A simple and sensitive colorimetric assay of zinc in serum using cationic porphyrin.

A direct colorimetric method is presented for simple and sensitive determination of serum zinc in 0.05-ml samples, using a cationic porphyrin, alpha,beta,gamma,delta-tetrakis(4-N-trimethylaminophenyl) porphine tetratoluenesulfonate salt (ttmapp, epsilon = 41.5 x 10(4) l/mol per cm at 421 nm). 7-Iodo-8-hydroxyquinoline-5-sulfonic acid (Ferron) as an accelerator for the incorporation of zinc into ttmapp was most effective. Interference of iron, copper and conjugated bilirubin in serum can be eliminated in the presence of proteins such as albumin in serum. Within-run and between-run coefficients of variation (CV) were in the ranges of 0.76-3.59 and 2.08-5.20%. A good correlation was observed between this method and atomic absorption spectrometry (AAS).