[Automatization of colorimetric serum zinc determination using the Bayer RA 1000 autoanalyzer]

A colorimetric method for the determination of zinc in serum was adapted for use with the Bayer RA 1000 autoanalyzer. Zinc is dissociated from proteins by guanidinium hydrochloride and complexed with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N- sulfopropylamino-)phenol (5-Br-PAPS). Precision (within-run CVs from 1.4 to 4.2%; between-run CVs from 3.5 to 8.1%), accuracy (93 to 103%) and detection limit (1.15 mumol/l) were sufficient for routine determinations. Moreover, results obtained with the proposed Bayer RA 1000 method were in good agreement with those obtained by flame atomic absorption spectrometry (FAAS) which could be considered the reference method. For 119 sera, the correlation coefficient r was found to be 0.958 and the regression line was as follows: serum zinc (RA 1000) = 0.96 serum zinc (FAAS) + 0.8 mumol/l. Moreover, 98% of the differences between colorimetry and FAAS were within the range Md +/- 1.96 SDd, where Md is the mean of the differences and SDd is the standard deviation of the differences.