INDIAN J. CHEM., VOL. 14A, JULY 1976

Spectrophotometric Determination of Aminesby Cu(II)

J. P. RAWAT & PRITI BHATTACHAR]EE

Chemistry Departmeit, Aligarh Muslim UniversityAligarh

Received 5 June 1975; accepted 15 September 1975

A spectrophotometric method for the determinationof amines using Cu(II) has been developed. Job'smethod and mole-ratio method have been used todetermine the metal-amine ratio in the colouredcomplex formed.

A SENSITIVE method for the spectrophoto-metric determination of amines using acetyl

chloride and ferric salts has been described in ourearlier report-. Recently copper sulphate has beenused for the determination of ethylene diamine-.We report here a method for the spectrophotometricdetermination of some amines using Cu(II).

Following amines were used: Ethylamine, ethanol-amine, isopropylamine, o-phenylenediamine, isoqui-noline and pipridine (Riedel); dimethylamine, tri-methylamine, 1,3-diaminopropane, aniline, p-tolui-dine, pyridine (BDH) ; methyl amine and morpholine(Koch-Light) CuS04 was a BDH (AR) product.

In most cases, 1M solution of amines was preparedin conductivity water. Those insoluble in waterwere dissolved in methanol. Copper sulphate solu-tion was prepared in conductivity water.

Determination of amines - A small amount ofamine (4-60 mg) was mixed with 1 ml of 0'5M coppersulphate solution. The solution was shaken welland volume made up to 10 ml by the addition of asolution of ammonium acetate buffer. The absorb-ance of the coloured complex against blank (1 ml of0'5M copper sulphate and 9 ml ammonium acetatesolution) was recorded at the specified wavelength.

It was observed that the increase in temperaturebrought about a slight decrease in the absorbance.However, for the sake of convenience all determi-nations were carried out at 25°. The optimum pHfor the Cu-amine complex was between 6 and 7 and,therefore, buffer of pH 6·5 was used. The effect ofchloride, nitrate, sulphate and acetate anions wasnegligible in this procedure of determination ofamines. It was found that benzamide, acetamide,chloro benzene , bromo benzene, nitrobenzene, phenol,methyl cyanide, acetone, benzophenone and propylalcohol did not affect the absorbance. Pyrogalloland catechol increased the absorbance while aceticacid and aldehydes decreased the absorbance.

Determination of 1,3-diaminopropane in the presenceof aniline, p-toluidine, pyrrote, diphenylamine, iso-quinoline, pyridine and ~-naPhthylamine - 1 ml ofthe sample containing 1-8 mg of 1,3-diaminopropanewas taken in an Erlenmeyer flask and heated on awater-bath for a few min to remove the solvent(particularly if the sample is di-solved in ethanol).To this was added 1 ml of O'IM copper sulphatesolution. The reaction mixture was shaken andvolume made up to 10 ml by the addition of 1 mlof saturated sodium thiosulphate and formate buffer(PH 7). It was again shaken well and kept for 10

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min. The contents were centrifuged to removeprecipitate if any. The clean solution was decantedand the absorbance measured at 590 nm. The %error in the determination of 1,3-diaminopropane inthe presence of other arnines was ± 2'8%. Thestandard deviation was O·OB.

Determination of o-phenylenediamine - To 0·5 mlof solution containing 50-250 (Jog of o-phenylene-diarnine, 1 ml of O'OlM copper sulphate and 0·1 mlacetyl chloride were added and reaction mixtureheated on a water-bath at BO° for 30 min. Reddish-brown coloured complex thus formed was shakenwith 20 ml of isobutanol for 2-3 min. The colouredcomplex was extracted in butanol layer. Theabsorbance was noted at 460 nm. Determination ofunknown samples of c-phenylenediamine showed anerror of ± 4%.

The optimum temperature for the determinationof o-phenylenediamine is BO°. It was found that thereaction is unaffected within PH range 1-7 while athigher PH the colour of the complex changes togreen. Benzarnide, acetamide, chlorobenzene, nitro-benzene, phenol, acetone, acetic acid and benzo-phenone did not interfere in the determination ofthis amine while aldehydes interfere.

The results of determination reveal that aminescan be determined using Cu(II). Extraction inisobutanol in the presence of acetyl chloride in-creases the sensitivity and selectivity in the deter-mination of o-phenylenediamine. Job's method ofcontinuous variation and mole-ratio method showedthat with o-phenylenediamine, a 1: 1 complex isformed while a 1: 2 complex is formed in the case of1,3-diaminopropane.

The authors are grateful to Prof. Wasiur Rehmanfor providing research facilities.

References1. RAWAT, J. P. & SINGH, J. P., Analyt. Chem., 47 (1975),

738.2. LEIZEROVICI, E· & OPERESCUM, C.,Chem. Abstr., 76

(1972), 148554y.

Sodium Phenobarbitone as a New Titrant forMicrodetermination of Aspartic & Glutamic

Acids

A. K. SAXENA

Chemistry Department, University of Delhi, Delhi 110007

Received 1 September 1975; accepted 27 October 1975

Aspartic and glutamic acids have been determinedtitrimetrically in micro amounts (67-294 I1g) employ-ing sodium phenobarbitone as titrant and bromocresolpurple as indicator. The end point is marked by theappearance of a faint pink colour. Only one carboxylicgroup of the acids reacts with sodium phenobarbitone.

SEVERAL tit rants have been used earlier="for the microdetermination of aspartic and

glutamic acids. We have now found that theseacids can also be determined titrimetrically inmicro amounts (67-294 (l.g) utilizing a new titrant,sodium phenobarbitone, in the pre~ence of bromo-cresol purple as indicator. The results of such a

TABLE 1 - MICRODETERMINATION OF ASPARTIC ANDGLUTAMIC ACIDS

Aspartic acid (ug) Glutamic acid (ug)

Taken Found Taken Found

266 269 294 300271 297274 300

133 136 147 150138 153138 153

67 69 74 7767 7969 77

study are presented in this note. Only one carboxylicgroup of the aspartic and glutamic acids was foundto react with sodium phenobarbitone. Further,the potentiometric titrations of hydrochloric acidby sodium phenobarbitone gave sharp inflexionsat one equivalence between pH 4·5 and 7·0. ~hemet hod described is accurate, less time consumingand gives reproducible results (Table 1). Howeverthe determination of the individual acid in theirbinary mixture is not feasible because of interference.

The reagents used were aspartic acid (E. Merck),glutamic acid (E. Merck), sodium phenobarbitone(K. Light), and bromocresol purple (BDH).

Procedure - An aliquot (0·5 rnl) of O'OOIM asparticor glutamic acid was diluted with distilled waterto about 15 ml, and 1 or 2 drops of 0·0053 % solutionof bromocresol purple added to it. The resultingyellow solution was titrated against O'OOIM sodiumphenobarbitone to the first faint pink colour. Theresults are given in Table l.

The author is grateful to Prof. R C. Mehrot rafor his guidance, and to the CSIR, New Delhi, forfinancial assistance.

References1. SAXENA, A. K., SRIVASTAVA, M. N. & SAXENA, II. B. L.,

Microcbem. j., 14 (1969),361.2. SAXENA, A. K., Michrochem, J., 17 (1972),757.3. SAXENA, A. K., J. Chem. UAR, 15 (1973),179.

Phenylazoacetaldoxime, a New Reagent for theEstimation of Co(II or III)

K. C. KALlA & ANIL KUMAR

Department of Chemistry, Punjabi University, Patiala

Received 30 June 1975; accepted 6 October 1975

The title reagent has been successfully used for thegravbnetric determination of Co(II or III). Co(III)-oxime complex absorbs strongly in UV-visible regionin benzene. This has led to the development of a spec-trophotometric method for the determination of micro-quantities of Co(III). Phenylazo-p-tolualdoxime isequally effective for the determination of cobalt.

THE commonly us~d reagents for the estimationof cobalt are oximesv". A new class of azo-

oximes (A, R=alkyl or aryl) found to have a very

NOTES

high affinity for C02+ and C03+ was synthesizedby Bamberger et al.8• In this paper some of theanalytical applications of this class of azooximesare reported. These compounds, commonly knownas C-nitrosohydrazones (B), actually exist as oximes(A)D.

The reaction between cobalt (II or III) salts andarylazooximes (A), leads to the formation of com-plexes of the type tris(arylazooximato)cobalt (III)(C)9 which have a dark red colour, show intenseabsorption bands in UV and visible region and arecompletely insoluble in aqueous medium. Theprecipitation of cobalt with arylazooximes in theaqueous medium is quantitative.

The arylazooximes (A) were prepared by therevised procedure of Bamberger et al.S,D. Phenyl-azoacetaldoxime (A, R=CHa, Ar=C6H5, m.p. 117°),phenylazobenzaldoxime (A, R=Ar=C6Hs, m.p.133°) and phenylazo-e-tolualdoxime (A, R=C6H4CHa,Ar=C6H5, m.p. 132°) were used for the estimationof Co(III). A slight excess of arylazooxime (A),dissolved in aq. ammonia (1: 1) was added dropwisewith continuous shaking to Co(II) salt solution inwater and pH of the solution adjusted to ,....,8byadding aq. ammonia. The dark brown precipitateswere digested on a water-bath for 30 min, the pre-cipitates filtered, heated to a constant weight andwashed with 5% ammoniacal solution till thesewere completely free of the precipitating reagent.The precipitates were finally washed with doublydistilled water and dried overnight at 1400 andcobalt estimated from the weight of the precipitatedcomplex (C).

RC(=NOH)N=N-ArA

RC(NO)=N-NH-ArB

[RC(NO)N=N-Ar].CoC

The anions NO;j, 50:-, CHaCOO-, Cl-, C104do not interfere with the estimation of Co(III).However, the transition metals like Fe, Mn, Ni, Cudo interfere. The method is particularly usefulfor the determination of Co(II) and Co(III) in theircoordination complexes. The aqueous solution ofthe C03+ or C02+ was obtained from the complexof cobalt (II or III) after digesting several timeswith an acid mixture containing cone. HNOa,conc. H2S04 and cone, HCl04• This solution wasthen used for the estimation of the metal gravi-metrically by arylazooximes as described above.The estimation of cobalt by this method was suc-cessfully carried out from its complexes of hydroxy-azophenols, salicylaldimines and o-hydroxyaceto-phenimines. The % error was always less thanO' 5. This method gives better results than (X.-

nitroso-B-naphthol method for the gravimetricestimation of cobalt-". The tris(phenylazoacetaldoxi-mato) Co(III) chelate (C, R=CHa) gives intensered purple colour in benzene; Amax 490, 390, 315(€ 11300, 14000, 41500). These solutions obeythe Lambert-Beer's law over a wide range of con-centrations. All these three bands were success-fully employed for the estimation of cobalt spectro-photometrically.

C02+ in aqueous solution was precipitatedby aq. ammoniacal solution of phenylazoacetal-

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