Polyurethane foam as a sorbent for continuous flow analysis: preconcentration and spectrophotometric determination of zinc in biological materials

Abstract

A simple and accurate procedure was developed to preconcentrate and determine zinc in biological matrices. A polyurethane foam (PUF) minicolumn was used for the first time for on-line preconcentration. This system was applied to preconcentrate zinc from aqueous solutions which is sorbed as zinc–thiocyanate complex. Then, the complex was eluted by water and zinc was determined by spectrophotometry using 4-(2-pyridylazo)-resorcinol. The method was validated by the analysis of several biological certified reference materials. The detection limit was 0.9 ng ml−1 and the RSD was 1.2% for 1 min preconcentration time. Generally, concentration of Fe(III), Al(III), Mo(VI), Ni(II), Mn(II), Cu(II), and Co(II) found in biological matrices did not interfere. Dynamic ranges of concentration from 20 to 100 ng ml−1 (1 min preconcentration time) and from 5 to 20 ng ml−1 (5 min preconcentration time) achieve a sample throughput of 20 and 8 samples per hour and a preconcentration factor of 8 and 32, respectively.