Non-Selective Desorption of Immuno Precolumns Coupled On-Line with Column Liquid Chromatography: Determination of Aflatoxins

Abstract

Immuno precolumns, i.e. short columns packed with immobilized antibodies, are used for selective sample pretreatment coupled on-line to column liquid chromatography (LC). A column-switching system with an anti-aflatoxin immuno precolumn as a model system is described, which allows on-line transfer of the analytes from the immuno precolumn to the LC separation column. After selective preconcentration on the immuno precolumn the analytes are desorbed non-selectively with methanol-water (70:30, v/v), diluted on-line with water, subsequently reconcentrated on a second, reversed-phase precolumn and finally transferred to the LC separation column. Aflatoxin M1 can be preconcentrated from 30-ml samples with recoveries of 70%. The detection limit is 10 ng/1 and the calibration plot is linear up to 1 μg/1. The analysis time of the fully automated procedure is 45 min. The selectivity of the system is demonstrated with direct injections of spiked urine and milk samples. The regeneration and the stability of the immuno precolumn and the general applicability of non-selective desorption for on-line coupled immuno precolumn/LC systems are discussed.