QUANTIFICATION OF OCHRATOXIN-A IN SWINE KIDNEYS BY ENZYME-LINKED-IMMUNOSORBENT-ASSAY USING A SIMPLIFIED SAMPLE PREPARATION PROCEDURE

An improved procedure for sample preparation and quantitation of ochratoxin A (OA) in swine kidneys was developed. Kidney samples were homogenized in acidified ethyl acetate, centrifuged, sub-sampled dried, reconstituted with methanol and directly assayed using an indirect competitive enzyme-linked immunosorbent assay (ELISA). The rabbit antisera used in the development of this assay was found to have a high degree of cross-reaction with ochratoxins A and C but not with ochratoxins B, alpha, 4-OH-OA and two structurally similar molecules L-phenylalanine and citrinin with the values being 100, 80, 3.33, 10, 1.4, 0 and 0.04%, respectively. Extraction recoveries as determined by high performance liquid chromatography in kidneys spiked with 0.97 to 15.62 ppb OA were determined. The recovery values ranged from 91 to 110% with acceptable inter-assay coefficients of variation (CV) being obtained at the 3.9 ppb spiking concentration or higher. The lowest reproducible OA detection limit for the ELISA in the spiked swine kidney samples was 7.81 ppb with inter-assay CV of 8.85%. The ELISA analysis of the spiked samples correlated highly with conventional high-performance liquid chromatography (HPLC) analysis but was dependent on the conditions of the assay. Standards prepared in methanol or extract prepared from a kidney had correlation coefficients (r) of 0.91 +/- 0.09 and 0.94 +/- 0.07, respectively. The assay is sensitive, specific, simple and sufficiently accurate for routine analysis of swine kidneys.