Determination of chloralose residues in animal tissues by liquid chromatography-electrospray ionisation tandem mass spectrometry

A relatively rapid and specific method for the determination of chloralose in animal tissues by LCMSMS was developed. Isocratic reverse phase HPLC was used to introduce samples for electrospray negative ionisation tandem mass spectrometry. Methanol extracts were diluted to approximate the mobile phase composition, then filtered prior to analysis. Residues were identified by monitoring the multiple reaction monitoring (MRM) transitions of precursor ions mass:charge (m/z) 309 and 307 to a common m/z 161 product ion. Qualitative and quantitative confirmation data were acquired simultaneously by monitoring alternative MRM transitions. Calibration was linear over a working range of 0.025–1.3 μg/ml, and the limit of quantitation (LOQ) was 0.28 mg/kg for liver. The mean recovery was 88.5% from chicken muscle tissue fortified at 198–237 mg/kg, and ranged from 81.3 to 94.3% from liver tissue fortified at 1–52 mg/kg. The method is compared to a gas chromatography (GC) procedure previously employed.