Residue analysis of pesticides in food by two-dimensional gas chromatography with capillary columns and parallel detection with flame-photometric and electron-capture detection

Abstract

Two-dimensional gas chromatography on two capillary columns is used for pesticide residue analysis in food samples. Both columns are connected by effluent splitting to the selective flame-photometric and electron-capture detectors, which are linked on-line to independent data processing channels. About 100 halogenated and organophosphorus pesticides, together with three internal standards, are screened on the first column with methylsilicone as the stationary phase. The compounds are recognized by their retention data and response to the two selective detectors. In a second analysis, peaks eluted from the first column are transferred by means of pneumatic switching to the second column with phenyl cyanopropyl methylsilicone as the stationary phase. This cutting of narrow fractions can be executed with high accuracy and reproducibility (“live chromatography”) by using time programming of the cutting valve. The final identification of all investigated pesticides is achieved by evaluating the set of linked retention data and, additionally, the response ratio of the two detectors characteristic for each compound. The application of the method to two real food samples, fortified with chlorinated and organophosphorus pesticides, is demonstrated.