Development and comparison of two competitive ELISAs for the detection of bisphenol A in human urine

Bisphenol A (BPA) is widely used to manufacture polycarbonate plastics and epoxy resins, which are in widespread use in China. Concerns about potential health impacts from exposure to BPA among the general population are increasing day by day. A sensitive and specific antibody was prepared to develop and compare direct and indirect competitive enzyme-linked immunosorbent assays (ELISAs) for the determination of BPA in human urine. The IC50 value and limit of detection (LOD) for the direct competitive ELISA were 5.5 ng mL(-1) and 0.03 ng mL(-1) respectively whereas, for the indirect competitive ELISA, the IC50 value and LOD were 7.0 ng mL(-1) and 0.08 ng mL(-1), respectively. We found that the direct competitive ELISA was more specific and sensitive than the indirect competitive ELISA. The established immunoassays were also applied in the determination of BPA in human urine samples. The results from fortified samples and real samples indicated that the direct competitive ELISA was more sensitive and reliable for the measurement of BPA in human urine as compared to the indirect competitive ELISA.