Abstrait

A simple spectrophotometric determination of trace level cadmium using 1,5-diphenylthiocarbazone in cationic micellar media

Humaira Khan, M.Jamaluddin Ahmed,M.Iqbal Bhanger

A very simple, selective and highly sensitive direct spectrophotometric method is presented for the rapid determination of cadmiumat ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) as a newmicellar spectrophotometric reagent(max=500nm) in aqueous solution. The presence of micellar system avoids the previous steps of solvent extraction and reduces the cost, toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The molar absorptivities of the cadmium-dithizone complex formed in the presence of the cationic cetyltrimethylammoniumbromide(CTAB) surfactant are almost ten times the value observed in the standardmethod and themaxima of the absorption are shifted about 20 nmwhen compared with the standard method, resulting in an increase in the sensitivity of the method. The reaction is instantaneous and the absorbance remains stable for over 24h. The average molar absorption coefficient and SandellÂ’s sensitivity were found to be 1.2ï‚´05 L mol-1cm-1 and 5ngcm-2 of Cd, respectively. Linear calibration graphs were obtained for 0.01-10mg L-1 of Cd; the stoichiometric composition of the chelate is 1:2(Cd: dithizone). Themethod is characterized by detection limit of 3g L-1 ofCd. The interference from over 60 cations, anions and complexing agents has been studied at 1mg L-1 of Cd. The method was successfully used in the determination of cadmium in several standard reference materials(alloys and steels, soil, bovine liver and human hair), environmental water samples(potable and polluted), biological samples(human blood and urine), soil samples and complex syntheticmixtures. Themethod has high precision and accuracy(s=0.01 for 0.1mgL-1).