Spectrofluorimetic determination of cysteine based on the fluorescence inhibition of Cd(II)-8-hydroxyquinoline-5-sulphonic acid complex by cysteine

A spectrofluorimetric method for the determination of cysteine at trace and ultra tract levels (0-1.82 x 10(-5) mol l(-1)) has been developed. It is based on the efficient inhibition action of cysteine on the fluorescent system of Cd(II)-8-hydroxyquinoline-5-sulphonic acid complex (Cd(II)-HQS) (lambda (ex) 364.8 nm, lambda (em) 510.4 nm) solution at pH 8.5. The method has been applied to protein hydrolysate and cystine electrolyte samples. (C) 2001 Elsevier Science B.V. All rights reserved.