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An enzyme mmmnoassay for sulphametbazme was developed usmg an antiserum rzused m rabtuts by unmumaatlon agamst a sulphamethazme dlazo derwatrve coupled to bovme serum albumm Horseradish perox~dase coupled to sulphametbazme by a carbodurmde method was selected as a tracer The dose of sulphametbazme that caused 50% bmclmg mhiilfion was 3 8 ng per well wth a 2-h mcubation tune at 37oC and 12 ng per well wrth a 16-h mcubatlon tune at 4'C The assay was evaluated by usmg control and sulphamethazme-fortdied mu&e and bver samples These samples were treated by the matnx sohd-phase dqerslon method for the subsequent lsolaaon of the drug The method allowed a dete.&on lmut well below the tolerance tit (0 1 mg kg-') generally appbed for sulphamethazme +r& Enzymatic methods, Immunoassay; Ammal &sues, Sulphamethazme, Trues
Sulphonanudes have a broad spectrum of antlbactenal atiwty and are frequently mcorporated 111 feeds as a practical method for the prevention or treatment of a variety of so-called "confinement diseases" 111 ammals, mamly pigs However, there are concerns for human health because of the possible presence of residues of the drug 111 meat [l] The US Food and Drug Admmlstratlon (FDA) requires a 19day mthdrawal period of feed contammg sulphamethazme before slaughter and has estabhshed Its tolerance hmlt m tissues for human consumption at 0 1 mg kg-' [2-51 Although dtierent sulphon-