[Indirect study of zinc-cystine complex reaction by FAAS]

Each state of cystine and zinc ion in aqueous solution under different pH conditions was calculated by computer, and the scatter diagram was given. Under the influence of solution pH, the mechanism of complex reaction in indirectly determining cystine by flame atomic absorption spectrometry with ZnS was studied. The soluble complex ion is composed of 0 valence cystine Cys-Cys+/-, -1 valence cystine Cys-Cys+/- and -2 valence cystine Cys-Cys(2-) with Zn(OH)2. The theoretical analysis from computing and scatter diagram dovetail very well with the data determined from the experiments. The structure of soluble zinc-cystine complex ion is, [(COO-) CH (NH3+) CH2S-SCH2 CH (NH3+) COO-] Zn (OH)2, [(COO-) CH (NH3+) CH2S-SCH2CH(NH2)COO-]Zn(OH)2 and [(COO-)CH(NH2)CH2S-SCH2CH(NH2)COO-]Zn(OH)2.