Rapid colorimetry of zinc in seminal fluid.

This colorimetric method for determination of zinc in seminal liquid is based on the reaction between zinc and 4-(2-pyridylazo)resorcinol in a buffered solution at pH 9.5. It is very simple, fast (approximately equal to 10 min), and economical. It can be used to determine zinc in "whole" semen, seminal plasma, or isolated spermatozoa. We verified its accuracy for sample concentrations up to 0.4 g/L by comparison with a reference method based on atomic absorption spectroscopy of acidic wet-ashed samples. Calcium and magnesium do not interfere, even in concentrations exceeding the physiological values. Between-run precision at a normal concentration of 0.14 g/L is about +/- 7 mg/L; within-run precision at the same concentration is about +/- 2 mg/L.