Membrane Preconcentration of Nalidixic and Piromidic Acids and Simultaneous Determination Using a Synchronous Solid‐Phase Phosphorescence Approach

Abstract

A preconcentration membrane for the retention and phosphorimetric determination of pharmaceuticals nalidixic and piromidic acids is proposed. The membrane has a circular zone of plasticized PVC adhered to the surface of a polyester strip, which constitutes the preconcentration area where the analytes are retained by absorption from a solution that contains it. Measurement of intrinsic phosphorescence in the synchronous phosphorescence spectra performed at 281/371 nm for nalidixic acid and 331/471 nm for piromidic acid make the resolution of the mixture possible. The applicable concentration range, detection limit, and precision (as relative standard deviation) are from 0.3 to 3.0 mg · l−1, 0.08 mg · l−1, and 5.1% for nalidixic acid and from 0.03 to 0.15 mg · l−1, 0.002 mg · l−1, and 5.2% for piromidic acid. The method was applied to the determination of residues of both pharmaceuticals in cow milk and human urine.