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A competitive bio-barcode immunoassay is described for the trace detection of parathion in water, pear, cabbage, and rice samples. It is based on amplification by platinum nanoparticle acting as a nanozyme. Gold nanoparticles (AuNPs) were modified with (a) monoclonal antibodies (mAbs) against parathion, and (b) thiolated single-stranded DNA (ssDNA) oligonucleotides. Magnetic nanoparticles (MNPs) were functionalized with ovalbumin coupled with parathion hapten. Parathion and its hapten compete with mAbs on the surface of the AuNPs. Subsequently, the platinum nanoparticles (PtNPs) probe, which was functionalized with the complementary thiolated ssDNA (C-ssDNA), was added to the reaction mixture for the detection of parathion. The signal was catalytically amplified by coupling with platinum nanozyme using teramethylbenzidine and H2O2 as the chromogenic system. The immunoassay has a linear range that extends from 0.01–50 μg·L−1, and the limit of detection is 2.0 × 10−3 μg·L−1. The recoveries and relative standard deviations (RSDs) ranged from 91.1–114.4% and 3.6–15.8%, respectively. The method correlates well with data obtained by gas chromatography-tandem mass spectrometry (GC-MS/MS). [ABSTRACT FROM AUTHOR]

A class-specific molecular imprinted polymer (MIP) is described for simultaneous recognition of prometryn and simetryn prior to their determination via a fingerprint signal (at 974 cm−1 and 1074 cm−1) in the surface enhanced Raman scattering (SERS) spectra that were acquired in the presence of gold nanoparticles. The imprinted nanoparticles were applied to the analysis of rice and wheat samples spiked with both herbicides. The method has fairly good recoveries (72.7-90.9%) with a relative standard deviation of 1.7-7.8%, and a 20 μg·kg−1 limit of detection. The imprint factors (compared to non-imprinted polymers) are 5.3 for prometryn and 4.2 for simetryn (both at 10 μg·mL−1 of the initial solution).A MIP-SERS method was developed for simultaneous detection of triazine herbicides (prometryn and simetryn) in food samples. [ABSTRACT FROM AUTHOR]