CONFIRMATION OF CHLORAMPHENICOL RESIDUES IN EGG BY GAS-CHROMATOGRAPHYHIGH-RESOLUTION MASS SPECTRORMETRY AND COMPARISON OF QUANTITATION WITH GAS-CHROMATOGRAPHY ELECTRON-CAPTURE DETECTION

Determination of chloramphenicol (CAP) residues in egg by gas chromato graphy/high-resolution mass spectrometry (GC/HRMS) with negative chemi cal ionization and gas chromatography with electron capture detection (GC-ECD) is described. A cleanup based on acetonitrile extraction foll owed by solid-phase extraction with silica gel and gel filtration colu mns was developed for extraction of CAP residues from whole egg. For q uantitation, the internal standards used were the meta isomer of CAP ( m-CAP) for GC-ECD and both m-CAP and deuterium-labeled CAP (D-5-CAP) f or GC/HRMS. For GC/HRMS, evaluation was performed by selecting charact eristic ions at m/z 466 for CAP and m-CAP and at m/z 471 for D-5-CAP. Both methods were validated with egg samples fortified at 0.4-2.0 mu g /kg and lyophilized egg samples from animals treated at the 1 mu g/kg concentration level. The coefficient of variation was below 10%. Limit s of detection and quantitation of both methods were about 0.3 and 0.5 mu g/kg, respectively, for confirmation of CAP residues, the relative ion abundance (m/z 466 and 468) was calculated. Further confidence wa s obtained by comparison of accurate monoisotopic masses from a spectr um library.