On‐line coupling of liquid chromatography and capillary gas chromatography for the determination of a trace pyrethroid insecticide in fruit extracts

Abstract

AbstractThe following paper presents a fast, selective, sensitive, and automated procedure for the residue analysis of the pyrethroid insecticide acrinathrin in various fruit samples by on‐line combination of Liquid Chromatography (LC) with capillary Gas Chromatography (GC) and an Electron‐Capture Detector (ECD). The loop‐type interface and Fully Concurrent Solvent Evaporation (FCSE) were chosen due to their ease of use and low volatility of acrinathrin. Commercially available LC diol columns with small internal diameters (2.1 mm) provided the selectivity required for the separation of the solute from matrix components and permitted the transfer of fraction volumes up to 500 μl into the retention gap, located inside the gas chromatograph. Optimization of the operating conditions with standard solutions showed the influence of the GC initial transfer temperature on the response of acrinathrin and the quantitative nature of the transfer was established by liquid scintillation counting. The linearity and precision were studied with the aid of calibration plots, whereas quantitative recoveries of the analyte (at least 95 %) were determined in spiked fruits. Compared to the corresponding off‐line technique, the on‐line approach allows us to reach lower detection limits (ppb level when 20 μl LC injections are performed) with excellent repeatability between 0.6 and 6.6 %. Moreover, the integrated analytical set‐up is robust, less time‐consuming and subsequently brings a marked improvement in the sample preparation step of complex biological matrices. Finally, the versatility of the system renders it highly suitable for the determination of other similar pyrethroids in order to develop a multiresidue method.