Fluorometric assay of cyanophoric pyrethroids based on benzothiazole modified carbon quantum dots

Abstract

A fluorometric assay based on benzothiazole carbon quantum dots (benzothiazole-CDs) was developed for the determination of cyanophoric pyrethroids (CPs, e.g., cypermethrin, deltamethrin and fenpropathrin). Benzothiazole-CDs were synthesized by amidation and condensation reaction of N, S-CDs based on a hydrothermal method. CPs could be hydrolyzed to generate cyanide ions under alkaline conditions, which reacted with the benzothiazole-CDs and destroyed the big conjugate system of the CDs inducing the quenching of fluorescence. Thus, CPs could be determined based on the fluorescence change. In order to obtain the optimum fluorescence conditions for the assay of CPs, the reaction time, temperature, the pH value of the detection system and the concentration of benzothiazole-CDs were optimized. The results demonstrated that under the optimum conditions, the concentration of CPs showed good linearity with the fluorescence quenching efficiency in the range of 0.01–2 mg L⁻¹ and the correlation coefficient (R²) was between 0.991 and 0.995. The limits of detection were between 2.7 and 2.8 μg L⁻¹. The assay was applied to the detection of CPs in real samples including underground water, rice and apples. The recoveries were between 74.2 and 103.5% and the relative standard deviations (RSDs) were between 1.4 and 9.7%.