Rapid monitoring of dicyclohexyl phthalate in foods using the direct competitive ELISA

A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) has been developed for the quantitative detection of the dicyclohexyl phthalate (DCHP) in some liquid food. Specific polyclonal antisera to DCHP was raised, using the hapten-bovine serum albumin conjugates as the immunogen. The conjugate of horseradish peroxidase (HRP) with antibody was used as the detectable probe to provide the direct measurement of the antigen and analyte, which was synthesised by a modified glutaraldehyde method. Under the optimised assay, the quantitative working range was from 0.1 to 100 ng mL⁻¹ (R ²=0.9989), with a limit of detection (LOD) of 0.03 ng mL⁻¹, and a recovery of 96.6–112.4%. The specificity and accuracy of developed method were evaluated. The cross-reactivities of antibody with structurally related phthalate esters were less than 10%. Results obtained indicated that the dc-ELISA was a sensitive, low expense method to improve the routine monitoring of trace constituents in some liquid food.