Simultaneous determination of three barbiturates in pork by gas chromatography-mass spectrometry

Solid phase extraction (SPE) and gas chromatography-mass spectrometric method have been developed for the determination of barbital, amobarbital and phenobarbital residues in pork. The conditions for extraction, clean-up on C-18 column and methylation with CH3I of barbiturates were investigated and optimized. The methylized analytes were separated by HP-5 chromatographic column, detected by mass detector in electron impact and time program-selected ion manitoring mode ( EI/MIS) and quantified with the external standard calibration curve method. Good linear correlations have been obtained between the peak areas and spiked concentrations of the three barbiturates ( the calibration coefficients were above 0.99). The linear range was 2.5 similar to 50 mu g/kg. The average recoveries of the three barbiturates spiked in pork ranged from 65% to 112% and their relative standard deviations were between 5.4% and 17.2%. The limit of detection was 1 mu g/kg for the all three barbiturates.