Determination of benzylpenicillin and other beta-lactam antibiotics in plasma and tissues using liquid chromatography mass spectrometry for residual and pharmacokinetic studies

A liquid chromatographic-atmospheric pressure ionization ion spray method for the simultaneous determination of four beta-lactam antibiotics in kidney, liver, meat, and plasma is described. The samples were extracted with acetone-trichloroacetic acid (4 mL), the organic layer then being evaporated and cleaned-up using LMS solid phase extraction columns. The method is simple, requires only small quantities of chemicals reagents and involves minimal manual work-up procedures. The lower limit of quantification was 15, 20, 40, and 60 ng/g, for kidney, liver, and meat and 40, 50, 80, and 100 ng/g for plasma, for benzylpenicillin (Penicillin G), phenoxymethyl penicillinic acid (Penicillin V), cloxacillin, and dicloxacillin, respectively.