 0. C., and True, M. B., Anal. Chim. Acta, 1977, 92, 223. Lijensky, W., and Epstein, S., Nature (London), 1970,225,21. Zhurauler. V. M., and Tsapkov, M. M., Gig. Sanit., 1983,1,62; Chem. Abstr., 1983, 98, 87670~. Lijinsky, W., Banbury Rep., 1982,12,257; Chem. Abstr., 1983, 98, 138502~. Patty, F. A., Industrial Hygiene and Toxicology, Interscience, New York, 1963, p. 919. Standard Methods for the Examination of Water, Sewage and Industrial Wastes, American Public Health Association, Wash- ington, DC, 14th edn., 1976, pp.406 and 434. Resource Agency of California, Water Quality Criteria, State Quality Control Board, Publication No. 3A, Makee, J. E., and Wolf, H. W., Edn. Sacramento, CA, 1958, p. 124. Cai. X., Li, P., and Zhoa, Z., Fenxi Huaxue, 1987, 15, 971; Anal. Abstr., 1988, 50, 6B117. Rolf, K., Jana, D., and Miloslav, P., Agrochemia, 1988,28,119; Chem. Abstr., 1988, 109, 89 151q. Fogg, A. G., and Alonso, R. M., Analyst, 1988, 113, 1337. van den Berg, C. M. G., and Hang, L., Anal. Chim. Acta, 1988, 212, 31. Griess, P., Chem. Ber., 1879, 12, 427. Babko. A. K., and Pilipenko, A. T., Photometric Analysis: Method of Determining Nonmetals, Mir, Moscow, 1976, p. 35. Jacobs, M. B., The Analytical Toxicology of Industrial Inorganic Poisons, Interscience, New York, 1976, p. 596. Nair, J., and Gupta, V. K., Anal. Chim. Acta, 1979, 111, 311. Choube, A., and Gupta, V. K., Anal. Chim. Acta, 1982, 143, 273. Baveja, A. K . , and Gupta, V. K., Chem. Anal. (Warsaw), 1983, 28, 6 . Sunita, S., and Gupta, V. K., Int. J. Environ. Anal. Chem., 1984, 19, 11. Baveja, A. K.. Nair, J., and Gupta, V. K., Analyst, 1981, 106, 955. Rathore, D. P. S., and Tarafder, P. K., J. Zndian Chem. SOC., 1989, 66, 185. Flamerz, S., and Bashir, W. A., Microchem. J., 1981, 26,586. Kaur, P., and Gupta, V. K., J. Indian Chem. SOC., 1987, 64, 428. Paper 010541 6J Received November 30th, 1990 Accepted February 7th, 1991

ISSN:0003-2654    

DOI:10.1039/AN9911600667

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST, JUNE 1991, VOL. 116 COMMUNICATION 67 1 Material for publication as a Communication must be on an urgent matter and be of obvious scientific importance. Rapidity of publication is enhanced if diagrams are omitted, but tables and formulae can be included. Communications receive priority and are usually published within 5-8 weeks of receipt. They are intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subsequently, if justified by later work. Manuscripts are usually examined by one referee and inclusion of a Communication is at the Editor's discretion. Water-soluble Copolymers: A New Class of Media for Fluorescence and Phosphorescence Analyses in Aqueous Systems? Ian Soutar and Linda Swanson The Polymer Centre, School of Physics and Materials, Lancaster University, Lancaster LA? 4YA, UK The first observations of room temperature stabilized phosphorescence (RTSP) from analytes solubilized in aqueous media by a water-soluble copolymer are reported. Pyrene and benzophenone were dispersed in the hydrophobic domains created within the coils of a copolymer of I-vinylnaphthalene and methacrylic acid, containing 36 mol-% of I-vinylnaphthalene.The hydrophobic cavities allow sufficient interactions with heavy ions, such as TI+, dissolved in the aqueous phase, to produce effective population of the triplet states of the sequestered analytes. In addition, the cavities are sufficiently protective to the excited states of the occluded guest molecules that room temperature phosphorescence can be generated readily with simple nitrogen purging.In terms of convenience of sample preparation, water-soh ble copolymers offer distinct advantages over alternative media, such as doped micelles, for the creation of RTSP. These preliminary studies point the way towards the 'custom design' of copolymers for specific analytical applications involving aromatic hydrocarbon analytes in aqueous media. Keywords : Nuo rescence; phosphorescence; heavy a tom effect; room temperature sta bilized phosphorescence; wa ter-solu ble copolymer In this paper we describe the ability of certain water-soluble copolymers to act as novel media for the emission spectro- scopic examination of occluded analytes.Fluorescence from sequestered aromatic guest molecules can be readily studied. However, the novel findings of this paper concern the ability of the hydrophobic domains, which can be generated in aqueous solutions of these copolymers, to afford sufficient protection to triplet states that (if the latter are present in sufficient number) allows room temperature stabilized phosphorescence (RTSP) to be observed. Although other solubilizing media, such as mi~ellesl-~ and cyclodex- trins,8 have previously been used for this purpose, consider- able difficulties can be encountered in attempts to use these materials in routine analyses.9 This is the first report of copolymer systems supporting RTSP from molecules, which do not, in themselves, demonstrate a high intrinsic tendency to phosphoresce. In view of the advantages in terms of the ease of preparation of these media for analysis, and their reliability and stability in use compared with either micelles or cyclodex- trins, water-soluble copolymers could be developed into extremely useful materials for luminescence studies in aqueous solutions. Experimental Materials Dilute (1 X lo-*% d m ) aqueous solutions of a copolymer containing 36 mol-% of 1-vinylnaphthalene and methacrylic acid were used in this work.(Details of the synthesis and characterization of this copolymer will be published subse- quently10.*1.) Pyrene (Aldrich) . Purified by recrystallization from tolu- ene. Benzophenone (BDH) . Purified by recrystallization from ethanol. ThaZliurn(r) nitrate (Fluka). Used as supplied.Instrumentation Fluorescence and phosphorescence spectra were recorded on a Perkin-Elmer LS 50 luminescence spectrometer. Phosphorescence decays were recorded using a specially constructed time-resolved spectrometer, the design of which will be reported at a later date." Transient fluorescence measurements were made on an Edinburgh Instruments 199 spectrometer operating on the time-correlated single photon counting principle. Results and Discussion Solubilization and Fluorescence of Analytes Pyrene (over-all concentration 1 X 10-6 mol dm-3) was dispersed in aqueous polymer solutions of pH 7. The 1-vinylnaphthalene content of the polymer was chosen such that it contained sufficient hydrophobicity that pyrene (and other organics) might be solubilized at this pH whilst retaining the solubility of the copolymer.At the low (1 x 10-2% drn)672 ANALYST, JUNE 1991, VOL. 116 concentration adopted, intermacromolecular interactions are obviated. The pyrene guest molecules are solubilized by a single polymer coil. At the low pyrene concentration employed, double occupancy of the hydrophobic cavities is not observed. (The pyrene fluorescence spectrum is charac- teristic of that of the monomeric, or unassociated, species. At concentrations sufficient to induce double occupancy of the cavities, excimer formation is observed.) [In addition, although we have purposely avoided intermacromolecular effects, there is little doubt that at sufficiently high concentra- tions the hydrophobic interactions would result in macromol- ecular aggregation producing a network of hydrophilic seg- ments joining areas of ‘pseudo-micellar’ hydrophobic vol- umes.These concentrated dispersions would permit solubil- ization of considerable amounts of organic species (as has been demonstrated recently, for other types of water-soluble copolymers, by Guillet and co-workers12-14). Such concen- trated systems, in turn, might present interesting possibilities for analytical application.] The combined spectral characteristics of the naphthyl species, which create the cavities, and of the pyrene guest molecules should be conducive to the occurrence of efficient non-radiative energy transfer; such is indeed observed. The fluorescence spectra, on excitation at 280 nm, where absorp- tion is very much dominated by naphthalene (that of pyrene is all but negligible under the conditions of the experiment), show significant quenching of the naphthalene fluorescence and a considerable proportion of pyrene fluorescence. This observation is of importance in consideration of the genera- tion of RTSP (see below).The pyrene fluorescence contains additional information regarding the nature of the cavity in which it is contained. On excitation at 290 nm (when the pyrene fluorescence generated originates almost exclusively from energy transfer involving the polymeric donor) the pyrene exhibits a highly structured emission band, characteristic of a hydrophobic environment. In contrast, on direct excitation, the aromatic guest molecule exhibits a fluorescence spectrum with altered vibronic band shape characteristic of a more polar environment.Clearly the latter procedure excites the entire pyrene population (given that molar absorption coefficients also will show a polarity dependence). Presumably the polymer ‘pumps’ best, by energy transfer, those species buried more deeply in the coil. The fluorescence generated on excitation directly into the absorption band of pyrene (or that of another analyte) could be used for both qualitative and quantitative purposes. That produced following excitation of the naphthyl species in the copolymer could not readily be used for analytical purposes. The pyrene fluorescence produced in the latter instance is ‘contaminated’ by that of the copolymer, particularly that of the excimeric states produced therein at this l-vinylnaph- thalene content, and pH.However, even this restriction could be removed, if desired, through the agency of dynamic quenching. If a cationic ‘heavy atom’ quencher is used, such as TI+, extremely efficient quenching of the cavity-forming chromophores occurs.11 The result is that the copolymer fluorescence can be reduced to virtually negligible proportions at T1+ concentrations such that quenching of the pyrene excited states, in the protective environment of the cavity, is not substantial. (Naturally, a considerable reduction of over-all pyrene fluorescence intensity occurs because much of the ‘feeder’ element is removed. The T1+ ions compete with the pyrene molecules for the energy donating ‘favours’ of the naphthyl excited states.) The degree of protection afforded by the cavity is illustrated by the trends in fluorescence lifetime, zf, which develop as a function of [TI+] (cf. Table 1).At higher [TI+] (within the range adopted here) the values of Ttf approach a ‘plateau-like’ state. At all non-zero [TI+] values listed in Table 1 copolymer fluorescence is negligible compared with that of occluded pyrenes. However, the real value of using T1+ as a quenching agent is Table 1 Average fluorescence, zf, and phosphorescence, tp, lifetimes for pyrene sequestered in the 1-vinylnaphthalene-methacrylic acid copolymer (T = 298 K; pH = 7) [T1+]/10-* mol dm-3 tf/ns*,t x2fS tdms*,§ x2p$ 0 98.4 68 ---TI -7 1 73.4 49 6.4 24 1.4 63.2 44 6.7 13 2.0 60.4 75 6.4 22 3.0 59.5 41 5.9 25 * Decays are markedly non-exponential (cf.values of x2). t he, = 290 nm; ha = 390 nm. $ The statistical parameters x2 should attain a value of less than 1.3 under conditions where the (single exponential) fits were deemed adequate. 3 A,, = 290 nm; ha = 600 nm. 7 No phosphorescence is observed in the absence of Tl+. its ability to promote triplet state populations via enhanced intersystem crossing rates from S1. As described below, this permits RTSP to be attained. Production of RTSP The attainment of RTSP requires: (a) that a sufficient population of triplet states be created for subsequent detec- tion; and (b) that the triplet states are afforded adequate protection from de-activation processes. Condition (a) can be achieved through the use of heavy atom quenching, as has been used for similar purposes in micellar media.1-7 Condition (b) is achieved first by attempting to lower the concentrations of adventitious quenchers, such as oxygen, to as low a level as possible (without loss of convenience in procedure for use in routine operation). Such is the quality of protection of the hydrophobic cavities that rigorous out-gassing of the solution is not necessary. Oxygen levels can be reduced (within minutes) to degrees which permit the generation of RTSP on commercial instrumentation (such as the LS 50 instrument used here). It is worthy of note that, based on our experience,ll it is apparent that copolymeric media would offer great advan- tages (once their full analytical potential has been realized) over other solubilization media, such as micelles, in the generation of RTSP.For example: (i) de-gassing using nitrogen bubbling is much easier (solutions of the polymeric surfactant do not foam to the same extent as do micellar dispersions); (ii) de-gassing using nitrogen bubbling is accom- plished in much shorter times and with greater reliability (we have witnessed none of the time-dependent photoillumination effects which can9 beset luminescent analyte determinations in micelles); and (iii) RTSP is attained at much lower TI+ doping levels than are required, e.g., for sodium dodecyl sulphate micellar dispersions. For pyrene, as sequestered solute, RTSP is manifest in the appearance of the characteristic emission band centred at about 600 nm. Typical mean phosphorescence decay times are listed in Table 1 following excitation into the absorption band of the naphthalene chromophores of the polymer.The decays are far from exponential (they would not be expected to follow simple first-order kinetics in a situation consisting of energy transfers from donors in a distribution of environments to acceptors similarly inhomogeneously dispersed) but these mean decay times were estimated from forced single exponen- tial fits to the decay curves. These estimates are, however, reasonable descriptors of the ‘average residence time’ in the pyrene triplet state. The lifetimes demonstrate the protective qualities of the cavity: (i) the values are superior to those quoted6 in micellar media; (ii) the lifetimes are not dramatic- ally affected by [Tl+], which will markedly quench triplet states when dynamic access is possible; and (iii) limitedANALYST, JUNE 1991, VOL.116 673 de-gassing times are required to sustain long-lived excited state lifetimes compared with those required for micellar media. This implies that the polymer cavities can (through a greater degree of oxygen exclusion) tolerate greater residual oxygen concentrations than can micelles in the production of RTSP. The advantage of this feature in analytical applications is obvious. In a similar manner we have observed copolymer-TI+ ion mediated RTSP from benzophenone. A more complete report of the spectroscopic and temporal characterization of the singlet and triplet excited states of both analytes dispersed in this l-vinylnaphthalene-methacrylic acid copolymer will be published in due course.11 Conclusions Certain water-soluble polymers can sustain RTSP within aromatic guest analytes. In this respect they hold out the promise for the generation of a whole new class of solubiliza- tion media for analyses involving RTSP.In the instance, as in this paper, where the hydrophobic species of the host are themselves aromatic, they can themselves be made to phos- phoresce. In addition, in circumstances of suitable spectro- scopic overlap between host and guest emission and absorp- tion bands, efficient ‘energy harvesting’ is observed allowing the polymer to ‘pump’ the excited energy states of the guest molecule. The requirements for the generation of RTSP would appear (at present) to be a copolymer composition, which: (i) confers water solubility; (ii) has sufficient hydrophobic interactions to produce formation of a cavity, which will both solubilize and protect the guest analyte under the desired conditions of pH; and (iii) does not exhibit hydrophobic interactions, which, under the prevailing experimental conditions, prohibit access of the heavy atom quencher (necessary for promotion of the TI state population) to the guest molecule.The study of the relationship between copolymer composi- tion and potential for analytical applications of luminescence is part of a continuing work programme centred on water- soluble polymers. The authors acknowledge with gratitude SERC support in terms of funding of equipment used in this study. Support of the Leverhulme trust in respect of continued funding of this research programme is acknowledged, with pleasure.This manuscript was prepared during a brief period of study leave at The University of Melbourne. I. S. thanks the University and, in particular, Dr. K. P. Ghiggino for provision of facilities conducive to this end. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 References Kalyanasundaram, K., Greiser, F., and Thomas, J. K., Chem. Phys. Lett., 1977, 51, 501. Turro, N. J., Lui, K.-C., Chow, N.-F., and Lee, P., Photochem. Photobiol., 1978,27, 523. Okubo, T., and Turro, N. J., J. Phys. Chem., 1981, 85, 4034. Turro, N. J., and Okubo, T., J. Phys. Chem., 1982, 86, 1535. Cline Love, L. J . , Skrilec, M., and Habarta. J. G., Anal. Chem., 1980, 52, 754. Skrilec, M., and Cline Love, L. J., Anal. Chem., 1980,52,1.559. Cline Love, L. J., Habarta, J. G., and Dorsey, J . G., Anal. Chem., 1984,56, 1133A. DeLuccia, F. J., and Cline Love, L. J., Anal. Chem., 1984,56, 2811. Mather. A., Scotland, W. R., Soutar, I., and Swanson, L., in preparation. Soutar, I.. and Swanson, L., Polym. Commun., in the press. Soutar, I . , and Swanson, L., in preparation. Nowakowska, M., White, B., and Guillet, J. E., Macromol- ecules, 1989, 22, 3903. White, B., Nowakowska, M.. and Guillet. J . E., J. Photochem. Photobiol. A : Chem., 1989, SO, 147. Nowakowska, M., White, B., and Guillet, J . E., Macromol- ecules, 1989, 22, 2317. Paper 1/01 050F Received March 6th, 1991

ISSN:0003-2654    

DOI:10.1039/AN9911600671

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST, JUNE 1991, VOL. 116 675 best to complement UV detection with other detectors such as fluorescence (for methylated guanosines) and electrochemical (for hydroxylated guanosines), but both these useful detection modes and series detection are not covered. In fact, little mention is made of these important groups of nucleosides free radical damage to cells. BOOK REVIEWS Chromatography and Modification Of Nucleosides. Part isolated from DNA and also found in urine following drug or A. Analytical Methods for Major and Modified Nucleos- ides. HPLC, GC, MS, NMR, UV and FT-IR Although there is much of value in these volumes there is also a great deal of repetition with some of it verging too volume includes photographs and short biographies of all of the authors, which although fascinating to workers in the same Edited by Charles w' Gehrke and Kenneth '' T' Kuo' + 400' Elsevierm Igg0.Price $141.00; Df'275'00' ISBN Of Chromatography Library' 45A. 'P' liv closely on duplication of material. The first part of each 0-444-88540-4. field, such as this reviewer, may not be of interest to the more rather poor and for such a mass of information the cumulative index in Part C is equally vague and disappointing. The text is reproduced in a low density typewriter face suggesting the use of camera ready copy. For this standard of production the cost of the series (a total of over E300) is excessive. The analytical Chromatography and Modification Of Nucleosides' Part casual reader. There is an index in each volume but these are B. Biological Roles and Function of Modification Edited by Char'es w* Gehrke and Kenneth '' T' Kuom Of Chromatography Library' 'ohme 45B' pp' 'Iv -k 370m Elsevier' 1990* Price 53*75; Df'300.00* ISBN 0-444-88505-6.science is very good, but I rather'feel that with better editing by the Editors and appropriate production by the publishers, a single volume could have contained the kernel of all that is said. Such a volume would have been highly David Perrett Chromatography and Modification of Nucleosides. Part c. Modified Nucleosides in Cancer and Normal Metab- olism Methods and Applications Journal of Chromatography Library. Volume 45C. Pp. Ivi + 452. Elsevier. 1990. Price $179.50; Df1350.00. ISBN Edited by Charles w* Gehrke and Kenneth '. Tm Kuo. readable, informative and not least affordable. 0-444-88598-6.This is a series of four substantial volumes dealing with the analysis and understanding of the growing number of modified nucleosides found in DNA and in particular tRNA, which evidence suggests may form useful cancer markers. The fourth book, Volume D, A Comprehensive Database for RNA and DNA Nucleosides: Chemical, Biochemical, Physical, Spectral and Sequence was not received for review. Parts A and C deal purely with the analytical aspects of measuring modified nucleosides, whereas Part B is a descrip- tive text dealing with their biochemistry. It can be argued that both the qualitative and quantitative study of nucleotide, nucleoside and base metabolism and degradation at its present level would not have been achieved without HPLC.It is, therefore, fitting that the studies included in Parts A and C are published in a chromatography series. With that in mind it is difficult to see the place of Part B in this series and for the general analyst a suitable summary chapter in one of the other volumes would possibly have been more appropriate. Without doubt the Editors of these volumes are the principal workers in the analytical aspects of this field and although they have assembled a large team of chapter co-authors they themselves have written or co-authored 8 of the 23 chapters in the analytical volumes. With so many chapters it is not surprising that the standard of individual chapters is variable. The following comments, therefore, relate to those I found of most interest. Chapters A1 and C2 are very similar dealing with isolated nucleic acid and biological fluids respectively.They are excellent metho- dology chapters giving not only detailed recipes for isolating the nucleosides, setting up the HPLC but, importantly, they also give the necessary optimization and validation criteria. Detailed case studies covering the isolation and characteriza- tion of novel nucleosides from nucleic acids and urine are given in chapters A4 and C5, respectively. A more difficult area is the determination of nucleosides in serum, which does not receive the same in-depth treatment. Chapters on the chromatography of nucleotides and oligonucleotides are also included. Finally the use of these nucleosides as markers of disease is covered in some of the analytical sections in addition to being in Part B.The chapters are on the whole up-to-date and reflect the state-of-the-art with respect to HPLC with UV detection. However, there are many modified nucleosides for which it is Troubleshooting LC Systems. A Comprehensive Approach to Troubleshooting LC Equipment and Separa- tions John W. Dolan and Lloyd R. Snyder. Pp. viii + 515. Humana Press. 1990. Price f63.10. ISBN 0-89603-151-9. An alternative English title for this book might be 'Over- coming Problems in Liquid Chromatography', but the pub- lishers assume we will know what they mean. There are three sections General Considerations, Individual LC Modules and Troubleshooting the Separation plus Other Problems. The first is short, giving instructions on how to use the book and suggesting manuals and guides available for further reference.The 'meat' is in the second and third sections. The former includes two important tabulations, one giving an overview of likely problems in this field and the other a detailed flow-chart for isolating them. There are descriptions of the various techniques of liquid chroma tograph y , with routine procedures for preventive maintenance. The third section deals mainly with actual problems in separation, including the quantifica- tion and pre-treatment of samples. The text as a whole covers the difficulties encountered with various aspects of liquid chromatography, including pumps, reservoirs and tubing, automatic sampling, columns, data systems, detectors, the fitting of accessories, injectors and recorders.In a reference or handbook of this nature a good index is essential. The one provided is adequate but it is suggested that the reader might find it helpful to familiarize himself (or herself) by looking quickly through the text pages before trying to use it (as an example of the value of this, in one Table the term 'OK' is used to denote a change solving a problem, this appears in the index as 'OK' and not, as might be expected, under 'symbols' or 'decoding of symbols'). As would be anticipated in a book from New Jersey, the language is American throughout, but the text is printed in large, clear type and is a joy to behold. I felt that even a beginner would find this book helpful and I have no hesitation in recommending it not only for libraries, in academic and industrial establishments, but also for easy reference within the laboratory.D . Simpson676 ANALYST, JUNE 1991, VOL. 116 Chromatographic Analysis of Pharmaceuticals Edited by John A. Adamovics. Chromatographic Science Series: No. 49. Marcel Dekker. 1990. Pp. vii + 661. Price $125.00 (USA and Canada); $150.00 (Export). ISBN 0 8247 7953 3. In some ways it could be considered that John Adamovics has combined two books into one. The first third of the book consists of three parts considering Regulatory Considerations, Sample Treatment and Chromatography, while the remainder is a substantial catalogue of applications, which is essentially self-contained. The opening section on Regulatory Considerations is a single chapter which introduces the drug development process and the method validation criteria that are proposed by various regulatory agencies.While providing a useful over- view and reference source, there is insufficient guidance here to permit an analyst to develop a method which would satisfy regulatory scrutiny. The second section begins with a chapter describing sample pre-treatment which focuses on manual preparative pro- cedures for formulated products; automation of solid-phase extraction procedures, however, is considered all too briefly by reference to one commercially available workstation. This section concludes with a chapter on robotics which, having described the four basic types of robots, reviews combinations of robots and chromatography as applied to a range of human and veterinary dosage forms.In the third part of the book, four chapters deal in turn with t hin-1 ayer chroma tograph y , gas chromatography , headspace analysis and high-performance liquid chromatography. While there is no common style, each does consider the mechanics of the technique, method development procedures and applica- tions. I have mixed feelings about this section. On the one hand it provides an interesting overview of the major techniques, but on the other there is insufficient detail to assist the novice chromatographer. There are few illustrations and some key areas receive very little discussion. For example, I could find but two sentences on supercritical fluid chromato- graphy, containing a simple referencing error; a single, four sentence paragraph on multichannel (diode-array) detection with just two references; and nothing at all on ion chromato- graphy-a technique widely used, certainly in my laboratories for both the drug substance and drug products.It is, however, in the final part that I feel the true value of this book emerges. Over some 400 pages are drawn together to form a comprehensive listing of drug analysis methods. The major pharmacopoeias primarily have been used as the source literature, plus primary chromatographic journals, up to 1988, and the details include the sample matrix plus a brief chromatographic method description. There is no doubt that this book should have wide appeal to all those involved in pharmaceutical analysis. Over 1300 drugs and related substances are considered and there are nearly 2000 references.What a shame it is that the index is so brief but, nevertheless, a veritable mine of information. J. C. Berridge Principles and Practice of Chromatography B. Ravindranath. Ellis Horwood Series in Analytical Chemistry. Pp. 502. Ellis Howood. 1989. Price f58.50. ISBN 0-7458-0296-6 (Ellis Horwood); 0-470-21 328-0 (Hal- sted Press). This is a well-presented book written in a style that makes it easy to follow. It is divided into four sections, dealing with basic principles, gas and liquid chromatography and some practical applications. Within the gas and liquid chromato- graphy sections there are chapters on basic features of chromatographic systems, and any special theoretical con- cepts associated with these. Emphasis is very much directed towards the practical chromatographer although sufficient theory is presented to explain these practicalities.Diagrams are clear and each chapter is well referenced. Dr. Ravindra- nath has managed to provide a book from which the beginner will learn much, but he also has something to say to the experienced chromatographer. There are some minor errors: ( i ) in Chapter 2 the derivation of the formula, which expresses the resolution of two closely eluting peaks, is incorrect; and ( i i ) it would have been useful to have had an explanation of eqn. 12 in Chapter 6. This is an important book in the general field of chromato- graphy and there should be few laboratories who don’t maintain a copy on their library shelves. I would strongly recommend it for what it purports to be, but for those looking for an in-depth review of specific aspects of chromatography they should look elsewhere.B. Caddy Trace Element Speciation. Analytical Methods and Prob- lems Graeme E. Batley. Pp. 350. CRC Press. 1990. Price f 136.00. ISBN 0-8493-471 2-2. This book is a recent publication in the familiar multi-author series produced by the CRC Press. The subject of trace elemental speciation is undoubtedly an emerging area in analytical chemistry and considerable interest is now being shown towards the subject in many fields, in particular, with reference to environmental and biological systems. The authors of the individual chapters (all recognized experts in the field) have attempted to review critically, the techniques and methodology used in trace elemental speciation studies.Unfortunately the structure of this multi-author book, whilst producing chapters, which in themselves are both critical and current, has led to a text that lacks integration and is correspondingly disjointed. Many of the chapters overlap in subject content and this is particularly apparent for one matrix where the subject has been extensively studied, that of water. As a consequence trace element speciation in biological systems is somewhat eclipsed by the references to aqueous based samples. The first chapter addresses the important area of sample collection, preparation and storage. This in the main covers aqueous samples but sediment, atmospheric and biological based samples are also reviewed. Many of the points outlined in this chapter are reiterated in later chapters, which focus on more specific applications or techniques.The importance of good laboratory practice in speciation work is briefly touched upon but this point is also picked up in later chapters. Chapter 2, on bioavailability and toxicity, represents a good introduction to the subject, and does a lot to promote the relevance and importance of this type of analysis. The transport mechanisms described illustrate the complexity of systems that we often wish or need to study. The following chapter is something of an oddball in the book, in that most of the physicochemical separation techniques described are covered to some extent in other chapters. One or two areas are unique but they are relatively minor in their analytical applications.In terms of technique development for speci- ation, identification and quantification, Chapters 4-7 rep- resent, arguably, the best sections in the book. The first by T. Florence is a very authoritative review of electrochemical techniques with a very comprehensive selection of examples.ANALYST, JUNE 1991, VOL. 116 677 Chapters 6 and 7 provide a good critical overview of chromatographic based techniques (Chapter 6 on HPLC and Chapter 7 on GC), which together with the electrochemical chapter, represent the major analytical techniques currently used in this subject area. Chapter 5 is mainly concerned with the growing area of equilibrium modelling, which is keeping pace and developing as more reliable experimental data become available. In this chapter a very useful review of many of the currently available computer models is presented.The final two chapters are sample oriented rather than being specifically directed towards methodology. As indicated previously, aqueous based samples dominate the earlier chapters but these later chapters concentrate on sediment and biological samples. Chapter 8, whilst describing techniques such as XRF, which is more common to sediment speciation, places most emphasis on selective wet chemical dissolution techniques. These tend to be more generally used in sediment and soil analyses and the subject is comprehensively covered, with an interesting small section on speciation in atmospheric deposits. The final chapter on biological systems is rather repetitive in terms of methodology, but the use of NMR described in this chapter is an interesting application of the technique in speciation studies. The strongest part of the chapter is the specific elements selected for review, these sub-sections are rather brief, but are well referenced.In conclusion, the book has attempted to discuss and review methods and problems associated with trace elemental speci- ation analysis. This it achieves but with some continuity and balance problems. The multi-author approach has led to inevitable overlaps and stylistic differences between the chapters. In addition, mainly for historic reasons, the aqueous matrix has received the major attention at the expense of the biological samples. Nevertheless, the book represents a timely, well-researched review of the subject area and will be of interest to readers currently working in or wishing to find out more about this growing area of analysis.S. J . Haswell Thermal Analysis. Proceedings of the Fourth European Symposium on Thermal Analysis and Calorimetry 1987. Part I Edited by D. Schultze. Pp. 565 + 3. Akademiai Kiado. 1990. Price $60.00. ISBN 5536-0-1-1 11 ; 5537-9-1. Thermal Analysis. Proceedings of the Fourth European Symposium on Thermal Analysis and Calorimetry 1987. Part II Edited by D. Schultze. Pp. 730. Akademiai Kiado. 1990. Price $60.00. ISBN 5536-0-1-1 11 ; 5538-7-1 1. These two volumes of the Proceedings of ESTAC 4 are merely the four issues of Vol. 33 of the Journal of Thermal Analysis bound together in hard covers. One could, perhaps, question the wisdom of such a ‘re-issue’ but, clearly, the long experience of the publishers must indicate that this is a financially viable proposition. The present reviewer readily admits that to have two hard-cover volumes on a bookshelf is more convenient than four issues of a soft-cover journal.However. a word of warning is necessary in this particular instance; the spines and fronts of both volumes are completely devoid of any lettering and thus, removal of the dust-covers banishes the volumes into anonymity. It is possible that this unfortunate omission is confined to review copies-one hopes SO! Part I contains 14 Plenary Lectures and 2 Award Lectures: the Netzsch-GEFTA Award for 1987 and the Thermal Methods Group Award. The text of all of these lectures is given in full.It is a pity that all of the Plenary Lectures could not be included since, according to the Foreword, 17 were delivered. Also included are 17 papers on Theory; 16 on Instrumentation; 9 on Earth Sciences and Raw Materials; and 18 on Solid State Reactions. The average length of these communications is 6 pages but it should be remembered that they were all presented as posters at the Symposium. A nice touch in Part I is that each Plenary Lecture is accompanied by a photograph of the lecturer ‘in action’, except where the lecture is under joint authorship, when no information is given as to the presenter. The photographs show some of the lecturers as being very young, although, in truth, this indicates that the present reviewer is getting old(er)! Part I1 contains 55 papers under the heading of Inorganic Chemistry, Glass and Ceramics; 4 on Pharmacy, Biology and Medicine; and 30 on Organic Chemistry and Polymers. Also included in Part TI are 7 summaries of topics covered during the Symposium and suggestions for future studies.In view of the nature of these volumes, it would be inappropriate to comment on any of the papers individually, except to say that several new approaches and some exciting new ideas are proposed. All papers are in English and where this is not thc mother tongue of the authors, the quality of the English is high throughout, indicating meticulous editing. In addition, both volumes are typeset rather than the more usual contemporary offset from typescript, making for easy reading. Without exception, the diagrams are very clearly reproduced.Part 11 concludes with useful author and subject indexes for both volumes. In conclusion, it is possible that these two volumes will appear on the bookshelves of more thermal analysts than the corresponding part of the Journal. It is also possible that it may also result in an increase in subscriptions to the Journal of Thermal Analysis. C. J . Keattch ~~~~ ~ Acronyms and Abbreviations in Molecular Spectroscopy. An Enzyclopedic Dictionary Detlef A. W. Wendisch. Pp. 315. Springer-Verlag. 1990. Price DM98.00. ISBN 3-540-51 348-5; 0-387-51 348-5. It is as difficult to review a book of acronyms as it is to write one. Inevitably there will be some omissions as far as the reviewer or readers are concerned, as often they are working in a specialized field.However, there are few omissions in this volume. The book is not just a collection of definitions of acronyms, each entry contains a concise and informative explanation of the origins of the technique or method to which it refers. A magnificent example is the explanation of circular dichroism (CD) and optical rotatory dispersion (ORD) complete with relevant formulae, which is better than many textbook descriptions. Each entry also carries with it a few key references and a comprehensive index, which this rcader will find very useful. By the authors own admission in the Preface. there is a heavy emphasis upon acronyms used in the field of nuclear magnetic resonance (NMR) spectroscopy. I was not aware of the huge number of acronyms in this field and I guess all but the most well informed will be in a similar situation.Reading some of these made me wonder whether they really are used in everyday NMR conversation. For example, the use of the acronym for proton enhanced nuclear induction spectroscopy might be re-considered in polite society. It also made me wonder why our NMR friends are intent on the use of so many acronyms, the proliferation of which is not generally of benefit to the English language or the transmission of knowledge to the uninitiated. Given that there is nothing that can be done about this proliferation, this book is a must for progression of any budding spectroscopist in this field of research. The emphasis on NMR spectroscopy does have disadvan- tages in some general areas.For example the definition of678 ANALYST, JUNE 1991, VOL. 116 signal-to-noise ratio (SNR) is very specific to peak signals, i.e., specifically associated with discrete line shapes. Those who are interested in continuous signals and the contribution of additive noise and multiplicative noise to a signal will find no help here. For an NMR person this well-researched and well-pre- sented book is a must, for the rest of us it is a useful hand-book to keep on the library shelves in the event of having to communicate with an NMR specialist. Right now I am going off to the lab to do some more work in my favourite area of molecular spectroscopy, mode-mismatched thermal lens spec- troscopy (MM-TLS), which incidentally does not feature in this book. R. D. Snook ~~~ ~ ~ ~~~ Analysis of Trace Organics in the Aquatic Environment Edited by B.K. Afghan and Alfred S. Y. Chau. Pp. 346. CRC Press. 1989. Price f 130.50. ISBN 0-8493-4626-6. This book is the latest offering from the generally excellent series of monographs published by CRC press, and is the final volume in a four volume set, which reviews the analysis of trace organics in the aquatic environment. The final volume has nine chapters devoted to volatile organics, toxaphene, organometallics, humic acids, PAH, phenols, dioxins, phthal- ates and PCBs. It is intended to provide a reference source for university students and practising environmental chemists, with sufficient detail to enable readers to determine trace constituents in an accurate manner. In general, the authors have achieved their objective with an excellent collection of comprehensive and informative reviews on the analysis of environmental chemicals of topical interest. Disappointingly, but almost inevitably in books of this type, the reviews only cover the literature up to, and including, 1986. This probably explains one of the notable omissions, namely references to the analysis of tributyl tin compounds in environmental samples by capillary GC. There is also, surprisingly, no reference in any of the chapters to the numerous ‘Blue Book’ methods produced by the UK Depart- ment of the Environment Standing Committee of Analysts, which provide validated methods for many of the organics covered in this book. Despite these limitations, and a few annoying typographical errors, I found the book a useful and timely reference work for practical information on the analysis of a range of organics. It will undoubtedly be widely consulted in my laboratory, and in other laboratories directly involved with the analysis of these compounds in aquatic samples. However, at f130 for some 346 pages it is expensive and this will unfortunately preclude its purchase by individual scientists involved or interested in this topic. c. n. Watts

ISSN:0003-2654    

DOI:10.1039/AN9911600675

出版商:RSC    

年代:1991

数据来源: RSC

摘要:

ANALYST, JUNE 1991, VOL. 116 CUMULATIVE AUTHOR INDEX JANUARY-JUNE 1991 Abbas, Nureddin M., 409 Abdallah. Amin M. A.. 663 Akiyama, Hideaki, 501 AI-Tamrah. S. A.. 183 Alarie, Jean Pierre, 117 Albero. Ma. Isabel, 653 Alegret. Salvador, 473 Alexiades, Costas A., 361 Alfassi, Zeev B . , 35 Altesor, Carmen, 69 Alvi, S. N., 405 Alwarthan. A. A.. 183 Analytical Methods Committee. Anderson, Fiona. 165 AntonijeviC, Biljana. 477 Apak, ReSat, 89 Apostolakis, John C., 233 Armfield, Susan J . . 569 Arowolo, Toyin A., 595 Askal, Hassan F., 387 Assclt, Kees van, 77 Attiyat, Abdulrahman S . . 353 Baba, Jun-ichi, 45 Bachas, Leonidas G.. 581 Balasubramanian, N., 207 Barnes, Ramon M., 489 Basak, Bidyut, 625 Baykut, Fikret, 89 Beh. S. K.. 459 Bendtsen, Anders Broe. 647 Bcrlot. Pedro E., 313 Bhattacharya, Utpal.625 BiCanid, Dane, 77 Birch, Brian J., 123, 573 Birnie. Albert, 601 Bisagni, E.. 159 Blais, J., 159 Bond. A. M., 257 Bowyer, James R.. 117 Bratinova, Stefanka P., 525 Brown. Richard H . , 437 Bunaciu. Andrei A., 239 Cacho, Juan, 399 Candillier, Marie-Paule, 505 Canesi. Laura, 605 Cardwell, Terence J., 253 Cattrall, Robert W., 253 Cepeda. A.. 159 Chan, Wing Hong, 39,245 Chang, Wen-Bao, 213 Chaurasia, Anupama, 641 Chen, Danhua, 171 Chen, Guo Nan, 253 Chen, Zeweng. 273 Cherian, Lata, 667 Cheung. Yu Man, 39 Chiswell. Barry, 657 Christopoulos. Theodore K., Ci, Yun-Xiang, 213, 297 Ciesielski. Witold, 85 Cohen, Arnold L.. 15 Cogofref, Vasile V., 239 Costa-Bauza, A . , 59 Covington, Arthur K., 135 Cowan, Faye J.. 339 Cresser, Malcolm S . , 141, 595 Daily. Simon, 569 Das, Pradip K., 321 Dawson, Bernard S.W., 339 de Faria, Lourival C.. 357 de la Torre, M., 81 de Oliveira Neto, Graciliano. Deb. Manas Kanti, 323 Debayle. Pascal. 409 Desai, M., 463 DeVasto, Joseph K., 443 Diamandis. Eleftherios P., 627 Dol. Isabel, 69 415. 421 627 357 Dona, Anne-Marie, 533 Donnelly, Garret, 165 Downs, Mark E. A., 569 Edmonds, Tony E., 573 Edwards. Anthony C., 601 Efstathiou, Constantinos E., Elagin, Anatoly, 145 Ellis, Andrew T.. 333 Ertas, F. Nil, 369 Esmadi, Fatima T.. 353 Evans, Otis, 15 Favier, Frederic, 479 Favier, Jan-Paul, 77 Feher, Zsofia, 483 Feng, Y. P., 469 Fernandez-Band, Beatriz. 305 Fernandez-Gamez, F., 81 Fernandez Muiiio, Miguel A., Fernhndez-Romero, J. M., 167 Ferris, Marie M., 379 Fleming, Paddy, 195 Florido, Antonio, 473 Fogg, Arnold G., 249, 369, 573, Fouques.Dominique, 529 Fu, Chengguang, 621 Gaind, Virindar S . . 21 Garcia Mateo, J . V., 327 Georgiou, Constantinos A., 233 Gielen, Johannes W. J.. 437 Glab, Stanislaw, 453 Goodlet, G . , 469 Gordon. Rhea L., 51 1 Grases, F., 59 Grayeski, Mary Lynn, 443 Griepink, Bernardus, 437 Guitart, Ana, 399 Gupta, V. K., 391, 667 Gushikem. Yoshitaka, 281 Hafez, Medhat Abd El-Hamied, 663 Haggett, Barry G . D., 569 Hamilton, Ian C., 253 Hansen. Elo Harald, 647 Harper, Alexander, 149 Harris, N. K., 469 Hart, John P., 123 Haswell, Stephen J., 333 Hawke, David T., 333 Hendrix, James L., 49 Hernandez Cordoba, Manuel. Hernandez Orte, Puri, 399 Himberg, Kimmo, 265 Hocquellet, Pierre. 505 Hofstetter, Alfons, 65 Hollander, Jacobus C. Th., 437 Hong, Jian, 213 Hong, Sung O., 339 Hulanicki.Adam, 453 Husain, Sajid, 405 Imai. Kazuhiro, 609 Ioannou, Pinelopi C., 373 Ionescu, Mariana S . , 239 Ishibashi, Mumio, 609 Ishida, Junichi, 301 Ishida. Ryoei, 199 Islam, M. M., 469 Israel, Yecheskel, 489 Ivanova, Christina R., 525 Jacobs, Betty J., 15 Jain, Archana, 641 Jana, Nikhil R., 321 Jqdrzejewski, Wlodzimierz, 85 Jerrow, Mohammad, 141 Jiang, Jian, 395 Jie. Niaqin, 395 Jones, Michael H., 449 Kakizaki, Teiji, 31 373 269 63 1 517 Kataky. Ritu, 135 Kaveeshwar, Rachana, 667 Keating, Paula, 165 Keramidas. Vissarion Z., 361 Khan, Shaukat H . , 585 Kharoaf, Maher A., 353 Kielbasinski, Piotr, 85 Knochen, MoisCs, 69 Kolbe. Ilona. 483 Koncki. Robert, 453 Konishi, Tetsuro, 261 Konstantianos, Dimitrios G., Koupparis, Michael A., 233 Kubota, Lauro T..281 Kudzin, Zbigniew H., 85 Kumar, B. S. M., 207 Lan, Chi-Ren, 35 Landry, Jacques, 529 Langelaan, Fred G. G . M.. 437 Laskar. Subrata, 625 Lazaro, F., 81 Lee, Albert Wai Ming, 39, 245 Lee, Yishiuan. 615 Leonard, Michael A.. 379 Li, Jie, 309 Lin, Chang-shan, 277 Linares, Pilar, 305 Liu, Dao-Jie, 497 Liu. Ren-Min, 497 Liu, Shaopu, 95 Liu, Weiping, 273 Liu, Xue-zhu, 277 Liu, Zhao-Lan, 213 Liu, Zhongfan, 95 Locascio, Guillermo A., 313 Lopez Garcia. Ignacio, 517 Lu, Qiongyan, 273 Lubbers, Marcel, 77 Lucas, S . , 463 Luque de Castro, M. D., 81, Lyons, David J . , 153 McCallum. Leith E., 153 McDonnell, M. B., 463 Mahuzier, G., 159 March, J. G., 59 Marr. Iain, 141 Marsel, Joie, 317 Martinez Calatayud, J., 327 Masuda, Toshihiko. 501 MatoviC, Vesna.477 Matthies. Dietmar. 65 Mattusch, Juergen. 53 Mazzucotelli, Ambrogio, 605 Menjyo, T., 257 Metcalf, Richard C.. 221 Mikolajczyk, Marian, 85 Miller, James N.. 3 MilosavljeviC, Emil B.. 49 Mishra, Neera, 323 Mishra, Rajendra Kumar, 323 Mitrakas, Manassis G., 361 Moody, G. J.. 459, 469 Moreira, JosC C., 281 Moreira, Josino C., 249. 369 Morimoto, Kazuhiro, 27 Moritz, Werner, 589 Mueller, Helmut, 53 Mukhtar, Sarfraz. 333 Miiller, Lothar, 589 Muiioz de la Peiia, Arsenio, 291 Nagaosa, Y., 257 Nageswara Rao, R., 405 Nakagawa. Genkichi, 45 Nakamura, Masaru, 301 NedeIjkoviC, Mirjana, 477 Nelson, John H., 49 Nicholas, C. V., 463 Nicholson, Patrick E . , 135 Nie uwenh uize, Joop. 347 373 167, 171, 305 679 Niinivaara, Kauko, 265 NikoliC, Sneiana D., 49 Nobbs, Peter E., 153 Nukatsuka, Ishoshi, 199 O’Dea, John, 195 O’Halloran, Kelvin R., 657 Ohzeki, Kunio.199 Ojanpera, Ilkka, 265 O’Kennedy, Richard, 165 Omar, Nabil M.. 387 Ortiz Sobejano, Francisca, 517 Osborne, William J., 153 Pal, Tarasankar, 32 1 Piilivan, Cornelia, 239 Pambid, Ernest0 R., 409 Parker, David, 135 Parker. Glenda F.. 339 Pascal, Jean Louis, 479 Pasquini, Celio, 357 Patel, Khageshwar Singh, 323 Peck, David V., 22 1 Pharr, Daniel Y., 5 1 1 Pickral, Elizabeth A . , 511 Pinto, Ivan, 285 Poky-Vos, Carla H., 347 Ponzano, Enrica. 605 Popova, Sijka A., 525 Powell. Francis E . , 631 Prince, Patrick K., 581 Prognon, P., 159 Prownpuntu, Anuchit, 191 Pungor, Erno, 483 Rios, Angel, 171 Rivaro, Paola, 605 Robards. Kevin, 549 Roianska, Barbara, 521 Ruan, Chuanmin, 99 Sakai, Tddao, 187 Sakurada, Osamu, 31 Saleh, Gamal A., 387 Salinas, Francisco, 291 Sanchez, Catalina, 653 Sanchez-Pedreiio, Concepcion, Sargi, L., 159 Sarkar, Mitali, 537 Saunders, Kevin J ., 437 Scollary, Geoffrey R., 253 Scullion, S. Paul, 573 Selnau, Henry E., 511 Sepaniak, Michael J., 117 Sherigara, B. S . 285 Shi, Yingyo, 273 Shijo, Yoshio. 27 Shinde, Vijay M., 541 Shivhare, Priti. 391 Si. Zhi-Kun, 309 Simal Lozano, Jesus , 269 Simonovska, Breda, 317 Singh, Raj P., 409 Soledad Duran, Maria, 291 Soledad Garcia, Ma., 653 Somasiri, Loku L. W., 601 Soutar, Ian, 671 Stoyanoff. Robert E . , 21 Strauss, Eugen, 77 Suetomi. Katsutoshi, 261 Sugawara, Kazuharu, 131 Sultan, Salah M., 177, 183 Sundaramurthi, N. M.. 541 Swanson, Linda, 671 Taga, Mitsuhiko, 31, 131 Takahashi, Hitoshi, 261 Takeda, Kikuo, 501 Takeda, Yasushi, 609 Tanaka.Shunitz. 31, 131 Tatehana, Miyoko, 199 Thomas. J. D. R., 459,469 Thompson, Robert Q.. 117 Tikhomirov, Sergei, 145 Titapiwatanakun. Umaporn. 191 653680 ANALYST, JUNE 1991, VOL. 116 Tong, Po Lin, 245 Toyo’oka, Toshirnasa, 609 Troll, Georg, 65 Tsai, Suhjen Jane, 615 Tsang, Kwok Yin, 245 Tseng, Chia-Liang, 35 Tutem, Esma. 89 Udupa, H . V. K . , 285 Uehara, Nobuo, 27 Vadgama, P.. 463 Valcarcel, Miguel, 81, 171. 305 van Delft. Wouter, 347 van den Akker, Adrianus H., van den Berg, Constant M. G., Vandcndriessche, Stefaan, 437 Vazqucz, M. L., 159 Verchkre, Jean-Franpis, 533 Verma. Archana, 641 Verma, Krishna K., 641 Viarengo, Aldo, 605 347 585 Vo-Dinh. Tuan, 117 Volynsky, Anatoly, 145 Vuori, Erkki, 265 Wada, Hiroko, 45 Wahdan. Tarek M. Abd El-Fatah. 663 Wang, Fang, 297 Waris, Matti. 265 Werner. Gerhard, 53 Wilson, B. William, 449 Worsfold, Paul, 549 Wotring. Vanessa J . . 581 Wring, Stephen A., 123 Wu, Wch S . . 21 Xu, Qiheng, 99 Yamaguchi. Masatoshi, 301 Yarnaguchi, Tokio, 501 Yang, Mo-Hsiung. 35 Yuchi. Akio, 45 Zhang, Xiao-song, 277 Zhao, Yi, 621 Zhu, Gui-Yun, 309

ISSN:0003-2654    

DOI:10.1039/AN9911600679

出版商:RSC    

年代:1991

数据来源: RSC