Incurred samples from a pig treated with sulphamethazine and spiked sa
mples of the same concentration were compared during frozen storage. T
he contents of sulphamethazine in the different types of samples decre
ased similarly to about 50% after 15 months. When the samples were hea
t treated before analysis the sulphamethazine concentration did not ch
ange over time. Samples of bovine and porcine muscle were spiked with
five different sulphonamide drugs and stored frozen for 3 months. Twen
ty-four hours at room temperature or 1 week at -20 degrees C did not a
ffect the drug levels but after 1 month of frozen storage the levels i
n bovine and porcine muscle had decreased significantly. After 3 month
s the average decrease was 35% in bovine and 55% in porcine muscle.