Extraction and enzyme immunoassay of sulfadimethoxine residues in channel catfish (Ictalurus punctatus) muscle.
Four commercially available enzyme immunoassays were evaluated for the detection of sulfadimethoxine (SDM) residues in channel catfish muscle. Matrix solid-phase dispersion (MSPD) extracts of samples (n = 60, 0.5 g) fortified with SDM at 0, 25, 50, 100, and 250 ng/g were used in all assays. Intra-assay variations for 2 MICROTITER well-based quantitative assays, SIGNAL sulfamethazine test and IDS SDM One-Step ELISA (enzyme-linked immunosorbent assay), were 5.6 and 7.7%. Interassay variations for these tests were 7.9 and 16.6%. The agreements between evaluators for 2 membrane-based, visually determined assays, CITE Sulfa Trio and EZ-SCREEN: SDM, were 77 and 95%. Performance values, as indicated by sensitivity, specificity, efficiency, and positive and negative predictive values, were 100, 92, 95, 89, and 100%, respectively for the SIGNAL test; 100, 94, 97, 92, and 100% for the IDS test; 98, 71, 82, 69, and 98% for the CITE test; and 98, 94, 96, 92, and 99% for the EZ-SCREEN assay. Eight sulfonamides cross-reacted in the SIGNAL test; EC-50 values (concentrations causing 50% inhibition of color development compared with blanks) varied from < 0.1 to 45 micrograms/mL. The EC-50 value for SDM was 0.25 microgram/mL. The CITE test cross-reacted with sulfachloropyridazine at 10 micrograms/mL. The IDS and EZ-SCREEN tests had no significant cross-reactivity with other sulfonamides. N-Acetyl SDM reacted like the parent SDM in all assays. Performance results indicated that MSPD extracts of catfish muscle may be used in these immunoassays to screen catfish muscle samples for violative levels of SDM residue.
Walker
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Louisiana State University, School of Veterinary Medicine, Department of Veterinary Physiology, Pharmacology, and Toxicology, Baton Rouge 70803-8420.
Barker
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D000818:Animals; D003429:Cross Reactions; D004350:Drug Residues / Q000032:analysis*; D007059:Ictaluridae; D007124:Immunoenzyme Techniques; D009132:Muscles / Q000737:chemistry*; D015588:Observer Variation; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013412:Sulfadimethoxine / Q000032:analysis*
D013412:Sulfadimethoxine