Gowda, H. Sanke

Keshavan, B.

English

NOPR

INDIAN J. CHEM., VOL. 14A, AUGUST 1976Spectrophotometric Determination ofRu(III) With Promethazine HydrochlorideH. SANKE GOWDA & B. KESHAVANPostgraduate Department of Chemistry, University of MysoreMysoreReceived 5 November 1975; accepted 26 December 1975Promethazine hydrochloride forms a red-colouredcomplex with Ru(III) in hydrochloric or sulphuric acidmedium. The complex exhibits absorption maximumat 514-518 nm. An eleven-fold molar excess of thereaient is necessary for the full development of colourintensity. The sensitivity of the reaction is 0·016 Ilg/ems in hydrochloric acid medium and 0·024 Ilg/cml in8ulphuric acid medium. Beer's law is valid over theconcentration ranges 0·4-4·4 ppm and 0·5-11·6 ppm inhydrochloric and sulphuric acids respectively. Theeffects of acidity, time, order of addition of reagents,temperature, reagent concentration and diverse ionsare reported. The composition of the complex asdetermined by molar ratio method is 1: 2. The stab-ility constant (log K) of the complex is 10·02±0·1 in3M hydrochloric acid and 10·65±0·1 in 1·5M sulphuricacid.pROMETHAZINE hydrochloride (PH) was pro-posed as a new reagent for the spectrophoto-metric determination of Pd(II)1. A survey ofchemical literature showed that no attempt wasmade to study the reaction between PH andRu(III). In the present investigation, the authorshave studied the reaction between Ru(III) and PHand proposed PH as a sensitive reagent for thespectrophotometric determination of Ru(III).A stock solution of ruthenium was prepared bydissolving 0·9850 g of Ru(III) chloride (M/s JohnsonMatthey, London) in dilute Analar hydrochloric acidand diluted to 1 litre to give 1M with respect tothe acid. It was standardized gravimetrically bythe thionalide methods. The stock solution wasfurther diluted to give a standard solution of 20ILg/ml.A 0·2% aqueous solution of PH (May & Baker)was prepared and stored in an amber-coloured bottlein a refrigerator.Solutions of acids and diverse ions of suitableconcentrations were prepared using analytical grade.reagents.Determination of Ru(III) ~ To an aliquot of thestock solution containing 10-290 ILg of rutheniumwere added 10 ml of 7·5M hydrochloric acid (or7·5 mlof 5M sulphuric acid) and 4 ml of 0·2% PHsolution and the volume made up to 25 ml by addingdoubly distilled water. The solution was mixedwell and the absorbance measured at 515nm afterstanding for 15 min against a reagent blank pre-pared in the same way, The amount of rutheniumwas then deduced from the standard calibrationcurve.PH reacts with Ru(III) at room temperature inthe presence of either hydrochloric or sulphuricacid to form a red-coloured complex. The rate ofreaction and stability of the colour depend on thenature and concentration of the acid medium.630Nitric acid cannot be used as reaction mediumbecause it oxidizes PH to a red-coloured radical.The absorption spectra of the ruthenium-PH com-plex exhibits maximum absorbance at 514-518 nmin both the acids. Reagent and ruthenium do notabsorb around this wavelength. Maximum absor-bance is achieved in the acid range 2'0+OM withrespect to hydrochloric acid and 1'0-2'2M withrespect to sulphuric acid. Below 2M H'Cl or 1MH,S04 the development of red cclour of the complexis slow. The reagent is slowly oxidized at aciditieshigher than 4'OM HCl or 2·2M H2S04, An acidstrength of 3'OM Hel or 1·5M H2S04 was chosenfor all subsequent work.The ruthenium-PH complex is formed at roomtemperature and constant absorbance values areobtained 15 min after adding the reagent toruthenium solution in Hel medium and immediatelyin sulphuric acid medium. The absorbance valuesremain constant for 45 min in Hel or 60 min inHlISO,. An eleven-fold molar excess of the reagentis required in order to obtain maximum absorbance.The optimum amount of the reagent is 4 ml of a0·2 % PH solution in a final volume of 25 ml inboth acids. The absorbance readings are constantin the temperature range 10-40°. No change in theabsorbance is observed when the order of additionof reactants was changed.Beer's law is valid over the concentration ranges0·4+4 ppm in Hf.l and 0·48-11·6 ppm in HzSO,.The optimum concentration range for the effectivespectrophotometric determination evaluated byRingborri's met hod8.4 is 1,2+2 ppm in Hel or1·4-11·0 ppm in H2S04, For A = 0'001, the sensiti-vity of the reaction is 0-016 ILg/cmt in Hel or0·024 ILg/cms in H2S04, Molar absorptivities of6·3 X 108 litre mole? cm-l in HCl and 4·2 X 108 litremole"! em? in H2S04 are obtained for the ruthe-nium-PH complex. Sample solutions containing 100ILgof ruthenium, prepared by the standard procedure.gave a mean absorbance of 0·250 and 0·165 in Heland H2S04 respectively with a standard deviationof 0·014 and a relative error of ± 0'4%.The effect of anions and cations which oftenaccompany ruthenium were studied with 4 ILg ofruthenium per ml in Hel or H2S04 medium. Anerror of 2% in the absorbance was consideredtolerable. The results presented in Table 1 showthat the tolerance limit is higher in H2S04 medium.TABLE 1 - TOLERANCE LIMIT OF DIVERSE IONS IN THEDETERMINATIONOF 4 PPM OF Ru(III)Anion Tolerance limit Cation Tolerance limitppm ppmHCl H2SO4 nci H.SO,cr 8500 9500 Rh(III) 21 24F" 1240 1460 Pd(II) 0'2 0·4Br- 980 1035 Os(VIII) 0·6 o-s1- 0·4 0·6 Ir(III) 9 10NOi 900 5450 Pt(IV) 30 32SOl- 6000 6000 Fe(lII) 1·5 2PO:- 1430 1470 Co(U) 90 96CH3COO- 7865 8080 Ni(U) 1100 1140EDTA 25 5800 Cu(II) 500 1235Efforts to increase the tolerance limit of cations bythe addition of masking agents were unsuccessful.The continuous variation! and slope ratio"methods failed to reveal any definite compositionfor Ru(III)-PH complex owing to the masking ofyellow colour of ruthenium at relatively low rangeof reagent concentration. However, the molar ratiomethod' shows a sharp break at the ruthenium toreagent ratio of 1: 2 in the presence of HCI orH2SO,. The apparent stability constant (log K) ofthe complex in 3M HCI and in 1·5M H2S04 at27° ± 1°C as evaluated by molar ratio method' is10'02±0'1 and 10·65±0·1 respectively.References1. SANKE GOWDA, H. & KESHAVAN, B., Indian J. Chem.,14 (1976), 293.2. BEAMISH, F. E., The analytical chemistry of the noble metals(Pergamon Press, London), 1966, 250.3. RINGBOM, A., Z. analyt, Chem., 115 (1938). 332.4. AYRES, G. H., Analyt. Chem., 21 (1949), 652.5. JOB, P., Ann. Chim., 9 (1928), 113.6. HARVEY, A. E. & MANNING, D. L., J. Am. chem . Soc., 72(1950), 4488.7. YOE, j. H. & JONES, A. L., Ind. Engng Chem., 16 (1944),111.Spectrophotometric Determination of Ru(III)with Trifluoperazine DihydrochlorideH. SANKE GOWDA & P. G. RAMAPPAPostgraduate Department of Chemistry, University of MysoreMysoreReceived 6 October 1975; accepted 11 December 1975A spectrophotometric method has been devised forthe determination of microgram amounts of Ru(III)utilizing the reaction between trifluoperazine dihydro-chloride and ruthenium(III) in strong sulphuric orhydrochloric acid. The orange-red complex hasabsorption maximum at 500 nm with molar absorpti-vity 4·285 x 103 litre mole= em>, The sensitivity is0·0233 I1g Ru cm! for log 1011=0.001. Beer's law isvalid over the concentration range 1·0-8·8 I1grutheniumml-l and the optimum range for the effective spectro-photometric determination is 2·0-8·0 I1gRu ml-l• Thecomposition of the complex is 1: 1. The influence ofsome common ions is reported.A WIDE variety of chromogenic reagents em-ployed for the spectrophotometric determinationof Ru(III) have been reviewedv+, Unfortunately,the formation of the complexes between rutheniumand the chromogenic reagents is quite slow inaqueous media at room temperature, and conditionsfor obtaining reproducible colour development areusually quite empirical, i.e. heating for a specifictime at a specific temperature is required.During the investigation+ on the spectrophoto-metric determination of Pd(II) with trifluoperazinedihydrochloride (TFP) , the latter was found to givean orange-red colour with Ru(III) instantaneouslyin the presence of sulphuric or hydrochloric acid.This has now been made the basis of a spectro-photometric method for the determination of micro-gram amounts of Ru(III). The proposed methodoffers the advantages of simplicity, reasonableNOTESsensitivity, insensitivity to temperature and rapiddetermination in higher acid concentration withoutthe need for extraction or heating.A stock solution of ruthenium was prepared bydissolving 0·9924 g of Ru(III) chloride (Mis JohnsonMatthey, London) in 500 ml of 1M hydrochloricacid and standardized gravimetrically by precipitat-ing ruthenium as the hydrated oxide, followed bycareful ignition in air and then reducing in hydrogenand cooling in an atmosphere of carbon dioxide.A stock solution of TFP (Smith, Kline & French)was prepared by dissolving O·50 g of TFP in 250 mlof doubly distilled water. This was stored in anamber-coloured bottle in a refrigerator.All other reagents were of analytical grade andwere used without further purification.Determination of Ru(III) - To a sample solutioncontaining 25-220 ILgof Ru(III) was added sulphuricacid so that the final solution was 1·5M in sulphuricacid. 5 ml of 0·2% TFP was added and the solu-tion diluted to 25 ml by adding doubly distilledwater. The solution was mixed thoroughly andthe absorbance measured at 500 nm against acorresponding reagent blank. The Ru(III) concen-tration of the sample solution was then deducedfrom the standard calibration curve.A detailed investigation of Ru-TFP complex hasshown that TFP forms an orange-red colouredcomplex instantaneously in the presence of sulphuricor hydrochloric acid (PH 0·0-3'5). The maximumcolour development takes place at room temperatureand requires no heating. The sensitivity of thereaction and the stability of the orange-red complexdepend on the nature and strength of the acidmedium. The sensitivity in four acid media is inthe order of HCl>H2SO,>HsPO,>AcOH. Themaximum colour development takes place imme-diately in hydrochloric or sulphuric acid medium andafter 10 min in phosphoric or acetic acid mediumafter mixing the reagents. The orange-red complexis stable in 1·5M H2S04, HCI, AcOH and HsPO, for40, 15, 10 and 5 min respectively. Hence thesulphuric acid medium has been selected. Nitricacid medium cannot be used as it oxidizes TFP to ared-coloured radical.The absorbance of the complex remains constantin 0·2-2·0M H2S04, At higher acid concentrations(>3·0M) the reagent slowly undergoes oxidationto a red- coloured radical.It was found that a nineteen-fold molar excess ofthe reagent was necessary in order to assure com-plete complexation. The orange-red complex exhi-bits absorption maximum at 500 nm at which pointthe reagent does not absorb. The absorbancevalues remained constant for 40 min and wereinsensitive to temperature in the range 5-60°C.The order of addition of reagents was not critical.Beer's law was obeyed in the concentration range1·0-8·8 (log Ru(III) ml'". The optimum concentra-tion range evaluated by Ringbom methodt-" was2·0-8·0 flg Ru(III) ml+, The molar absorptivity is4·285 X 103 litre mole+ em+ and the Sandell sensiti-vity index is 0·0233 p.g Ru(III) crrr".Composition and nature of , the complex - Thecomposition of the complex was studied by Job'smethod9,lo of continuous variation using equimolar631

Spectrophotometric Determination of Ru(III) With Promethazine Hydrochloride

http://nopr.niscair.res.in/bitstream/123456789/53802/1/IJCA%2014A%288%29%20630-631.pdf

Spectrophotometric Determination of Ru(III) With Promethazine Hydrochloride

Abstract

Similar works

Full text

Available Versions

NOPR