Direct and fast detection of chlorothalonil in soil samples using laser desorption VUV single photon post-ionization mass spectrometry†
Wide and abusive applications of fungicides (such as chlorothalonil) in agricultural production have caused various adverse effects on the environment, especially on soil. Herein, a novel laser desorption VUV single photon post-ionization mass spectrometry (LDPI-MS) method has been applied for the first time for the direct and fast detection of chlorothalonil in soil. In the experiment, three different wavelength lasers were used as the ionization sources (SPI at 118 nm, REMPI at 266 nm and 355 nm) and the results showed that only SPI at 118 nm could achieve expected “soft” ionization. The limit of detection at 118 nm ionization was determined to be 0.5 pmol per spot, ca. 1 mg kg−1 of chlorothalonil in soil. Moreover, no other additives were needed to assist desorption/evaporation of chlorothalonil from soil samples and the detection process could be rapidly completed on the basis of a time-saving sample pretreatment. The results demonstrated that the LDPI-MS method holds great potential for detecting real natural soil contaminated with chlorothalonil.