Development of determination of di-n-octyl phthalate (DOP) residue by an indirect enzyme-linked immunosorbent assay

Abstract

In this research, the hapten di-n-octyl 4-aminophthalate (DOAP) was designed and synthesised successfully. It was used to couple with carrier proteins, bovine serum albumin (BSA) and ovalbumin (OVA) by diazotization reaction for immunogen (DOP–BSA) and coating antigen (DOP–OVA), respectively. Rabbits were immunised with DOP–BSA; polyclonal antiserum was raised and determined by competitive indirect enzyme-linked immunosorbent assay (ciELISA). After optimisation, a ciELISA was established. The quantitative working range for DOP was 5–75 ng/mL with the detection limit of 1.9±0.1 ng/mL and the IC₅₀ of 19.2±1.1 ng/mL. The optimised ELISA had cross-reactivity of 22.6%, 17.6% and 21.2% with di-iso-octyl phthalate (DIOP), di-n-butyl phthalate (DBP) and di-hexyl phthalate (DHP), respectively. The result of the detection of polyvinyl chloride (PVC) samples showed that the immunoassay we developed had high-accuracy contrast with high-performance liquid chromatography electrospray ionisation tandem mass spectrometry analysis and it could be qualified to determine di-n-octyl phthalate (DOP) residue in PVC samples.

Keywords:

• phthalates
• residues
• hapten synthesis
• ciELISA
• polyvinyl chloride
• immunoassay