Adsorptive stripping voltammetric and differantial pulse polarograpmc determination of selenium

(Ph. D. Thesis) Recai ÎNAM GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY October 1997 ABSTRACT In the first part of this study, determination of Se(IV) with thioglycollic acid (TGA) by adsorptive stripping voltammetry (Ads. CSV) on hanging mercury drop electrode (HMDE) was aimed. In 4 M HC1 solution, by applying -0,10 V deposition potential for 2 min on adsorption peak at -0,46 V (vs. SCE) belonging to Se(TV)-TGA complex was obtained. This peak showed linearity within 6,0x10"* - 8,5x1 0"7 M Se(IV) concentration range with a detection limit of 2,0x1 0"8 M Se(IV). With the developed method, lower quantities of selenium could be determined by increasing the deposition time and because of the good selectivity the interference of some metals could be prevented. Since TGA and Se(TV)-TGA complex have not been studied by electrochemical techniques before, they were investigated by d-c polarography, cyclic voltammetry (CV), constant potential coulometry (bulk electrolysis) and chrono-techniques. New reaction mechanisms were suggested according to the determined kinetic parameters. The metal to ligand ratio and the stability constant of the complex were determined spektrophotometrically. In the second part, a new determination method for selenium in the presence of lead, cadmium and copper was suggested using differential pulse polarography (DPP). Because of the observed interaction between selenium and the mentioned ions which was not known before, the previous works for the determination of selenium and these ions using DPP would not correct. During the polarographic determination of selenium in the presence of these ions a new peak was observed. This observation was attributed to an intermetallic compound formation and a mechanism for this formation was proposed Pb+2 + Se^) + 2 e +=£ PhSe^. Using the Ads. CSV for human blood sample 345±45 ng/L Se and applying DPP for the same blood sample 328+23 jig/L Se and 850±62 ug/L Pb were detected with a %90 confidence level. Science Code : 405.03.01 Key Words : Differential pulse polarography, adsorptive stripping voltammetry, chrono- tecniques thioglycollic acid, selenium (TV), lead-cadmium determination, blood Page Number : 21 1 Adviser : Prof. Dr. Güler SOMER