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Hg2+ is a serious environmental contaminant that can cause severe damage to the immune and nervous systems, and Hg2+ monitoring is critical. Herein, we report a novel, simple, and sensitive Hg2+ sensor based on the enhanced peroxidase‐like activity of chitosan–gold nanoparticles (CS‐AuNPs). The peroxidase‐like activity of the CS‐AuNPs can be markedly enhanced by Hg2+ as seen by the deeper color and increased absorbance at 652 nm. This improved catalytic ability was used to develop a sensitive and selective colorimetric sensor for Hg2+ detection. The limit of detection via the absorption spectra is as low as 0.02 μM. The mechanism underlying the enhanced catalytic ability is discussed. This approach is label‐free, simple, and offers detection with the naked eye. Thus, it has potential applications for the detection of Hg2+ in environmental and food samples. [ABSTRACT FROM AUTHOR]

A rapid, reliable and sensitive reverse-phase high-performance liquid chromatography method with fluorescence detection (RP-FLD-HPLC) was developed and validated for simultaneous analysis of the abamectin (ABA), emamectin (EMA) benzoate and ivermectin (IVM) residues in rice. After extraction with acetonitrile/water (2 : 1) with sonication, the avermectin (AVMs) residues were directly derivatised by N-methylimidazole (N-NMIM) and trifluoroacetic anhydride (TFAA) and then analysed on RP-FLD-HPLC. A good linear relationship (r2 > 0.99) was obtained for three AVMs ranging from 0.01 to 5 µg ml−1, i.e. 0.01–5.0 µg g−1 in rice matrix. The limit of detection (LOD) and the limit of quantification (LOQ) were between 0.001 and 0.002 µg g−1 and between 0.004 and 0.006 µg g−1, respectively. Recoveries were from 81.9% to 105.4% and precision less than 12.4%. The proposed method was successfully applied to routine analysis of the AVMs residues in rice. [ABSTRACT FROM AUTHOR]