On-site Simultaneous Determination of Neonicotinoids, Carbamates, and Phenyl Pyrazole Insecticides in Vegetables by QuEChERS Extraction on Nitrogen and Sulfur co-doped Carbon Dots and Portable Mass Spectrometry.

In food safety monitoring, on-site and simultaneous detection of a variety of insecticides with different concentrations in the same matrix is necessary. However, the task remains challenging. In this study, a novel nitrogen and sulfur co-doped carbon dot (N, S-CD) was synthesized and used as a QuEChERS clean-up reagent to reduce matrix interferences in the determination of insecticides in vegetables. In addition, a portable mass spectrometer (µ-MS) was employed, without chromatography separation, to directly determine neonicotinoids, carbamates, and benzopyrazole insecticides (with acetamiprid, imidacloprid, thiamethoxam, fipronil, and carbofuran as models) in the pretreated samples. The N,S-CD µ-MS method exhibited effective clean-up performance with satisfactory matrix effects between -15.2% and 15.7%. The recoveries of spiked vegetable samples ranged from 82.2% to 109.7% for the five target insecticides, and the relative standard deviations (RSDs) ranged from 3.8% to 16.5%. The linear ranges were from 2.0 to 5.0 ng/g, with low detection limits (LOD) from 0.5 to 1.0 ng/g. Moreover, the total pretreatment and detection time was within 20 min. Thus, the incorporation of N,S-CD with QuEChERS extraction, together with the portable µ-MS system, could be a promising and feasible strategy for on-site, rapid, and simultaneous detection of various insecticides in vegetables.