An indirect competitive biotin-streptavidin enzyme-linked immunosorbent assay for the determination of dimethyl phthalate (DMP) in milk and milk products.
After the "plasticizer event" in Taiwan, phthalic acid esters (PAEs) have been listed in "Inedible materials possibly added into food illegally" and "Commonly abused food additives." As one of the PAEs family, DMP has long been a problem of great concern due to its potential impacts on human health. In order to detect DMP with high sensitivity and specificity, a sensitive indirect competitive biotin-streptavidin enzyme-linked immunosorbent assay (BA-ELISA) has been established in this study. A high-titer rabbit polyclonal antibody (pAb-DMP) targeting DMP was obtained, and the procedures of BA-ELISA were optimized for the determination of DMP in milk and milk products. Under optimal conditions, good linearity was achieved within a range of 0.024 to 6.027 μg L(-1), with low cross-reactivity values for DMP structural analogues (lower than 10%). The median inhibitory concentration (IC50) was 0.356 μg L(-1) and the limit of detection (LOD) was 0.0082 μg L(-1). Finally, the concentrations of DMP in milk and milk products ranged from 1.03 μg kg(-1) to 7.23 μg kg(-1) by BA-ELISA. Satisfactory recoveries (90.26-112.38%) and coefficient of variation (CV) values (5.08-8.46%) were obtained. These results were consistent with those using gas chromatography-mass spectrometry (GC-MS), which further confirmed that the proposed BA-ELISA was accurate, specific, reliable and rapid for routine monitoring trace DMP residues in foodstuff, especially milk and milk products.