摘要:

608 Analyst May 1983 Vol. 108 PP. 608-614 Spectrophotometric Determination of Trace Amounts of Quaternary Ammonium Salts in Drugs by Ion-pair Extraction with Bromophenol Blue and Quinine Tadao Sakai De9artment of Chemistry Gifu College of Dentistry 1851 Takano Hozumi-cho Gifu 501-02 Jafian The sensitive and selective method reported here is based on the reaction of quinine cations with bromophenol blue (BPB) to form a 1 1 complex anion, which with a quaternary ammonium salt a t pH 6.7 is extractable into chloroform as an ion pair. Berberine and benzethonium were extracted in large amounts into chloroform with BPB only when quinine in a pH 6.7 buffered aqueous solution co-existed with them. In addition when this showed a strong ion associate ability then berberine and benzethonium could react in the organic phase with BPB to give a blue product.The absorbance of the ion associate in chloroform was measured at 610 nm. Calibration graphs were linear in the range 0.5 x 10-g-3.0 x 10-6 M for berberine and benzethonium. Molar absorptivities were 3.75 x lo4 1 mol-l cm-l for the berberine associate and 3.14 x lo4 1 mol-1 cm-l for the benzethonium associate. The blue associate can be used for selective and sensitive spectro-photometric determination of berberine and benzethonium in multi-com-ponent drugs. Keywords Berberine assay ; benzethonium assay ; co-extraction spectrophoto-metry ; bromophenol blue - quinine associate Most of the procedures proposed for the extraction-spectrophotometric determination of onium compounds depend on the formation of ion associates between an onium cation and dye anion.ll2 With monoprotic acid dyes such as tetrabromophenolphthalein ethyl ester (TBPE), 2,6-dibromophenolindophenol (DBIP) and potassium picrate (PCA) the optimum pH range for the extraction of alkaloids and quaternary ammonium salts was found to be ~ i d e .~ - ~ TBPE is an excellent reagent for the determination of trace amounts of tertiary amines, alkaloidss and quaternary ammonium salts,3 but it is not selective enough for the determination of amines and quaternary ammonium compounds in complicated samples because the absorp-tion spectra (Amax. = 555-610 nm) of the ion associates and the optimum pH range (pH = 6-10) overlap. On the other hand with multi-protic acid dyes such as bromophenol blue (BPB)' and bromocresol green (BCG),8 the extraction behaviour is very complex because the ion associates formed between onium cations and dye anions depend on the pH level in the aqueous solutions.In a pH 4.7 medium the ion associates of H.BCG- - amines and quater-nary ammonium salts were successfully extracted into organic solvents with both ion associates showing a yellow colour.8 Accordingly the method is sensitive but not selective for the assay of complicated samples. In contrast in alkaline media (about pH ll.0),9 only BPB2- - (R4N+)2 associates were extracted into organic solvents showing a blue colour. However the extracta-bility was poor (molar absorptivities were about 2 x lo4 1 mol-l cm-l in 1,2-dichl~roethane~) and calibration graphs did not obey Beer's law in the low concentration region of quaternary ammonium salts and also did not pass through the origin.In this investigation it was found that berberine and benzethonium being quaternary ammonium compounds (R4N+) when in a pH 6.7 medium can be completely co-extracted with BPB into chloroform to form a ternary ion associate R4N+ - BPB - quinine only in the presence of a quinine solution even though the R,N+ - BPB associate cannot be extracted in the absence of quinine. The BPB - quinine ion associate is used to improve extractability detectability of and selectability for berberine and benzethonium. Berberine and benzethonium are widely used as a stomach and bowels medicine and as disinfect ants and antiseptics . This paper describes the extraction and spectropliotometric assay of berberine and benze-thonium in multi-component drugs SAKAI 609 I H OH Quinine CH3 CH3 CH, CH3 CHs CHB Benzethonium CH36 Berberine Experimental Apparatus A Hitachi Model 556 double-beam spectrophotometer and a Hitachi Model 057 X - Y recorder were used with stoppered 1-cm light-path cells.Extractions were carried out by shak-ing with an Iwaki Model KM shaker. A Hitachi-Horiba pH meter with a glass electrode, Model M-5 was used to measure the pH of aqueous phases after extraction. Centrifugation was performed with a Kubota KS-4000 centrifuge. Reagents All reagents used were of analytical-reagent grade. Standard berberine solution. A stock solution of 1 x 1 0 - 3 ~ berberine was prepared by dissolving 0.407 8 g of berberine hydrochloride (dried at 105 "C) in distilled water and diluting to 1 1.Standard benzethoniurn solution. A stock solution of 1 x M benzethonium was prepared by dissolving 0.4650 g of benzethonium chloride in distilled water and diluting to 100 ml. Standard quinine solution. A stock solution of 1 x M quinine was prepared by dis-solving 0.3969 g of quinine hydrochloride in distilled water and diluting to 100 ml. Working standard solutions were prepared by accurate dilution of the above solutions. Bromophenol blue solution. Bufer solution j5H 6.7. Chloroform. Used without further purification. The stock solution was standardised by the official method.1° Bromophenol blue (0.1608 g) (Nakarai Chemicals Ltd.) was dissolved in buffer solution of pH 6.7 to give a 2.4 x The borate - phosphate buffer was prepared by adding 1 N sul-phuric acid or 1 N sodium hydroxide solution to 0.3 M potassium dihydrogen orthophosphate solution containing 0.1 M sodium tetrahydroborate(II1).M solution. Procedure Measure 2 ml of a sample solution containing 200-1 200 pg 1-1 of berberine or 230-1 400 pg 1-1 of benzethonium into a 50-ml calibrated flask and add 1 ml of 2.4 x M BPB solution buffered at pH 6.7 10 ml of phosphate - borate buffer solution (pH 6.7) and 1 ml of 5 x M standard quinine solution. Dilute the mixture to the mark with distilled water and transfer the solution into a 100-ml separating funnel and shake with 10 ml of chloroform for 5 min then centrifuge to remove water droplets. After separation of the organic layer measure the absorbance of the organic phase at 610 nm against a reagent blank.Results and Discussion Absorption Spectra of Ion Associates with BPB Fig. 1 shows absorption spectra of ion associates formed between onium compounds and BPB anions at different pH values. Both quinine and berberine were extracted into chloro-form with the univalent BPB anion at pH 3.8 to form H.BPB- - quinine and - berberin 610 SAKAI SPECTROPHOTOMETRY OF QUATERNARY Analyst Vol. 108 0.3 2 0 a 0.2 0.1 / A l l j 400 ~~ ~ 500 600 700 Wavelengthlnrn Fig. 1. Absorption spectra of 1 BPB -quinine at pH 3.8 quinine 3 x M ; 2 BPB -berberine at pH 3.8 berberine 4 x M ; 3, BPB - quinine at pH 6.7 quinine 1 x M ; 4, BPB - berberine at pH 6.7 berberine 2 x M ; 5 BPB - quinine - berberine at pH 6.7 quinine 1 x M berberine 2 x M ; solvent, chloroform.associates and both ion associates in the organic phase showed a yellow colour having a wave-length of 418 nm (graphs 1 and 2). The extraction of ion associates with BPB in this pH region is sensitive; quinine and berberine of concentration M in the aqueous solutions can be determined but it is not selective because of the extraction of both quinine and berberine. At pH 6.7 the absorption maximum of BPB - quinine associates occurred at 590 nm (graph 3) ; nevertheless other amines such as procaine dibucaine ephedrine eserine and diphenhydramine were not completely extracted with BPB in the same medium. However it was found that among quaternary ammonium compounds berberine and benzethonium not extracted with BPB a t pH 6.7 (graph 4) could be extracted successfully at the same pH only in the presence of 1 x 10-5-1.5 x M standard quinine solution.The extractability of the berberine and benzethonium associates is very high. For instance, although the absorbance was zero for 2 x 1 0 - 6 ~ berberine in the absence of quinine when 1 x lop5 M quinine was added to the extraction system AA (Fig. 1) was 0.375 (graph 5) where AA = Amix-Aqllin Amix representing the absorbance of the 1 x M quinine - berberine mixture and Aquin the absorbance of the BPB - quinine associate and the value was 0.145 for 1 x lob5 M quinine. The absorbance of the reagent blank was high but constant and very stable. It is assumed that the high extractability of the ion associate with BPB causes a ternary and bulky associate among BPB2- quinine and berberine to form.Effect of pH on Extraction The effect of pH on the extraction of BPB - quinine and BPB - quinine - quaternary ammonium salt ion associates was examined by a general procedure similar to that recommended above. The concentrations of BPB and quinine in the BPB - quinine extraction system were 1.2 x and 4.8 x M respectively and the concentrations of BPB, quinine berberine and benzethonium in the BPB - quinine - berberine and BPB - quinine -benzethonium systems were 4.8 x 1 x 2 x loA6 and 2 x M respectively. As shown in Fig. 2 the optimum pH regions where the absorbances of the organic phase were maximum and constant were 6.2-6.4 for the BPB - quinine associate and 6.5-7.1 for the BPB - quinine - berberine complex.In a more acidic or more alkaline solution the absorbance at 590 nm tended to decrease because of the alternation of the extracted species in the BPB May 1983 AMMONIUM SALTS I N DRUGS BY ION-PAIR EXTRACTION 611 quinine co-extraction system. For instance in alkaline solutions the BPB - quinine associate cannot be extracted completely and cannot cause the co-extraction. On the other hand the BPB2- - berberine associate was extracted but the extractability was very low (graph 3). Moreover the calibration graph did not obey Beer's law for the berberine and benzethonium solutions at low concentrations. Accordingly the extraction with BPB in alkaline media is not suitable for the assay of trace amounts of quaternary ammonium salts. In the proposed extraction system at pH 6.7 amines and quaternary ammonium salts such as procaine ephe-drine diphenhydramine tetraethylammonium and neostigmine gave no interference so the extraction of the ternary complexes was carried out at pH 6.7 in order to increase the detecta-bility and selectivity for berberine and benzethonium assay.0.4 0.3 Q) C m + 0.2 s a 9 0.1 6.0 6.5 7.0 7.5 PH Fig. 2. Effect of pH on extraction of associ-ates with BPB with the following conditions 1, BPB - quinine associate quinine 1 x M ; 2, BPB - quinine - berberine quinine 1 x M, berberine 2 x M; 3 BPB - berberine, berberine 2 x M ; wavelength 610 nm; pH, 6.7; and water as reference. Effect of BPB Concentration berberine was complete and constant from 1.6 x quinine.BPB concentration affects colour development and it was observed that the extraction of M BPB in the presence of to 4.8 x The run was carried out a t 4.8 x M BPB. Effect of Shaking Time The shaking time was varied from 30 s to 10 min. A shaking time of 2 min was found sufficient for complete extraction and the colour intensity of the chloroform phase remained constant for at least 2 h at 20 "C (room temperature). TABLE I MOLAR ABSORPTIVITIES AND COEFFICIENTS OF VARIATION (CV) FOR QUATERNARY AMMONIUM SALTS WITH DIFFERENT CONCENTRATIONS OF QUININE The values were calculated from the results for ten determinations of 2 x M quaternary ammonium salts. The BPB concentration was 4.8 x 10-5 M and the solvent used was chloroform. With 1 x M With 1.5 x M quinine quinine Quaternary ammonium - r compound ~ / 1 mol-l cm-1 CV ~ / 1 mol-l cm-l CV % Berberine .. 3.75 x 104 0.8 4.35 x 104 1 .o Benzethonium . . . . 3.14 x 104 1.8 3.23 x 104 2. 612 SAKAI SPECTROPHOTOMETRY OF QUATERNARY Analyst Vot?. 108 Calibration Graphs and Molar Absorptivities The calibration graphs obtained by the standard procedure showed a good linear relation-ship over the range 0.5 x 10-6-3 x M of berberine and benzethonium but only in the presence of standard quinine solution. Table I shows the molar absorptivities of BPB-quinine - R4N+ ion associates (R,N+ - berberine and - benzethonium) in chloroform and the coefficients of variation calculated from the results for ten determinations of 2 x 10-6 M R4N+ standard solutions. The molar absorptivities of ternary ion associates were larger than the molar absorptivities of BPB2- - R4N+ associates9 in alkaline media.The absorbances of 1 x 10-5 and 1.5 x M quinine - BPB associates were 0.145 and 0.265 respectively against water as a reference. Although the ion associate with 1.5 x M quinine showed a larger molar absorptivity than that of 1 x l W 5 ~ quinine the latter was used in the extraction system because of the low absorbance of the reagent blank and small coefficients of variation. The degree of extraction of quaternary ammonium salts with BPB - quinine was about 98%. 2.0 1.5 E e 1.0 8 9 Q 0.5 2 4 I 0.5 [Quinine]/[quinine] + [BPB] Fig. 3. Continuous variation graphs be-tween BPB and quinine with the following conditions 1 pH 6.7 wavelength 690 nm; 2, pH 3.8 wavelength 418 nm; 3 pH 2.8 wave-length 418 nm; and [quinine] + [BPB] 4 x 10-5 M.Extraction Mechanism of Ion- Associates with BPB The continuous variation graphs as shown in Fig. 3 seem to indicate that the extraction mechanism of ion associates with BPB in the different pH media can be represented as follows. In pH 3.8 medium : H.BPB- + H.Quinine+ + H.BPB-.H.Quinine+ (1) Amax = 418nm * . ’ ‘ (2) H.BPB- + Berberine+ + H.BPB-.Berberine+ Yellow Yellow, Amax = 418nm Yellow, Amax = 418nm and in pH 6.7 medium: BPB” + ZH.Quinine+ + BPB2-.(H.Quinine+) . . * * (3) BPB2- + Berberine+ . . . . not extractable * (4) Red - violet, Amax. = 590 nm Red - violet; Amax. = 590 nm BPB” + H.Quinine+ + Berberine+ + [BPB.H.Quinine]-.[Berberine]+ .. (5) Blue Amax. = 610 n May 1983 AMMONIUM SALTS I N DRUGS BY ION-PAIR EXTRACTION 613 Reactions (1) and (2) occurred at around pH 3.8 ; the extraction of the ion associates is sensitive but not selective because each ion associate showed the same extraction behaviour. At pH 6.7 only reaction (3) occurred and berberine and benzethonium were not entirely extracted even in the presence of BPB [reaction (4)]. However in the presence of an adequate amount of quinine at pH 6.7 berberine and benzethonium can be extracted into chloroform by the forma-tion of new ternary ion associates [BPB.H.quinine]-. [berberine]+ as shown in reaction (5). Moreover most amines cannot be extracted even in the presence of quinine. Consequently, this extraction system including quinine has an advantage for selective and sensitive extrac-tion of quaternary ammonium salts.Influence of Concomitant Substances M quinine were added various amounts of foreign compounds including pharmaceutical excipients and their interferences were then investigated by the proposed procedure. The usual tablet diluents that accompany berberine in drugs such as glucose lactose and starch were found not to interfere. Co-additives such as ephedrine procaine diphenhydramine and chlorpheniramine contained in pharmaceuticals did not interfere at the 2 x M level (10-fold molar ratio to berberine and benzethonium) nor did other quaternary ammonium compounds such as neostigmine tetraethylammonium and methylatropine at the lo-* M level. The results are summarised in Table 11.To a solution containing 2 x M berberine or benzethonium and 1 x TABLE I1 INFLUENCE OF ADMIXTURES ON THE DETERMINATION OF BERBERINE AND BENZETHONIUM The conditions were as follows berberine 2 x M ; benzethonium 2 x M ; quinine, 1 x M ; BPB 4.8 x M ; pH 6.7; wavelength 610 nm; and solvent chloroform. Added extraneous substance Procaine . . Ephedrine Methylephedrine . . Papaverine . . . . Eserine . . . . Dibucaine . . . . Diphenhydramine . . Chlorpheniramine Chlorpheniramine Triethanolamine . . . . Triethylamine . . Trimethylamine . . Tetramethylammonium . . Tetraethylammonium . . Neostigmine . . Acrinol . . . . . . Molar ratio M/M, [Substance added] [R,N+I 20 20 20 20 20 10 10 5 3 40 40 40 40 40 40 40 Recovery % C - m 101 103 101 100 99 102 100 100 101 102 101 102 101 102 103 102 101 101 99 100 101 103 100 100 99 98 100 100 100 99 100 100 Application to the Determination of Berberine and Benzethonium in Pharmaceuticals Artificial samples were prepared according to a prescription and commercial samples, containing berberine or benzethonium were analysed according to the proposed method.The results are shown in Tables I11 and IV. Of the co-existing substances acrinol chlorphenir-amine dibucaine and ephedrine which have given some interference in the reaction with H.BPB- in a pH 3.8 medium and in other methods,l1*l2 did not interfere in the proposed met hod.Consequently co-extraction spectrophotometry proposed here is simple and convenient to use for the selective and sensitive assay of berberine and benzethonium in multi-component formulations containing bulky aromatic amines used as adjuvants and buffering agents 614 SAKAI TABLE I11 DETERMINATION OF BERBERINE IN ARTIFICIAL SAMPLES Excipients were as follows samples 1 and 2 guanoflacin 15 mg acrinol 10 mg and chlorpheniramine 0.75 mg ; sample 3 papaverine 30 mg diphenhydramine 230 mg and bismuth subnitrate 270 mg; sample 4 acrinol30 mg chlorpheniramine 2 mg, thiamine 10 mg and carboxymethylcellulose 20 mg; and sample 5 acrinol 15 mg, chlorpheniramine 10 mg thiamine 10 mg and sodium carboxymethylcellulose 20 mg. Sample Amount of berberine Amount of berberine No added/mg per 100 ml found/mg per 100 ml Recovery,* % 1 30 31.2 104 2 40 40.5 101 3 300 302.6 101 4 120 118.3 99 5 60 60.2 100 * Average recovery from three determinations.Conclusion BPB - quinine ion associates in a pH 6.7 medium can react with some quaternary ammonium compounds such as berberine and benzethonium to form new ternary ion associates [BPB.H.Quinine]-. [R4N+] that can be extracted completely into chloroform by a single extraction. The ternary ion associate is very stable in the organic phase and the stoicheio-metric ratio is 1 1 1. 3 x 1 0 - 6 ~ for berberine or benzethonium and the apparent molar absorptivities are 3.75 x lo4 1 mol-l cm-l for the berberine associate and 3.14 x lo4 1 mol-l cm-l for benze-thonium at 610 nm when they are in the presence of 1 x M quinine.This method is more selective and sensitive than other methods using anionic dyestuffs for the determination of berberine and benzethonium. The calibration graphs are straight lines over the range 0.5 x TABLE IV DETERMINATION OF BENZETHONIUM IN COMMERCIAL EXTERNAL REMEDIES Amount of benzethonium Amount of benzethonium Recovery,* External remedy stated/mg per 100 ml found/mg per 100 ml % Liquid type . . 60 60 100 Spray type . . . . 100 101 101 Liquid type . . ,. 100 101 101 * Average recovery from three determinations. The author is grateful to Professor Y. Yamamoto of Hiroshima University and K. T8ei of Okayama University for their valuable discussion and thanks Mrs. N. Ohno for kind assistance. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Auerbach M. E. Ind. Eng. Chem. Anal. Ed. 1943 15 492. Schill G. Acta Pharm. Suec. 1964 1 101. Tsubouchi M. Bull. Chem. SOG. Jpn. 1971 44 1560. Tsurubo S. Ohno N. and Sakai T. Nippon Kagaku Zasshi 1980 1328. Sakai T. Bunseki Kagaku 1978 27 444. Sakai T. and Tsubouchi M. Chem. Pharm. Bull. 1976 24 2883. Horioka M. Yakugaku Zasshi 1957 77 200. Irving H. M. N. H. and Markham J. J. Anal. Chim. Acta 1967 39 7. Kaneda Y . and Iwada M. Eisei Kagaku 1976 22 370. “The Japanese Pharmacopoeia IX,” Hirokawa Publishing Tokyo 1976 p. C-312. Tsubouchi M. Anal. Chem. 1981 53 1957. Sakai T. Bunseki Kagaku 1975 24 135. Received July 20th 1982 Accepted November 29th 198

ISSN:0003-2654    

DOI:10.1039/AN9830800608

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

Analyst, May, 1983, Vol. 108, $9. 615-620 615 Simple Method for the Determination of Gypsum, with Some Observations on the Solubilities of Gypsum, Anhydrite, Calcite and Dolomite Henry A. Foner and Sarah Ehrlich Geochemistry Department, Geological SUYVEY of Israel, 30 Malchei Israel Street, Jerusalem. 95 501, Israel A rapid method is presented for the determination of gypsum and related minerals in natural and synthetic materials, based on the extraction of calcium from the matrix material using slightly ammoniacal water as a solvent with subsequent complexometric titration of the calcium using EDTA. The results compare reasonably well with those obtained by the conventional gravimetric procedure. The interferences due to other sparingly soluble calcium com- pounds, such as calcite and dolomite, commonly found in conjunction with gypsum were examined, as were the solubilities of anhydrite, calcite and dolomite in both water and sodium chloride solution.The method is particu- larly suitable for industrial control and deposit assessment purposes. Keywords : Gypsum detevnziwation ; anhydrite ; calcite ; dolomite ; solubility Gypsum is an important mineral both geologically and industrially. It is used as the basis for the manufacture of plaster and plaster boards, as the raw material for the preparation of plaster of Paris and as an additive to Portland cement. In nature, calcium siilphate is found in two principal forms: gypsum (CaS0,.2H20) and anhydrite (CaSO,). The principal form used in industry is the hemihydrate, plaster of Paris (CaS0,.0.5 H,O), which is made by heating gypsum.After addition of water, the plaster sets and reverts to gypsum. The usual method for determining the amount of gypsum (or other forms of calcium sulphate) in a rock, mineral or industrial product is to dissolve the material in acid and then to determine the sulphate dissolved.lS2 The determination is usually carried out gravimetrically using barium chloride solution to precipitate barium sulphate. This is the classical method for the determination of sulphate and can be traced back in the literature at least as far as 1927.l Although the gravimetric method for sulphate determination is a very common procedure, it is a time-consuming operation involving filtration and weighing and requires a skilled operator for good results. To obtain correct sulphate values, the recommended conditions have to be carefully observed as the method depends on the compensation of errors due to the solubility of barium sulphate in hydrochloric acid on the one hand and the adsorption of extraneous ions on the precipitate on the 0ther.~94 Various other methods of determining sulphate have been suggested but they have generally not been very successful and the gravi- metric method still holds its own. The determination of calcium sulphate in a given sample depends on the assumption that the only acid-soluble sulphate present is that of calcium.This is indeed generally so and the only common salts that would interfere in the determinations are sodium and magnesium sulphates. Fortunately, these are rarely present in natural gypsum deposits or in industrial products.Now gypsum (and the other forms of calcium sulphate) is moderately soluble in water (see Table I), and the question arises as to whether it is possible to determine gypsum by determin- ing the water-soluble calcium. To us this seemed to be a potentially attractive method as in naturally occurring deposits of gypsum and anhydrite, and a€so in most industrial products, there are usually no other water-soluble calcium salts present. The determination of calcium with EDTA is well known, convenient and rapid. To the best of our knowledge, it has not previously been used for this application. The method developed in this work is particularly suited to simple laboratories as it avoids the use of cyanide as a complexant in the calcium titration.The method is not suitable for the determination of gypsum in Portland cement because of the presence of readily soluble calcium silicates.616 FONER AND EHRLICH : DETERMINATION OF GYPSUM, AND Analyst, VoZ. 108 Experimental Many of the experiments described below were carried out on a series of natural gypsum- containing samples obtained from the quarries of Kibbutz Gesher in Israel. The deposits range from almost pure gypsum rock (98% gypsum) to an overburden containing only a few per cent. of gypsum with major amounts of calcite, dolomite, clays and quartz. A small amount of magnetite (Fe,O,) is also present. Other samples containing anhydrite, gypsum, calcite or dolomite were obtained from a variety of sources, including deep drillings. Analytical Method Reagents Distilled water and analytical-reagent grade reagents were used throughout.EDTA solutioiz, 0.05 M. Weigh 18.612 g of EDTA, disodium salt. dilute to 1 1. Indicator. Potassium hydroxide bufer solution. 2 N . Triethanolamine solution (1 + 1). Dissolve in water and Hydroxynaphthol blue (Mallinckrodt, No. 5630). Dissolve 112 g of potassium hydroxide in 1 1 of Add 500 ml of triethanolamine to 500 ml of water and water. stir until homogeneous. Procedure Accurately weigh about 1 g of sample into a 600-ml beaker, add 450 ml water and 1.0 ml of ammonia solution (sp. gr. 0.880) and boil for 15 min. Allow to cool, transfer the solution (including solid) into a 500-ml calibrated flask and dilute to volume. Allow to settle, take a 50- or 100-ml volume of the clear supernatant solution (depending on the sample) and transfer it into a 250-ml conical flask.If necessary, filter the supernatant liquid before pipetting. Add 5 ml of triethanolamine solution (1 + l), 10 ml of 2 N potassium hydroxide solution and approximately 100 mg of the indicator. Titrate with 0.05 M EDTA solution until the red solution turns blue. Use a similar procedure to the above but with 0.25 g of sample. Leave the solid in contact with the liquid for 24 h before diluting to volume (see next section). For samples containing gypsum and hemihydrate. For samples containing anhydrite. Stirring in the cold for 30 min is slightly preferable to boiling. 1.00 ml of 0.05 M EDTA solution = 2.004 mg of Ca. Development of the Method Solubility of anhydrite in water The solubilities of the various forms of calcium sulphate in water are shown in Table I.TABLE I SOLUBILITIES OF VARIOUS FORMS OF CALCIUM SULPHATE IN WATER Data from “Handbook of Chemistry and Physics.”& Solubility/mg 1-1 r- Mineral Foriiiula 2O0C l O 0 O d . Gypsum . . .. . . CaS04.2H,0 2 400 2 200 Hemihydrate . . . . CaS04.0.5H,0 3 000 - Anhydrite . . .. . . CaSO, 2 loo* 1600 * At 30 “C. Anhydrite is generally considered to be difficult to dissolve. To check that it is indeed soluble under the conditions suggested in this paper, a number of samples of naturally occurring anhydrites were analysed using the above procedure. In most instances the samples dissolved completely after stirring for 30 min in the cold (0.25 g of sample in 350 ml of water).One sample would not dissolve under these conditions and required standing for 21 h for completeM a y , 1983 SOLUBILITIES OF GYPSUM, ANHYDRITE, CALCITE AND DOLOMITE 617 dissolution. The solubility of synthetic anhydrite at 20 “C under these conditions was 2590 mg 1-l. The solubility of anhydrite, unlike that of gypsum, decreases with increasing temperature.61’ A series of experiments were carried out to study the effect of dissolving anhydrite in both hot and cold water. Recoveries were slightly worse when the sample was boiled in water at the start of the dissolution procedure. The conclusion to be drawn from the above experiments is that to be absolutely sure of completely dissolving anhydrite it is necessary to leave the samples in contact with cold water for 24 h.Solubility of calcite amd dolomite in water calcite and dolomite. Other than calcium sulphate, the only calcium salts present in the samples examined were The solubilities of these compounds, as quoted in the “Handbook of Chemistry and Physics,”5 are shown in Table 11. TABLE I1 SOLUBILITIES OF CALCITE AND Mineral Formula Calcite. . . . . . CaCO, Dolomite . . . . CaCO,.MgCO, DOLOMITE I N WATER Solubility/mg 1-1 Cold Hot 14 (25 “C) 18 (75 “C) 320 (18 “C) - An attempt was made to check the accuracy of these data. The solubility of calcite obtained experimentally (after standing for 24 h to attain equilibrium) was 13.5 mg l-l, which agrees well with the figure quoted above. However, it soon became apparent that the solubility of dolomite was completely at variance with that quoted above.Indeed, geological experience indicates that dolomite should be less soluble than calcite.8 I t is clear from the figures shown in Table I1 that the presence of a substance (dolomite) with a solubility of 130/, of that of gypsum would seriously limit the use of the suggested method, particularly at low gypsum concentrations. Solubility of dolomite. Any investigation of the solubility of dolomite is complicated by the fact that dolomite has never been precipitated from solutions in the laboratory under normal conditions of temperature and pre~sure.~ Garrels et aZ.1° studied the solubility of dolomite in water under a carbon dioxide pressure of 1 atm. They found that finely ground dolomite had a higher solubility than relatively coarsely ground rock and suggested that the very fine material dissolved incongruently, yielding a magnesium-rich solution.This phenomenon was attributed either to the disordering of the crystals on the grain surfaces and hence preferential solution of magnesium, or to super- saturation from excessive fineness of the dolomite particles. Yanat’eval1,l2 found that at 25 “C and a normal atmospheric partial pressure of carbon dioxide, dolomite dissolves in- congruently to yield calcite and a magnesium-rich solution. Hsu,13 on the other hand, casts doubt on the validity of Garrels et al.’s low figure for dolomite solubility and calculated it from a study of ground-water chemistry. At all events, all of the figures quoted in the studies mentioned above show that the solubility of dolomite is lower than that of calcite.The compositions of a number of dolomitic rock samples are shown in Table 111, which also gives an indication of the amount of calcite present. The latter information was obtained from X-ray diffractograms of the samples. Only samples B 1, YD 614 and BR 2 were free from calcite and of these only YD 614 had the theoretical molar [Mg] : [Ca] molar ratio of 1.00. Dolomites with up to 5 mol-% of structural calcite have been described by Goldsmith and Graf.l4 Israeli dolomites with up to 11 mol-% of excess of structural calcium carbonate (i.e., [Mg]: [Ca] molar ratio = 0.80) have been investigated by Katz.l5 One-gram samples of these rocks were boiled in 200 ml of distilled water for periods of 15 and 30 min.The solutions were allowed to cool to room temperature, filtered through Whatman No. 42 filter-papers and diluted to 250 ml. The calcium and magnesium contents of the solutions were determined by atomic-absorption spectrophotometry. Table IV shows the results for the samples boiled for 15 min. The samples boiled for 30 min gave identical results.618 FONER AND EHRLICH: DETERMINATION OF GYPSUM, AND Analyst, Vol. 108 In every instance the calcium in solution from the “dolomite” is less than that due to the solubility of calcite alone, even when the latter mineral is present, e.g., samples YD 411 and H 2. I t is also clear that dolomites are less soluble than calcites under these conditions. TABLE I11 COMPOSITION OF SOME “DOLOMITE” SAMPLES Sample B 1 .. .. H 2 .. YD 409 .. YD 411 .. YD 614 . . B R 1 .. B R 2 .. MgCO3, Yo . . 31.7 . . 34.6 . . 36.2 . . 37.6 . . 43.5 . . 38.3 . . 38.9 Total CaCO, + CaCO,, % MgCO,, % 44.2 75.9 60.8 95.4 51.0 87.2 54.4 92.0 51.9 95.4 55.0 93.3 56.7 95.6 [Mg] : [Ca] molar ratio 0.85 0.67 0.84 0.82 0.99 0.83 0.81 Calcite Trace Major Minor Present Trace Present Absent E$ect of pH on the solubility of calcite, dolomite and gypsum in water Theoretically, increasing the pH of the solvent should decrease the solubility of both calcite and dolomite. A series of experiments were carried out to confirm this supposition; the results are shown in Table IV. In each instance 1 g of finely ground rock sample was boiled in 200 ml of alkaline water for 15- and 30-min periods.A l-ml volume of ammonia solution (sp. gr. 0.880) was added to the mixture before boiling. The solutions were cooled to room temperature, filtered through a Whatman No. 42 filter-paper and the filtrate was diluted to 250 ml. The calcium and magnesium in the solutions was then determined. Only the results for the 15-min boilings are shown in Table IV, as the amount of alkaline earths in solution was greater for the 30- than for the 15-min boiling period. This is because ammonia is expelled during prolonged boiling, causing a decrease in pH. In all instances the total concentration of calcium + magnesium is less than that obtained in similar experiments without the addition of ammonia. The solubility of anhydrite under these experimental conditions was 2560 mg l-l, i.e., the same as in water (see Solubility of anhydrite in water).An attempt to work at a fixed pH of 10 using an ammonium chloride - ammonia buffer was abandoned when it was found that the solubility of calcite increased dramatically in this medium to a value of 68.5 mg 1-l of CaCO,. A standard method for the determination of gypsum in gypsum products2 is based on the high solubility of gypsum in ammoniacal am- monium acetate solution. Experiment showed that in this solution too, the solubility of calcium carbonate was much higher than in water (approximately 250 mg 1-1 of CaCO,). This, of course, limits the method to samples that contain no calcium carbonate or dolomite. TABLE IV CALCIUM AND MAGNESIUM CONCENTRATIONS DUE TO THE SOLUBILITY OF SOLUTIONS (AFTER BOILING FOR 15 MIN) CALCITE AND VARIOUS DOLOMITIC ROCKS IN WATER AND IN ALKALINE Solubility in water Sample B 1 .. .... H 2 .. .. .. YD 409 .. .. YD 411 .. .. YD 614 .. .. B R 1 ,. .. .. B R 2 .. .. .. Natural . . .. Reagent . . .. Type Dolomitic Dolomitic Dolomitic Dolomitic Dolomitic Dolomitic Dolomi tic Calcite Limestone r- Mg -7 mg I-’ mmol 1-1 1.1 0.046 3.1 0.129 1.4 0.058 0.55 0.023 1.1 0.046 0.6 0.025 0.9 0.037 - - - - 7 mg 1-l 2.6 2.3 2.2 2.2 1.4 2.8 2.0 3.6 4.3 1 Ca - mmol 1-I 0.065 0.058 0.055 0.055 0.035 0.070 0.050 0.09t 0 . l l t Solubility in alkaline solution 7 h - F Mg/mg 1-l Ca/mg 1-I 0.6 2.0 0.4 2.4 0.6 1.4 0.2 1.1 0.5 1 .0 0.7 2.4 1 . 1 0.8 - 1.8* -- 2.2 * Corresponds to 4.5 mg 1-1 of CaCO,. t Non-equilibrium value.May, 1983 SOLUBILITIES OF GYPSUM, ANHYDRITE, CALCITE AND DOLOMITE 619 Solubility of calcite, dolomite and calcium sulphate in sodium chloride solution Both anhydrite and gypsum approximately double their solubilities when the salt concentration of the dissolving brine is about 7% ; at higher salinities their solubility decreases again.6Yl6 Unfortunately, both calcite1' and dolomite also show increasing solubility with increasing salt content of the solvent. Table V shows the effect of increasing salt concentration in the solvent brine on the solubility of calcite and dolomite.The increased supersaturation of calcite and dolomite solutions with increasing salinity has been discussed by Sass.l8 The increased solubility of gypsum in salt solution is well known.6p16 TABLE V EFFECT OF SODIUM CHLORIDE CONCENTRATION IN THE SOLVENT ON THE SOLUBILITY OF CALCIUM IONS FROM CALCITE AND DOLOMITE Solubility/mg 1-1 of Ca I \ Sample Type In water In 1.4% NaCl In 3.5% NaCl Reagent .. . . Calcite 3.6 8 17 YD 614 . . . . Dolomite 1.4 5 9 RR 1 . . . . Dolomite 2.8 8 14 Interestingly, experiment shows that the [Mg] : [Ca] molar ratio in the dolomite solution (sample YD 614) decreases from 1.3 for water to 1.02 for 1.4% sodium chloride solution and to 0.80 for 3.5% sodium chloride solution. Similar behaviour was noticed in other dolomites. This indicates that calcium ion is preferentially dissolved with increasing salt concentration of the solvent. Because of the increased solubility of the carbonate minerals in brines, it was decided not to develop 1;his method further for the analysis of gypsum and related minerals. Results A comparison of the results of the analysis of various samples by the proposed method and The results are averages of by the conventional gravimetric method is shown in Table VI.from two to five individual determinations. TABLE VI COMPARISON OF (a) SUGGESTED AND (b) CONVENTIONAL METHODS FOR THE DETERMINATION OF CALCIUM SULPHATE Results as % SO,. Sample SM 114 .. . . A . . D 7 (29-30) . . D 7 (2-4) . . Reagent. . .. Synthetic mixture 704-3 . . D 7 (0-2j ' D 7 (23-24) . . . . . . . . . . . . . . .. .. . . . . Description Theoretical Gypsum ore Phosphate rock Dolomitic rock Gypsum ore Pure gypsum 46.51 Pure gypsum - calcite - dolomite 26.6 Gypsum rock Gypsum rock Gypsum rock Water dissolution 16.45 3.16 6.3 25.23 46.52 (4 26.8 26.5 36.30 14.70 -7 BaSO, gravimetric 16.53 2.93 6.5 25.23 46.52 (b) 26.6 27.17 36.23 15.35 (b) / ( a ) 1.005 0.93 1.03 1 .ooo 1.000 0.991 1.03 0.998 1.04 Accuracy I t is difficult to assess the accuracy of the suggested'method, which depends partly on the proportion of calcium sulphate in the sample and partly on the blank value due to impurities. Table VII lists the maximum blank values obtained when samples of pure analytical-reagent grade calcium carbonate and limestone were processed by the suggested methods, both with and without the use of ammonia.These values represent maxima due to calcite solubility.620 FONER AND EHRLICH TABLE VII MAXIMUM BLANK VALUES ON PURE CALCIUM CARBONATE AND LIMESTONE WITH AND WITHOUT AMMONIA CaCO, in solution/ Equivalent gypsum Titrationlml per Equivalent gypsum mg 1-1 in solution/mg 1-1 100-ml aliquot in original sample, yo In water .. .. 14 24.1 0.30 1.3 In ammonia . . .. 6 10.3 0.12 0.52 With samples containing only calcium sulphate and no calcium carbonates, the accuracy is determined by the size of the titration blank, which is approximately 0.05 ml of 0.05 M EDTA solution (equivalent to 0.2% of gypsum). The last column in Table VI illustrates the accuracies obtained on some actual samples; these are well within the requirements of an industrial analysis. Conclusion A simplified method for the determination of gypsum and related minerals in rocks and industrial products has been developed. The method is based on the fact that calcium sulphate is essentially the only soluble calcium salt in these materials.The solubility of other calcium salts in the extraction medium is reduced by increasing the pH of the latter. The method is particularly suited to industrial control and mineral deposit assessment purposes. The solubilities of gypsum, anhydrite, calcite and dolomite in water, ammoniacal water and brines have been studied. Because of increased calcite solubility in the brines, further investigation of this method was abandoned. It was shown that by addition of ammonia to the extraction medium it was possible to reduce the amount of calcium entering the solution from calcite and dolomite to negligible proportions. The solubility of dolomite in water was shown to be much lower than that quoted in the “Handbook of Chemistry and physic^."^ The authors thank Dr, Y.Druckman of the Geological Survey of Israel for kindly supplying samples of gypsum, anhydrite and dolomite. They also thank Prof. E. Sass of the Geology Department, The Hebrew University, and Drs. Y. Nathan and Y. Druckman of the Geological Survey of Israel for much helpful discussion. We are grateful to Kibbutz Gesher for kindly supplying samples. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. References Scott, W. W., and Furman, N. H., “Standard Methods of Chemical Analysis,” Fifth Edition, Van “Standard Methods for the Analysis of Gypsum and Gypsum Products,” ASTM Standard C 471-75, Hillebrand, W. F., Lundell, G. E. F., and Bright, H. A., “Applied Inorganic Analysis,” Second Vogel, A. I., “A Textbook of Quantitative Inorganic Analysis,” Third Edition, Longman, London, Weast, K. C., Editor, “Handbook of Chemistry and Physics,” Sixtieth Edition, CRC Press, Boca Deer, W. A., Howie, R. A., and Zussnian, J., “Rock Forming Minerals, Volume V, Non-silicates,” Posnjak, E., Am. J . Sci., 1938, 35A, 247. Palache, C., Berman, H., and Frondel, C., “Dana’s System of Mineralogy,” Seventh Edition, Volume Deer, W. A., Howie, R. A., and Zussman, J . , “Rock Forming Minerals. I‘olume V, Non-silicates,” Garrels, I<. M., Thompson, M. E., and Siever, R., Am. J . Sci., 1960, 258, 402. Yanat’eva, 0. K., Izv. Akad. Nauk SSSR, Otdel. I<hi?n. Nauk, 1954, 6, 1119. Yanat’eva, 0. K., Zh. Neorg. Khim., 1955, 1, 1473. Hsu, K. J., J . Hydrol., 1963, 1, 288. Goldsmith, J . R., and Graf, D. L., J . Geol., 1958, 66, 678. Katz, A., PhD Thesis, Hebrew University, Jerusalem, 196s (in Hebrew). Posnjak, E., Am. J . Sci., 1940, 238, 559. Miller, J . P., Am. J . Sci., 1952, 250, 161. Sass, E., J . Sediment. Petrol., 1965, 35, 339. Nostrand, New York, 1939, p. 214. American Society for Testing and Materials, Philadelphia, 1975. Edition, John Wiley, New York, 1953, p. 716. 1961, p. 462. Raton, 1979. Longmans, London, 1962, p. 209. 11, John Wiley, New York, 1951, p. 213. Longman, London, 1962, p. 281. Received July 20th, 1982 Accepted Decenibev 14th, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800615

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

Analyst, M a y , 1983, Vol. 108, pjb. 621-625 62 1 Effect of On-line Complex Formation Kinetics on the Flow Injection Analysis Signal: the Spectrophotometric Determination of Chromium(V1) JoZo Carlos de Andrade," Julio Cesar Rocha, Celio Pasquini and N ivaldi Baccan Univevsidade Estadual de Campinas, Instituto de Quhnica, C.P. 6154, 13100-Cawpinas, S?io Paulo, Brazil The sensitivity of the flow injection analysis (FIA) method for determination of chromium(V1) using 1,5-cliphenylcarbazide (DPC) depends on the concentra- tion of the acid used in confluence with the DPC solution. At low acid con- centrations slower on-line reaction kinetics are observed for Cr - L)PC complex formation. Hence the chemical contribution to the over-all dispersion value cannot be ignored. This indicates that the best experimental conditions for the static procedure may not always translate directly to the dynamic condi- tions of FIA.In the present instance the maximum signal is obtained with acid concentrations a t or above 0.130 M . Although sulphuric acid may be used, as in the conventional procedure, the best working conditions are achieved using nitric acid. Keywords : Flow injection analysis ; on-line kinetics ; cliroiiaiuiia ( V I ) determina- tion The reaction between chromium(V1) and 1,5-diplienylcarbazide (DPC) is the basis of the most sensitive spectrophotometric method for the determination of minute amounts of chr~mium.l-~ This method is widely used for the routine determinations of chromium. On the other hand, the use of the continuous flow injection technique (I;IA)495 for rapid and precise analysis can make routine determinations easier and more reliable.Thus the reaction of chromium(V1) with DPC should be thoroughly studied using the flow injection approach. Jargensen and Regitano6 reported the determination of chromium(V1) using DPC and 0.040 M sulphuric acid. Work in our laboratory has shown that tlie sensitivity of their FIA - DPC method can be improved, achieving a sensitivity closer to that of the conventional st at ic spec trophot omet ric procedure. Experimental Reagents All solutions were prepared using analytical-reagent grade chemicals and de-ionised water. The solutions were stored in high-density polyethylene bottles. 1,5-Di$he.~zyZcarhaxidc working solutions. Prepared daily by dissolving 0.250 g of DPC (Merck) in 20 ml of acetone (Carlo Erba) and diluting to 500 ml with water.Stock standard chromiztm(VI) solutiovz, 1000 pg ml-l. Prepared by dissolving 2.829 g of K,Cr,O, (G. Frederick Smith Chemical Co., 1000/, purity certified) in 0.10 M sulphuric acid (Merck). The K,Cr,O, was heated at 160 "C for 2 h. Working solutions were prepared daily by dilution of aliquots taken from the stock solution. Acids. Hydrochloric acid (Carlo Erba), nitric acid (Carlo Erba), perchloric acid (Carlo Erba) and sulphuric acid (Merck) of concentrations 0.10-1.5 M were prepared by diluting appropriate volumes of the concentrated acids with water. Experimental Conditions reported,6 for the determination of chromium(V1). in the stopped-flow experiments. Fig. 1 ( a ) shows the single-line H A configuration used in this work, and also that previously Fig.1 ( h ) indicates the arrangement used Except where stated otherwise, the reagents and the sample * To whom correspondence should be addressed.622 Analyst, VoZ. 108 were pumped at a flow-rate of 1.2 ml min-l using an Ismatec Mini-S 840 peristaltic pump and Tygon peristaltic pump tubing (Technicon). Samples of 77 pl were injected into the mixed stream of acid and DPC by means of a modified home-made acrylic proportional injector.' Polyethylene tubing (i.d. 0.8 mm) was used for both the mixing and the reaction coils. The absorbance measurements were made in a Zeiss PM 2A spectrophotometer at 540 nm, using an 80-pl Zeiss flow cell (optical path 10 mm). ANDRADE et a,?.: EFFECT OF ON-LINE COMPLEX FORMATION -y++@-y L Ill - B W Injector in the loading position @+W Hew 111 B w w Injector in the stopped position Fig. 1. The FIA system used for the determination of Cr(V1): (a) the single-line configuration; and (b) the stopped-flow configuration. A = Mixing coil, length 1.00 m; B = proportional injector; C = reaction coil, length 0.70m; L = injection loop; W 1 waste; FC = flow cell, h = 540 nm. I .= Acid solution or water; I1 = DPC solution or water; I11 = Cr(V1) or pre-formed Cr - DPC. Results and Discussion The reaction between ciromium(V1) and DPC is highly dependent on the pH.l The con- ventional procedure1p2 USFS sulphuric acid at 0.05-0.10 M (pH % 1) as the medium for the full colour development of tht Cr - DPC complex. According to the literature,l at acid concentra- tions of less than 0.05 M the colour does not develop immediately and at acid concentrations above 0.10 M the complex is less stable.Fig. 2 shows the influen-e of the concentration of the nitric acid used in confluence with the DPC solution on the FIA signal. The shapes of the curves for perchloric, sulphuric and hydrochloric acids are tht! same as those observed for nitric acid. However, the sensitivity observed with nitric acid is better, although sulphuric acid is the acid specified in the conven- tional procedure.1*2 For example, at an acid concentration of 0.80 M with nitric acid, the FIA - DPC procedure is about 5% more sensitive than with sulphuric acid. Lower sensitivity is noted at lower acid concentrations, more pronounced for hydrochloric acid than the other acids.The best results were obtained using nitric acid of concentration at least 0.80 M (see Fig. 2) in confluence with 0.05% m/V DPC solution, in a single line 1;IA approach. The use of a higher DPC concentration is not compensated for by a corresponding gain in signal, as shown by Fig. 3. The calibration graph obtained using the conditions described above is linear up to 4 pg ml-I [ A = 0.0008 + 0.1987[Cr] (pg ml-l), where A = absorbance; correlation coefficient, Y = 0.9991. The relative standard deviation (RSD) of ten replicate determinations ranged from ll.Oyo at the 50 ng ml-l level to 2.5% at the 4 pg ml-I level (minimum RSD = 1.2% at 1 pg ml-l). The detection limit (signal to noise ratio = 3) of 15 ng ml-l was calculated from the observed sensitivity and the noise associated with the measurement of the absorbance signal of the carrier solution.*May, I983 KINETICS ON FIA SIGMAL : SPECTROPHOTOMETRY OF CR(VI) 0.2 Q) C m e 0.1 s: 2 0 623 ' 0 0.5 1 .o 1.5 CHNOJM Fig.2. Variations of the absorbanccs measured for various concentrations of Cr(V1) with respect to the analytical concentration of nitric acid (CHXOJ used in confluence with the DPC solution (0.05% m/V). Cr(VI) concentration: A, 0.05; €3, 0.10; C, 0.20; L), 0.50; E, 0.70; and F, 1.00 pg inl-l. The dispersion values for the FIA manifold used in these experiments were determined and are given in Table I. Note that as the kinetic parameters of the reaction between chromium(V1) and DPC and the chemical stability of the Cr - DPC complex are pH dependent, both the physical dispersion (D,) and the over-all dispersion (Do) must be calculated. The chemical contribution to the Do value is given simply by the equationg D, = Do - D,.Assuming that Beer's law is obeyed, these dispersion values (defined by RdiiEka and HansenlO as Co/Cmax.) can be calculated by the ratio /l,JAmax.. The A , values were obtained experiment- ally by pumping 0.05% m/V DPC solution containing 0.80 pg ml-l of chromium(V1) in either sulphuric or nitric acid, prepared according to the conventional ~x-ocedure,~~~ continuously through the detector. The Amax. values used for the calculatox of D, were obtained by injecting 77 p1 of the pre-formed Cr - DPC complex into the FIA line, using water as a carrier.Stopped-flow experiments shows that no decomposition of the complex occurs during a typical measurement, but it is convenient to measure these values using fresh solutions otherwise apparent dispersion values can be found. For the calculation of Do, the A,,,. values are those obtained from the FIA peak maxima observed when the reaction between chromium(V1) and DPC takes place in the line. Using 0.040 M sulphuric acid in confluence with the DPC solution, with the other experi- 0) C m 0 0.4 P a a 0 0.075 0.15 Concentration of DPC, O/O m/V 1;ig. 3. \'ariation of the absorbancc Tor various concentrations of DI'C, in confluence with 0.80 RI nitric acid. Conccnt~-;~tioii oC Cr(\*I) : 3.0 pg mk1.624 AN,alyst, Vol. 108 mental conditions as described above, the over-all dispersion is 11.2, which is coincidently close to the value of 11.6 found by Jerrgensen and Regitano6 for similar conditions of flow-rate and residence time.As FIA sensitivity is related to the dispersion, it can be shown that the sensitivity of the FIA - DPC method for chromium could be improved by a factor of 2.8 only by using 0.80 M instead 0.040 M sulphuric acid (see Table I). These results are three times more sensitive than those obtained by Jgrgensen and Regitano6 under their most favourable conditions (dispersion of 9.7) and about nine times more sensitive than those obtained under their routine conditions ( dispersion of 29.1). TABLE I DISPERSION VALUES FOUND FOR THE REACTION BETWEEN ANDRADE et al. : EFFECT OF ON-LINE COMPLEX FORMATION CHROMIUM(V1) AND 1 ,&DIPHENYLCARBAZIDE USING A SINGLE-LINE FIA APPROACH Working conditions as described under Experimental.Concentration of chromium(V1) : 0.80 pg ml-l. Acid Acid concentration*/M A , A,,,. D, A,,,. Do HNO, .. .. 0.040 - - 0.03 17.6 0.80 0.18 2.9 0.16 3.3 H,SO, . . . . 0.040 - - 0.05 11.2 0.80 0.20 2.8 0.14 4.0 0.53 0.56 *The acid concentration refers to the acid solution used in confluence with 1,5- diphenylcarbazide in the FIA system. The dispersion values found by Jerrgensen and Regitan06 probably have a high contribution from the chemical dispersion term owing to slower reaction kinetics in the FIA line, caused by the low concentration of acid that they used . Stopped-flow experiments, as shown in Fig. 4, indicate that there is not enough time for complete formation of the complex in the FIA line when 0.040 M sulphuric acid is used in confluence with DPC.The use of a longer reaction coil might permit full colour development, but the increased contribution of the physical dispersion would be highly undesirable. 50 60 8 70 m 4- CI .- E z 80 ‘i 90 100 stop \ 1 min 1 min 1 min H - H Flow -. A I-I B stop r C 1 min - Fli Y li D I Time -b Fig. 4. Stopped-flow studies using nitric ant1 sulphuric acids in confluence with DPC solution (0.05O4 i n / V ) . A, 0.80 RI HNO,; 13, 0.040 31 HXO,; C. 0.80 31 H,SO,; and D, 0.040 &I H,SO,. Thc first t\vo pcaks in each instnncc iirc thc transient F I - \ pcaks at the statctl acidic conditions and the third signal is formctl untlcr stopyctl-flo\\- coritljtioris. Conccntratioii of Cr(VI) = 0 .S O pg ml-l.May, 1983 KINETICS ON FIA SIGNAL : SPECTROPHOTOMETRY OF CR(VI) 625 These results explain the inconsistencies found previously,6 namely the constant sensitivity found when changing the length of the reaction coil and the large variation of the dispersion values observed on changing the flow-rate. In the first instance there is probably a compensa- tion between an increase in D, and a decrease in D,. In the second instance, as a lower flow- rate means a higher residence time, more time exists for the formation of the Cr - DPC com- plex, which would result in a lower Do value. Table I1 shows that the effect of changing the flow-rate conditions on the Do values is small if the reaction is really completed in the FIA line. TABLE I1 OVER-ALL DISPERSION VALUES OBSERVED ON CHANGING THE FLOW-RATE IN THE SINGLE-LINE FIA APPROACH USED FOR CHROMIUM(VI) DETERMINATIONS BY THE I,&DIPHENYLCARBAZIDE METHOD Concentration of chromium(V1) = 0.80 pg ml-l and of DPC = 0.05% m/V Flow-ratelm1 min-’ r Nitric acid 0.4 0.7 1.2 1.4 2.0 2.8 3.4 \ 1,5-Diphenylcarbazide 0.4 0.7 1.2 1.4 2.0 2.8 3.4 DO 7- 0.040 M HNO, 0.80 M HNO, 6.8 3.3 12.0 3.3 17.6 3.3 25.0 4.1 37.9 4.1 48.2 4.4 66.3 5.6 Fig.4 also indicates that the use of the stopped-flow technique could improve the sensitivity of the Jlzrrgensen and Regitano procedure,6 but the sampling rate will decrease. Fig. 4A and C show that the Cr - DPC complex is almost completely formed in the FIA line when an acid concentration of 0.80 M is used. Although the complex is less stable when Cacid > 0.80 M, there is plenty of time to record the maximum of the FIA signal.The higher stability of the complex in 0.80 M nitric acid can also be seen on comparing Fig. 4A and C. The over-all dispersion of our working conditions in relation to the conventional spectro- photometric procedure1-2 is 3.5, calculated by the ratio A,(H2S0,)/A,,,~ (HNO,, 0.80 M). Such a value indicates that the observed FIA sensitivity is about three times lower than that of the conventional static spectrophotometric procedure at 540 nm, mainly owing to physical dispersion. Despite this lower sensitivity, the FIA procedure still has several advantages over the conventional method, e.g., better reproducibility, fast sampling rate and low cost. Under the experimental conditions described here a sampling rate of 120 samples per hour, with negligible carry-over, is possible. The authors are pleased to acknowledge helpful discussions with Prof. P. C. Uden and Prof. They also thank the Conselho Nacional de Desenvolvimento Cientifico e C. H. Collins. Tecnol6gico (CNPq) for a Fellowship to J.C.R. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. References Sandell, E. B., “Colorimetric Determination of Traces of Metals,” Second Edition, Interscience, New Marczenko, Z., “Spectrophotometric Determination of Elements,” Ellis Horwood, Chichester, 1976. Berman, E., “Toxic Metals and Their Analysis,” Heyden, London, 1980. RbiiCka, J., and Hansen, E. H., Anal. Chim. A d a , 1975, 78, 145. RiiiiCka, J., and Hansen, E. H., “Flow Injection Analysis,” John Wiley, New York, 1981. Jsrgensen, S. S., and Regitano, M. A. B., Analyst, 1980, 105, 292. Reis, B. F., Zagatto, E. A. G., Jacintho, A. O., Krug, F. J., and Bergamin F O , H., Anal. Ckim. A d a , Poppe, H., Anal. Chim. Acta, 1980, 114, 59. Painton, C. C., and Mottola, H. A., Anal. Cham., 1981, 53, 1713. RiiiiEka, J., and Hansen, E. H., Anal. Chim. Acta, 1978, 99, 37. York, 1950. 1980, 119, 305. Received August 25th, 1982 Accepted December 14th, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800621

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

626 Analyst, May, 1983, Vol. 108, pp. 626-632 Titrimetric Determination of Some N-Substituted Phenothiazine Derivatives* Mohamed lbrahim Walash, Mohamed Rizk, Abdel-Malik Abou-Ouf and Fathalla Belal Department of Analytical Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura, Egyfit An indirect titrimetric method is described for the determination of some N-substituted phenothiazine derivatives. The method involves the use of 1,3-dibromo-5,5-dimethylhydantoin or N-bromosuccinimide as the titrant. A known excess of either reagent is added and, after a specified time, the residual reagent is determined iodimetrically. The proposed method was applied to the analysis of pharmaceutical preparations containing the drugs, and the results obtained compared favourably with those obtained by pharmacopoeia1 methods.Keywords : N-Substituted phenothiazine determination ; titrimetry ; 1,3-dibromo- 5,5-dimethylhydantoin ; N-bromosuccinimide Increasing interest in the therapy of mental disorders has led to the widespread use of phenothiazines. Phenothiazine derivatives are available under various names and chemical modifications. The official method depends on non-aqueous titration or spectrophotometry of the dosage forms.1s2 Among the methods used for the determination of phenothiazines are titrimetr~,~ spectr~fluorimetry,~ ~pectrophotometry,~ col0rimetry,69~ amperometry* and voltammetryg by oxidation at different solid microelectrodes10 or indirectly.ll These pro- cedures have been reviewed by Blazek,12 Rlazek et aZ.13 and Fairbrother.14 In this paper a study of the determination of some N-substituted phenothiazine derivatives is described.The proposed method involves the use of N-bromosuccinimide (NBS) or 1,3- dibromo-5,5-dimethylhydantoin (DBH) as the titrant. NBS has been utilised extensively in the determination of a vast number of compounds, especially those of pharmaceutical interest.15 However, work in our laboratory indicated the usefulness of the recently intro- duced reagent, DBH, in the determination of pharmaceutical compounds.16-18 This reagent proved to be as satisfactory as NBS. The reaction conditions were thoroughly studied and the molar ratio of the reaction was calculated. The reaction mechanism was confirmed by isolation and identification of the reaction products. Experimental Apparatus The apparatus used consisted of a Pye Unicam SP 1000 infrared spectrophotometer, a Pye Unicam SP 1800 spectrophotometer, equipped with a matched pair of l-cm quartz cells, a Varian EM-390 NMR spectrometer (90 MHz) and a Tacussel d.c.polarograph equipped with three electrodes (saturated calomel electrode, platinum counter electrode and dropping- mercury electrode). Materials The purity of these com- pounds was established by applying official methods.1*2 Pharmaceutical preparations were obtained from different Egyptian commercial sources and were analysed by the recommended official methods. Pure drugs were obtained from a variety of manufacturers. Reagents 1,3-Dibrom0-5,5-dimethylhydantoin. Prepared according to the method described by Bury * Preliminary results were presented at the XVIIth Conference on Pharmaceutical Science, February 23rd-27th, 1982, Cairo, Egypt.WALASH, RIZK, ABO-OUF AND BELAL 627 et aL19 A 5 x low3 M solution is prepared by dissolving 1.43 g of the pure, crystalline powder in 1 1 of water and is standardised iodimetrically.N-Bromosuccinimide solution, 1 x M. Prepared by dissolving 1.78 g of the freshly crystallised powder in 1 1 of water and standardised iodimetrically. Sodium tlziosulphate solution, 0.02 M. Potassium iodide solution, 10%. Hydrochloric acid, 10% m/V. Starch mucilage. Procedures Recommended procedure Prepare a solution containing the phenothiazine (1 .O mg ml-l) in 10% m/V hydrochloric acid and add an aliquot to a known volume of 0.005 M DRH or 0.01 M NBS solution in a glass-stoppered Erlenmeyer flask.Shake the mixture occasionally and, after the specified time (Table I), add 10 ml of 10% potassium iodide solution. Titrate the liberated iodine with 0.02 M thiosulphate solution ( Vz). Repeat the experiment without the phenothiazine (W TABLE I DETERMINATION OF PHENOTHIAZINE DERIVATIVES WITH ORGANIC BROMINATING AGENTS The results given are averages of eight separate determinations. The figures in parentheses are the percentage relative standard deviations. Compound Chlorpromazine.HC1 . . Promazine.HC1 . . .. Levomepromazine. HC1 Trifluoperazine.HC1 . . Prochlorperazine dimaleate Perphenazine . . .. Mesoridazine besylate . . Reaction time/min .. . . 15.0 .. . . 15.0 .. . . 15.0 .. , . 30.0 .. . . 20.0 .. . . 20.0 ... . 15.0 DBH 7- Molar Found, ratio yo 1:2 99.1 (0.77 5) 1:2 99.5 (0.606) 1:3 99.7 (0.635) 1:3 99.8 (0.994) 1 : 3 99.9 (0.8 15) 1:3 98.9 (1.084) 1:2 100.1 (1.053) NBS r-+ Molar Found, ratio % 1:4 98.7 (0.839) 1:4 99.0 (0.933) 1:6 99.3 (0.655) 1:6 99.2 (0.706) 1:6 99.5 (1.039) 1:6 99.5 (0.992) 1:4 99.3 (1.0549) Official method, 98.8 (0.405) 98.1 (0.064) 99.7 (0.196) 98.9 (0.531) 99.9 (0.1902) 100.0 (0.205) 100.1 (0.3 14 8) %I Calculate the amount of the drug from the equation (V1- VZ) M R N Amount of drug (mg) = where V , = volume of sodium thiosulphate solution consumed in the blank titration (ml), V2 = volume of sodium thiosulphate solution consumed in the experiment (ml), M = relative molecular mass of the drug, R = molarity of the DBH or NBS solution and N = number of moles of DBH or NBS per mole of the sample.Assay procedure for dosage forms Extract an accurately weighed amount of the pulverised tablets or a volume of the mixed contents of the ampoules three times with 10% m/V hydrochloric acid. Filter into a 100-ml calibrated flask and dilute to volume with the same solvent. Transfer an accurately measured volume of the prepared solution equivalent to 5.0mg into an iodine flask and proceed as described above.628 Analyst, Vo,?. 108 Isolation of the reaction flroducts Add about 50 ml of 10% m/V hydrochloric acid, then add slowly with stirring 1.5 1 of 0.005 M DBH or 0.01 M NBS solution and leave the mixture in a stoppered flask with occasional shaking for 15 min. Filter the precipitate formed and wash with water until free from chloride.Purify the precipitate by crystallisation from chloroform. WALASH et al. : TITRIMETRY OF SOME Dissolve about 0.5g of chlorpromazine hydrochloride in 20 ml of water. Results and Discussion The percentage recovery of the phenothiazines studied and their dosage forms are abridged The results obtained by the proposed method are compared with results in Tables I and 11. from official methods and are found to be in good agreement. the sulphide group and the tertiary amino group in the side-chain. The reaction of phenothiazines with organic brominating agents is localised in TABLE I1 ANALYSIS OF PHARMACEUTICAL PREPARATIONS CONTAINING PHENOTHIAZINE DERIVATIVES The figures in parentheses are percentage relative standard deviations. yo of label claim 7+ Preparation DBH NBS Neurazine tablets (chlorpromazine.HC1, 25 mg per tablet) .. . . Promacid ampoules (chlorpromazine.HC1, 50 mg per ampoule) Sparin Vial (promazine.HC1, 50 mg ml-l) .. .. .. .. Siquil tablets (trifluoperazine.HC1, 25 mg per tablet) . . . . . . Stemetil ampoule (prochlorperazine.HC1, 12.5 mg ml-l) . . .. .. Trilafon tablet (perphinazine, 8 mg per tablet) . . . . . . . . Sparine tablet (promazine.HC1, 50 mg per tablet) .. .. .. The Sulphide Group . . 103.1 (0.698) 98.0 (1.244) 99.4 (0.261 6) 102.2 (0.626) 101.7 (1.084) 98.4 (0.594) 97.8 (0.0132) 101.6 98.3 (0.8748) 99.5 (0.258 3) 100.6 (0.252) 102.2 (0.557) 99.2 (0.594 7) 97.8 (0.8077) (1.210) two sites: Official method, 100.3 (0.358) 99.4 99.5 (0.422) 100.6 (0.3379) 100.7 99.8 (0.330) 98.8 (0.656 6) %' (0.09) (0.102 3) In all reported UV spectrophotometric methods,12-14 the corresponding sulphoxide is formed and is measured spectrophotometrically.The reaction with organic brominating agents produces a coloured product that quickly fades. The net reaction product was found to be the corresponding sulphone. This conclusion was drawn from the following results (obtained with chlorpromazine as a model example). The reaction product was not electrochemically reducible at the dropping-mercury electrode under the conditions described for the determination of the corresponding sulphoxide.20 The ultraviolet spectrum of the reaction product in 0.2 N hydrochloric acid did not show the characteristic absorption maxima at 345 nm reported for the sulphoxide21; instead, it peaked at 287 nm.The infrared spectrum of the reaction product revealed an absorption band at 1130 cm-l characteristic of the sulphone group,22 whereas the strong absorption band at 732 cm-1 of the -C-S-C- group had disappeared. A thin-layer chromatographic study of the reaction product utilising the system described by Kofoed and Lucas23 (15% ammonium acetate solution-methanol, 20 + 80) for pheno- thiazines and their sulphoxides, gave one spot with an R, value of 0.54, while that of the sulphoxide (reported and found) was 0.42. Fragmentation of the chlorpromazine sulphone showed that the main molecular ion was at m/z 414 with a relative intensity of loo%, together with other peaks M + 2, M + 4 and M + 6 corresponding to 37C1, 8lBr and 33s isotopes at m/x 416, 418 and 420, respectively.The Tertiary Amino Group substituted piperazine or pyridyl group. The tertiary amino group in the side-chain is present in the form of a dialkylamino or N- In any of these groups, owing to its basicity, theMay, 1983 N-SUBSTITUTED PHENOTHIAZINE DERVATIVES 629 loo? 90 8 80- 70- 3 0 - 20 - n / Br CH2-CH2 -CHp-N I ‘CH, I Wavelengt h/ym 6 l o 0 L 38003500 3000 2500 2000 1800 1600 1400 1200 1000 800 625 Waven u m ber/crn- ’ Fig. 1. Infrared spectrum of 2-chloro, 10- [3-(N-bromo-N-methyl)aminopropyl]- phenothiazine-9,9-dione, I. nitrogen atom is the site of the reaction with organic brominating agents. Tertiary amines are reported to react with NBS to form a secondary amine with the separation of one of the alkyl groups in the form of an a1deh~de.l~ The applicability of this reaction to pheno- thiazines was confirmed from the following results.Formaldehyde, which is separated from the reaction of chlorpromazine with either NBS or DBH, was distilled from the reaction mixture and tested with either chromotropic acid or potassium hexacyanoferrate( 111) and pheny1hydrazine.l The reaction product was tested for the tertiary amino group with aconitic anhydride reagent, which gives a violet colour ~~ 10 9 8 7 6 5 4 3 2 l o Shift (61, p.p.m. Fig. 2. NMIi spectrum of compound I. Conditions: spectrum ampli- tude 4 000; filter 0.1 s ; RF power 0.045 mG; sweep time 5.0 min; sweep width 10.0 p.p.m.; end of sweep 0.0. p.p.m.; nucleus ’H; zero reference TMS (external) ; room temperature ; and solvent CDC1,.630 Analyst, Vol.108 with phenothiazines depending on the presence of the tertiary amino The reaction product failed to give this colour reaction. The infrared spectrum (Fig. 1) of the proposed chlorpromazine sulphone reveals the absence of a vibration band at 985 cm-l characteristic of the tertiary amino group; instead, a band of the secondary amino group at 950 cm-l was present. The NMR spectrum (Fig. 2) of the proposed chlorpromazine sulphone solution in deuteri- ated chloroform (CDC1,) and using tetramethylsilane (TMS) as a reference material, contained three integral peaks with peak heights in the ratio 6.4: 3.7: 4.3. The empirical formula of the proposed sulphone is C16H16ClN2S0,.Br. Dividing the sum of the integral peak heights by the number of protons gives 0.9 as the increment per proton.The types of protons present are seven protons in the aromatic region, indicating that no bromination in the phenothiazine nucleus had occurred, four protons in similar methylene groups in the chain and five protons in the methyl and methylene groups attached to the terminal nitrogen atom. Also with levomepromazine, the NMR spectrum (Fig. 3) shows three integral peaks with WALASH et al. : TITRIMETRY OF SOME I I I I I I I I I 10 9 8 7 6 5 4 3 2 1 0 Shiit (61, p.p.m. Fig. 3. NMR spectrum of 1,3-dibromo-2-methoxy-l0 [3-N-bromo- N-methyl]aminopropylphenothiazine-9,9-dione, 11. Conditions : spectrum amplitude 5500; filter 0.1 s; RF power 0.046 mG; sweep time 5.0 min; sweep width 10.0 p.p.m.; end of sweep 0.0 p.p.m.; nucleus 'H; zero reference TMS (external) ; room temperature; solvent CDC1, - DMSO.peak heights in the ratio 3.6: 1.4:4.0. Dividing the total integral peak heights (9.0) by the number of protons (empirical formula C,,H,,N2S0,Br,) gives 0.47 as the increment per proton. The number of protons in the region of 6 p.p.m. is eight; three of them belong to the methoxy group and five to the aromatic moieties. This indicates that the phenothiazine nucleus was brominated by two bromine atoms, probably owing to the presence of the methoxy group in the 2-position, which activates the ring for electrophilic substitution. The proposed structure is as follows:May, 1983 N-SUBSTITUTED PHENOTHIAZINE DERVATIVES 63 1 The above evidence is valid for chlorpromazine, promazine and mesoridazine, for which 2 mol of DBH or 4 mol of NBS are consumed per mole of the substrate.Prochlorperazine, perphenazine and trifluoperazine, on the other hand, consume 3 mol of DBH or 6 mol of NBS, because they possess two tertiary amino groups in the side-chain. Levomepromazine, although it possesses only one tertiary amino group in the side-chain, consumes 3 mol of DBH or 6 mol of NBS; this extra mole of DBH is involved in the bromination of the pheno- thiazine nucleus. Conclusion Although phenothiazines have been exhaustively determined by various techniques, the proposed method is a simple, rapid and accurate alternative for this determination, either in bulk or in dosage forms. Attempts to titrate the phenothiazines directly with the described reagents were un- successful.The results were not reproducible and several factors affect the accuracy of the results. The major factor is the time of the titration, because the reaction of the amino group with NBS is slow. A recently described procedure for the determination of pheno- thiazines with NBS25 depends on the decolorisation of methyl red indicator, but the intense red colour of the phenothiazirie sulphoxide would mask the colour of the indicator. The authors also neglected the reaction of the tertiary amino group with NBS, which is time dependent, and thus a direct titrimetric procedure cannot be applied. If these times were significantly exceeded, the consumption of the reagent would increase slightly, but no significant molar ratio would be obtained even after a prolonged period.The reaction involves the intact molecule. The degradation or oxidation products of the pheno- thiazines will not react with DBH or NBS in a quantitative manner. On the other hand, the non-aqueous titration described in the BP1 depends on the presence of a basic nitrogen atom in the side-chain, Similarly, the spectrophotometric method recommended by the USP for the formulations depends on absorption in the ultraviolet region in which the sulphoxide still has a high molar absorptivity. The reaction times specified in Table I are critical. The proposed method can be considered as a specific method for phenothiazines. 'The over-all reaction can be expressed as follows: CH3 'CH3 CH2-CH2-CH2 -N' + 2 cH3'&y0 + 3 H20 Or-NKN-Br 0 1 Chlorpromazine Pr CH2-CH2-CH2-N a!nc, + 'CH3 HCHO + 3HBr + 2 C H 3 - T = f 0 O H \o "-NYN-H 0632 For prochlorperazine : WALASH, RIZK, ABOU-OUF AND BELAL CHZ-CH2- CHO A CH3 &yo + HCHO + 4HBr + Br-N H-NYN-H CI wN-Br + 0 The authors thank Specia Company, France, for kindly providing some of the samples of the pure drugs.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. References “The British Pharmacopoeia 1980,” HM Stationery Office, London, 1980. “The United States Pharmacopoeia, XV Revision,” American Pharmaceutical Association, Washing- Sobhi, A. S., Hassan, A., and Nashaat, A. Z., J . Pharm. Sci., 1975, 64, 129. Mellinger, T. J., and Keeler, C. E., Anal. Chem., 1964, 36, 1840. Kurc, B., and Morres, M. D., Talanta, 1976, 23, 398.Youssef, M. K., and Attia, I. A., Indian J . Pharm., 1975, 37, 121. Issa, A. S., Beltagy, Y. A., and Mahrous, M. S., Talanta, 1978, 25, 710. Vasilewska, L., and Syzszko, E., Diss. Pharm. Phavmacol., 1969, 21, 591. Patriache, G., Microchim. Ada, 1970, 5 , 950. Kabasakalian, P., and McGlotten, J., Anal. Chem., 1959, 31, 431. Porter, G. S.. and Beresford, J., J . Pharm. Pharmacol., 1966, 18, 223. Blazek, J., Pharmazie, 1967, 22, 129. Blazek, J., Dymes, A., and Stejskal, Z., Pharmazie, 1976, 31, 10. Fairbrother, J. E., Pharm. J . , 1979, 222, 271. Mathur, N. K., and Narang, C. K., “Determination of Organic Compounds with N-Bromosuccinimide Abou-Ouf, A. A., Walash, M. I., Rizk, M., and Belal, F., Pharmazie, 1979, 34, 224. Abou-Ouf, A., Walash, M. I., Rizk, M., and Belal, F., Analyst, 1979, 104, 566. Rizk, M., Walash, M. I., Belal, F., and Abou-Ouf, A. .4., Anal. Lett., 1981, 17, 1407. Bury, S., Kuit, D., and Jawarska, R., Polish. Pat., 511580, 1966; Chem. Abslr., 1967, 67, 90811a. Ellaithy, M. M., Indian J . Pharm. Sci., 1980, Nos. 3-4, 41. Davidson, A. G., J . Pharm. Pharmacol., 1976, 28, 795. Nilson, L. A., William, E. K., and Herman, A. S., ‘‘113, Theory and Practice,” Plenum, New York, Kofoed, I., and Lucas, G. H. N., J . Forensic Sci., 1965, 10, 308. Beltagy, Y. A., Issa, A. S., and Mahrous, A. S., Egypt. J . Pharm. Sci., 1978, 19, 107. Pathak, V. N., Shukla, I. C . , and Shukla, S. li., Talanta, 1982, 29, 58. ton, DC, 1980. and Allied Reagents,” Academic Press, London, 1975. 1973, p. 288. Received April 15th, 1982 Accepted September 14fh, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800626

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

Analyst, May, 1983 SHORT PAPERS 633 Ligand-exchange Reactions in the Analysis of Cobalt Complexes by Atomic-absorption Spectrophotometry W. James Swindall, Duncan Thorburn Burns and Elmugdad A. AIi Department of Analytical Chemistry, The Queen’s University of Belfast, Belfast, BT9 5AG Keywords Ligand-exchange reactions ; cobalt complexes ; dithizone ; atomic- absorption spectvophotounetry Colleagues in inorganic research produce a variety of cobalt complexes and a method of analysis was sought to allow the direct determination of cobalt without prior wet digestion of samples. Earlier work had shown that nickel could be determined in nickel complexes that were dissolved in an organic solvent with the addition of diethylammonium diethyldithio- carbamate as a ligand exchanger to ensure that all the nickel was in the same bonding environ- ment.l This work shows that a similar procedure is suitable for many cobalt complexes although dithizone proved to be a more universal exchange ligand in this instance. Experimental Apparatus A Perkin-Elmer 403 atomic-absorption spectrophotometer with an air - acetylene burner head and a Perkin-Elmer Intensitron Co, Cr, Cu, Mn, Ni multi-element hollow-cathode lamp were used.Reagents 14.3% cobalt. Cobalt cyclohexylbutyrate standard. Carlo Erba organometallic standard. Analysis gave Diethylammonium diethyldithiocarbamate (DDDC) . Dithizone (Dz) . BDH Chemicals Ltd. Formamide. Koch-Light Laboratories. 4-Methylfientan-2-one. BDH Chemicals Ltd. Ethanol. BP Ltd. BDH Chemicals Ltd. Procedure Standards Dissolve 2.697 mg of pure cobalt cyclohexylbutyrate standard in 20 ml of 4-methylpentan-2- one and make up to 50 ml with a solution of 2 g 1-1 dithizone in a mixture of equal volumes of ethanol and formamide.This solution contains 8 p.p.m. of cobalt and 3 molar proportions of dithizone to cobalt. To 20-ml flasks containing 6,4 and 2 ml of 4-methylpentan-2-one add 5, 10 and 15 ml of the 8 p.p.m. stock solution and make up to the mark with dithizone in ethanol - formamide to give solutions containing 2, 4 and 6 pep.”. of cobalt. Spray these solutions into the flame under the given conditions using the mixed solvent to obtain the base-line value in order to produce data to establish the calibration graph. Samples Dissolve a weighed amount of the cobalt sample, sufficient to give a final solution of approxi- mately 4 p.p.m.of cobalt, in 15 ml of formamide. When dissolution is complete make up to 50 ml with a solution of 3 g 1-1 dithizone in ethanol - 4-methylpentan-2-one (1.5 + 2 V / V ) . Spray this solution into the flame using the same conditions as for obtaining the calibration graph. Calculate the percentage of cobalt in the sample using the calibration graph.TABLE I PERCENTAGE COBALT FOUND Cobalt found, % Calculated cobalt content, % . . 12.74 . . 10.82 . . 13.14 . . 13.60 . . 11.99 . . 20.64 . . 14.59 . . 15.63 . . 16.54 . . 11.98 Digestion and aq. AAT 12.74 10.90 13.14 13.80 12.20 20.64 12.78 12.74 17.77 11.98 Burner up-position Organic Organic Organic solution solution solution A I \ AA +DDDCAA +DzAA 15.02 11.85 12.87% 10.02 11.01% 10.863 15.51 12.04 13.22% 13.923 13.88% 13.64% 12.38% 12.253 12.15% 26.30 20.10 20.93 11.92 14.53 13.08 11.59 11.31 11.41 20.27 17.67% 17.923 10.70 14.52 11.863 Burner mid-position 7 A \ Organic Organic Organic solution solution solution AA +DDDCAA +DzAA 13.46 12.90% 12.93% 10.62 10.81% 11.04% 13.82 12.87 13.46 13.71% 13.64% 14.21 11.87 12.23% 12.63 22.13 21.01 21.63 12.95% 15.66 12.90% 12.993 12.633 12.813 18.32 17.18 17.673 10.07 14.97 12.063 Burner down-position I 3 Organic Organic Organic soh tion solution solution AA +DDDCAA +DzAA 12.87% 13.40 12.972 11.14% 11.14% 11.04% 12.80 13.24% 13.02% 13.733 14.05% 13.963 12.23% 12.36% 12.3St 20.643 21.80 21.09 13.22 16.60 12.93% 13.06 13.14 12.8SZ 16.96 17.27 17.58% 11.53 15.32 11.943 $ cn 8 8 * Abbreviations: acac = acetylacetonate; en = ethylenediamine; Py = pyridine; Q = quinoline.i AA, atomic absorption. $ Values within &0.25% of digestion value. bMay, 1983 SHORT PAPERS 635 Results and Discussion Good agreement was obtained between the results obtained by prior wet digestion of the various cobalt samples listed in Table I and by the ligand-exchange method described above. The mixed solvent was necessary in order to dissolve all the samples and the standard in the same solvent. As expected from the previous work on nickel complexes when solutions were analysed in the absence of a ligand exchanger some high and low results were obtained. It is considered that this is due to the different bonding environments of the cobalt in the various complexes, for example in the standard, cobalt cyclohexylbutyrate, cobalt is bonded to oxygen whereas in sample 1, containing a macrocyclic ligand, it is bonded to nitrogen.Sastri et aL2 “0 1 2 3 4 5 6 Burner height, divisions Fig. 1. Plot of burner height veyszts apparent concentration for cobalt cyclo- A, Organic solution; B, organic solution with DDDC; and C, hexylbutyrate. organic solution with Dz. have suggested that when metal-oxygen bonds are involved in the breakdown of a complex in a flame this leads directly to metal oxides, which reduces the concentration of free metal atoms low down in the flame. Thus, we expect the maximum absorbance for those complexes having cobalt-oxygen bonds to occur higher in the flame than those having cobalt-nitrogen or cobalt-sulphur bonds.The addition of a material that complexes preferentially with cobalt and displaces all other ligands would result in the cobalt having the same bonding environment in all the solutions This is in fact observed and is illustrated by the data in Figs. 1-3. -0 1 2 3 4 5 6 Burner height, divisions Plot of burner height versus apparent concentration for Na,[CO(NO,),]. A, Organic solution; B, organic solution with DDDC; and C, organic solution with Dz. Fig. 2.636 SHORT PAPERS Analyst, Vol. 108 3 k I C 8 2 p. I I I I I 0 1 2 3 4 5 6 Burner height, divisions 2 . Fig. 3. A, Organic solution; B, organic solution with DDDC; and C, organic solution with DZ. Plot of burner height veisus apparent concentration for CoB(NCS),. and should lead to correct results. It has not proved possible to find an organic ligand that will readily exchange with all other ligands. Samples 1, 2 and 3, which contain macrocyclic ligands did not exchange with DDDC even on long standing. When solutions of samples plus various ligand exchangers were analysed it was found that Dz was best, but not universal as shown by the results for Co[(en),Cl,]Cl. Provided the complexes are labile and more weakly bonded than the added ligand, exchange procedures allow a considerable saving of time com- pared with the wet digestion - atomic-absorption method. We thank Dr. S. M. Nelson for donating the macrocyclic cobalt complexes. References 1. 2. Leonard, M. A., and Swindall, W. J., Analyst, 1973, 98, 133. Sastri, V. S., Chakrabarti, C. L., and Willis, D. E., Can. J . Chew., 1969, 47, 587 Received August 24th, 1982 Accepted November 26th, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800633

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

636 SHORT PAPERS Analyst, Vol. 108 Differential Determination of Cationic and Anionic Surfactants in Mixtures by Two-phase Titration Masahiro Tsubouchi Laboratory of Chemistry, Kochi Medical School, Oko, Nankoku, Kochi 781-51, Japan and John H. Mallory Purex Corporation, 24600 South Main Street, Carson, CA 90749, USA Keywords : Two-phase titration ; cationic and anionic surfactant determination ; sodium tetraphenylborate titrant; tetrabromophenolphthalein ethyl ester imdicator Titrimetric methodsl-l1 employing visual indicators provide a means for the rapid determina- tion of cationic and anionic surfactants without the need for complex instrumentation. Tetraphenylboratel-6 is often used as the titrant for the determination of anionic surfactants. Until now the direct determination of cationic or anionic surfactants, when in admixture, by such techniques, has not been possible.This paper presents a two-phase titrimetric method for the determination of total cationic or anionic surfactants in mixtures thereof. In this procedure, tetraphenylborate is used as the titrant with tetrabromophenolphthalein ethyl esterMay, 1983 SHORT PAPERS 637 as the indicator. The procedure works only when the concentration of anionic surfactants is lower than that of cationic surfactants. Experimental Apparatus 10-ml burette were used. A Toa, Model HM-SES, pH meter equipped with a combined electrode (GTS-155C) and a Reagents All reagents used were from Wako Pure Chemical Industries (Osaka, Japan). Indicator, 0.03% m/V. Dissolve 30 mg of potassium tetrabromophenolphthalein ethyl ester12 in 100 ml of ethanol.Titrant, 5 x 10-5 M. Prepare a 2 x 10-2 M solution of sodium tetraphenylborate and check it according to the gravimetric method as follows. Add 1 ml of 1 N acetic acid and 25 ml of 0.1 M potassium hydrogen phthalate solution to 50 ml of the tetraphenylborate solution. After 2 h, filter the precipitate using a glass filter and wash it with saturated potassium tetra- phenylborate solution. Use the tetraphenylborate solution after accurate dilution to the 5 x low5 M level with N sodium hydroxide solution. Store it in a dark bottle; it is stable for 1 month. Cationic surfactant solzttion, 5 x 10-5 M. Prepare a 5 x 10-3 M solution of Zephiramine (tetradecyldimethylbenzylammonium chloride) and standardise it according to the titrimetric method6 using tetraphenylborate as the titrant with methyl orange as the indicator; after accurate dilution, use it as a reference surfactant solution for standardising the procedures.Anionic surfactant solution, 5 x M. Prepare a 5 x M solution of sodium dodecyl- benzenesulphonate and standardise it according to the titrimetric methodll using standard cationic surfactant solution with methylene blue as the indicator; after accurate dilution, use it as a reference surfactant solution for standardising the procedures. Prepare two solutions, each 0.3 M with respect to disodium hydrogen orthophosphate and 0.05 M with respect to sodium tetraborate. Adjust one solution to pH 6.0 by dropwise addition of 10 N sulphuric acid and adjust the other solution to pH 12.5 by dropwise addition of 10 N sodium hydroxide solution.Dry it at 105 "C and weigh it. Bu,,er solution, p H 6.0 and 12.5. Procedure 1 Place 5 ml of sample solution (ca. lO-5-lO-* M ; concentration of the anionic surfactant lower than that of the cationic surfactant), 5 ml of buffer solution (pH 12.5), 1 drop of the indicator and 3 ml of 1,2-dichloroethane in a glass-stoppered cylinder. Titrate the mixture with sodium tetraphenylborate solution with intermittent vigorous manual shaking between additions of titrant to ensure equilibrium between the two phases. A colour change from blue to colourless takes place in the organic phase at the equivalence point. Procedure 2 1 drop of the indicator and 3 ml of chloroform in a glass-stoppered cylinder.mixture in the same way as in procedure 1. place in the organic phase at the equivalence point. Place 5 ml of the same sample solution, as in procedure 1, 5 ml of buffer solution (pH 6.0), Titrate the A colour change from blue to faint yellow takes Total cationic surfactant in 5 ml of sample (M) = (A x C)/5 Total anionic surfactant in 5 ml of sample (M) = C ( A - B)/5 where A and B are the volumes of titrant in millilitres (concentration C M) required to titrate 5 ml of sample in procedures 1 and 2, respectively. Results and Discussion Based on the results obtained at various pH values and in various organic solvents, Chloroform (at pH 5.5-6.5). and 1,2-dichloroethane (at procedures 1 and 2 are recommended. pH 12-13) gave the best end-points and most consistent titres.638 SHORT PAPERS Analyst, Vol.108 The ion pair formed between a cationic surfactant and the indicator is not decomposed by anionic surfactants at pH 12-13, but it is decomposed at pH 5.5-6.5 and the CS+ - AS- ion pair (CS = cationic surfactant; AS = anionic surfactant) is formed in chloroform. Tetraphenyl- borate forms an ion pair with cationic surfactants stoicheiometrically.1-6 The titre in pro- cedure 1 corresponds to the total amount of cationic surfactant independent of anionic surfac- tant. Only residual cationic surfactant (cationic surfactant uncombined with anionic surfac- tant) is titrated at pH 5.5-6.5, and the titre in procedure 2 corresponds to free cationic surfac- tant. The difference between the titres in procedures 1 and 2 is proportional to the total amount of anionic surfactant present.The method retains its validity only when the concentration of anionic surfactant is lower than that of cationic surfactant. Variations in the initial volume of the aqueous layer (8-15 ml) had no influence on the deter- mination of the titration end-point. The aqueous phase is colourless in procedure 2 and is colour- less or faint blue - violet in procedure 1 throughout the titration. A blank titration is un- necessary because the organic phase is faint yellow or colourless in the absence of cationic surfactant. With 2 x M titrant, the colour change a t the end-point was not sharp. The procedure retains its validity when the concentration of cationic surfactant is in the range ca. 10-4-10-5 M. Sodium dodecylsulphate, Aerosol OT (sodium di-2-ethylhexyl sulpho- succinate) and benzethonium chloride (benzyldimethyl(2- [2-$-( 1,1,3,3-tetramethylbutyl- phenoxy)ethoxy]ethyl )ammonium chloride) were also suitable reference surfactants for standardising the method.Certain cationic surfactants such as the alkylpyridiniums may decompose at pH 12.5 and will not be titrated quantitatively. The following ions did not interfere at the M level: K+, Ca2+, Zn2+, Mg2+, AP+, NH4+, C1-, NO3- and oleate; mercury(I1) caused positive errors at even the The results of the titration of Zephiramine and sodium dodecylbenzenesulphonate mixtures are shown in Table I. The indicator is hardly soluble in water and organic solvents form a film on the surface of the titrated solution, which is helpful for end-point detection in this procedure with a dilute titrant.Benzethonium chloride and benzalkonium chloride [C6H5CH,N(CH3),RC1, R = C,Hl,- C,H3,) are used as disinfectants and sodium dodecylbenzenesulphonate as a detergent in hospitals. The procedures were specifically applied to the determination of these surfactants in effluents (wash liquors) from a hospital. One of the samples contained 6.45 x 1 0 - 5 ~ of cationic surfactant and 9.10 x A recovery test using 2 ml of 5.0 x 10-5 M sodium dod cylsulphate solution yielded a result of 97% of the added anionic surfactant. In another s. mple, the concentration of anionic surfactant was higher than that of cationic surfactant. A known amount of benzethonium chloride solution (4.5 x loa5 M, 5 ml) was added to this sa nple, and it was then titrated by the above procedure.The results were 1.75 x M of cationic surfactant (with standard addition) and 4.20 x M of anionic surfactant in the sample, compared with 2.158 x M of anionic surfactant by an alternative spectrophoto- metric method14 using me :hylene blue. The methylene blue method measures only the free M level. M of anionic surfactant. M of c,itionic surfactant (without standard addition), 6.35 x TABLE I TITRATIO?r OF CATIONIC (cs) AND ANIONIC SURFACTANT (AS) MIXTURES WITX 5.0 x 10-5 M SODIUM TETRAPHENYLBORATE SOLUTION Mixturelml r > cs, AS, 5.2 x 1 0 - 6 ~ 4.9 x 10-5 M 4 0 4 2 4 3 4 5 6 3 6 5 A Titre*/ml r 1 Procedure 1 Procedure 2 4.17 4.17 4.16 2.24 4.18 1.19 4.14 0 6.25t 3.31; 6.23 1.35 5.2 x 10-5 M 4.9 x 10-5 M CS found/ml AS found/ml 4.01 0 4.00 1.96 4.02 3.05 3.98 - 6.01 3.00 5.99 4.98 * Mean of ten determinations.t Standard deviation 0.05 ml. $ Standard deviation 0.04 ml.May, 1983 SHORT PAPERS 639 anionic surfactant present. The recovery of a known amount of benzethonium chloride was ca. 102%. 1 . 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. References Patel, n. 11.. and .biderson, I<. A . , Dviig Stand., 1958, 26, 189. Epps, 15. JZ., and Burden, J . C., Anal. Chew., 1958, 30, 1882. Illlo, T., 3Iiyajima. Ti., and Tsukatani. H., ./. Phavuz. SOC. .]PI?, 1960, 80, 153. Tyno, T., and Miyajinia, I<., Chcm. Plzavm. Bztll., 19633, 11, 193. Cross, J . T., Analyst, 1965, 90, 315. “The Japanese Pharmacopoeia,” Ninth Edition, Hirokawa Publishing, Tokyo, 1976, p. C-317. Carkhuff, 15. D., and Boyd, WM. l:., J . Am. Phavnz. Assoc., 1954, 43, 240. Jansson, S. O., Modin, R., and Schill, G., Talanta, 1974, 21, 905. Reid, V. W., Longman, G. F., and Heinerth, E., Tenside, 1967, 4, 292; 1968, 5, 90. Wang, I,. K., and Panzardi, P. J., Anal. Chena., 1975, 47, 1472. Pharmaceutical Society of Japan, “Standard Methods of Analysis for Hygiene Chemists,” liinbara Feigl, F., and Anger, V., Micvoclzint. Acta, 1937, 2, 107. “The Japanese Pharmacopocia,’’ Ninth Edition, Hirokawa I’ublishing, Tokyo, 1076, p. B-458. Japanese Industrial Standard, I< 0102, 1981. Publishing, Tokyo, 1980, p. 660. Received September 27th, 1982 Accepted December 14th, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800636

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年代:1983

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May, 1983 SHORT PAPERS 639 Adsorption of Metals on Polypropylene During Cold Vapour Atomic-absorption Determination of Mercury* Hart B. MacPherson and Shier S. Berman Division of Chemistry, National Research Council of Canada, Ottawa, Ontario, Canada, K1A OR9 Keywords : Mercury determination ; atomic-absorption spectrophotometry ; metal adsorption ; polypropylene Kuldverel recently reported that the polypropylene mixing chamber of the Perkin-Elmer MHS-1 accessory for hydride generation and cold vapour atomic-absorption spectrophotometry (CVAAS) can adsorb tin(I1) chloride that is not removed by a distilled water rinse. As a result, the Hg2+ in subsequent sample solutions is reduced prior to the addition of fresh reduc- ing agent. Kuldvere speculated that this had given rise to earlier reports of the apparent ability of polypropylene to reduce Hg2+ to HgO.In this laboratory we use a Varian, Model 65, hydride generation ; ccessory, which also has a polypropylene mixing chamber, for CVAAS determinations of I iercury. In one method developed here2 the sample solutions, usually 15-ml aliquots, are ma le alkaline to a pH greater than 12 by addition of an excess of 11 M sodium hydroxide solutim (10 ml). The reducing agent is 20% sodium tetrahydroborate(II1) solution, used in 1 ml volumes. During an investigation of interferences associated with this method another memory effect was observed. When the mixing chamber was rinsed with distilled water in the usual manner between each measurement with the noble metals, selenium or tellurium present, interference occurred with subsequent standard mercury solutions.However, when an aqua regia leach was performed between measurements no memory effect was observed. Presumably, upon reduction the metals were adsorbed on the polypropylene surface, were still capable of causing interference and were not removed by the distilled water rinse. Mercury standards were spiked with Ag+, Pd2+ and Tes+ and analysed for mercury using our method.2 After the mixing chamber had been rinsed in the usual manner with distilled water, 20 ml of distilled water, 2.5 ml of 16 M nitric acid and 2.5 ml of 12 M hydrochloric acid were added and the Several experiments were performed to confirm this assumption. * N.R.C.C. No. 20862.640 SHORT PAPERS Analyst, Vol. I08 solution was stirred for 5 min and transferred into a bottle.One spiked standard was intro- duced six consecutive times prior to leaching. The spiked levels of these metals were much higher than would be encountered with most sediments and soils. The resulting sample solutions were analysed using flame atomic-absorption methods for silver and palladium and inductively coupled plasma atomic-emission methods for boron and tellurium. The results shown in Table I indicate that these elements were indeed adsorbed on the polypropylene mixing chamber surface at high pH. Particularly important is the result for the consecutively introduced sample, which indicates that these metals can accumulate during a run of samples, possibly from a lower non-interfering level to a higher interfering one.TABLE I ADSORPTION OF METALS BY THE POLYPROPYLENE MIXING CHAMBER OF THE VARIAN, MODEL 65, ACCESSORY AT pH GREATER THAN 12 Amount Metal addedlpg Ag .. .. .. 107 213 320 171* Pd . . .. .. 125 250 375 200* Amount adsorbedlpg Metal 7 Te . . . . 36 35 10 3 B .. .. 6 11 3 .. .. Amount added1p.g 125 249 374 199* 57 000 57 000 57 000 342 OOO* Amount adsorbed1p.g 7 10 17 9 103 120 114 199 * Cumulative value for six consecutive additions. If boron was adsorbed as BH4- the effect on subsequent samples should be similar to that of adsorbed tin(I1) chloride, as reported by Ku1dvere.l Sodium was also identified in each solution by the colour of the atomic-absorption flame, indicating that it too was adsorbed. It would appear that many species are adsorbed on polypropylene at high pH.For example, during other work performed here involving the analysis of acid-digested fish samples, the emanation of fish odours from the mixing chamber, obviously resulting from the adsorption of incompletely decomposed fish material, persisted throughout several distilled water rinses. The emanations ceased after an acid leach. It has been reported3 that the only potential metallic interferences in most soil and sediment samples that can affect CVAAS results are the noble metals, selenium and tellurium. How- ever, these metals are usually present a t levels too low to interfere. The analyst also assumes the absence of adsorption effects that would allow the interfering species to accumulate to a higher significant level. It is obvious, therefore, that caution is required if polypropylene apparatus is to be used when the sample solutions are made alkaline for CVAAS determinations of mercury regardless of the reducing agent used.Periodic checks of the sensitivity throughout the set of determinations should be performed. Further, the mixing chamber should be cleaned by leaching with dilute aqua regia, or, perhaps, dilute nitric acid, prior to a set of determinations. It should there- after be conditioned with a mercury standard as described below. It is worth noting that the interference effects of the above-mentioned metals have been found to be much less serious in alkaline solution than in acidic solution3 and therefore there is impetus for alkaline conditions to become more commonly used. It is not known, to us, whether or not borosilicate glassware exhibits similar adsorption effects.A property of the Varian, Model 65, accessory that may also be an adsorption phenomenon of polypropylene is the requirement for the apparatus to be conditioned for optimum calibration sensitivity. The conditioning, which improves the sensitivity by 20-30y0, can be accomplished in our method2 by analysing a sample solution spiked with about 2000 ng of Hg2+ with the stirring time increased to 5 min and the carrier gas flow-rate reduced to about 0.2 1 min-l. This allows a long contact time between the solution, the mercury vapour and the apparatus. This work demonstrates that such an accumulation can occur.May, 1983 SHORT PAPERS 641 It may be worth noting that the adsorption of tin(I1) chloride reported by Kuldverel or that of sodium tetrahydroborate( 111) should not affect analytical results if the lid of the accessory is replaced within a reasonable length of time after sample introduction and before stirring. For our method,2 equivalent results were obtained any time up to 30 s after introduction of the sodium tetrahydroborate( 111) reductant. It would appear that without agitation Hgo diffuses slowly out of the sample solution and is not lost from the mixing chamber. We are grateful to Dr. J. W. McLaren and Mr. V. Royko of this laboratory for the inductively coupled plasma atoniic-emission determination of boron and tellurium. References 1 . 2 . 3 . Kuldvere, A . , Analyst, 1982, 107, 179. MacPherson, H. B., Mykytiuk, A. P., Russell, D. S., and Berman, S. S., Can. J . Spectrosc., 1982,27, 132, Bartha, A., and Ikrhyi, I<., Anal. Chim. Acta, 1982, 139, 329. Received September 13th, 1982 Accepted December 3rd, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800639

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年代:1983

数据来源: RSC

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May, 1983 SHORT PAPERS 641 Spectrophotometric Study of the Reaction of Titanium( IV) with Chlorophosphonazo I Qiu Xing-chu and Zhu Ying-quan Agricultural Science Research Institute of Ganzhou Prefecture, Jiangxi, China PO Box 82, Chengdu, China Keywovds : Titanium determination ; chlorophosphonazo I ; spectrophoto- metry In 1961, Nemodruk et aZ.l recommended chlorophosphonazo I (CPA I) as a reagent for the spectrophotometric determination of uranium, and this reagent has since been applied to the spectrophotometric determination of protactinium,2 cadmium, copper, zirconium, thorium, lanthanum and y t t r i ~ m , ~ aluminium* and calcium and magnesi~m.~ The spectrophoto- metric determination of titanium by this method has not been reported and we have therefore explored the analytical potential of this colour reaction.Experimental Apparatus the absorbance measurements. ments Factory), equipped with a combined calomel - glass electrode assembly. A Model 72 spectrophotometer (Shanghai Analytical Instruments Factory) was used for All pH measurements were made with an S-73-pH pH meter (Tianjin Analytical Instru- Reagents Weigh 0.834 g of suitably pure titanium(1V) oxide that has been ignited at about 900 "C and fuse it with 8 g of potassium disulphate (K2S20,) in a quartz or platinum crucible. Dissolve the melt in 150 ml of hot sulphuric acid (1 + 2). Dilute the solution to 500 ml in a calibrated flask with sulphuric acid (1 + 5). A 20 pg ml-l solution of titanium was prepared by suitable dilution. Dilute the stock standard solution with an appropriate volume of distilled water.Mix equal volumes of 1 N acetic acid and 1 N sodium acetate solution. Titanium stock standard solution, 1 mg ml-l. Titanium working standard soldion, 20 pg ml-l. Acetate bu$er solution, pH 4.74.642 SHORT PAPERS Analyst, Vol. 108 Dissolve 0.1000 g of CPA I (East China Normal University Chem. Indus. Mfg.) in PO0 ml of water. Dissolve 3.7 g of complexone I11 in a suitable volume of water, add 2.2 g of zinc acetate and dilute the solution with water to 1 1. General Procedure Transfer a test solution containing not more than 100pg of titanium into a 25-ml cali- brated flask and add 4 ml of acetate buffer solution (pH 4.74) and 3 ml of CPA I solution. Mix the solution well and digest for 20 min on a water-bath at 40 "C.After cooling to room temperature, dilute the solution with water to the mark. Determine the absorbance at 580 nm in a 1.0-cm cell against a reagent blank. CPA I solution, 0.1%. EDTA zinc salt solutiolz, 0.01 M. I Results and Discussion Absorption Spectrum of the Complex Fig. 1. blank at 500 nm. Optimum Experimental Conditions A study of the complexation of CPA I with titanium at different pH values showed that the coloured complex has a constant absorbance in the pH range 4.1-5.1 (see Fig. 2). Consequently, a pH of 4.74 was chosen as the optimum for this work. In 25 ml of solution, 2.5-6.0 ml of 0.1% CPA I solution gave a maximum and constant absorbance with 50 pg of titanium, so 3.0 ml of 0.1% CPA I solution were used in the deter- minations. The amount of acetate buffer solution added, over the range 3.5-6.0m1, had no effect on the absorbance measured by the general procedure.Hence an addition of 4.0ml was chosen. Temperature affected the time required for full colour development of the complex. The absorbance was unaffected by temperature over the range 30-60 "C. The development of colour was complete after 20 min at 40 "C. The absorbance of the coloured complex was stable for 24 h. The absorption spectrum of the titanium ion complex with CPA I at pH 4.74 is shown in The absorption maximum of the complex was at 580 nm and that of the reagent 0.5 8 0.4 3 0.3 t $ P - - - \ \ q \ II \ I s I \ - '. -- /- , I 540 580 620 680 Wavelengthhm 3 4 5 PH Fig. 2. Effect of pH on Ti(1V) - CPA I complex (Ti taken, 40 pg; 1.0-cm cell).Fig. 1. Absorption curves of I, reagent blank against water, and 11, titanium-CPA I com- plex. All of the reagents given under General Procedure are included (Ti taken, 60 pg; 1 .O-cm cell). Stoicheiometry of the Complex Job's method of continuous variation. The molar ratio between the metal and the ligand in the complex was ascertained by The colour of complementary mixtures of equimolarMay, 1983 0.7 0.5 C 3 a 2 0.3 SHORT PAPERS - - - 643 0.1 I I / - 1 I 1 , I I I I 1 Ti /m I Fig. 3. Job plot. Concentration of Ti(1V) solution taken = 1.0 x M and concentra- tion of CPA I solution added = 1.0 x M ; pH = 4.74; wavelength = 580nm; 1.0-cm cell. solutions of the metal and the ligand was developed at the recommended pH, and absorb- ances were recorded at Amax., The maximum in Fig.3 indicates the formation of 1 : 1 com- plex. The binary complex therefore probably has the following structure : Effect of Other Ions Using the above general procedure with 50pg of titanium(I\r) and different amounts of various ions, it was found that Ba(I1) (1 mg), V(V) (0.25 mg), Sb(II1) (0.5 mg), Cu(1I) (0.1 mg), Pb(I1) (1 mg), Cr(V1) (0.2 mg), Mn(I1) (1 mg), Ni(I1) (0.2 mg), Mo(V1) (0.1 mg), Bi(II1) (0.5 mg), W(VI), (0.25 mg) and Sn(I1) (0.1 mg) do not interfere. Fe(II1) (2 mg) can be masked by the addition of EDTA zinc salt solution (0.01 M ) . Aluminium(II1) seriously interfered in the determination. It may be possible to over- come this interference, e.g., by masking aluminium with salicylic acid,6 by precipitation separation’ or by solvent extraction of the titanium - cupferron complex.8 However, none of these methods was investigated in this work.Conformance with Beer’s Law A series of standard titanium solutions were prepared and the absorbances were measured and plotted against concentration. In the concentration range 0-100 pg of titanium per 25 ml there is a linear relationship between absorbance and concentration. From this straight line, the average molar absorptivity of the titanium(1V) - CPA I complex was calcu- lated to be 8.79 x lo3 1 mol-l cm-l. Comparison with Other Reagents A comparison of various methods is shown in Table I. Application alloys, The proposed method has been applied to the determination of titanium in titanium - iron A sample of alloy (0.1000 g) was dissolved in 10 ml of nitric acid (1 + 3), oxides of nitro-644 SHORT PAPERS TABLE I COMPARISON OF REAGENTS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF TITANIUM pH or acidity Interfering ions References €1 Reagent A/nm 1 mol-1 cm-l range H2SO'l Hydrogen peroxide .. .. 410 7.0 x lo2 1.4-3.6 N V, Cr, Mo, W 9-1 1 Cr, Pb, Mo, W 12, 13 Tiron . . .. .. . . 390 1.5 x lo4 4.7 Diantipyrylmethane . . . . 390 1.45 x lo4 1 N HC1 Fe, V, Nb, Mo 14 Sulphosalicylic acid . . . . 410 3.5 x 103 3.5 N H2S04 Fe, V 15 N-Benzoyl-N-phenyl- hydroxylamine (N-BPHA)" 380 6.6 x lo3 10 N HC1 V, Nb 16, 17 CPAI .. .. .. .. 580 8.79 x los 4.1-5.1 A1 This work gen were removed by boiling and the solution was cooled, transferred into a 100-ml calibrated flask and diluted to volume with water. A 2.0-ml aliquot of the sample solution was pipetted into a 25-ml calibrated flask and 2 ml of EDTA zinc salt solution (0.01 M) were added. The general procedure was carried out, and the concentration of titanium was calculated using a calibration graph obtained by applying the procedure to a series of samples of 2 mg of iron (containing no titanium) to which 0, 10, 20, 30, 40, 50 and 80 pg of titanium (as a standard solution) had been added. The results obtained by the recommended method are shown in Table 11.TABLE I1 RESULTS FOR DETERMINATION OF TITANIUM IN TITANIUM - IRON ALLOYS Ti, % A f Standard Coefficient of Sample Certified value This work* deviation, yo variation, % Alloy 1 . . . . 0.496 0.482 0.025 7 5.33 Alloy 3 . . . . 1.493 1.505 0.028 7 1.91 Alloy 2 .. . , 0.995 1.009 0.024 8 2.46 Alloy 4 . . . . 1.990 2.002 0.021 2 1.06 * Mean of eight determinations. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. Nemodruk, A. A., Novikov, Yu. P., Lukin, A. M., and Kalinina, I. D., Zh. Anal. Khim., 1961, 16, Nemodruk, A. A., and Palei, P. N., Radiokhimiya, 1963, 5, 335. BudeSinskq, B., and Haas, K., Collect. Czech. Chem. Commun., 1964, 29, 2758. Zhu Ying-quan and Zhang Lin, Talanta, in the press. Qiu Xing-chu and Zhu Ying-quan, in the press. Pfibil, R., and Veselq, V., Talanta, 1963, 10, 383. Pfibil, R., and Veselq, V., Chemist-Analyst, 1963, 52, 43. Cheng, K. L., Anal. Chem., 1958, 30, 1941. Babko, A. K., and Volkova, A. I . , Z h . Obshch. Khim., 1951, 21, 1949. Babko, A. K., Volkova, A. I . , and Lisichenok, S. L., Zh. Neovg. Khim., 1966, 11, 478. Mori, M., Shibato, M., Kyuno, E., and Ito, S., Bull. Chem. SOC. J p n . , 1956, 29, 904. Sommer, L., Collect. Czech. Chem. Commun., 1963, 28, 2102. Bahr, H., and Jagielski, J., Chem. Anal. (Wuvsam), 1967, 12, 363. Corbett, J. A., Analyst, 1968, 93, 383. Qureshi, M., Rawat, J . P., and Khan, F., Anal. Chim. Acta, 1968, 41, 164. Zharovoskii, F. G., Shpak, E. A., and Piskunova, E. V., Ukv. Khim. Zh., 1962, 28, 1104. Afghan, B. K., Marryatt, R. G., and Ryan, D. E., Anal. Chim. Acta, 1968, 41, 131. 292. Received April 14th, 1982 Accepted October 18th, 1982

ISSN:0003-2654    

DOI:10.1039/AN9830800641

出版商:RSC    

年代:1983

数据来源: RSC

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Analyst, May, 1983 Book Reviews 645 COVALENT CATALYSIS BY ENZYMES. By LEONARD B. SPECTOR. Pp. xii + 276. Springer-Verlag. 1982. Price DM 78; $34.70. ISBN 3 540 90616 9; 0 387 90616 9. As long as enzymes continue to catalyse, the analytical chemist will use them as components of a sensitive, highly selective, analytically useful reaction. For him, the details of the mechanistic aspects of enzyme catalysis are usually of secondary importance to the occurrence of the catalysed reaction. Yet the advance of science, including analytical chemistry, ultimately depends on an understanding of all aspects of a subject, and this book provides an unconventional look at the mechanisms of enzyme catalysis. Its thesis is that enzymes, like many other catalysts, function by removing a molecular fragment from a substrate (reactant) to form a compound between that fragment and the enzyme.That fragment is subsequently transferred to a second reactant. This contrasts with the popular view that the enzyme merely provides a favourable configuration and environment for direct transfer of the fragment between reactants. This “covalent” mechanism is supported by information concerning 465 enzymes, which contrast with a complete lack of information in favour of the “popular” interpretation. To the non-biochemist, a t least, the arguments seem very persuasive, and do not need the extra lessons inlogic, which the author throws in for good measure. The book itself is well prepared and produced, with an abundance of formulae and references, and with a combined author and subject index.A. TOWNSHEND TRACE ANALYSIS. Volume 1. Edited by JAMES F. LAWRENCE. Pp. x + 331. Academic Press. 1981. Price k26.20; $39.50. ISBN 0 12 682101 1. The first volume in a continuing multi-volume series entitled “Trace Analysis” is devoted to five high-quality review articles of state-of-the-art high-performance liquid chromatography in organic and inorganic analysis. A suitable sub-title would have been most helpful in defining this area of coverage. That, however, is the only notable criticism of an excellent review volume, hopefully the forerunner of many others. The Editor is to be congratulated on the choice of an attractive range of chromatographic topics of diverse interest but all germane to current HPLC applications ; few chromatographers will fail to find material to interest them.Four of the review articles focus on application areas for practical chromatographic analysis, while the fifth concentrates on electrochemical detection in HPLC and flow injection analysis (FIA). Brunt has assembled a survey of detector principles and design for the various voltam- metric systems that respond to solute properties, and the bulk property detectors that rely on conductance and capacitance measurements. Emphasis is on design development with sufficient theoretical background and application coverage to interest any who use or contemplate using such detectors. The article by Graham on HPLC determination of trace organic compounds in aqueous environmental samples is broad-ranging and fairly comprehensive.Sufficient back- ground on separation methodology, detection systems, sample isolation, clean-up and pre- concentration and trace enrichment is given to set the scene for a wide range of practical problems and separation examples. Pollution studies in effluents and drinking water are covered and macromolecular characterisation by size exclusion chromatography is noted. Cassidy has assembled the most complete review to date on the separation and determination of metal species by liquid chromatography. This very worthwhile article covers the specific problems of separation and detection associated with ionic and neutral metallic compounds. Partition, adsorption, exclusion and ion-exchange systems are compared for metal complexes, organometallics and ionic compounds.Ion pairing is well covered, as is the area of bonded complexing phases. This is a well structured, coherent, all-encompassing review of the state of LC applied to metallic species and should prove a valuable asset to both veteran and novice in this area of analysis. Mycotoxin analysis is reviewed by Scott, who considers the conditions pertaining to HPLC separation of toxins with a wide range of chemical structures. Detailed analytical factors are covered for each group of compounds. The reference style adopted in this review is that of author designations rather than number reference, which this reviewer would have preferred. This review seems essential for any involved in this area of clinical or regulatory analysis. The final article, on ion Chromatography, is useful both for beginners and experienced users, deriving646 BOOK REVIEWS Analyst, Vol.108 as it does from the originator of the technique. Small covers theory and applications effectively, the latter being tabulated in a useful fashion. Its references are generally up to date and clarity and presentation are of a high standard. This book is much more worthwhile than many such collections of review articles. PETER C. UDEN ANALYSE AUTOMATIQUE DES EAUX: UNE TRENTAINE DE PARAMETRES USUELS. By PI~RRE WARZEE and SERGE MARTIN. Pp. 130. Fondation Universitaire Luxembourgeoise. 1981. Price BFr400. (In French). This book is a collection of methods of analysis using as the common theme the operating principle of air-segmented continuous flow. The equipment used is from the Technicon Auto- Analyzer I1 series and the end-point detection is that of either colorimetry, flame photometry or spectrofluorimetry.The 30 parameters considered are designated by the authors as common for water analysis. It offers a concise introduction, aptly followed by the all important information on preservation of samples. Also, for the uninitiated there are brief details of the function of each component part of an AutoAnalyzer I1 system. There then follow the suggested methodologies pertaining to each parameter noted in the previous list of contents. Here, for each method, are given the chemical principle, the reagents and standard solutions together with their concentration and their preparation. All methods offer a line (flow) diagram of the chemical reaction path and for some methods there is a mention of interferences.In addition, a brief review is given of the method options available for one of the parameters, which conveniently leads into the description of the method of choice. The first impression, therefore, is that care has been given to the presentation of the contents of the book and that an analytical result will be obtained with any method for any water (at least surface water) sample. The authors’ procedure for calculating the concentration of the parameter in the sample is given. Also, there is no reason to challenge the claims for sample throughput stated in the conclusion as it is well known that AutoAnalyzer systems can be highly productive, especially in the simultaneous mode.It is understood from the translation that the analytical methods are used or are recommended for use by the authors and the bibliography would suggest that they have not developed the methods themselves. Indeed, the majority of the methods are found in common use in water laboratories in the United Kingdom (UK). I t is therefore disappointing to highlight the fact that there is no real evidence offered by the authors of the precision and accuracy of the analytical results obtained with the methods. Both elements are important measures of the performance of an analytical technique and there is a large effort being made in the UK, through the frame- work of the DOE/NWC Standing Committee of Analysts, to publish recommended methods of analysis that include this type of performance data.However, in spite of the criticism of the non-appearance of performance data, the authors have produced a book that contains a package of information, even though semi-quantitative, on how to measure 30 parameters in a water sample using modifications to one basic analyser system. Collective information of this nature is not of common occurrence and the book is therefore of merit in this respect. The over-all presentation of the book is good. K. W. PETTS MARTINDALE: THE EXTRA PHARMACOPOEIA. 28th Edition. Edited by JAMES E. F. REYNOLDS. It is now 100 years since the First Edition of William Martindale’s “little book,” and the latest edition contains monographs on over 5000 drugs and ancillary substances, over 900 monographs having been added to the 27th Edition (and 97 deleted).This has led to an increase of 25% in the amount of information in the book, but i t is still contained in a single volume. However, with its larger page size and sheer bulk, it is now physically unwieldy to use and some form of division would seem desirable for the next volume. As ever, the volume contains a vast amount of information on the properties, actions and uses of drugs and medicines, intended mainly for pharmacists, pharmacologists and medical practioners, but invaluable also to the analytical chemist working in this area. All of the material in this edition has been revised, much of it rewritten and some of the monographs and chapters have been rearranged. Pp. xxxii + 2025. The Pharmaceutical Press. 1982. Price L57.ISBN 0 85369 160 6.May, 1983 BOOK REVIEWS 647 Virtually all proprietary medicinal products available in the UK are included, together with greatly expanded coverage of proprietary products throughout the world. The exhaustive General Index now contains about 50000 entries and is complemented by a Directory of Manufacturers, with over 3 000 manufacturers and distributors with their full addresses, and an Index to Clinical Uses. Other useful features are a list of common abbreviations for the systematic names of radicals and groups, a section on weights and measures with definitions and explanations of SI and other units, and a list of dissociation constants. Computer techniques were used to organise the information in this edition for printing and for retrieval from computerised information systems.All the information in Martindale is now avail- able online to those with access to suitable terminals. As the information will be updated regularly, online users will gain access to the more recent changes in drug information. Martindale is truly the Drug Bible (or, as the blurb describes the Martindale Online service, “The Drugs Information Store”), and this latest edition is even more impressive than previous versions. The Pharmaceutical Society are providing an indispensable service, and the Editor and his staff are to be congratulated. P. C. WESTON POLYMER SEPARATION MEDIA. Edited by ANTHONY R. COOPER. Polymer Science and Technology, VoZurpze 16. Pp. x + 276. Plenum. 1982. Price $39.50. ISBN 0 306 40902 X.This volume collects together the 23 presentations (one of these is an 11-line abstract) at a Symposium on the title theme held at Las Vegas in 1980. Its contents cannot, therefore, be com- prehensive and although it covers a range of areas, only some are of direct analytical interest. The four parts are of almost equal length, devoted to transport in polymeric media, functionalised polymers as separation media, polymeric membranes as separation media and a final miscellaneous part entitled “Novel polymeric separation media : structure and properties.” Analytical chemists will benefit from a browse of the various contributions, but it is fair to add that there are plenty of books available that are more attuned to their interests on the theme subjects of affinity chrom- atography, protein separations, steric exclusion chromatography, ion exchange, ultrafiltration in drug analysis, ion-selective electrodes, etc.J. D. R. THOMAS INTRODUCTION TO SAFETY IN THE CHEMICAL LABORATORY. By N. T. FREEMAN and J. WHITEHEAD. Pp. x + 244. Academic Press. 1982. Price L16; $29. ISBN 0 12 267220 8. This is a book of great contrasts, of which the first to be encountered is the discrepancy between the title and the extent of the subject matter. Not an introduction, but a wide ranging and de- tailed text, it is roughly comparable in scope to the RSC book “Hazards in the Chemical Laboratory,” but perhaps more slanted towards development and application activities. Its 14 chapters cover most safety aspects of laboratory design, organisation, procedures, tech- niques and operations ; protective equipment, fire prevention, first aid, legal considerations, hand- ling chemicals, compressed gases and ancillary services.The longest chapter is devoted to electro- magnetic radiation hazards (26 pp.), and the shortest to the achievement of safety goals (5 pp.). The latter, another section on motivation for safety and the codes of practice on various topics throughout the book are particularly good. These codes and most of the clear illustrations appear to originate from the well known laboratory complex in which the authors have both worked for many years. There is relatively little systematic data on the hazards of particular chemicals, other than to illustrate aspects of the many topics under discussion. Further degrees of contrast, perhaps deriving from enthusiasm, arise from the inclusion of detailed major disaster planning procedures in the organisation chapter and of synchrocyclotrons and other high energy physics equipment in the radiation chapter.The most glaring contrast orginates from the differences between the well written text, largely free from errors, and the references and some of the tables, where publishing conventions and proof- reading seem largely to have been dispensed with. Some dates, titles and names are wrong or648 BOOK REVIEWS Artalyst, Vol. 108 missing, and the chemical nomenclature is poor. Table 5.3 on odours of chemicals states “4 Mercapto 4 Methyl/onton 2 ore has ‘Catty’ odour” while “Alkyl chloride is ‘Foslic-pungent’.” ! Most of the references for further reading given at the end of each chapter have been consolidated unnecessarily (complete with errors) into a.final additional bibliography. Overall, a potentially good book has been marred by a lack of attention to detail, which it is to be hoped will soon be applied to produce a worthy revised edition. It would be false modesty and economy not to point out that the cost per page of the equivalent RSC book (containing also details on 480 hazardous chemicals) is less than half that for this book (less than one third for RSC members). L. BRETHERICK RECENT ADVANCES IN ANALYTICAL SPECTROSCOPY. PROCEEDINGS OF THE STH INTERNATIONAL INTERNATIONALE, TOKYO, JAPAN, 4-8 SEPTEMBER 1981. Edited by KEIICHIRO FUWA. IUPAC Symposium Series. Pp. x + 325.Pergamon. 1982. Price $75; L37.50. ISBN 0 08 026221 X. CONFERFERENCE ON ATOMIC SPECTROSCOPY AND 22ND COLLOQUIUM SPECTROSCOPICUM Proceedings of symposia often meet with disapproval because their information density is small and their information retrieval probability is low. The present text avoids the first pitfall by presenting a selection of the invited lectures presented at this Tokyo conference. Almost all are authoritative reviews, and the outcome is an extremely useful survey of the status of the subjects covered. These are mainly plasma sources (Fassel, Koirtyohann, Boumans, Robin and Keliher), graphite furnace atomisation (Rubeska, Chakrabarti and Fuwa) , surface and X-ray analysis (Birks, Kuwana, Somorjai, Ichinokawa and Szargan) and infrared techniques (Fateley and Griffiths) . There are also useful articles on atomic-fluorescence spectrometry (Winefordner) , imaging (Kirk- bright), automation and computerisation (De Galan, Minami and Savitzky) and photoacoustics Rosencwaig) as well as a brief report on flow injection analysis (Ruzicka) and discussion of syn- chrotron radiation (Sonntag), sputtered atom line sources (R. J. Macdonald) , extended electron spectroscopy (Ikeda) and the interfacing of atomic spectroscopy with other techniques (J. C. Van Loon). The book is assembled from camera-ready copy, which leads to some unevenness in presentation, but many of the articles, including the diagrams, reach an unusually high standard in this respect. Most of the fields covered are developing quickly, thus the collected articles will provide all analyti- cal spectroscopists with material of timely relevance as well as predictions of future developments. Like all such texts, it will date fairly quickly, but a t the present time it deserves to be widely read. ALAN TOWNSHEND

ISSN:0003-2654    

DOI:10.1039/AN9830800645

出版商:RSC    

年代:1983

数据来源: RSC

摘要:

648 BOOK REVIEWS Artalyst, Vol. 108 Erratum JANUARY (1983) ISSUE, p. 112, Table V. Some of the values for Laboratory 3 with the Hydrochloric acid boil were incorrect. The correct values are given below. Hydrochloric acid boil I 7 L-- Laboratory A1 A2 B1 B2 3 ND, ND ND, ND 33, 33 31, 34

ISSN:0003-2654    

DOI:10.1039/AN9830800648

出版商:RSC    

年代:1983

数据来源: RSC