ISSN:0003-2654    

DOI:10.1039/AN98005FX037

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

ANALAO 105 (1255) 969-1008 (1980)ISSN 0003-2654October 1980THE ANALYSTTHE ANALYTICAL JOURNAL OF THE ROYAL SOCIETY OF CHEMISTRYCONTENTS929 Polarographic Behaviour and Analysis of Some Azo Dyes o f BiologicalSignificance-J. P. Hart and W. Franklin Smyth939 A New Approach t o the Quantitative Analysis of Overlapping Anodic-strippingVoltammograms-Juei H. Liu944 A New Type of Biological Reference Material for Multi-element Analysis-the Fungus Penicillium ochro-chloron ATCC 36741---Miwako Suzuki, YukikoDokiya, Sunao Yarnazaki and Shozo Toda950 Spectrophotometric Determination of Hydrogen Peroxide Using PotassiumTitanium(1V) Oxalate-Robin M. Sellers955 Improved Extraction Method for the Spectrophotornetric Determination o fTrace Amounts of Boron i n River Water w i t h 1,8-C)ihydroxynaphthalene-4-sulphonic Acid and Removal of the Excess of Retagent-Takashi Korenaga,Shoji Motornizu and Kyoji TBeiPyridine-2-acetaldehyde Salicyloylhydrazone as an Analytical Reagent and i t sApplication t o the Determination of Vanadium-M.Garcia-Vargas, M.Gallego and M. de la GuardiaDetermination o f Cyanide in Animal Feeding Stuffs-J. R. Harris, G. H. J. Merson,M. J. Hardy and D. J. Curtis965974SHORT PAPERS981 A Simple Non-dispersive Atomic-fluorescence Spectrometer for MercuryDetermination, Using Cold-vapour Generation-R. C. Hutton and B. Preston984 Determination of Sulphide i n Flooded Acid - Sulphate Soils by an IndirectAtomic-absorption Spectrophotometric Method-Rarnesh C. Ray, P. K.Nayar, A.K. Misra and N. SethunathanDetermination o f Diuron Residues i n Soil: Comparison o f Determinations byHigh-performance Liquid Chromatography and Gas - Liquid Chromato-graphy-E. G. CotterillRapid Extraction o f Some Persistent Chlorinated Hydrocarbons from BiologicalMaterial w i t h Low Fat Content-Gunnar Norheirn aiid Elisabet Mo BklandDetermination o f the Anthelmintic Levamisole i n Plasma and Gastro-intestinalFluids by High-performance Liquid Chromatography-S. Marriner, E. A.Galbraith and J. A. Bogan996 Spectrophotometric Micro-determination of Silver(l) and Iodide lons-Sudarsan Barua, B. S. Garg, R. P. Singh and lshwar Singh998 Rapid Gas - Liquid Chromatographic Determination of Cotinine in BiologicalFluids-C. Feyerabend and M. A. H.Russell987990993C 0 M M U N I CAT1 0 NLimit of Detection in Analysis w i t h Ion-selective Electrodes-Derek Midgley 10021006 Book ReviewsSummaries o f Papers in this Issue-Pages iv, v, vii, x, x i iPrinted by Heffers Printers Ltd Cambridge EnglandEntered as Second Class at New York USA. Post OfficSelected Annual Reviewsof the Analytical SciencesVolume 4CONTENTS'Advances in Voltammetric Techniques,' byB. Fleet and R D. Jee'High-frequency Electrodeless PlasmaSpectrometry,' by B. L. SharpPp. vi f 73 f 9.50ISBN 0 85990 204 8RSC Members' mice f4.00Orders should be sent direct, with remittance, orthrough your usual bookseller to-THE ROYAL SOCIETY OF CHEMISTRYDistribution Centre,Blackhorse Road, Letchworth,Herts. SG6 1 HN, EnglandPATENTSB r i t i s h Patent No.1356 512.Contractor Mixing Device.Owner desires commercial exploitation on reasonable terms bylicense or sale. Inquiries, Fitzpatricks, Chartered Patent Agents,48 St. Vincent Street, Glasgow G 2 5TT, and Warwick House,Warwick Court, London WC1R 5DJ.B r i t i s h Patent No. I490 137.Chemical Compositions Suitable for Use as InsectRepellents.Owner desires commercial exploitation on reasonable terms bylicense or sale. Inquiries, Fitzpatricks, Chartered Patent Agents,48 St. Vincent Street, Glasgow G2 5TT, and U'arwick House,Warwick Court, London \\'ClR 5DJ.B r i t i s h Patent No. 1 346 389.An Anti-Adhesive Composition.Owner desires commercial exploitation on reasonable terms bylicense or sale.Inquiries Fitzpatricks Chartered Patent Agents48 St. Vincent Street, Clasgow G2 6TT, and Warwick House:Warwick Court, London WClR 5DJ.Notice to SubscribersSubscriptions for The Analyst, Analytical Abstracts and Analytical Proceedingsshould be sent to:The Royal Society of Chemistry, Distribution Centre,Blackhorse Road, Letchworth, Herts., SG6 1 HN, EnglandRates for 1980 (including indexes)U K/ Rest ofEire USA WorldThe Analyst, and Analytical Abstracts . , .. .... .. .. f120 $280 f126The Analyst, and Analytical Abstracts printed on one side of the paper f 129 $300 f135The Analyst, Analytical Abstracts, and Analytical Proceedings . . . . f136 $310 f143The Ana/yst, Analytical Abstracts printed on one side of the paper . . . . . . f145 $335 f152 and Analytical Proceedings . . . . ..Analytical Abstracts . . .. . . * . . . . . . . f92.50 $215 f97Analytical Abstracts printed on one side of the paper . . .. .. flOl $235 f106Subscriptions are not accepted for The Ana/yst and/or for Analytical Proceedings alon

ISSN:0003-2654    

DOI:10.1039/AN98005BX039

出版商:RSC    

年代:1980

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN98005FP117

出版商:RSC    

年代:1980

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN98005BP123

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

OCTOBER 1980 The Analyst Vol. 105 No. 1255 Polarographic Behaviour and Analysis of Some Azo Dyes of Biological Significance J. P. Hart Orthopaedic Department, Charing Cross Hospital, London, W.6 and W. Franklin Smyth Chemistry Department, University College, Cork, Republic of Ireland The polarographic behaviour of the azo dyes CI Direct Orange 34, Acid Red 73, Direct Blue 84 and Direct Red 80 over the pH range 1-13 was studied. Mechanisms of reduction are postulated, the optimum pH ranges for the determination of the dyes by differential-pulse polarography are selected and the appropriate linear ranges deduced from calibration graphs. Keywords: Azo dyes; fiolarography Azo compounds are widely used in industry as textile dyes, colouring agents in foods and pharmaceuticals, etc.As a result they can become environmental pollutants through dis- charge of the contents of plating baths from textile works into rivers, especially if not treated by the activated sludge process, as has been observed in certain instances.lV2 They can also enter the body through the intake of certain foods and drugs that contain these azo compounds. Concern has been voiced about the potential carcinogenicity of compounds containing azo group(^).^-^ Therefore, a study of the mechanism of the polarographic reduction of azo compounds, which often parallels the metabolism of these compounds in vivo (e.g., reductive fission of the azo linkage to the parent aromatic amines), is worthy of investigation. Differen- tial-pulse polarography can also be used to determine the parent compounds and their electroactive metabolites at trace levels.The electrochemical behaviour of a variety of azo compounds has been investigated over the years, and a brief survey of the literature on monoazo compounds alone illustrates the complexity of the electrode reactions involved. Issa et aL6 studied the polarographic reduction of some 4-hydroxy monoazo compounds containing different substituents, and found that reduction proceeded in acidic and alkaline solutions with the consumption of four and two electrons, respectively. In the same study the authors reported that 4-hydroxyazobenzene and azo compounds with weak donor or acceptor groups were capable of catalysing the reduction of H+, this process producing a wave that gave the appearance of a maximum. Similar results were obtained by other In contrast, Solochrome mordant dyes were found by Malik and GuptalO to undergo reduction with the transfer of two electrons in both acidic and alkaline solutions.These dyes produced one wave in acidic solution, but in some instances two waves developed in alkaline media. It has been shown, in an investigation on some para-substituted azobenzenes, that electron-accepting sub- stituents promote reduction to hydrazo derivatives, whereas electron donors drive the reaction partially or totally to the corresponding amines.ll Florence and co-workerslL1* have contributed a number of publications on the study of azo compounds. They suggested that certain species formed unstable hydrazo intermediates, and over-all polarographic n values of 4 were obtained.This paper is concerned with a polarographic study of the four azo dyes CI Direct Orange 34 (I), CI Acid Red 73 (11), CI Direct Blue 84 (111) and CI Direct Red 80 (IV) over the pH range Mechanisms of reduction are postulated on the basis of controlled-potential electrolysis at a large mercury pool and cyclic voltammetry as additional electroanalytical techniques. Optimum pH values ior the determination of the azo dyes by differential-pulse polarography (DPP) are selected and the appropriate linear ranges deduced from calibration graphs. 929 on compounds closely related to those mentioned above. 1-13.930 HART AND FRANKLIN SMYTH POLAROGRAPHIC BEHAVIOUIR AND A%dySt, VOz. 105 Experimental Reagents and Chemicals 0.1 N sulphuric acid and 0.1 N sodium hydroxide prepared in distilled water.Britton - Robinson buffers of pH 2-12 were used and the pH range was extended with S 0 3 - e N = N o N H 2 CI Direct orange 34 (I) C I Acid red 73 ( 1 1 ) OH OH OH OH SO3- SO3- SO3- CI Direct blue 84 ( I l l ) SO3- 0 1 S C ) - O N = N d N = N h so3- \ H N-.C-l 11 I , Mirror image I CI Direct red 80 ( I V ) All four dyes were recrystallised twice from ethanol - water (1 + 1) after which stock solutions were prepared by dissolving the appropriate amounts un distilled water to give concentrations of approximately 5 x Instrumentation All pH measurements were made using an EIL, Model 23A, pH meter, incorporating a glass indicator electrode, saturated calomel reference electrode and a ternperature compensator.Polarography was carried out with a PAR, Model 174A, polarographic analyser operated in the differential pulse mode, and polarograms were recorded on an Advance HR2000 X - Y recorder. A three-electrode system was used for polarography and consisted of a saturated calomel reference electrode, a platinum counter electrode and dropping-mercury electrode (D.M.E.). The dropping-mercury electrode used had the following cha.rac1.eristics: outflow velocity, m = 1.57 mg s-l; drop time, t = 4.3 s at the potential of the saturaked calomel electrode and at a mercury pressure of h = 68 cm in 1 M potassium chloride solution. For the analyser the controlled drop time was 0.5 s (sampled d.c. polarography), 1.0 s (DPP) with a modulation amplitude of 50-100 mV, scan speed 5 mV s-l and low-pass filtler 0.3 s.Cyclic voltammetry was performed with the aid of a PAR, Model 9323, hanging mercury-drop electrode. Con- trolled-potential electrolysis was carried out with the PAR 174A polarographic analyser and a cell containing a large mercury pool. Experimental Techniques M solutions of the dyes in the pH range 1-13. Blanks were obtained by recording polarograms of the appro- priate buffer solutions only, under the same conditions as used for sample solutions. All solutions were de-aerated for 5 min with oxygen-free nitrogen prior to polarography. From the polarographic data obtained by this technique graphs of ilim. v e m a pH and E, versus pH were constructed. M. Sampled d.c. polarography was performed on approximately 5 xOctober, 1980 ANALYSIS OF SOME AZO DYES OF BIOLOGICAL SIGNIFICANCE 93 1 The nature of the electrode process was determined by recording the d.c.polarogram a t varying heights of the mercury column in the appropriate buffer, and graphs of ilim, versus htcorr, were constructed. M solutions of the dyes I-IV in 0.1 N sulphuric acid a t potentials on the plateau of the most negative d.c. polarographic wave. Electrolysis was continued until the current decayed to zero and the electrolysed solution was diluted to give a final concentration of 5 x This final solution was then submitted to spectral and d.c. polarographic analysis using the conditions given previously. Differential-pulse polarography was performed on the four azo dyes I-IV a t the same concentration and using the same pH range as for sampled d.c.polarography. Differential- pulse polarograms of buffer solutions only were recorded using the same conditions. From these polarographic data the optimum pH for determination of the dyes was chosen, and this was used in the construction of calibration graphs. M using a scan rate of 50 mV s-l. Controlled-potential electrolysis was performed on 5 x M. Cyclic voltammetry was performed on some of the dyes a t a concentration of 5 x Results and Discussion CI Direct Orange 34 (I) The variations of iIi,,,. versus pH and E, versus pH show that the dye was reduced in one main wave, i,, which decreased in height a t pH > 5. The height of this wave continued to decrease with increasing pH, then became constant in the pH range 11-13. A small pre-wave, i,, also appeared on the i versus E curves in the pH range 4-13, the height of which remained independent of pH throughout the whole pH range.The E, versus pH relationship of i, in the pH range 1-6 was E+ = 0.06 - 0.09pH. A break occurred on the E+ versus pH plot at pH 6, which is probably a pK, value associated with the protonation of a nitrogen atom in I. Logarithmic analysis [i.e., ED.M.E. versus log i/(id-i)] of the wave i, in 0.1 N sulphuric acid yielded an ma, value of 1.55 and a 9 value of 2.3 for the rate-determining step evaluated from the equation dE,,, - - 0.0599 -- dPH un The variation of limiting current with mercury pressure was determined in 0.1 N sulphuric acid and wave i, showed a linear relationship of ilim. versw ht,,,,. indicating a diffusion- controlled current.When the drop time decreased from 18.2 to 7.0 s the half-wave potential shifted to more negative potentials by 10 mV, suggesting that the electrode reaction was not totally irreversible. At the end of electrolysis the colour and polarographic wave of the compound had both dis- appeared, and ultraviolet - visible spectral analysis of the electrolysed solution showed that the band a t 420 nm had disappeared and a new band had appeared at 300 nm. This suggests that the dye had been reduced in strong acid (pH 1.0) to give a mixture of amines. The mechanism of reduction of this dye (I) in acidic media (pH 1-6) would appear to involve formation of the hydrazo compound, which can then undergo protonation. This two-electron step (E‘) is then followed by another one of similar magnitude (E”) to produce a mixture of 4-aminobenzenesulphonic acid and 1,4-diaminobenzene.In alkaline media the reduction reaction is stopped a t the hydrazo stage, which causes the wave height to decrease by half. The pre-wave i, is believed to be due to product adsorption and it disappeared with the addition of 50% methanol to the buffers a t pH > 7.0. The mechanism of reduction can be illustrated as shown on p. 932. GI Acid Red 73 (11) that I1 is reduced in one main wave (i,) in the pH range 1-4. was Ea = 0.1 - 0.077pH. p value of 2.73 for the rate-determining step, Electrolysis a t a mercury pool in stirred solution was carried out as described earlier. The polarographic waves recorded for CI Acid Red 73 (11) over the pH range 2-12 show The E+ versus pH relationship Logarithmic analysis a t pH 2 yielded an a%, value of 2.0 and a932 HART AND FRANKLIN SMYTH : POLAROGRAPHIC BEHAYIOUR AND Analyst, VOl.105 The variation of ilim, veYsus hacorr, was determined in 0.1 N sulphuric acid and was found to be linear, indicating that the electrode process was diffusion controlled. When the drop time decreased from 16.8 to 6.8 s the Eh value did not shift significantly, which indicates that the rate-determining step at pH 1.0 is reversible. Electrolysis was performed at an applied potential of - 0.2 V f l x 40 min in a supporting electrolyte of 0.1 N sulphuric acid. At the end of the electrolysis period the red colour and polarographic wave (il) had disappeared, and no new waves were observed in the available potential region.Ultraviolet - visible spectral analysis of a portion of this electrolysed solution showed that the band at 513 nm had disappeared completely and the other bands at 346, 330(s) and 245 nm had moved towards the blue end of the spectrum. I H' E" 2e.H' 1 S O 3 - 0 N H 2 t N H z c , F N H 2 Y S It is expected that the azo group (-N = N-) would be first to reduce in a step E', which can be deduced from the work of Florence and co-workers, who found that l-phenylazo-2- naphthol was reduced a t considerably more negative potentials than azobenzene. This is likely to be a reversible step involving 2e and 2H+, followed by protonation of the newly formed hydrazo group and subsequent 4e reduction (E") of the other azo group (-N = N-) to a mixture of amines.The species 4-aminohydrazobenzene can reduce in acidic media to the corresponding amines (E"'). As has been suggested by Florence and co-workers, the rate-determining step is protonation of the hydrazo group, which occurs very rapidly in the pH range 1-4 and thus processes E', E" and E"' occur in one Be step (il). In the pH range 6.0-12.0 the main wave i, is replaced by two waves i, and i, (the latter at considerably more negative potentials) in the ratio 1: 2 with respect to their limiting currents. In this pH range, protonation of the hydrazo compound is difficult and thus the over-all electrochemical process occurs in two steps, involving 2e and 4e, respectively, as shown in the scheme. M (pH 7.0) showed that the steps corresponding to i, and i, are irreversible. In more alkaline media and coinciding with ionisation of the hydroxy moiety (pK, = 1 l.2),19 the polarographic behaviour of I1 changes again in that three waves occur.This could possibly be explained by disproportionation reactions to product 3 such as quinone hydrazones that are reduced in a different manner from azo-containing compounds. CI Direct Blue 84 (111) auersus pH relationship at pH < 2. a P Cyclic voltammetry of CI Acid Red 73 at 5 x In buffer solutions of pH < 6 one wave only was observed, which showed a change in E, This probably arises as a consequence of ionisation of aOctober, 1980 933 sulphonic acid group and also affected absorption bands in the ultraviolet spectrum around the same pH value. The E , versus pH relationship in the pH range 1-2 was The variation of ilim.versus Mcorr, for I11 in 0.1 N sulphuric acid was linear and showed the current to be diffusion controlled. A change in drop time from 16.2 to 7.1 s caused the E , to shift to more negative potentials by 45 mV, which indicates that the electrode process is irreversible. Electrolysis was performed at a potential of -0.6 V for 40 min. At the end of the electrolysis time the visible band and ultraviolet bands a t 290 and 350 nm had dis- appeared, and a low-intensity band appeared a t 270 nm upon which two shoulders were ANALYSIS OF SOME AZO DYES OF BIOLOGICAL SIGNIFICASCE E , 3 -0.43 - 0.04pH. k Hi934 HART AND FRANKLIN SMYTH : POLAROGRAPHIC BEHAVIOUR AND Analyst, VOl. 105 observed at 240 and 220 nm.The polarogram obtained after electrolysis at -0.6 V did not show any waves in the potential range 0 to -1.0 V, which again suggests the formation of amine derivatives upon electrolysis in strong acid (pH 1.0). Logarithmic analysis of the polarographic waves obtained in Britton - Robinson buffers of pH 3.0 and 4.0 yielded cma values of 1.3 and 1.6 and p values of 1.5 and 1.9, respectively. This suggests that in acidic media the rate-determining step involves 2e and 2H + and, unlike species I and 11, that protonation of the hydrazo intermediate is not rate determining. The E, value of I11 in acidic solution is far more negative than that of either I or 11, which illustrates both the effect of hydrogen bonding between the azo group and two ortho-hydroxy groups and inductive effects.The mechanism of reduction of CI Direct Blue 84 in the pH range 1-6 can be represented by the scheme shown below, in which hydrogen bonding has been omitted. OH OH OF The changes in Ea veysus pH and ilim. versus pH graphs at pH 6 suggest an acid - base equilibrium with pKa = 6.0. This is in reasonable agreement with the value obtained spectrophotometrically, i.e., pK, = 5.2, which was considered to reflect ionisation of the hydroxy moieties at the naphthalene 8-positions.19 Between pH 6 and 12 a new wave, i,, appeared on the current - potential curves, which increased in height with increasing pH while the height of the main wave i, decreased. At pH 12 the wave i, reached a height equivalent to a four-electron reduction. One explanation for the appearance of wave i, is the reduction of a quinone hydrazone species (V), which is formed after the 8-hydroxynaphthalene group has ionised (i.e,, at pH 6.0).As the pH increased the formation of species V is facilitated, until at p H 12 maximum electro- reduction is attained. The equilibrium existing in solution at pH m pK, can be represented as shown on p. 935. Tautomerism similar to that shown has been reported to exist for other dyes of closely related structure in aqueous solutions.October, 1980 CI Direct Red 80 (IV) The variations of ilim. versus pH and Eb versus pH for CI Direct Red 80 show two waves, i, and i,, with relative heights of 1:4, observed on the current - potential curves between pH 1 and 4 with E , = $0.1 - 0.066pH and E , = O-O.O66pH, respectively.The variations of limiting current and half-wave potential with mercury pressure were examined in 0.1 N sulphuric acid. Both i, and i, showed linear relationships in the graphs of ilim. versus h+,,,,., indicating diffusion-controlled electrode reactions. When the drop time decreased from 18.7 to 6.8 s the Ei value of i, and i, shifted by 10 mV, which suggests that the electrode processes giving rise to these waves are not totally irreversible. ANALYSIS OF SOME A 2 0 DYES OF BIOLOGICAL SIGNIFICANCE 935 f i N = N w N = N f i 0- OH OH 0- SO3- SO3- SO3- SO3- ( I l l ) / / It (V) Electrolysis was carried out a t a stirred mercury pool held a t a potential of -0.2 V for 40 min. At the end of the electrolysis period the red colour of the solution had disappeared and ultraviolet - visible spectral analysis showed that the visible bands a t 420, 520 and 545 nm had completely disappeared and a new band of low intensity appeared at 340 nm.All the bands in the ultraviolet region showed blue shifts after electrolysis. Polarographic analysis was carried out on the same electrolysed solution and no waves appeared on the current - potential curve in the potential range s0.160 to - 1.080 V. This indicates that reduction of IV in strong acid (pH 1.0) proceeds with the consumption of 16 electrons, giving the corresponding amines. Logarithmic analysis of the wave i, at pH 2 gave an a.n, value of 2.3 and a $ value of 2.7. The large an, value was considered to reflect the simultaneous addition of two electrons to each of the azo end-groups in the rate-determining step.However, although the p value apparently indicates the addition of three protons in the reaction, it was believed to involve six protons. This may be explained by considering that the linear portion of the E , veYws pH graph of i, represents two identical graphs superimposed on each other. This is not unreasonable when it is noticed that the molecule is symmetrical and that the azo end-groups are in identical environments. Thus the Ea values associated with the respective reductions of these two moieties might be expected to be so close that they would be indistinguishable. The an, and p values obtained for wave i, at the same pH were 2.7 and 2.8, respectively, which again suggests that four electrons and six protons are involved in the rate-determining step.The mechanism of the reduction of CI Direct Red 80 in the pH range 1-4 may be rep- resented as shown in Fig. 1. The wave i, arises from process E' and i, from E", E"' and E"", which occur simultaneously. In the pH range 6-12 process E"" no longer occurs because protonation of the hydrazo end-groups is difficult. This is reflected by the decrease in the height of i, to a value equivalent to eight electrons while i, remains independent of pH through the pH range 1-12. At pH greater than 12 both i, and i, decrease in height and two new waves, i, and i,, appear on the current - potential curves. This indicates an acid - base equilibrium with pK, = 12-13 and is associated with ionisation of hydroxy groups.lg936 HART AND FRANKLIN SMYTH : POLAROGRAPHIC BEHAVIOU;R AND Afialyst, Vol.105 M solution of the dye in 0.1 x sodium hydroxide solution and on scanning in a negative direction a peak was observed at -0.700 V and another broader peak at -0.860 V. On reverse scanning only one peak was observed, at -0.680 V, which was believed to arise from re-oxidation of the hydrazo derivative (VI) to the parent dye. Cyclic voltammetry was performed on a 5 x Variation of ip with Concentration and Differentiation of I-IV by Differential-pulse Polarography The optimum pH for analysis of the azo dyes I-IV was chosen from a consideration of both the magnitude and shape of the differential-pulse polarographic peaks, recorded at con- centrations of approximately 5 x M in the pH range 1-13. OH s o 3 - e ; ; : e N = N b H \ / - , N-C- I Mirror image SO3- E"" 4e.2HC I so3- 2 N H 2 d NH:, f 2 SO3- +NH2 Fig.1. Reduction scheme for CI Direct Red 80. All four dyes showed the best defined peaks for quantitative analysis in acidic media, e.g., the variation of log[peak current (PA)] veysus log[concentration (pmol 1-l)] for CI Direct Red 80 at pH 1.0 shows linearity of response over the concentration range 5 x 10-'-4 x M. Above 4 x M the graph begins to level off, probably as the reijult of adsorption processes. Table I summarises the differential-pulse polarographic data for the four dyes obtained at the selected pH values. It can be seen that the dyes showed linearity of response to varyingOctober, 1980 ANALYSIS OF SOME AZO DYES OF BIOLOGICAL SIGNIFICANCE 937 TABLE I DIFFERENTIAL-PULSE POLAROGRAPHIC DATA FOR AZO DYES Supporting Response Range of concentration Compound electrolyte Ei; V factor/@.Gmol-'l for linear responselhl CI Direct Orange 34 , . Britton . Robinson buffer, pH 4.0 - 0.280 It 0.005 3.6 x 5 X 10-'-3 X lo-' CI Acid Red 73 . , , . Britton - Robinson buffer, pH 4.0 - 0.220 i 0.005 1.38 x lo-* 5 x lo-'-5 x CI Direct Blue 84 . . Britton . Robinson buffer, pH 3.0 - 0.605 It 0.005 2.05 x 1 X 10-'-5 X CI Direct Red 80 , . . . 0.1 N H,SO, -0,010 + 0.005 1.15 x lo-* 5 x 10-'-4 x lo-& extents, but all gave a linear response in the lower concentration range. The response factor was determined from the slope of the i, (PA) veYsus concentration (kmol 1-l) graphs, where concentrations in the range 5 x 10-7-5 x Table I shows that all four dyes I-IV can be determined a t the trace level by using differential-pulse polarography.A further aspect of the differential-pulse polarographic technique is that it offers the possibility of differentiating and identifying the azo dyes in alkaline media. This is illustrated in Fig. 2, which shows the unique profiles obtained a t concentrations of approximately 5 x M were investigated. M in 0.1 N sodium hydroxide solution. n, Potential Fig. 2. Differential-pulse polarograms of (A) CI Direct Blue 84, (B) CI Direct Red 80, (C) CI Direct Initial potential, -0.2 V. Supporting electrolyte, 0.1 N sodium Orange 34 and (D) CI Acid Red 73. hydroxide solution. Conclusion The polarographic behaviour in acidic solution suggested that all four azo dyes were reduced to the corresponding amines.However, at pH > 6 end-groups containing sub- stituted azobenzenes in CI Direct Orange 34, CI Acid Red 73 and CI Direct Red 80 were reduced only to the hydrazo derivatives, whereas the remaining azo groups in the red dyes reduced to the amines. The polarographic behaviour of CI Direct Blue 84 in the same pH region was different to that of the other three dyes, which was considered to reflect the presence of tautomerism. The optimum conditions for quantitative analysis of the four azo dyes were in acidic media, where as alkaline solutions proved more suitable for qualitative purposes.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. HART AND FRANKLIN SMYTH References Games, L. M., and Hites, R. A., Alzal. Chew., 1977, 49, 1433. Donaldson, E., DIFS, Belfast, personal communication. Howe, J. R., Lab. Pract., 1975, 24, 457. Miller, J. A,, and Miller, E. C., Adv. Cancer Res., 1953, 1, 339. Cilento, G., Miller, E. C., and Miller, J. A,, J . Am. Chem. Soc., 1956, 78, 1718. Issa, I. M., Issa, R. M., Temerk, Y . M., and Mahmoud, M. R., Electrochim. Acta, 1973, 18, 139. Holleck, L., and Holleck, G., Naturwissenschaften, 1964, 51, 433. Castor, C. R., and Saylor, J. H., J . Am. Chem. Soc., 1953, 75, 1427. Shams El-din, A. M., J . Electroanal. Chem. Interfacial Electrochem., 1969, 21, 377. Malik, W. V., and Gupta, P. N., J . Electvoanal. C h e w Interfacial Electrochem., 1974, 54, 417. Jannakoudakis, D., Kokkinidis, G., and Mauridis, P. G., J . Chim. Phys. Chim. B i d , 1976, 73, 872. Florence, T. M., and Farrar, Y . J., Aust. J . Chem., 1964, 17, 1085. Florence, T. M., and Aylward, G. H., Aust. J . Chem., 1962, 15, 65. Florence, T. M., and Aylward, G. H., Aust. J . Chem., 1962, 15, 416. Florence, T. M., Aust. J . Chem., 1965, 18, 609. Florence, T. M., and Belew, W. L., J . Electroanal. Chem., 1969, 21, 157. Florence, T. M., Johnson, D. A., and Batley, G. E., J . Electroanal. Chem., 1974, 50, 113. Florence, T. M., J . Electroanal. Chem. Interfacial Electrochem., 1974, 52, 115. Hart, J. P., and Franklin Smyth, W., Spectrochim. Acta, 1980, 36A, 279. Received May 2nd, 1979 Accepted June Znd, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500929

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

Analyst, October, 1980, Vol. 105, $$. 939-943 939 A New Approach to the Quantitative Analysis of Overlapping Anodic-stripping Voltammograms Juei H. Liu Department of Criminal Justice, University of Illinois at Chicago Circle, Chicago, Ill. 60680, USA A method, analogous to that used for studying overlapping bands in absorption spectroscopy, has been developed for the quantitative analysis of overlapping anodic-stripping voltammograms. Six simultaneous equations were formulated to resolve general overlapping voltammograms. When the second species is not oxidised at the peak potential of the first species these six equations are reduced to four. Provided that the oxidation currents are additive, this approach is not limited by the degree of overlap. The method has been shown to be satisfactory by studying the cadmium - lead pair as an example.Keywords : A nodic-stripping voltawametvy ; overlapping voltawanvnograms; quantitative analysis Anodic-stripping analysis of mixtures often involves dealing with overlapping voltammograms. For quantitative determination of individual species the contribution of each species to the overlapped signal has to be resolved. The standard pr~cedurel-~ involves extrapolation of the preceding peak and determination of the peak height from this extrapolated base line. Sophisticated measurements4 have also been made using an on-line computer. An empirical equation was first developed that described the general voltammograms for a wide variety of electroactive species, then this function was fitted to a number of standard voltammograms and the constants in the function, specifically determined for each species, were stored in a library.When analysing an unknown mixture these constants were used to regenerate the standard graph, a composite of which was then fitted to the unknown signal. In this work an alternative approach, analogous to those usedin handling overlapping bands in absorption spectroscopy, was developed for solving the problem of overlapping voltammo- grams. Resolution of overlapping voltammograms is achieved by solving four or six simul- taneous equations, depending upon the severity of the overlap. This approach eliminates the uncertainty of the traditional extrapolation pr~cedurel-~ which cannot be used for severely overlapped voltammograms. In contrast to the numerical deconvolution method, it does not require any additional instrumentation. Essentially this approach involves the measurement of two current values a t the peak potentials of the two species involved and the solution of equations derived from the following assumptions: (i) the current values measured are the sum of the oxidation currents of each species; (ii) the ratio of the currents contributed by the species in a peak potential is determined by their concentration ratio and their specific current height ratio; and (iii) peak current is proportional to concentration with a proportionality constant that can be obtained by plotting the current height newus concentration results obtained for each individual species in isolation.Information required for the interpretation of overlapping voltammograms can therefore readily be derived from the voltammograms of individual species in isolation.Two individual voltammograms are therefore obtained using known concentrations of the species under study. The information obtained is then used to solve the simultaneous equations derived, to obtain the concentration of each species in the mixture. Experimental Apparatus All experiments were performed on a polarograph constructed in our laboratory (Fig. 1). A saturated calomel electrode (S.C.E.), a platinum electrode and a hanging mercury drop electrode were used as the reference, counter and working electrodes, respectively. A two- channel Hewlett Packard, Model 7100-15, recorder was used for recording the voltammograms and the anodic-voltage scans.940 LIU: NEW APPROACH TO QUANTITATIVE ANALYSIS OF Analyst, Vd.105 0 t15 V I I Fig. 1. Simplified schematic diagram of the polarograph. Solution Preparation A 1 M buffer solution of pH 5.9 & 0.1 was prepared by dissolving 2.4 ml of 99.77; acetic acid and 129.2 g of sodium acetate trihydrate in de-ionised distilled water and diluting to 1 1. A 0.1 M acetate buffer, prepared from the 1 M stock solution, was used as the supporting electrolyte. The buffer solution was passed through a Chelex 100 (Bio-Rad Laboratories, Richmond, Calif.) column to remove trace amounts of copper. M) of cadmium and lead were prepared by dissolving appropriate amounts of analytical-reagent grade cadmium nitrate and lead nitrate in the 0.1 M acetate buffer.Stock solutions Procedure In a typical experiment the following conditions were used: (i) a mercury drop with radius and surface area of 0.0490 cm and 0.0302 cm2, respectively; (ii) a 5-min de-aereation of 50 ml of 0.1 M acetate buffer solution in the electrolysis cell, before the addition of thesolution containing the species to be determined; (iii) pre-electrolysis a t .- 0.85 V (zleysus S.C.E.) for 3 min with stirring and then I min without stirring; and ( ~ z J ) an anodic scan rate of 1.22 V min-I. Concentrations of working solutions were changed as necessary by the addition of 2.5 x M standard solutions. Results and Discussions In most instances the second species is not oxidised a t the peak potential of the first species (Type I). The overlapping therefore involves only the addition of the tailing oxidation current of the first species to the oxidation current of the second species.Severely overlapped voltammograms (Type 11) also include the oxidation current of the second species at the peak potential of the first species. The cadmium -lead voltammogram (Fig. 2 B) obtained under the experimental conditions described represents Type I overlapping. Type I1 overlapping would be shown on the same voltammogram by imagining that the peak potential of the cadmium voltammogram was - 0.42 V ( v c y s m S.C.E.). Current measured at this potential is then considered to be the peak current of the hypothetical cadmium species. Two types of overlapped anodic-stripping voltammograms are commonly observed.Voltammograms preceding this potential are ignored.October, 1980 OVERLAPPING ANODIC-STRIPPING VOLTAMMOGRAMS 94 1 I -0.55 -0.42 -0.38 VoltagelV, versus S.C.E. Fig. 2. Voltammoerams of A. 0.1 ;acetate buffer (PH = 5.9); B, 12.38 x lO-'nr Cd and Pb mixture; C, 7.48 x IO-'M Cd; and D, 9.96 x lo-' M Pb. In the simultaneous determinations of several species by electrochemical methods, it is commonly assumed that the electrochemical behaviour of a species is not affected by the presence of the other species in the mixture by, for example, the formation of an inter-metallic compound. IVith this assumption six equations can be presented for the examples used in this work: Hsurn,Cd = HCd,Cd + HPbrCd * * . . . . . . (la) H8um9Pb = HCd,Pb + HPb,Pb * a . . * . . . (lb) HCd,Cd = BCdCCd * * .. . . . . . . (2a) HPb,Pb = BPbCPb * . . .. .. . . (2b) . . * . . . (3a) HCd,Cd hCd,Cd cCd HPbvCd hPb,Cd cPb x - . . __=__ . . .. . . . . (3b) where C, is the concentration of species w in the mixture, B, is the slope of the peak current versus concentration graph for species x , H,,, is the current of species y measured a t the peak potential of species z and h,,, is the same as H V , , but measured with the species in isolation. The values of h,,, in Equations (3a) and (3b) are obtained a t the same concentrations and represent the currents produced by unit concentration of species y. For the best statistical results5 the h,,, ratios are replaced by the corresponding slope ratios from the current versus concentration graphs. Equations (3a) and (3b) can therefore be rewritten as HCd,Pb = hCd,Pb CCd HPb,Pb hPb,Pb cPb ... . . . . . (4a) HCd,Cd - bCd,Cd cCd HPb,Cd bPb,Cd cPb X- . . . . . . . . . . (4b) H x b - bCd,Pb HPb,Pb bPb,Pb942 LIU: NEW APPROACH TO QUANTITATIVE ANALYSIS OF Analyst, Vol. 105 where by,z is the slope of the current versus concentration graph of species y measured at the peak potential of species z measured with species y in isolation. It should be noted that all currents are measured from the base line rather than from the extrapolated voltammogram of any species. The cadmium - lead pair is an example of Type I overlapping. As lead is not oxidised at the cadmium peak potential, Hpb,Cd = bpb,Cd = 0 (entries 11 B and 11 c in Table I) and equations (la) and (4a) may be eliminated, leaving four simultaneous equations.Before the quantitative analysis of the overlapped unknown mixture data (entries I11 A and I11 F in Table I), BCd (= bCd,Cd), B,, (= and bCd,,, are derived from the current uerszhs concentration graph for the species in isolation. Under the experimental conditions used, these values are 0.248, 0.174 and 0.0607, respectively (entries I C, I1 G and I G in Table I). Equations (lb), (2a), (2b) and (4b) are solved. The calculated values of CCd and Cp, are 12.18 x and 12.10 x 1 0 - 7 ~ , respectively, which are in excellent agreement with the expected value of 12.38 x lo-' M. TABLE I ANODIC-STRIPPING VOLTAMMETRY DATA FOR CADMIUM, LEAD AND A CADMIUM - LEAD MIXTURE IN 0.1 M ACETATE BUFFER (pH = 6.9)#6 Column A B C D E F c' L---------' L-- -Y--- L-- ---d At Cd peak At hypothetical A t Pb peak potentials potential? Cd peak potential: 7 Concen- ?-----h--- - r----_A ~ r---L--- tration Slope of current Slope of current Slope of current Row Species x lo-' M IT versus concentration IT versus concentration 18 versus concentration graph graph I Cd 0.00 0.00 BCd= bcdtcd 0.00 Bed= bcd,cd 2.50 0.595 =0.248 0.165 = 0.0815 4.99 1.18 0.335 7.48 1.80 0.603 9.96 2.44 0.802 12.4 3.08 0.980 I1 Pb 0.00 0.00 BPb,Cd= bpb,cd 0.00 BPbrCd= bPb,cd 2.50 0.00 = O .O O 0.150 = 0.0632 4.99 0.00 0.262 7.48 0.00 0.374 9.96 0.00 0.531 12.4 0.00 0.673 I11 Cd - Pb 12.38 Hsum,Cd mixture each 3.01 2.99 Hsum,Cd 1.62 1.64 graph 0.00 bcd,pb= 0.0607 0.165 0.290 0.395 0.630 0.755 0.00 &b= bpb,pb= 0.174 0.344 0.770 1.24 1.67 2.13 2.88 * Symbols used in the table are defined in the test.t -0.55 V (ocvsus S.C.E.). -0.42 V (vevws S.C.E.). 5 -0.38 V (oevsus S.C.E.). 7 In units of 0.1 FA. Assuming that currents measured at -0.42 V (versus S.C.E.) (Fig. 2) are peak currents of cadmium and, ignoring voltammograms preceding this potential, a Type I1 overlap is pro- respectively (entries I E and 11 E, respectively, in Table I). CCd and c,, are then calculated from equations (la), (Ib), (2a), (2b), (4a) and (4b); the values obtained are 12.27 x and 12.11 x These results are in excellent agreement with those expected. Compared with the peak lead current the hypothetical cadmium, peak currents measured at -0.42 V (versus S.C.E.) (entry I D in Table I) are considerably lower. This indicates that this approach can be used even when the preceding species is in much lower concentration. The consistently low concentrations calculated for both cadmium and lead with both types of overlap are probably caused by the reduction in the mercury surface available to each species in the mixture.This error should be reduced by working at lower concentration levels. duced. The Values Of B C d (= bCd,Cd) and B p b , c d ( = bpb,,,) aIe niDw 0.081 5 and 0.053 2, M, respectively.October, 1980 OVERLAPPING ANODIC-STRIPPING VOLTAMMOGRAMS 943 If the solution in the electrolysis cell is changed reproducible results may not be obtained. The approach described here requires three separate solutions, one for the unknown mixture, one for cadmium and one for lead. A constant concentration of bismuth was added to each solution before the solution was changed. The peak current of the constant concentration of bismuth in each solution was used to check the reproducibility and to make corrections if necessary. A definite advantage of this approach compared with the traditional extrapolation method, is that all currents are measured from the supporting electrolyte solution base line. These measurements should eliminate the uncertainty caused by extrapolation. This procedure allows severely overlapped voltammograms to be resolved. References 1 . 2. 3. 4. 6. Delahay, P., “Sew Instrumental Methods in Electrochemistry,” Interscience, New York, 1954, p. 129. Ben-Bassar, A. M, I., Blinderman, J.-M., Salomon, A,, and Wakshal, E., Anal. Chem., 1975, 50, 534. Vydra, F., Stulik, K., and Julakora, E . , “Electrochemical Stripping Analysis,” Halsted Press, New Gutknecht, W. F., and Perone, S. P., Anal. Chem., 1970, 42, 906. Bauer, E. L., “A Statistical Manual for Chemists,” Second Edition, Academic Press, New York, Received March 13th. 1980 Accepted May 15th, 1980 York, 1976. 1971, p. 140.

ISSN:0003-2654    

DOI:10.1039/AN9800500939

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

944 Analyst, October, 1980, Vol. 105, #$. 944-949 A New Type of Biological Reference Material for M u I t i - e I e m e n t An a I ysi s-t h e F u n g us PenicNium ochro-ch/oron ATCC 36741 Miwako Suzuki, Yukiko Dokiya, * Sunao Yamazaki and Shozo Toda Department of Agricultural Chemistry, Faculty of Agriculture, Universaty of Tokyo, Bunkyo-ku, Tokyo, Japan 113 Several series of standard disk samples were prepared using dried mycelia of Penicillaum ochvo-chloron, a fungus extremely tolerant to heavy metals. Be- cause of the ready availability of the homogeneous dry material with arbitrary metal concentrations, the fungus is very suitable for calibration in metal analysis by X-ray fluorescence spectrometry, especially for biological samples. Based on the calibration graph for the reference material, the metal contents of edible wild plants were determined. The reliability of the data was checked by using biological reference materials and by atomic-absorption spectrometry.Keywords: Biological reference material; Penicillium ochro-chloron fungus; heavy metals; biological materials; X-ray fluorescence spectrometvy Many standard reference materials or certified reference materials have been reported for use in calibration and checking the reliability of biological samp1es.l-5 Kale powderl, NBS orchard leaves and bovine liver5 are the best known and widely utilised examples. As the requirements for reference materials are still increasing, the authors have participated in studies to prepare new biological reference materials in Japan, such as tea leaves,6 shark paste7 and shark powder.8 In this paper, the preparation of a fungal-pellet reference material is described and pro- posed for use as a calibration material in the X-ray fluorescence determination of metals in biological samples.As a non-destructive multi-element method of determination, X-ray fluorescence spectrometry is widely applied to biological samples, but interference by matrix elements may limit the accuracy obtainable. Hence there is a need for reliable calibration utilising the reference material. For the analysis of alloy and ore samples by X-ray fluorescence spectrometry, NBS SRM 625-629 zinc-base alloys, SRM 461-464 low-alloy steels, SRM 1636-1638 lead in fuel, SRM 330-333 copper in ores and so on are well established.However, no trials have been carried out with biological samples, partly because of the difficulty in obtaining appropriate concen- tration ranges using biological reference materials. Penicilliuwa ochro-chloron ATCC 36741 is a fungus tolerant to heavy metals that has been studied for several years in the authors’ laboratory. This fungus can grow well even in media containing 105 pg ml-l (saturated solution) of copper, zinc and mangane~e.~ It also has a high tolerance against lead, cadmium and iron (2 x lo5 pg ml-l).lo The fungus has the important specific characteristic that the cellular contents of rnetals can be controlled arbi- trarily over a wide range for the metals added to the media. The ranges of cellular metal contents are much wider than for other biological samples.Investigations were carried out with this fungus in order to prepare a suitable calibration material for X-ray fluorescence spectrometry. Incubation conditions of the fungus were studied, and determination of metals was performed by X-ray fluorescence spectrometry and atomic-absorption spectrometry. Experimental Preparation of Penicillium ochro-chloron Reference Material After pre-incubation for 7 d on Czapek’s agar slant, the spores, of P. ochro-chloron were inoculated into 150 ml of sterilised culture media containirig various concentrations of metals. The compositions of the basal medium and the metals and concentrations * Present address: Geochemical Laboratory, Meteorological Research Institute, Nagamine, Yatabe, Tsukuba-gun, Ibaragi, Japan 305.SUZUKI, DOKIYA, YAMAZAKI AND TODA 945 After incubation for 96 h on a rotary shaker a t 30 "C, The added are shown in Tables I and 11.the fungal mycelia were harvested, lyophilised and dried a t 105 "C to constant mass. dried mycelia were pulverised and homogenised in an agate mortar. TABLE I COMPOSITION OF BASAL MEDIUM Component Content/g 1-1 Component Content (as metal)/mg 1-l Glucose . . .. .. 40 FeSO, .. .. .. 5 (XH,) $0,. . . . .. 3.3 ZnSO, ,. .. .. 5 KH,PO, . . .. . . 2.5 MnSO, .. .. .. 1 MgS0,.7H,O . . .. 1 Na,MoO, . . .. . . 0.5 Ca(N0,),.4Ha0 . . . . 0.5 c u s o , .. .. .. 0.1 coso, .. .. . * 0.1 hTaVO, . . .. . . 0.01 Determination of Metals X-ray j%uorescence spectrometry To make standard disk samples for X-ray fluorescence calibration, 100 mg of the dried fungal powder were weighed, mixed with 400 mg of "binder" [made with poly(viny1 alcohol); Somar Co.] and pressed into disks (1500 kg cm-2 for 10 min) using an oil hydraulic press (Lumis Products Co.).Copper, zinc and manganese were determined by X-ray fluorescence spectrometry using an Ortec TEFA 6110 energy-dispersive X-ray fluorescence spectrometer. The intensity of the K, line of each metal was determined using a molybdenum target and molybdenum filter (40 kV, 50 A). A silicon (lithium) counter was used as the detector, requiring 200-1000 s per sample. c u Zn TABLE I1 COMBINATIOKS AND CONCENTRATIONS OF METALS ADDED TO THE BASAL MEDIA First metal Concentration/pg ml-1 Second metal Concentration/pg ml- 1 . . . . 0.1 (control) Ni .. . . . . 100 10 200 100 c o .. . . . . 100 500 500 1000 1000 10000 2 000 50 000 1000 100000 5 (control) 100 1000 10000 50000 100 000 Cd . . . . Zn . . .. . . Mn . . . . . . Ni . . . . . . c o . . . . . . . . . . . . Cd 5000 10000 1000 10000 1000 10 000 100 200 100 1000 2000 1000 5 000 10000 Atomic-absorption spectrometry A 500-mg amount of dried powder sample was transferred into Kjeldahl flasks and digested with a mixture of concentrated nitric and sulphuric acids. The digest was diluted to 50 ml with de-ionised water and used for determinations. Copper, zinc and manganese were determined by atomic-absorption spectrometry using a Seiko SAS 721 atomic-absorption spectrophotometer. The analytical lines for copper, zinc and manganese were a t 324.8, 213.8 and 279.5 nm, respectively, with a spectral band width of 1.0 nm.An air - acetylene flame was used under regular burning conditions.946 SUZUKI et al. : NEW BIOLOGICAL REFEREKCE MATERIAL FOR Analyst, Vol. 105 Results and Discussion Metal Characteristics in Penicillium ochro-chloron The copper, zinc, manganese, cobalt, nickel, iron, potassium, calcium and magnesium contents in P. ochzro-chloron are compared with those in NBS Biological Standard Reference Materials in Table 111. The metal contents of the fungus were determined by atomic- absorption spectrometry. The most typical characteristic of this fu.ngus is the high and wide concentrations of metals that can be controlled by appropriate addition of metals to the basal media. The ranges of the metal contents of the fungus are generally consistent for plants species.TABLE I11 ELEMENTAL COMPOSITIONS OF NBS BIOLOGICAL STANDARD REFERENCE MATERIALS AND PENICILLIUM OCHRO-CHLORON Metalcontent/wg g-1 (dry mass) -- > Material cu Zn Mn co Ni Fe IK Ca Mg Spinach . . Orchard leaves Tomato leaves Pine needles Oyster tissue Bovine liver Ranges , . .. 1212 5012 16516 (1.5) , . 12+1 2513 9114 (0.2) , . 1151 6216 2381.7 . . 3.010.3 61-74 675115 /ili] . . 63.0 13.5 852 114 17.5 11.2 , , 193 110 130i10 10.3 +LO (0.18) .. 3.0-193 25-852 10-675 0.1-1.5 (6) 1.3 10.2 1.03 i0.19 I:::\ - 0.2-6 550 f 20 300 120 690 +25 200 1 10 195 134 270 +20 195-690 36 600 1300 14 700 i.300 $4 600 1300 3 700 = 200 9 690 +50 9 700 160 3 700-44 600 13 500 i300 20 900 *300 30 000 h300 4 100 = 200 1 500 = 200 123-30 000 (123) - 6200 1200 ( 7 0 ~ 0 ) - 1280 i90 (605) 605-7 000 P .ochro-c/2~07on. . 5.0-4 700 5.0-5 500 0-2 000 0-940 10-490 0-1300 140-40 000 0-900 10-6 000 The metal contents of ten samples of P. ochro-chloron (each 500 mg of powder of dried The homogeneities with respect to No apparent change mycelia) selected at random are given in Table IV. copper, zinc and manganese were found to be within 6.5% (relative standard deviation). in the colour or the state was observed. Dried mycelia were preserved in a silica gel desiccator for 14 months. The change in mass was also negligible. TABLE IV ELEMENTAL COMPOSITION OF PENICILLIUM OCHRO-CHLORON Bottle a . . . . . . . . b . . . . .. . . d . . . . . . . . f . . . . .. .. g ” h . . . . . . . . i . . . . . . . . c . . . . . . . . e .. . . I . . . . . . . . . j . . . . .. . . Average . . . . . . deviation, % . . . . Relative standard Metal contentlpg g-1 (dry mass) r---L-‘p- 7 c u Zn Mn 1800 115 1500 1850 112 1500 1800 120 1500 1800 100 1500 1800 105 1700 1800 115 1500 1800 110 1500 1800 112 1500 1800 112 1700 1900 108 1400 1820 110 1530 1.8 4. I 6.2 Preparation of Calibration Samples for X-ray Fluorescence Spectrometry In order to establish the appropriate mixing ratio of dried mycelia and binder [poly(vinyl alcohol) powder], X-ray fluorescence intensities were measured for amounts of mycelia from 100 to 400 mg veysus 400 mg of binder. As linearity between the mass of mycelia and the X-ray fluorescence intensities was obtained, 100 mg of dried mycelia in 400 mg binder were adopted in further work.No visual changes and no changes in composition and metal contents occurred after 14 months in a desiccator. The mass of the disks increased slightly, but this might be improved by changing the binder material. In addition, samples in a disk shape are suitable for storage and repeated utilisation. The results are summarised in Fig. 1. The preservation of such “disk” samples was also tested.October, 1980 MULTI-ELEMENT ANALYSIS-FUNGUS Penzcillizlm ochro-chloron m m o o / - 0 3 2 0 947 0 I I 100 200 300 400 100 200 300 400 Dried mycelia in 400 mg of binderimg Fig. 1. Relationship between sample mass in disk binder and X-ray fluorescence intensities. Concentration of copper in culture media: (a) 4500 pg ml-l; (b) 225 p g ml-l; and (c) 5 p g ml-I. Concentration of zinc in culture media: ( d ) 900 p g ml-l; and (e) 115 p g ml-1.The relationships between the X-ray fluorescence intensities and the metal concentrations The correla- Hence the calibration for copper, determined by atomic-absorption spectrometry were linear, as shown in Fig. 2. tion coefficients were 0.973, 0.987 and 0.989, respectively. zinc and manganese in biological samples is reliable. 50 7 40 v) m 4- C 2 30 >: 4- m .- 5 20 +- C U .- 10 80 ... m +- Y) 60 C 3 8 .- 5 40 C C 4- ._ & 20 X 6 ... - 5 YI 4- C ; 4 >: ‘I 3 5 2 a 4- C c U x 1 0 2 000 4000 0 1000 2000 3000 4000 5000 0 500 1000 1500 2000 cu content in mycelia/pg g-’ Zn content in mycelialpg g-’ (dry mass) (dry mass) (dry mass) M n content in mycelialpg g-’ Fig. 2. Relationship between X-ray fluorescence intensities and metal contents determined by atomic- absorption spectrometry: (a) copper; (b) zinc; and (c) manganese.Application of Penicillium ochro-chloron Calibration Graph to Other Biological Samples Some NBS Standard Reference Materials and other biological materials whose metal contents are known were used to check the method. Table V shows a comparison between values obtained for most plant and animal samples, except for copper and zinc in orchard leaves, copper in pine needles and manganese in oyster tissue. It can be concluded that calibration for other biological materials is also reliable, with few exceptions.948 SUZUKI et al. : NEW BIOLOGICAL REFERENCE MATERIAL FOR Analyst, VoZ. 105 TABLE V RESULTS OF APPLICATION OF THE PROPOSED METHOD Metalcontentlwg g-1 (dry mass) cu Zn Mn Values reference values Values reference values Values reference values determined r-'-, determined determined ,--*-, Type Material by XRF' Source? Value by XRF' Source? Value by XRF' Source? Value ,-- -----, I 7 Certified or Certified or Certified or Plants .. Orchard leaves Pine needles Tea leaves B Tea leaves D Alfalfa . . Timothy . . .. .. .. .. .. 30 53 15 18 6 20 A 12A1 3.0 ~ 0 . 3 12-15 27-31 9 13 45 67 56 56 23 39 25 i3 61-74 56-66 65-95 27 50 98 727 532 760 69 21 165 * 6 675 215 530-620 890-1010 48 25 Animals . . Bovine liver . , 167 A 1 9 3 ~ 1 0 112 A 130 4.10 19 A 10.311.0 Oyster tissue . . 61 A 63.013.5 750 A 852+14 3 A 17.5+1.2 Shark powder 2 . , 10 F 1.1 14 F 14 10-:?2 19 F < 1 - F - Shark powder 1 , .11 F 1.4 12 F ' X-ray fluorescence spectrometry. t A Certified values for NBS Biological Standard Reference Materialss; B, H. L. Rook personal #communication; C, certified values for JapaAese tea leavesB; D, samples provided by Dr. Jones, Jr., of the Ohio Agricultural Research and Development Centre, U'ooster, Ohio; E, values determined by atomic-absorption spectrometry; F, T. Uchida, personal communication. Next, the metal contents of wild plants were determined by using the proposed method. Some edible wild plants that have traditionally been used in daily dishes in Japan have recently aroused interest from the point of view of sources of trac,e metals for human nutrition. Fifty kinds of edible wild plants were collected in Fukushima Prefecture, dried at 105 "C to constant mass and homogenised in an agate mortar.A 100-mg amount of each was mixed with 400 mg of binder and pressed in the same way as for P. ochro-ckloron. Their metal contents were then measured by X-ray fluorescence and atomic-absorption spectrometry. Some results obtained by X-ray fluorescence analysis utilising the calibration graplis for P. ochyo-chloron reference materials are shown in Table VI, and the values are compared with those obtained by atomic-absorption spectrometry. TABLE VI DETERMINATION OF METALS IN EDIBLE WILD PLANTS Botanical name Sambucus sieboldiana (bud) . . . . Houttuynia cordata . . . . . . Petasites japonicus (bud) . . . . Laportea macrostachya (leaf) . . . . Vicia unijuga . , . . . . . . Plantago asiatica . . . . .. Matteuccia struthiopteris .. . . Cacalia farfaraefolia . . . . . . Acarthopamax spinosum (bud) . . Elatostema umbellatum . . . . * X-ray fluorescence spectrometry. t Atomic-absorption spectrometry. Japanese name Niwatoko-no-me Dokudami Fuki-no-me Miyama-irakusa-no-ha Nanten-hagi Ohbako Tara-no-me Kogomi Uwabami-so Tamabuki Metal. contentlpg g-l (dry mass) -------A----- Cll Zn Mn r - y - v - 7 XRF* AASt XRF* AASt XRF* AASt 43 38 59 67 184 190 14 11 81 67 151 140 22 11 22 25 112 110 20 14 88 85 103 70 25 13 49 53 83 85 19 11 31 33 112 110 20 14 74 75 268 240 35 35 63 90 41 40 11 10 24 29 89 82 15 19 65 65 78 100 7 From these results, it is concluded that the dried mycelia of P. ocho-chloyon serve as a good calibration material for the determination of metals in biological samples by X-ray fluorescence spectrometry. The next step in this study might be to find better binder ingredients and to determine the optimum diameter and thickness of the disks.Further studies on other metals such as cobalt and nickel are under investigation. The authors thank Dr. Yoko Saito of Koriyama Women's College for her help in collecting the Japanese wild plants, and Mr. Toshihiro Aota and Mr. Nobuo Matsumori of Daini Seiko-sha for their assistance in measuring the elements in fungal mycelia and wild plants by X-ray fluorescence spectrometry.October, 1980 MULTI-ELEMENT ANALYSIS-FUNGUS Penicillium ochro-chloron 949 References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Bowen, H. J . M., A~zalyst, 1967, 92, 124. Jones, J . B., Jr., “Abstracts of the Pittsburg Conference on Analytical Chemistry and Applied Yamagata, N., Bunseki Kagaku, 1971, 20, 515. Fukai, R., “Intercalibration of Analytical Methods on Marine Environmental Samples,” Progress “Catalog of NBS Standard Reference Materials,” NBS Special Publication 260, 1978-79 Edition, Fuwa, K., Notsu, K., Tsunoda, K., Kato, H., Yamamoto, Y . , Okamoto, K., Dokiya, Y., and Toda, S., Dokiya, Y . , Taguchi, M., Toda, S., and Fuaw, K., 4 n a l . C h e w , 1978, 50, 533. Dokiya, Y , , Kurosawa, S., Toda, S., and Fuwa, K., Bull. Chem. SOC. Jpn., 1978, 51, 3649. Okamoto, K., and Fuwa, K., Agvic. Bid. Chern., 1974, 38, 1405. Okamoto, K., Suzuki, &I., Fukami, >I., Toda, S., and Fuwa, K., Agric. Bid. Chem., 1977, 41, 17. Spectroscopy, Pittsburg, Pa., 1967,” paper no. 200. Report KO. 13, International Laboratory of Marine Radioactivity, Monaco, 1976. US Department of Commerce, Washington, D.C., 1978. Bull. Chern. Soc. J p ~ z . , 1978, 51, 1078. Received March 20th. 1980 Accepted d p r i l 24th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500944

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

950 Analyst, October, 1990, Vol. 105, pp. 950-954 Spectrophotometric Determination of Hydrogen Peroxide Using Potassium Titanium( IV) Oxalate Robin M. Sellers Central Electricity Generating Board, Berkeley Nuclear Laboratoracs, Berkeley, Gloucestershtre, GL 13 9PB A simple and rapid method for the spectrophotometric determination of hydrogen peroxide using potassium titanium(1V) oxalate is described. The method can be used to measure peroxide concentrations down to about 10 p~hz (0.3mgkg-l) under the most favourable conditions. A variety of corn- plexing and reducing agents, and catalysts of peroxide decomposition, known to interfere with the alternative iodide method for peroxide determination, had no effect. Keywords: Hydrogen peroxide determination; spectrophotounetry; titunium(I V ) Fluoride was found to interfere.oxalate Many methods have been described in the literature for the spectrophotometric determination of hydrogen peroxide.l-lO One of the most sensitive and widely used is that based on the oxidation of I- to This test is not specific for hydrogen peroxide (organic peroxides and many other oxidising agents convert I- into 13-), although the analysis is usually performed in the presence of molybdate, a specific catalyst of the reactiom2 Other redox reactions, such as iron(I1) to iron(III), have also been employed.3 These too measure total peroxides, rather than hydrogen peroxide alone. A specific spectrophotometric test based on the formation of a complex, often written as Ti022 +, between hydrogen peroxide and the titanium(1V) ion has been de~cribed.~-S The published procedures involve lengthy preparations of titanium( IV) sulphate, and little seems to be known about either the optimum conditions for carrying out the measurements, or interference by compounds such as complexing or reducing agents.This paper describes the development of a method for the determination of hydrogen peroxide using potassium titanium(1V) oxalate, the only analytical-reagent grade salt of titanium readily available commercially, and the influence of various additives known to interfere with the iodide method. Experimental Reagents The reagents used in the determina- tion of the hydrogen peroxide, i.e., hydrogen peroxide, potassium titanium(1V) oxalate, [K,TiO(C,04),.2H,0] and sulphuric acid, were from BDH, AnalaR.grade, and were used as received. The organic compounds used in the tests for interference were of laboratory-reagent grade, and were obtained from BDH [ethylenediamine, iminodiacetic acid (IDA)], Aldrich [ethylene- diaminediacetic acid (EDDA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA)] and Eastman Organic Chemicals [ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA)]; glycine and 2,2’-bipyridyl were BDH AnalaR grade, and picolinic acid was Aldrich laboratory-reagent grade, re-crystallised once from water. All other inorganic compounds were BDH AnalaR grade. Hydrogen peroxide solutions were standardised by the iodide method of Allen et a1.,2 taking E for I,- at 350 nm as 25700 1 mol-l cm-I. All solutions were prepared from triply distilled water.Apparatus Absorbance measurements were made with a Cecil CE505 spectrophotometer. Results Development of the Method The titanium(1V) - peroxide complex is yellow - orange in colour and absorbs with a Amax. of about 400 nm. The intensity of this absorption was found to be dependent on theSELLERS 1200 c 1000 E 800 u .- - 0 600 E 8 400 - . 200 0 n I I 951 ~ 0 0.5 1 0 1 5 2 0 2.5 3.0 3 5 4 t log [titanium (IV) oxalatel Fig. 1. Dependence of the absorption of the titanium(1V) - peroxide complex on titanium(1V) oxalate concentration. Measure- ments were made in solutions containing 6 x lo-* M H,O, and 0.1( A), l.O(n) or 4.0(0) M H,SO,,. The arrow indicates the point a t which the concentrations of the titanium(1V) oxalate and hydrogen peroxide were equal. concentrations of titanium(1V) oxalate and sulphuric acid as shown in Figs. 1 and 2 .The measurements were made in solutions containing 6 x M hydrogen peroxide; for the measurements of dependence on the concentration of titanium(1V) oxalate, the sulphuric acid concentrations were 0.1, 1.0 or 4.0 M; and for the measurements of dependence on the concentration of sulphuric acid the titanium(1V) oxalate concentrations were 0.01, 0.02 or 0.04 M. Absorption by components other than Ti0,2+ was allowed for by subtracting the absorbances of solutions prepared in the same way but omitting hydrogen peroxide. -u 600 2.0 2.5 3.0 3.5 4.0 4.5 5.0 4 + log [H*S041 Fig. 2. Dependence of the absorption of the titanium(1V) - peroxide complex on sulphuric acid concentration.Measurements were in solutions containing 6 x M H,,O, and 0.01( 0). 0.02( A) or 0.04( 0) M titanium(1V) oxalate. When the titanium(1V) concentration was greater than the hydrogen peroxide concentra- tion (i.e., under conditions where all the hydrogen peroxide was complexed) only a small dependence on the concentration of titanium(1V) oxalate was found at titanium(1V) oxalate concentrations less than 0.1 M. At higher concentrations the intensity of the absorbance of the titanium(1V) - peroxide complex was much reduced. Varying the sulphuric acid con- centration a t a constant titanium(1V) oxalate concentration had only a small effect. The absorption was a t its most intense at a titanium(1V) oxalate concentration of about 0.02 M and 0.1-1.0 hi sulphuric acid.The A,,,. for the absorption increased with decreasing titanium(1V) oxalate concentration or increasing sulphuric acid concentration. Some experiments were also carried out in which the hydrogen peroxide concentration was varied at constant titanium(1V) oxalate and sulphuric acid concentrations. In all instances the absorbance a t a particular wavelength varied linearly with hydrogen peroxide concentra- tion, a t peroxide concentrations up to about 2 x M, the highest employed.952 SELLERS : SPECTROPHOTOMETRIC DETERMINATION OF HYDROGEN Analyst, Vol. 105 Recommended Procedure Based on the conditions under which the absorption of the titanium(1V) - peroxide complex was at its most intense (i.e., was most sensitive to hydrogen peroxide) the procedure described below appears most suitable for the determination of hydrogen peroxide using titanium(1V) oxalate.Titanium reagent Mix 272 ml of concentrated sulphuric acid (BDH AnalaR) with about 300 ml of distilled water (care should be taken and cooling is required). Dissolve in this mixture 35.4 g of potassium titanium(1V) oxalate, K,TiO(C204),.2H,0, (BDH AnalaR), and make up to 1 1 with distilled water. Procedure Pipette 5 ml of the titanium reagent and 5 ml (or as appropriate) of the sample into a 25-ml calibrated flask and make up to the mark. Measure the absorbance of the solution at 400 nm. A blank, consisting of 5 ml of the titanium reagent and 5 ml (or as appropriate) of sample without the hydrogen peroxide present made up to 25 ml, should also be measured.(The hydrogen peroxide may be destroyed by the addition of platinum black followed by filtration, or by boiling.) Calculation of hydrogen peroxide concentration the molar absorptivity of the titanium(1V) - peroxide complex. of solution the concentration of hydrogen peroxide (in moles per litre) is given by: The concentration of hydrogen peroxide is calculated taking elOO = 935 1 mol-l cm-1 as For x ml of sample per 25 ml where A and A , are the absorbances of the test and blank solutions, respectively, and 1 is the path length of the spectrophotometer cell in centimetres. Effect of Other Solutes The effect of other solutes on the method was investigated by measuring the apparent molar absorptivity of the titanium(1V) - peroxide complex at 400 nm in solutions made up to contain 0.02 M in titanium(1V) oxalate plus 1.0 M in sulphuric acid, 6 x M in hydrogen peroxide and about 0.02 M in solute.The results are summarisedl in Table I. The solutes included a variety of complexing and reducing agents and catalysts of peroxide decomposition. TABLE I EFFECT OF SOME ADDITIVES ON THE TITANIUM(IV) OXAL.ATE METHOD FOR THE DETERMINATION OF HYDROGEN PEROXIDE: All solutions also contained 0.020 M titanium(1V) oxalate, 1.0 IN sulphuric acid and 6.0 x lo-, M hydrogen peroxide. Additive concentration/M :2400/1. mol-1 cm -l Additive None - 935 NaF 0.020 805 coso, 0.020 956 cuso, 0.020 935 NiSO, 0.020 936 Hydrazinium sulphate 0.020 935 Ethylenediamine 0.018 949 Glycine 0.020 936 EDDA 0.002 935 EDTA 0.020 957 HEDTA 0.020 969 IDA 0.020 927 NTA 0.020 950 Picolinic acid 0.024 940 2,2’-Bipyridyl 0.012 949October, 1980 PEROXIDE USING POTASSIUM TITANIUM(IV) OXALATE 953 Only for fluoride was any appreciable interference found.A similar series of tests was per- formed in which the hydrogen peroxide was determined by the iodide method of Allen et aL2 The results can be summarised as follows: (i) Ethylenediamine, EDTA, HEDTA, IDA and NTA, no I,- was formed, as these solutes reduce I,- back to I-. (ii) 2,2'-Bipyridyl and picolinic acid, 1,- formed slowly, and with 2,2'-bipyridyl a purple - black precipitate was obtained. This behaviour probably results from complexation of the molybdate catalyst by these solutes. Hydrazinium sulphate is a reducing agent and not only converts I,- into I-, but also molybdate into a heteropoly blue.(iv) Copper sulphate, large amounts of I, were formed, due to oxidation of I- by Cu2+. ( v ) Glycine, cobalt sulphate, nickel sulphate and sodium fluoride, no interference. (iii) Hydrazinium sulphate, no I,- was formed and the solution turned blue. Discussion The recommended procedure gives concentrations of 0.02 M titanium(1V) oxalate and 1.0 M sulphuric acid in the analysis solution. The high acid concentration prevents precipitation of titanium(1V) hydroxide and ensures that relatively large amounts of base can be present in the peroxide containing solution without interfering unduly with the method through the consumption of protons. An upper limit of about 0.1 M of base in the peroxide sample is probably advisable. The precision of the method is around 1% for peroxide concentrations of 0.5-2.0 x lo-, M (an absorbance of 0.5-2.0 in l-cm cells).Thus, the 13 measurements in Table I that relate to solutes that do not interfere have a relative mean deviation of 1.1%. The relative mean error of the values is also 1.1%. At lower peroxide concentrations the method becomes less precise, the size of the blank reading becoming important. This averaged about 0.001 absorbance units, as measured in l-cm cells, in the absence of any additional solutes, and about double this in the presence of solutes, such as the complexing agents, or higher still in the presence of coloured substances such as Cu2r. The upper limit for detection of peroxide is about 2 mM using l-cm spectrophotometer cells (with an absorbance of 2).This is well below the titanium(1V) oxalate concentration in the mixture, ensuring that all peroxide is complexed. The calculation of the hydrogen peroxide present is based on the measured molar absorp- tivity of the complex a t 400 nm. The intensity of the absorption follows the Beer - Lambert law, so that little or no additional precision is obtained by constructing a calibration graph, although some improvement should be possible by adaptation of the method described by Nea1.O It is clearly important to check for possible interference by other solutes that may be present. The experiments summarised in Table I suggest that the method is relatively free from interference, and appears to be particularly suitable for the determination of hydrogen peroxide in the presence of complexing and reducing agents.Interference by fluoride is not unexpected in view of the ease of formation and stability of the fluorotitanate ion, TiFe2-. I t may also be noted that the method involves considerable savings in time over the earlier procedures, which required lengthy preparations of titanium(1V) by digestion of titanium(1V) oxide in sulphuric acid. It is reportedlo that the sensitivity of the method can be improved by addition of xylenol orange, and experiments have shownll that potassium titanium(1V) oxalate is suitable for use as a source of titanium(1V) under these conditions. The pH of the solution seems to be critical, however, and the effect of complexing and reducing agents is unknown. The lower limit with 1-cm cells is 10 PM under favourable circumstances. I am indebted to Mr. B. Daniel for assistance with some of the measurements. This paper is published by permission of the Central Electricity Generating Board.954 SELLERS References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Schumb, W. C., Satterfield, C. N., and Wentworth, R. L., “Hyclrogm Peroxide,” Reinhold, New Allen, A. 0.. Hochanadel, C. J., Ghormley, J. A., and Davies, R. W., J . Phys. Chem., 1952, 56, 575. Michaels, H. B., and Hunt, J . W., Anal. Biochem., 1978, 87, 135. Jackson, E., Chem. News, 1883, 47, 157. Richardson, A,, J . Chem. Soc., 1883, 63, 1109. Allsopp, C. B., Analyst, 1941, 66, 371. Eisenberg, G. M., Ind. Eng. Chem., Anal. Ed., 1943, 15, 327. Humpoletz, J. E., Aust. J . Sci., 1949, 12, 111. Neal, W. T. L., Analyst, 1954, 79, 403. Gupta, B. L., Microchem. I., 1973, 18, 363. Sellers, R. M., unpublished data. York, 1955, p. 561. Received April 9th, 1980 Accepted May 29th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500950

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

Analyst, October, 1980, Vol. 105, @. 955-964 Improved Extraction Method for the Spectrophotometric Determination of Trace Amounts of Boron in River Water with 1,8-Dihydroxynaphthalene-4-suIphonic Acid and Removal of the Excess of Reagent 955 Takashi Korenaga,* Shoji Motomizu a n d Kyoji Toei Department of Chemistvy, Faculty of Science. Okayama Cnivevsity, Tsushima-naka, Okayama-shi 700, Japan A simple method for removing the excess of co-extracted reagent in the ion- association extraction of metal complex anions with quaternary ammonium salts has been applied successfully to the spectrophotometric determination of boron at the parts per log level in river water with 1,8-dihydroxynaphthalene 4-sulphonic acid (DHKS) and tetradecyldimethylbenzylammonium chloride (zephiramine) , The procedure using DHKS described here greatly improves the previous method using chromotropic acid.Acetate buffer (pH 3.8), EDTA and DHYS are added to the sample solution (less than 50 ml) and the pH of the resulting solution is adjusted to 10.2. Then sodium chloride is added and the mixture is shaken with 5 ml of a 2 x M solution of zephira- mine in 1,2-dichloroethane (DCE). The organic phase is washed once with 10 mi of a back-washing solution (1.0 h.~ in sodium chloride, pH 10.2) and the absorbance of the organic phase is measured in a quartz cell. The boron complex with DHNS is extracted quantitatively into DCE and its apparent molar absorptivity in DCE is 2.4 x lo4 1 mol-l cm-l a t 341 nm. The detection limit and precision achieved with the method are 1 p g 1-1 and 5%, respectively.EDTA allows most interferences caused by metals to be suppressed, and other sources of bias due to the effect of co-extractable anions are almost eliminated by adding relatively large amounts of sodium chloride to the extraction system. Parts per lo9 amounts of boron present as boric acid in river water are determined spectrophotometrically, and the results obtained are successfully compared with those obtained by the methylene blue method. Keywords; Boron trace determination; river water awalysis; spectrophotometry ; ion-association extraction In a previous paper, we have proposed a spectrophotometric method for the determination of boron in natural waters involving solvent extraction with 1,8-dihydroxynaphthalene-3,6- disulphonic acid (chromotropic acid).l In that method, a large amount of reagent (250-fold excess of boron) was used in order to complete the complex formation and the principle presented earlier by the authors2 was applied to the removal of a large excess of co-extracted reagent (chromotropic acid) from the organic phase.Recently, we developed 1,8-dihydroxy- naphthalene-4-sulphonic acid (DHNS) as a reagent for the solvent extraction of boric acid.3 DHNS was synthesised in order to improve the extractability of the boron complex and was found to be much superior to chromotropic acid as an analytical reagent for the solvent extraction - spectrophotometric determination of boron. In that work,3 the method using DHNS was applied to the determination of boron a t the parts per million level in sea water and hot-spring water, but not a t the parts per billion (lo9) level in river water.In this work, the previous method using chromotropic acid1 was greatly improved by using DHNS and it could be used successfully for the concentration and determination of boron a t the parts per billion level in river water, as the extractability of the boron complex with DHNS is much superior to that with chromotropic acid in the ion-association extraction using tetradecyldimethylbenzylammonium chloride (zephiramine). This paper therefore presents a greatly improved method for the spectrophotometric determination of boron present as boric acid in river water with DHNS and zephiramine and removal of the excess of DHXS reagent in the organic phase. * Present address: School of Engineering, Okayama University, Tsushima-naka, Okayama-shi 700, Japan.956 Reagents KORENAGA et al.: EXTRACTION FOR SPECTROPHOTOMETRY OF BORON Analyst, V o l . 105 Experimental All of the reagents used were of analytical reagent grade. 1,8-Dihydroxyna$hthalene-4-sul$honic acid (DHNS) solution, 0.01 M. Dissol\re 1.311 g of DHNS, sodium salt, in 500 ml of de-ionised water and transfer the solution obtained into an amber polyethylene bottle. The solution can be kept for at least 1 month in a refrigerator. Prepare a stock solution by dissolving 154.6 mg of boric acid in 250 ml of de-ionised water. Store the solution in a polyethylene bottle and dilute aliquots of it with de-ionised water to give working solutions of the required concen- trations.Dissolve 369.0 mg of dried zephiramine4 in 500 ml of DCE (analytical-reagent grade, used as received) to give a 2 x 10-3 M solution. Store the zephiramine solution in a glass bottle ; it is stable for at least 6 months. (1) An aqueous solution 0.01 M in EDTA and 0.25 M in acetic acid - sodium acetate (pH 3.8) and (2) an aqueous solution 4 M in sodium chloride and 0.8 M in sodium hydrogen carbonate - sodium carbonate (pH 10.2) were used. An aqueous solution 1.0 M in sodium chloride and 0.2 M in sodium hydrogen carbonate - sodium carbonate (pH 10.2) was used. Standard boron solution, 1.000 X M. Extraction solvent, 1,2-dichloroethane (DCE), 2 x M in zefilzira~nzine. Bufler solutions. Back-w'ashing solutiort. Apparatus A Hitachi, Model 139, spectrophotometer and a Hitachi, Model EPS-3T, recording spectro- photometer were used for measuring absorbances in a quartz cell of 1-cm path length.A Hitachi-Horiba, Model F-Bss, pH meter equipped with a combined electrode (6026-05T) was used for pH measurements. An Iwaki, Model KM, shaker (frequency 250 strokes min-l) was used for shaking separating funnels and stoppered test-tubes. Recommended Procedure Transfer by pipette the sample solution (less than 50 ml), which is not acidified and is first filtered with a membrane filter of 0.45-pm pore size, into a 100-nil polyethylene separating funnel. Dilute the solution to 50 ml with de-ionised water and add 5 ml of acetate buffer solution (1) and 5 ml of 0.01 M DHNS solution, in that order. Mix the solutions thoroughly and allow the mixture to stand for 30 min.Then add 5 ml of carbonate buffer solution (2) to adjust the pH of the resulting solution to the extraction pH, and also add 5 ml of 1.5 M sodium sulphate solution to accelerate the phase separation Add 5 ml of 2 x M zephiramine in DCE solution. Shake the separating funnel for 30 inin and allow two phases to separate. Transfer the organic phase into a stopped 25-ml glasi; test-tube and add 10 ml of the back-washing solution. Shake the test-tube for 10 min and then allow it to stand for about 30min to remove the excess of reagent from the orgaiiic phase. Measure the absorbance of the organic phase in a quartz cell of 1-cm path length a t 341 nm against a reagent blank as reference. Prepare a calibration graph by using standard boron solutions corresponding to 0 4 x 10-5 M of boron in the organic phase.Results and Discussion In the extraction of the ion associate formed between the boron - ;DHNS complex anion and the zephiramine cation, the extraction was previously carried out with 5 ml of aqueous solution and 5 ml of DCE s ~ l u t i o n . ~ In this work, however, as i he extraction was carried out with 70 ml of aqueous phase and 5 ml of organic solution, the choice of the extraction solvent (DCE or chloroform) was re-examined. The equilibrium constants for exchange of chloride (log F s C ) between DCE and water were determined for DHNS reagent and its boron compIex in previous work,3 but those between chloroform and water were not. Therefore, the constants for chloride between chloroform and water were ,also determined in this work, and shown in Table I for comparison with those between DCE and water.From Table I, the difference in the constants between HR2- and BR,% and the extractability of theOctober, 1980 IN RIVERS WITH 1,8-DIHYDROXYXAPHTHALENE-4-SULPHONIC ACID TABLE I EXCHANGE EQUILIBRIUM CONSTANTS FOR CHLORIDE OBTAINED AT 25 "c Extraction solvent 1 r--------_h------ Constant* 1,2-Dichloroethane Chloroform Log KZi- 2.51 j, 0.05 1.01 i: 0.02 Log KZ'i- 4.39 & 0.07 3.55 j, 0.06 Log K22i- 9.77 & 0.04 6.42 0.11 957 * The exchange equilibrium constant for chloride (Ki2C) refers to the following equation2.3: A"-(&) + nZCl(o) nCl-(a) + Z,A(o) KlEL- = ([Cl -l"(a)[Z,Al(o)) / ([A" -](a) [ZC11"(0)) where An- and Z+ are the n-valent anion and the zephiramine cation, respectively, and subscripts a and o refer to the aqueous and organic phase, respectively.boron - DHNS complex using DCE were found to be larger than those obtained when chloro- form was used. As shown in the previous the exchange constants for four univalent anions (chloride, bromide, nitrate and iodide) also indicated that chloride gave the highest concentration range for the removal of the excess of reagent and therefore caused very effective salting-out. In this work, DCE and chloride were therefore used as the extraction solvent and the univalent anion for the removal of the excess of reagent from the organic phase, respectively. For reference, the percentage extraction of reagent and boron complex with DHNS, which was calculated by using the equilibrium constants listed in Table I, is shown in Fig.1. It is obvious that the reagent in the form HR2- is removed more easily than that in the form H,R-. DCE was therefore suitable for the separation of complex and reagent. 100 80 8 . 60 0 ? 40 .- c 4- X w 20 0 -2 -1 0 1 2 Log [CI- 1 a Fig. 1. DCE against chloride concentration of aqueous solution for 2 x zephiramine. in the form BRS3- a t pH 9 ; and 3, DHNS in the form H,R- a t pH 3. Percentage extraction of reagent and boron complex into M 1, DHNS in the form HR2- a t pH 9 ; 2, boron complex De-ionised water, obtained from a common de-ionisation apparatus, must be used in this work, as the absorbance of the reagent blank with de-ionised water is more constant and smaller than that with distilled water obtained from a commercially available glass distilla- tion apparatus.The reason why the distilled water blank is higher and more variable than the de-ionised water blank is assumed to be based on the dissolution of boron present in the glass of the distillation apparatus. Hence, the former blank might decrease the accuracy, precision and detection limit of the proposed method in an actual determination.958 XORENAGA et d. : EXTRACTION FOR SPECTROPHOTOMETRY OF BORON AnUlySt, T’d. 105 Effect of pH on the Formation and Extraction of the Boron Complex The effective pH range for the formation of the boron - DHNS complex in aqueous solution without EDTA was found to be 3-10.3 ’The effect of pH on the formation of the complex with EDTA was also examined. The results obtained indicate that the optimum pH range is 3.5-9 in the presence of EDTA (Fig.2) and the absorbance of the complex decreases at pH above 9. The formation of the boron complex was therefore ctarried out a t about pH 3.8 by using an acetate buffer. 0.6 I 1 I I 0 2 4 6 8 1 0 1 2 PH Fig. 2. Effect of pH on complex formation. 1, Complex obtained with 2 x M boron, measured against reagent blank; and 2, reagent blank as 1 but no boron present, measured against DCE:. The effect of pH on the extraction of the boron - DHNS complex with EDTA is shown in Fig. 3. Constant absorbance was obtained at pH 4-12, the optimum pH range being 7-11. Because the absorbance of the reagent blank was constant at pH above 7, but not re- producible a t pH 12, the extraction of the boron complex was carried out a t about pH 10.2 by using carbonate buffer. Accordingly, the complex was formed a t pH 3.8 in the presence of EDTA and then extracted with zephiramine into DCE a t pH 10.2 with addition of chloride.0 2 4 6 8 1 0 1 2 PH Fig. 3. Effect of pH on the extraction of the boron complex into DCE. 1, Complex obtained with 2 x M boron, measured against reagent blank; and 2, reagent blank as 1 but no boron present, measured against DCE. The effect of pH on the back-washing of the organic phase, which was transferred into a When the concentration of chloride ion in the The back- stoppered 25-ml test-tube, was examined. back-washing solution was 1 M, the optimum pH region was found to be 5-12. washing was therefore carried out a t about pH 10.2.Effect of Chloride Concentration on the Extraction of the Boron Complex and on the Back-washing of the Organic Phase The effect of chloride concentration on the extraction of the boron complex was examined at pH 10.2 (Fig. 4 ) . The optimum concentration of chloride was found to be about 0.3 M. To complete and accelerate the phase separation in the ion-association extraction, 5 ml of 1.5 M sodium sulphate solution were also added as the salting-out agent in the extraction system.October, 1980 IN RIVERS WITH 1,8-DIHYDROXYNAPHTHALENE-4-SULPHONIC ACID 0.6 , I 959 0 0.1 0.2 0.3 0.4 0.5 0.6 iCI-1 ,/M Fig. 4. Effect of chloride concentration on the extraction of the boron complex. 1, Complex obtained with 2 x M boron, measured against reagent blank: and 2, reagent blank as 1 but no boron present, measured against DCE.Effect of pH on the Back-washing of the Organic Phase The effect of chloride concentration on the back-washing of the organic phase, which was transferred into a stoppered 25-ml test-tube, was examined at pH 10.2, and the results obtained are shown in Fig. 5. The optimum concentration of chloride was about 1.3 M. 0 0.2 0.4 0.6 0.8 1.0 1.2 “21-1 ,/M Fig. 5. Effect of chloride concentration on the back-washing of the organic phase. 1, Complex obtained with 2 x M boron, measured against reagent blank; and 2, reagent blank as 1 but no boron present, measured against DCE. The effect of the volume of the back-washing solution on the back-washing of the organic phase was examined. The volume of the back-washing solution taken being varied from 5 to 20 ml, and 10 ml was found to be the most effective.The efficiency of the back-washing with sodium chloride solution was examined a t pH 10.2. When 13 ml of back-washing solution were used, the absorbances of the boron complex and reagent blank were 1.289 and 0.764 (no back-washing), 0.605 and 0.119 (one back-washing) and 0.564 and 0.102 (two back-washings), respectively. Accordingly, the back-washing was carried out once with 10 ml of solution. Effect of Concentration of DHNS and Zephiramine The effect of the DHNS concentration on the formation of the boron complex was examined. Fig. 6 shows that the amount of 0.01 M DHNS solution necessary for the complete reaction was more than 4 ml when the concentration of boron was about 1.4 X M in 70 ml of aqueous solution and 5 ml of 2 x l o 3 M zephiramine in DCE solution was used as the extracting solvent.The zffect of the zephiramine concentration on the extraction of the boron complex was examined by using 0.01 M aqueous zephiramine solution4 (Fig. 7). A 1-ml volume of this960 solution was found to be necessary for the complete extraction of the boron complex. fore, 5 ml of 0.01 M DHNS solution and 5 ml of 2 x (equivalent to 1 ml of 0.01 M aqueous zephiramine solution) were used in this work. KORENAGA et al. : EXTRACTION FOR SPECTROPHOTOMETRY OF BORON Analyst, Vol. 105 There- M zepkiramine in DCE solution 0.6 1 0.6 7- , 0 2 4 6 8 1 0 Volume of 0.01 M DHNS/ml 0 0.4 0.8 1.2 1.6 2.0 Voluime of 0.01 M zephiramine/ml Fig.6. Effect of the concentration of Fig. 7. Effect of the concentration of DHNS. 1, Complex obtained with 2 x zephiramine. 1, Complex obtained with M boron, measured against reagent 2 x loe5 M boron, measured against reagent blank: and 2, reagent blank as 1 but no blank; and 2, reagent blank as 1 but no boron boron present, measured against DCE. present, measured against DCE. Effect of Time The time necessary for the complete formation of the boron complex was examined (Fig. 8). When the concentrations of boron (present as boric acid) and DHNS reagent were 1.4 x and 7.1 x lo-* M a t pH 3.8, respectively, the complete reaction was found to be achieved within 30 min. The time necessary for the complete extraction of the complex into DCE was examined. Fig. 9 shows that a suitable shaking time was 30 min when 5 ml of 2 x M zephiramine in DCE solution were used.I 0 10 20 30 40 50 60 0 10 2'0 30 40 50 60 Ti m e/m i n Time/rnin complex. Absorbance measured against reagent Fig. 9. Effect of 'shaking time. Absorbance blank. measured against reagent blank. Fig. 8. Effect of time on the formation of boron The shaking time necessary for the complete back-washing of the organic phase when 10 ml of the back-washing solution were used was examined. A shaking time of 5 min was found to be sufficient, so the shaking time for the back-washing was fixed a t 10 min. The separation of the two phases was immediate on the extraction of the complex from 70 ml of aqueous solution into 5 ml of DCE solution, and standing for a t most 30 min was found to be preferable to the complete separation of the two phases on the back-washing of the organic phase before measurement of the absorbance. Absorption Spectra and Calibration Graph The absorption spectra of the boron complex with DHNS and the reagent blank in DCE are shown in Fig.10 (solid lines 1-3). When the excess of co-extracted reagent in the organic phase is removed, the absorption maximum is obtained at 341 nm with a minimum reagentOctober, 1980 IN RIVERS WITH 1,8-DIHYDROXYNAPHTHALENE-4-SULPHONIC ACID 961 n v - 300 320 340 360 Wavelengthinm Fig. 10. Absorption spectra in DCE. 1, Complex obtained with 2 x M boron (0.216 pg of boron), measured against DCE in reference beam; 2, complex obtained with 1 x M boron (0.108 pg of boron), measured against DCE in reference beam; 3, reagent blank as 1 and 2 but no boron present, measured against DCE in reference beam; 4, solution obtained with 25 ml of Mino sample, measured against reagent blank in reference beam; 5, solution obtained with 50 ml of Mino sample, measured against reagent blank in reference beam; and 6, solution obtained with 25 ml of Mino sample plus 0.108 pg of boron, measured against reagent blank in reference beam.blank. The absorbance in DCE was measured in a quartz cell of l-cm path length at 341 nm against the reagent blank as reference. The calibration graph at 341 nm was a straight line that passed through the origin and obeyed Beer’s law over the range 0-3.6 x M boron present as boric acid in aqueous solution (corresponding to 0-5 x M boron in DCE).The apparent molar absorptivity in DCE calculated from the slope of the calibration graph was 2.4 x lo4 1 mol-l cm-l (con- verted into E = 3.4 x lo5 1 mol-l cm-l in aqueous solution) at 341 nm. The reagent blank at 341 nm was 0.119 & 0.006 (mean value of seven determinations), but reproducible when de-ionised water was used. Consequently, the detection limit and pre- cision achieved with the method are 1 pg 1-1 (difference in absorbance 0.03) and 5%, res- pectively. Determination of Boron in River Water with DHNS Interferences and masking agent DHNS reacts with some metal ions, such as aluminium, copper, iron, titanium and moly- bdenum. The tolerance limits of these metals and other ions generally present in river water were examined without EDTA according to the recommended procedure.The tolerance limit is defined as the concentration level at which the interferent causes an error of not more than 50/,. When EDTA was used as a masking agent for metals, the pH was adjusted to about 3.8 with acetate buffer. As shown in Table 11, the tolerance limits with EDTA were also deter- The results obtained are shown in Table 11.962 KORENAGA et al. : EXTRACTION FOR SPECTROPHOTOMETRY OF BORON Analyst, VoZ. 105 TABLE I1 TOLERANCE LIMITS FOR DIVERSE IONS WITH AND WITHOUT EDTA Ion Tolerance limit*/= .. I t Na+, K+, Sot- . . .. .. .. .. .. .. HCO- H,PO, .. .. .. .. .. .. .. .. 0 . l t Caz+, Sr2+, Baa+, Br-, NO;, Si'0:- .. .. .. .. 2 x 10-3 UOg+, A13+, Cr3+, F -, SCN -, I - . . .. .. .. .. 2 x 10-4 Fe3+, Ti4+, &foe+, ClOa, dodecylbenzenesulphonate .. .. .. 2 x 10-5 NO; .. .. . * .. .. .. .. 2 x 10-8: Ag+, Mna+;'Coa+,'Nia+, Cu2+, Zn2+, Cda+ . . .. .. . * 1 x io-3tf Hg2+, PbZ+, UOZ,+, AP+, Cra+, Fea+, Ti4+, Mo*+ .. .. 1 x 10-4s M g Z a ' .. .. .. .. .. .. .. 0.0lt Ag+, Mn*+, Fez+, &a+, Ni2+, Cuz+, ZAa+, Cda+, Hg2+, Pba+, * The tolerance limit is defined as the concentration level a t which the interferent causes an error of not more than 6% (precision of the method). t Maximum tested. If samples are acidified to pH below 2 by adding more than 0.5 ml of concentrated sulphuric acid per litre, nitritk ion may be almostcompletely removed as nitrogen monoxide gas. Add 5 ml of 0.01 N EDTA solution to 70 ml of the aqueous test solution. mined when 5 ml of 0.01 M EDTA solution were added to 70 ml of aqueous solution a t pH 3.8.Hence, the interferences of these metals and other metals commonly present in river water are eliminated by adding EDTA to the extraction system a t a concentration of about 10-3 M. Contamination from glassware In order to test for possible contamination from the glassware, DHNS, EDTA and acetate buffer were allowed to stand a t pH 3.8 in a 100-ml glass separating funnel for 2 h. The solution was examined by the proposed procedure and little boron was found (absorbance 0.130). However, when the solution was allowed to stand a t pH 10.2 (carbonate buffer) for 2 h, the absorbance was found to be higher. Polyethylene separating funnels were therefore used in order to prevent any possible contamination caused by the solution standing for a long time in glass.Polyethylene bottles were also used for storage of sample and reagents solutions. Pre-treatment of samflle solution When the sample was immediately treated with 0.5 ml of concentrated sulphuric acid per litre after collection, the boron content was found to be identical with that obtained without acidification. The stability of boron in sample solutions was examined with and without sulphuric acid. The results obtained for boron content did not vary for a t least a week in both instances, The sample therefore need not be acidified. When the membrane filter (0.45-pm pore size and 47-mm diameter circle) was used, no loss or gain of boron was found and reproducible results were obtained. The effect of sample acidification was examined.The effect of sample filtration was examined. Results of determination The results obtained by the recommended procedure for the determination of boron in water samples from the River Asahi, Okayama Prefecture, Japan, ai-e given in Table 111. An example of absorption spectra in the determination of boron in river water is shown in Fig. 10 (broken line 4). Boron present in sample solutions as boric acid and as tetraborate can be determined by this method, but not boron present as fluoroborate. In generad, river water contains boron in the form of boric acid and seldom in the form of tetraborate and fluoroborate. Accordingly, the total boron in river water can be determined by the use of the recommended procedure. In order to check the results of the determination of boron in river water, two series of experiments were carried out.In the first experiment, the amount of sample solution taken was varied between 10 and 50 ml and de-ionised water was added to each so as to give a constant volume. For all samples, linear graphs were obtained and the lines could beOctober, 1980 I N RIVERS WITH 1,8-DIHYDROXYN.4PHTHALENE-4-SlJLPHONIC ACID TABLE I11 DETERMINATION OF BORON I N RIVER ASAHI WATER Boron contentt/,pg 1-1 Sample source* Shimotokuyama . . . . Hatsuwa . . . . . . Katsuyama , . . . . . Ochiai . . . . . . Nishikawakami . . . . Eyomi . . . . . . Asahigawa-damu . . . . Shinada . . . . . . Kanagawa . . . . . . Ohara . . . . . . Mino . . . . . . Xanokaichit . . . . Hot-spring a t Misasa . . Hot-spring a t Yubara .. Seto Inland Sea a t Shibukawa Seto Inland Sea a t Teshima Pacific Ocean a t Tanohama Japan Sea a t Aoya . . . . Distance from estuary/ km . . 137 . . 122 . . 89 . . 76 . . 68 . . 62 . . 54 . . 49 . . 32 . . 16 . . 12 . . 4.6 963 Proposed method 8 . 8 & 0.3 8.4 & 0.2 8.7 i: 0.3 9.4 & 0.4 11.5 rt 0.5 8.6 i 0.4 11.4 i: 0.3 10.4 i: 0.3 11.4 0.1 9.3 & 0 . 4 11.7 rt 0.4 360 & 20 Methylene blue method; 8.4 7.6 8.7 9.7 10.9 8.1 11.5 9.8 10.8 10.0 11.6 i: 0 . 9 400 34 & 2 38 2300 i: 100 1900 4400 & 100 4 200 4500 i: 200 4300 4400 i: 100 4 600 3900 200 4 200 * Samples from the River hsahi were sampled on May 3rd and 4th, 1978. t Average values of four determinations i: standard deviations. $ This sample contained 0.043% of chloride, probably caused by sea water.The boron contents of hot- The values without standard deviations spring and sea waters are also given; the samples used were the same as those in previous are averages of two determinations. extrapolated to the same point, which coincided with the point obtained for 50 ml of de-ionised water. It was concluded that the determination of boron in river water was quantitative and de-ionised water could be used as the reagent blank. An example of absorption spectra in the experiment is shown in Fig. 10 (broken lines 4 and 5 ) . In the second experiment, the recovery of boron was examined by adding various amounts of boron to the sample solutions. All of the results obtained were linear and the slopes of the graphs were identical with those of the calibration graph obtained with de-ionised water. An example of absorption spectra in this experiment is shown in Fig.10 (broken lines 4 and 6). Comparison zeith the conventional wtethylene blue method The analytical values obtained by the proposed method were compared with those obtained by the methylene blue m e t h ~ d . ~ The results obtained by the latter method, conventionally available in Japan, are shown in Table 111. From Table 111, two methods were found to be comparable and the sample from the River Asahi at Mino showed that the relative standard deviation obtained when using the proposed method was smaller than that with the methylene blue method. The correlation coefficient of two methods was 0.95 in the determination of boron in 11 samples from the River Asahi, except for the sample from Nanokaichi ( a = - 0.05 and b = 0.98 in the equation y = a + bx, where x is the value obtained by the proposed method and y value obtained by the methylene blue method).Consequently, the results of the proposed method using DHNS are almost identical with those of the conventional methylene blue method5 so that the accuracy of the method is good in the practical analysis of river water samples. Conclusion The method proposed here could be applied to the spectrophotometric determination of parts per billion amounts of boron in river water with satisfactory results. This method of determining trace amounts of boron with DHNS is a great improvement on the previous method employing chromotropic acid,l and possesses the following advantages: (a) the complex formed with DHNS has a large molar absorptivity, which is about 1.7 times greater than that with chromotropic acid; (b) the extractability of the complex with DHNS is higher964 KORENAGA, MOTOMIZU AND TdEI than that with chromotropic acid, so that the concentration of boron by extraction from aqueous solution into DCE is complete and precise; (c) there is a llarge difference in the ex- change equilibrium constants between the complex and reagent, i.e., the removal of the excess of reagent can easily be achieved without loss of the boron complex; (d) the procedure is simple and back-washing is preferably carried out only once; and (e) the synthesis and purification of DHNS reagent are simple.As described here, the simple method for the removal of the elccesj of reagent in the organic phase must lead to a greatly improved sensitivity in a given ion-association extraction system, as the measurement can be carried out at the most sensitive wavelength of the complex, which cannot be measured without removal of the excess of reagent. As a sufficient amount of the reagent and a cationic surfactant can be added, the complex can easily be formed and extracted over a wide pH range. Moreover, the addition of relatively large amounts of salts such as sodium chloride causes very effective salting-out, so that the phase separation becomes more rapid. Also, the absorbances of the complex and reagent blank become more constant and reproducible on adding salts t o the ion-association extraction system, because the inter- ferences caused by co-existing anions are effectively eliminated. References 1. 2. 3. 4. 5 . Korenaga, T., Motomizu, S., and TBei, K., Analyst, 1978, 103, 745. Motomizu, S., and TBei, K., Anal. Chim. Acta, 1977, 89, 167. Korenaga, T., Motomizu, S., and TBei, K., Anal. Chinz. Acta, in th.e press. TBei, K., and Kawada, K., Bunseki Kagaku, 1972, 21, 1610. Japan Industrial Standard (JIS), K 0102, 1974. Received December loth, 1979 Accepted June 2nd, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500955

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

A%a(yst, October, 1980, Vol. 105, j!@. 965-973 965 Pyr i d i n e- 2 - aceta I d e h yd e Sa I icy I oy I h yd razo ne as an Analytical Reagent and its Application to the Determination of Vanadium M. Garcia-Vargas, M. Gallego * and M. de la Guardiat Department of Analytical Chemistry, Faculty of Sciences, University of Seville, Seville, Spain The synthesis, characteristics and analytical applications of pyridine-2- acetaldehyde salicyloylhydrazone (PASH) are described. The reagent reacts with vanadium(V) to produce a yellow 1 : 1 complex (A,,, =415 nm, E = 1.87 x lo4 1 mol -I cm-I in chloroform). The yellow complex, extracted into chloroform, has been used for the spectrophotometric determination of vanadium in a steel, a lead - vanadium concentrate and a phosphoric acid sample.A procedure based on the standard additions method has been applied satisfactorily to the determination of trace amounts of vanadium a t the parts per billion level (parts per lo9). Keywords: Pyridine-2-acetaldehyde salicyloylhydvazone reagent; vanadium determination; standard additions method; spectropkotometvy The uses of aroy1hydrazones1-l2 as analytical reagents have been described in an earlier paper.13 Aroylhydrazones behave as bidentate,s9Q tridentatel0*l1J3 or tetradentate12 ligands, forming coloured chelates with transition metal ions. In moderately acidic media or alkaline solution the hydrogen atom of the -CONH- group can split off and neutral metal chelates are formed.10~11J3 In this paper, the synthesis, properties and analytical applications of pyridine-2-acetal- dehyde salicyloylhydrazone (PASH) are reported.An extraction - spectrophotometric method for the determination of trace amounts of vanadium has been investigated and the effects of interferences have been widely studied. In order to avoid some interferences, masking and cation-exchange procedures have been used. The determination of small amounts of vanadium in different materials is described. The standard additions method has been used to determine vanadium a t the sub-parts per million level. PASH Experimental Apparatus A Pye Unicam SP8000 spectrophotometer was used for recording spectra in the ultraviolet and visible regions of the spectrum. A Perkin-Elmer - Coleman 55 (digital) and a Beckmann DU spectrophotometer were used for absorbance measurements at fixed wavelengths in the visible and ultraviolet regions of the spectrum, respectively; 1-cm silica or glass cells were used.A Philips PW 9408 pH meter, with glass - calomel electrodes, was used for pH measurements. * Present address: Faculty of Sciences, University of Cordoba, Cordoba, Spain. t Present address: Faculty of Sciences, University of Valencia, Valencia, Spain. A Pye Unicam SPlOOO infrared spectrophotometer was also used.966 GARCIA-VARGAS et al. : PYRIDINE-2-ACETALI)EHYDE Analyst, vd. 105 Reagents All solutions were prepared with analytical-reagent grade chemicals using distilled water. Synthesis of PASH. A 1.05-ml volume of pyridine-2-acetaldehyde was added to 2 g of salicyloylhydrazide dissolved in 20 ml of hot absolute ethanol.TWO drops of concentrated hydrochloric acid were added and the mixture was heated in a water-bath. The yellow crystals were filtered off and recrystallised twice from ethanol. The product (yield about 64%) had a melting-point of 230-234 "C, and elemental analysis gave C 65.85%, H 5.15% and N 16.70°/0; the calculated values for C,,H,,O,N, are: C 65.87y0, H 5.13% and N 16.460/,. A 0.05y0 mi V solution was prepared by dissolving 0.05 g of the reagent in 3 ml of hrN-dimeth:glformamide and diluting to 100 ml with chloroform. This solution was prepared by dissolving vanadium(V) oxide in 1 M sodium hydroxide solution, standardising it gravimetric- ally using ~upferr0n.l~ Dowlex 50-X8 resin, hydrogen form. Slurry 5.0 g of cation-exchange resin, 20-50 mesh, with distilled water and pour into a column 30 cm long and 2 cm in diameter with glass sinter bed support and a tap a t the bottom.Procedure for the Determination of Vanadium(V) To 10-50 ml of sample solution in a separating funnel containing up to 100 pg of vanadium(V), add 2 ml of 0.5 M potassium chloride solution and 1.5 ml of 1 M hydrochloric acid and extract the mixture with one 10-ml volume of PASH reagent solution. Shake the funnel vigorously for 2 min, allow the phases to separate and transfer the lower (organic) layer into a 10-ml flask containing anhydrous sodium sulphate. Measure the absorbance of the yellow chloroform extracts after 45 min a t 425 nm against distilled water or at 415 nm against a reagent blank, prepared in a similar way but without the vanadium.The calibration graph was prepared by using standard solutions of vanadium(V) treated in the same way. Pyridine-2-acetaldehyde salicyloylhydrazone reagent solution. This solution was stable for several days. Vanadium( V ) standard solution, 5.295 g 1-1 of vanadium( V ) . Working standards were prepared from this solution as necessary. Results and Discussion Properties of Pyridine-2-acetaldehyde Salicyloylhydrazone The bands were assigned to the stretching vibrations of the N-H bond (3290 cni-l), the =C-H bond (3050 cm-l), the C=O bond (1640 cm-l), the C=N bond (1550 cm-I) and the N-N bond (920 and 875 cm-l). The solubility in other solvents, such as water, methanol, ethanol, chloroform and benzene, is about 1 g 1-1 or less. A reagent solution in ethanol or chloroform of 5 x M concentration shows two absorption maxima at 298 and 311 or a t 300 and 323 nm, with molar absorptivities of 2.6 x lo4 and 2.56 x lo4 or 1.94 x lo4 and 1.92 x lo4 1 mol-l cm-l, respectively.M) shows bathochromic shifts a t pH less than 4 or greater than 6. Hydrolysis of PASH to pyridine-2- acetaldehyde and salicyloylhydrazide occurs slowly in aqueous solution. The percentage of decomposed reagent at pH 2.6,4.4,7.0 and 9.0 after 1 h was 33.3,13.5,0 and O%, respectively. The method used by Phillips and Merrit16 was used for the determination of the ionisation constants. The first pK may be caused by protonation of the pyridine nitrogen atom and the second by deprotonation of the hydroxyl group. Oxidising and reducing substances in moderate concentration do not alter the absorption spectra of PASH.PASH appears to be a bidentate or tridentate ligand with a convenient steric arrangement of its donor groups and contains a conjugated system of x electrons connected with the donor system. The reaction of the reagent in aqueous ethanolic solution a t different pH values with 40 cations was investigated. It forms soluble, coloured complexes with lead(II), iron(III), The infrared spectrum of PASH in potassium bromide dics was obtained. PASH has a solubility in NN-dimethylformamide of 35.7 g 1-l. The change in pH on the spectra of aqueous solutions of the reagent (3.14 x The average pK values were found to be 4.0 and 6.0. The chelates of PASH are generally uncharged.October, 1980 SALICYLOYLHYDRAZONE AS A REAGENT FOR VANADIUM 967 chromium(III), bismuth(III), cerium(IV), zirconium(1V) and vanadium(V).With uranium(V1) a soluble yellow complex that precipitates after several minutes is formed (Table I). TABLE I CHARACTERISTICS OF PASH REACTIONS WITH METAL IONS IN ACETATE BUFFER Colour of complex Metal ion in solution Amsx./nm Fe(II1) . . . . Yellow - brown 350 Pb(I1) . . . . Yellow - green 360 Cr(II1) . . . . Yellow - green 358 Bi(II1) , . . . Yellow 378 Ce(1V) . . . . Yellow 358 V(V) . . . . Yellow 386 U(V1) . . . . Yellow 360 Zr(1V) . . . . Yellow 355 PD* 4.78 4.20 4.20 4.78 3.54 3.81 4.92 4.49 * pD = -log (minimum detectable mass of metal ion, g/volume, ml). Study of Vanadium - PASH System Formation of vanadium complex in aqueous ethanolic solution produces a yellow complex.Absorption spectra of the complex are shown in Fig. 1(A). complex remains stable for a t least 12 h at pH 4.7 (acetate buffer). The addition of a 0.05;/, m/V solution of PASH in ethanol to a solution of vanadium(V) ions The 350 400 450 Wavelengthinrn Fig. 1. Absorption spectra of vanadium complexes with PASH. A, Vanadium(V) complex in aqueous ethanolic medium a t pH 4.7 (C, = 2.3 pg ml-l); B, vanadium(1V) complex in aqueous ethanolic medium a t pH 4.7 (C, = 2.3 pg ml-l); and C, vanadium(V) com- plex extracted into chloroform a t pH 1.3 (C, = 1.4 pg ml-I); D and E, reagent blanks of A and C, respectively. The influence of pH on absorbance is shown in Fig. 2(A), a t 386 nm after a 30-min reaction time. The yellow complex is formed immediately in aqueous media (at the optimum pH range) but most of the metallic chelates are insoluble and this causes numerous interferences.It is concluded that in aqueous media the vanadium(V) - PASH complex is not of great analytical interest. Stoicheiometry of the complex and oxidation state of vanadium method and was found to be 1:l [Fig. 3(A)]. under analogous conditions, was also 1:l [Fig. 3(B)]. The optimum pH range is 3.5-6.0. The stoicheiometry of the vanadium(V) complex was evaluated by the continuous variation The metal to ligand ratio for vanadium(IV),968 GARCIA-VARGAS et d. : PYRIDISE-%ACETALDEHYDE Analyst, VOl. 105 0 1 2 3 4 5 6 7 8 PH Fig. 2. Influence of pH on the formation crf vanadium(V) - PASH complex: A, in aqueous ethanolic solution a t 386 nm (C, = 1.2 pg ml-l); and B, extracted into chloroform a t 415 nm (C, == 1.4 pg ml-l). From the experimental evidence it was concluded that the reagent forms the yellow complex with vanadium(V).The presence of ascorbic acid in the vanaccliurn(V) solution, before the PASH reagent was added, changed the absorption peak from 386 to1 380 nm. When vanad- ium(1V) was used the presence of ascorbic acid did not alter the absorption peak at 380 nm [Fig. 1(A) and (B)]. 0.8 1 0.7 0.6 0.5 -? p 0.4 n a 0.3 0.2 0.1 OI m I t I / I l l , I , 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 [VI [ V l + [PASHI Fig. 3. Stoicheiometry of vanadium complexes, in aqueous media a t pH 4.7 (continuous variation method) : A, vanadium(V) - PASH complex: and B, vanadium(1V) - PASH complex. Extraction of the complex of vanadium(V), the yellow complex is formed immediately in the organic phase.When a solution of PASH in an organic solvent is shaken with an aqueous acidic solution WhenOctober, 1980 SALICYLOYLHYDRAZONE AS A REAGENT FOR VANADIUM 969 chlorobenzene is used the resulting complex is stable; the interferences of foreign ions are high. Of the other solvents tried, chloroform proved to be the best as the complex shows a major bathochromic shift. The absorption spectrum of the vanadium(V) - PASH complex in chloroform is shown in Fig. 1(C). It is stable for at least 10 h after a 35-min reaction time and presents one band in the visible region, at 415 nm. A bathochromic shift is produced in the absorption spectra of the complex, from 386 nm (aqueous media) to 415 nm (organic media).The reported absorb- ances were measured at 415 and 425 nm. The latter wavelength was used as the reagent itself does not absorb at this wavelength. The maximum constant absorbances were obtained in the pH range 0.9-2.8 [Fig. 2(B)]. An aliquot of 10-50 ml of solution containing 14 pg of vanadium(V) was extracted with 10 ml of a solution of 0.01-0.05~0 m/V PASH in chloroform. The extraction was quantitative with 0.03% m/V of the reagent solution and remained constant with increasing concentration. Therefore, 10 ml of 0.0576 m/V reagent solution was adopted as the concentration of solution containing the complexing ligand to be used. The shaking time was varied from 0.25 to 5 min, while the other variables were kept constant. A shaking time of between 1 and 2.5 min did not produce any change in absorbance if the volume ratio Vorg.:Vas.was between 1 : l and 1: 2.5. On the other hand, shaking for 2 min was necessary for the complete extraction of vanadium(V) if the volume ratio Vorg.:Vaa. was 1 : 5. Spectrophotometric Determination of Vanadium(V) with PASH Based on the experimental work, a method is proposed for the determination of trace amounts of vanadium involving the formation of the yellow complex with PASH and its extraction into chloroform. Beer’s law is obeyed between 0.5 and 2 pg ml-l of vanad- ium(V) in the organic phase at 415 nm. The optimum concentration range, evaluated by Ringbom’s method, is 1-1.75 pg ml-l of vanadium. The yellow complex gave a molar absorptivity of E = 1.87 x lo4 1 mol-l cm-l at 415 nm [in the chloroform phase (10 ml)].The Sandell sensitivity of the method is 0.003 pg cm-2 of vanadium. The precision was estimated for 10-50-ml aliquots of 10 pg of vanadium(V) solu- tion, and the relative error of the method is 0.44%. The method is more sensitive for vanadium than many existing methods, and it has been compared, advantageously, with other methods previously reported that use related ligands (Table 11). TABLE I1 CHARACTERISTICS OF VANADIUM - HYDRAZONE COMPLEXES Molar Metal t o Optimum absorptivity/ ligand Compound acidity h,,,,/nm 1 mol-1 cm-1 ratio Reference Hydrazinium hydrazinecarbodithioate pH 4-6 460 1100 1 : 2 16 Anthranilic acid isopropylidenehydrazide . . . . 0.2-1.0 N H,SO, 525 5 100 1 : 2 17 Nicotinic acid hydrazide . ... pH 1.8-2.2 420 750 1 : 1 18 Pyridine-2-acetaldehyde - salicyloylhydrazone . . .. . . pH 0.9-2.8 415 18700 1 : 1 Effect of Foreign Ions For the determination of 10 pg of vanadium by this method, the foreign ions can be tolerated at the levels given in Tables I11 and IV. The limiting value of the concentration of foreign ions was taken as that value which caused an error of not more than 2.5% in the absorbance. Cations were added in the form of chlorides, nitrates or acetates to a maximum of 10000 pg ml-1; anions were added in the form of sodium or potassium salts. Several foreign ions, at high concentrations, produce a general decrease in the absorbance of the vanadium - PASH chelate in a wide range of concentrations. This effect is summarised in Table V. From the data in this table it may be assumed that vanadium can be determined, without great error, in the presence of these ionic concentrations, but with a lower sensitivity.In these instances, standards and samples must be matched for the foreign ion Concentration.970 GARCIA-VARGAS et al. : PYRIDINE-2-ACETALDEHYDE Analyst, Val. 105 TABLE I11 TOLERANCE LIMITS OF EXTRACTIVE DETERMINATION OF VANADIUM(V) Results obtained using a 10-1.18 sample of vanadium, Ion added La(III), Cd(II), Pb(II), As(V), Ba(II), Sr(II), ammonium, alkali metals, C1-, Br-, C104-, C104-, NO,-, BO,-, SOa2-, COs2-,* PO,,-, BO,,-, benzoate, acetate, cltrate . , .. .. . . .. .. .. .. .. Mg(II), Ca(II), SiOSa- . * .. .. .. .. .. .. . * Mn(II), Be(II), tartrate .. .. .. .. phthalate, dimethylglyoxime (DMG) .. .. .. .. .. . * Zr(IV), In(III), S,O,e- * . .. .. .. .. .. * . .. Th(IV), EDTA .. . . .. .. .. .. .. .. .. U(VI), oxalate .. .. * . * . .. .. .. .. .. H,O% .. .. .. .. Al(III), Cr(III), Se(IV), Ag(Ij; Hg(I), Zn(II), Tl(I): A s ( I ~ ~ ) , CO,;-, B,0,2 -, F-, Sn(IV), Hg(II),'Co(II); Fe(IIii, Ti(IV), CNL, Fe(CN),3 -. . .. .. .. * Heating gently before extracting. Amount tolerated/ pg ml-1 10000 5 000 2 500 1000 750 500 250 200 100 TABLE IV ELIMINATION OF INTERFERENCES BY ADDITION OF MASKING AGENTS Amount tolerated/pg ml-1 7 r-----. -___ Without With masking Foreign ion masking agent agent Masking agent Mo(V1) . . . . 50 250 Tartrate, 1000 p g ml- . . . . 10 100 Tartrate, 10100 pg ml-1 . . .. 2 100* H,O,, 200 pg ml-1 w (VI) Fe(I1) Sn(I1) . . .. 25 100* HNO,, 1 ml Ce(1V) .. . . 2 10 PO4$-, 500 p,g ml-1 Pd(I1) . . . . 1 25 DMG,? 10 mg Sb(II1) . . . . 1 10 Tartrate, 2500 p g ml-1 I - . . . . . . 50 100* HNO,, 'J ml * Heating before extracting. t DMG = dimethylglyoxime. The tolerance limits for the extractive determination of 10 pg of vanadium for copper(II), nickel(I1) and bismuth(II1) are low, 1, 2 and 2 pg ml-l, respectively. To remove these metal ions, when present, a cation-exchange column was used.19120 The fodlowing solutions were percolated through 5 g of cation-exchange resin: 10 mg of nickel(] 1) in 10 ml of 1 M hydro- chloric acid; 5 mg of copper(I1) in 10 In1 of 1 M hydrochloric acid; LO mg of nickel(I1) in 10 ml of 1 M nitric acid; 5 mg of copper(I1) in 10 ml of 1 M nitric acid; 10 mg of bismuth(II1) in 10 ml of 1 M nitric acid.In addition each of these solutions contained 10 pg of vanadium(V) and 2 drops of a 3% rn/V solution of hydrogen peroxide. The vanadium(V) was eluted using 20 ml of 1 M hydrochloric acid [when copper(I1) and nickel(I1) were present] or 1 M nitric acid [when copper(II), nickel(I1) and bismuth(II1) were present:. The flow-rate was kept a t 3 ml min-l. The eluate was neutralised with concentrated sodium hydroxide solution and then the extractive - spectrophotometric method was applied as described above. The recovery of vanadium was 92.6-105.7%. The precision was estimated for 10 pg of vanadium in 10 ml of 1 M hydrochloric acid or 1 M nitric acid, and the relative error of the method was less than 3%. If necessary this cation-exchange procedure may be applied to other foreign ions; for example, 10mg of cobalt(I1) can be separated from 10 pg of vanadium by applying this procedure to 10 ml of a solution in 1 M hydrochloric acid.Applications materials. The method has been applied satisfactorily to the determination of vanadium in differentOctober, 1980 EFFECT OF SALICYLOYLHYDRAZOKE AS A REAGENT FOR VANADIUM TABLE V SOME FOREIGN IONS AT HIGH CONCENTRATIONS ON THE ABSORPTION OF VANADIUM - PASH CHELATE Absorbance of a 10-pg sample of vanadium is 0.367. Concentration/ Vanadium recovery*/ Ion added pg ml-1 Absorbance pg ml-1 97 1 Zn(I1) , . . . 5 000 7 500 Cr(II1) . . . . 5 000 7 500 10000 . . 5 000 7 500 10000 W I ) ' ' . . 2 500 5 000 Al(II1) . . . * 2 500 5 000 7 600 10000 As(I1) . . . .2 500 5 000 7 500 A m ' . 0.470 0.465 0.210 0.216 0.212 0.268 0.275 0.268 0.250 0.253 0.295 0.269 0.293 0.297 0.344 0.335 0.342 1.28 1.27 0.57 0.59 0.58 0.73 0.75 0.73 0.68 0.69 0.80 0.73 0.80 0.81 0.94 0.92 0.93 * Results are the means of three determinations. Determination of vanadium in a mineral, a steel and a phosphoric acid sample Results of the analysis of vanadium in mineral and steel samples from the Bureau of Analysed Samples Ltd. support the precision and reliability of this method. Lead - vanadium concentrates and high-speed steel were dissolved in a mixture of concentrated nitric and perchloric acids (2 + 1 VjV) and aqua regia, respectively. Triplicate results were obtained in both instances. Lead - vanadium concentrates (BAS No. 70aG) had the following certificate composition: lead 65.4 and vanadium(V) oxide 3.20y0.The vanadium content found was 3.18 & 0.030/0 (for V,O,). High-speed steel (BAS No. 64b) had the following certificate composition: carbon 0.9, vanadium 1.99, chromium 4.55, molybdenum 4.95 and tungsten 7.05%. The vanadium content found was 1.96 f 0.02y0. A phosphoric acid sample, used in the detergent industry, has also been analysed for vanadium. The average composition of the phosphoric acid analysed was phosphorus(V) oxide 38, sulphuric acid 3.5, calcium oxide 0.15, silica 1, magnesium oxide 0.7, aluminium oxide 0.3, fluoride 2, iron 0.190,; m/V, and vanadium and chromium 204 and 215 pg ml-l, respectively. The vanadium found by the spectrophotometric determination was 207 & 2 pg ml-l (the mean result of four determinations).Determination of vanadium by the standard additions method The majority of the methods for the determination of parts per million and sub-parts per million amounts of vanadium require pre-concentration of vanadium by c~precipitation,~~-*~ ion e x c h a x ~ g e ~ ~ ~ ~ ~ - ~ ~ or liquid - liquid extra~tion.*~-~4 The PASH method may also be applied to the determination of vanadium at parts per billion levels (parts per lo9), which decreases the lower limit of the vanadium determination through the taking of a larger volume of the aqueous phase in relation to the chloroform phase and applying the standard additions method.l3 The method consists in adding several increasing known amounts of vanadium(V) (0, 1.25, 2.5 and 3.75 pg) to four aliquots of sample solution.The extraction procedure described above is then applied and the absorbances are measured a t 425 nm. The absorbances are plotted against the concentrations of the four vanadium-containing solutions of each sample. The straight line is extrapolated back to the concentration axis and the negative intercept gives the concentration of the sample solution.972 GARCIA-VARGAS et al. : PYRIDINE-2-ACETALDEHYDE Analyst, VoL. 105 All parameters in the regression equation were calculated by the principle of least squares and all regression curves were practically linear, the correlation coefficients being equal to or higher than 0.995. This method was applied to the phosphoric acid sample mentioned above. The sample solution was first diluted 1000 times and then aliquots of 5, 10 or 20 ml were taken.The results obtained are shown in Table VI. The vanadium content was found to be 4.12 3 0.13 pg (sample A, 20-ml aliquots of the dilute sample), 2.05 & 0.06 pg (sample B, 10-ml aliquots of the dilute sample) and 1.07 & 0.04 pg (sample C, 5-ml aliquots of the dilute sample). TABLE VI REGRESSION ANALYSIS OF CURVES BASED ON STANDARD ADDITIONS METHOD FOR DETERMINATION OF VANADIUM Equation of regression Correlation Sample* Aliquot taken/ml curve coefficient A . . .. 20 y = 0.0296% & 0.1221 0.998 B .. . . 10 y = 0 . 0 3 0 4 ~ & 0.0624 0.998 D . . .. 50 y = 0.0367% & 0.0887 0.999 E . . .. 50 y = 0.0354% & 0.0466 0.998 c .. .. 5 y = 0.0295% f 0.0316 0.996 * A, B and C correspond to the phosphoric acid sample mentioned in text (dilute 1000 times, previously).D and E correspond to vanadium-containing solutions in 0.1 M potassium chloride (50 and 25 pg 1-1, respectively). In order to study the accuracy of the standard additions method, two vanadium-containing solutions were made, containing 50 and 25 pg of vanadium(V) in 1000 1111 of 0.1 M potassium chloride solution. The method was applied to 50-ml aliquots of both samples as described above. The results obtained are shown in Table VI, samples D and E. The vanadium recovery was 96.7% for 50 pg 1-1 of vanadium(V) and 105.2% for 25 pg 1-1 of vanadium(V). Conclusion Other methods are available for the determination of trace amounts of vanadium using hydrazones (Table 11), but none of them is completely satisfactory.This paper describes a study of the optimum conditions for a selective and sensitive spectrophotometric method for the determination of vanadium. The method is relatively free from interferences because most of the metallic chelates of PASH are not extracted into chloroforin and the absorption peaks of these chelates are in the ultraviolet region. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. References Katiyar, S. S., and Tandon, S. N., Talanta, 1964, 11, 892. Vasilikiotis, G. S., and Tossidis, J . A,, Microchem. J., 1969, 14, 380. Uno, T., and Taniguchi, H., Bunseki Kagaku, 1971, 20, 997. Odashima, T., and Ishii, H., Nippon Kagaku Kaishi; 1973, 729. Vasilikiotis, G. S., Micvochem. J . , 1968, 13, 526.Capitan, F., Salinas, F., and Gimenez Plaza, J., Ars Pharm., 1975, 16, 293. Gallego, M., Garcia-Vargas, M., Pino, F., and Valcarcel, M., Microchem. J . , 1978, 23, 353. Aggarwal, R. C., and Rao, T. R., Transition Met. Chem., 1977, 2, 21. Aggarwal, R. C., and Rgo, T. R., Transition Met. Chem.. 1977, 2, 59. Domiano, P., Musatti, A., Nardelli, M., and Pelizzi, C., J . Chem. Soc., Dalton Trans., 1975, 295. Vasilikiotis, G. S., and Kouimtzis, Th. A,, Microchem. J . , 1973, 18, 85. Rastogi, D. K., Sahni, S. K., Rana, V. B., and Dua, S. K., Transition Met. Chem., 1978, 3, 56. Gallego, M., Garcia-Vargas, M., and Valcarcel, M., Analyst, 1979, 104, 613. Erdey, L., “Gravimetric Analysis,” Part 11, Pergamon Press, Oxford, 1!365, p. 562. Phillips, J. P., and Merrit, L. L., J . Am. Chem. Soc., 1948, 70, 410. Byr’ko, V. M., Busev, A. I., Tikhonova, T. I., Baibakoba, N. V., and Shepel, L. I., Zh. Anal. Khim., 1975, 30, 1885. Dolgorev, A. V., and Karpova, 0. I., Zavod. Lab., 1974, 40, 771. Krych, 2.. and Lipiec, T., Chem. Anal. (Warsaw), 1967, 12, 535. Strelow. F. W. E.. Rethemever. R.. and Bothma. C. 1. C.. Anal. Chem.. 1965. 37, 106 Strelow, F. W. E.; Van Zy1,’C. ‘R., ’and Bothma, C. J: C . , .Anal. Chirn. Acta, 1969, 45, 81. Chan, K. M., and Riley, J. P., Anal. Chim. Acta, 1966, 34, 337. Sugawara, K., Tanaka, M., and NaitB, H., Bull. Chem. Soc. Jpn., 1953, 26, 4.17.October, 1980 SALICYLOYLHYDRAZONE AS A REAGENT FOR VANADIUM 973 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. NaitB, H., and Sugawara, K., Bull. Chem. Soc. Jpn, 1957, 30, 799. Ishiabshi, M., Fujinaga, T., Kuwamoto, T., and Sawamoto, H., J . Chem. Soc. Jpn, Pure Chem. Sect., Kiriyama, T., and Kuroda, R., Anal. Chim. Acta, 1972, 62, 464. Nevoral, V., and OkaE, h., Cesk. Farm., 1966, 15, 229. Linstedt, K. D., and Kruger, P., Anal. Chem., 1970, 42, 113. Korkisch, J., and Krivanec, H., Anal. Chim. Acta, 1976, 83, 111. Chan, Y . K., and Lum-Shue-Chan, K., Anal. Chiw. Acta, 1970, 50, 201. Crump-Wiesner, H. J.. Feltz, H. R., and Purdy, W. C., Anal. Chim. Acta, 1971, 55, 29. Zhavoronkina, T. K., Tr. Morsk. Gidrofiz. Inst., 1960, 19, 38. Morris, A. W., Anal. Chim. Acta, 1970, 42, 113. Kishimura, M., Matsunaga, K., Kudo, T., and Obara, F., Anal. Chim. Acta, 1973, 65, 466. Abbasi, S. A,, Anal. Chem., 1976, 48, 714. 1964, 85, 763. Received March 27th, 1980 Accepted April 25th, 1980

ISSN:0003-2654    

DOI:10.1039/AN9800500965

出版商:RSC    

年代:1980

数据来源: RSC