Determination of thyreostatics in animal feed by micellar electrokinetic chromatography

The determination of the thyreostatics 2-thiouracil, its derivatives (4-methyl-2-thiouracil, 4-propyl-2-thiouracil and 4-phenyl-2-thiouracil) and methimazole in manufactured dried animal feed by micellar electrokinetic chromatography (MEKC) is described. A 99 +/- 5% extraction yield at the 20 micrograms g-1 level (n = 8) was achieved by shaking the milled fodder with methanol-1 M NaOH (80 + 20). Aliquots of the supernatant were injected in a 75 microns x 33.5 cm uncoated silica capillary using pressure; separation was performed at 23 degrees C with 15 kV (positive polarity) in a background electrolyte (BGE) containing 40 mM sodium dihydrogenphosphate, 50 mM sodium dodecyl sulfate and 15 mM …