ONLINE COUPLING OF LIQUID-CHROMATOGRAPHY AND CAPILLARY GAS-CHROMATOGRAPHY FOR THE DETERMINATION OF A TRACE PYRETHROID INSECTICIDE IN FRUIT EXTRACTS

The following paper presents a fast, selective, sensitive, and automat ed procedure for the residue analysis of the pyrethroid insecticide ac rinathrin in various fruit samples by on-line combination of Liquid Ch romatography (LC) with capillary Gas Chromatography (GC) and an Electr on-Capture Detector (ECD). The loop-type interface and Fully Concurren t 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 requir ed for the separation of the solute from matrix components and permitt ed the transfer of fraction volumes up to 500 mu l into the retention gap, located inside the gas chromatograph. Optimization of the operati ng conditions with standard solutions showed the influence of the GC i nitial transfer temperature on the response of acrinathrin and the qua ntitative nature of the transfer was established by liquid scintillati on 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 correspon ding off-line technique, the on-line approach allows us to reach lower detection limits (ppb level when 20 mu l LC injections are performed) with excellent repeatability between 0.6 and 6.6%. Moreover, the inte grated analytical set-up is robust, less time-consuming and subsequent ly brings a marked improvement in the sample preparation step of compl ex 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.