Rapid multiresidue extraction method of organochlorinated pesticides from fish feed

A rapid multiresidue extraction method for organochlorinated pesticides from fish feed was developed, which is based on the extracted fat treatment by n-hexane, concentrated sulphuric acid and ENVI-carb, a graphitized non-porous carbon material. The final residue, obtained in about 50 min, was dissolved in isooctane and analysed by gas chromatography with an electron capture detector (GC/ECD). The presence of the extracted pesticides was confirmed by gas chromatography-mass spectrometry (GC/MS). Concentration of sulphuric acid and amount of ENVI-carb were optimized in order to improve analytes recovery, accuracy and detection limits. This simple and relatively fast method allowed a high recovery of the HCB, Lindane, HEPO, p,p'-DDE, p,p'-DDD, p,p'-DDT residues, with mean values in the range 68-124% at four fortification levels (12.5, 25.0, 50.0, 100.0 ng/g), and coefficients of variation between 1.9 and 20.2%. Detection limit were equal to 3.0 ng/g, related to fat, for all pesticides, and calibration curves were linear (r > 0.999) in the range of explored concentrations from the detection limit to 100 ng/g. For all pesticides a good repeatability was obtained (CV% values in the range 0.23-4.16%) when a sequence of six injections of the isooctane extraction solution was performed. The usefulness of the proposed method has been tested by the analysis of fish feed samples.