Sensitivity Enhancement for Non-Volatile Fungicide Chlorothalonil Via Solvent Reduction of Particle Size in Thermal Desorption Photoionization Ion Mobility Spectrometry

The toxic hazard and residue increase caused by the widespread use of the fungicide chlorothalonil has attracted worldwide attention. Herein, a stand-alone thermal desorption photoionization ion mobility spectrometer was developed for rapid and sensitive determination of non-volatile chlorothalonil. The addition of solvent isopropanol successfully achieved a substantial increase in the signal intensity of chlorothalonil. Further investigation by scanning electron microscope showed that the particle size of the sample caused by isopropanol was reduced to one-seventh of the original, and the thermal desorption efficiency was greatly improved, which was the main reason for the sensitivity enhancement of chlorothalonil. In addition, isopropanol could also increase the signal intensity of CO 4 - by regulating the generation of the reactant ions in the negative ion mode, which was beneficial to the stable and sensitive detection of the sample. With the assistance of isopropanol, the quantification limit of chlorothalonil detected by thermal desorption on the aluminum foil sampling substrate was 0.046 ng μL −1 , which was sufficient to meet the current regulations for the analysis of chlorothalonil residues in food. As a demonstration, the proposed method, which required only a simple one-step pretreatment and took only 2 min for the whole process, has been successfully applied to analyze the effects of sunlight and rain on the residue of chlorothalonil in chili leaves.