An ultrasensitive gold nanoparticles improved real-time immuno-PCR assay for detecting diethyl phthalate in foodstuff samples.

A specific polyclonal antibody targeting diethyl phthalate (DEP) with the higher antibody titer at 1:120,000 has been obtained, and an ultrasensitive and high-throughput direct competitive gold nanoparticles improved real-time immuno-PCR (GNP-rt-IPCR) technique has been developed for detecting DEP in foodstuff samples. Under optimal conditions, a rather low linearity is achieved within a range of 4 pg L(-1) to 40 ng L(-1), and the limit of detection (LOD) is 1.06 pg L(-1). Otherwise, the GNP-rt-IPCR technique is highly selective, with low cross-reactivity values for DEP analogs (<5%). Finally, the concentrations of DEP in foodstuff samples by the GNP-rt-IPCR method range from 0.48 to 41.88 μg kg(-1). Satisfactory recoveries (88.39-112.79%) and coefficient of variation values (8.38-12.77%) are obtained. The consistency between the results obtained from GNP-rt-IPCR and gas chromatography-mass spectrometry (GC-MS) is 98.3%, which further proves that GNP-rt-IPCR is an accurate, reliable, rapid, ultrasensitive, and high-throughput method for batch determination of trace amounts of DEP in foodstuff samples.