GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC DETERMINATION OF SULFAMETHAZINE IN ANIMAL-TISSUES USING A METHYL TRIMETHYLSILYL DERIVATIVE/

A method is described for the determination of sulfamethazine in swine tissues by GC-MS,Samples are extracted with chloroform-acetone, follo wed sequentially by two solid-phase clean-up steps using silica gel an d SCX ion exchange, The extracts are then partitioned between sodium d ihydrogenphosphate (0.1 mol l(-1)) and methyl tert-butyl ether, the or ganic phase is evaporated to dryness and the sulfamethazine subjected to a double derivatization via methylation and silylation and determin ed by GC-MS in the selected-ion monitoring mode. Quantification is ach ieved by measuring the ratio of the abundances of the M - 65 (-HSO2) i ons of the derivatives of sulfamethazine and the internal standard, [p henyl-C-13(6)]sulfamethazine, at m/z 299 and 305, respectively. The pr esence of sulfamethazine can be confirmed using the abundance ratios o f the ions of mit 299, 300 (-SO2) and 349 (-CH3). Recovery values from muscle, kidney and liver spiked at 0.05, 0.2 and 0.4 ppm ranged from 86 to 114% with RSDs between 2.8 and 9.0%, The limit of detection for the assay is 0.01-0.02 ppm, The methyl/trimethylsilyl derivatives exhi bited better chromatography than the commonly used N-1-methyl derivati ves; for the same conditions, the peak was sharper and tailing was sig nificantly reduced.