Solid-phase extraction of sulfamethazine in milk with quantitation at low ppb levels using thin-layer chromatography.

Abstract A method for the solid-phase extraction and thin-layer chromatographic (TLC) quantitation of sulfamethazine (SMZ) residues in milk is presented. Sulfabromomethazine was added as an internal standard to homogenized milk samples which were then diluted and passed through C 18 solid-phase extraction columns. The C 18 columns were eluted with methanol, and interfering components in the methanol were removed by passing eluate over an acidic alumina column. The analyte was then concentrated on a small ion-exchange resin. SMZ was eluted and applied to a silica gel TLC plate. Fluorescence detection was induced with fluorescamine and quantitated with a scanning densitometer. Recoveries were 88.36–103.15% in the analysis range [0.51–15.34 ppb (μg/l)]. The average recovery over the analysis range was 96.07%, with a coefficient of variation of 12.52%.