Direct and fast detection of chlorothalonil in soil samples using laser desorption VUV single photon post-ionization mass spectrometry

Abstract

Wide and abusive applications of fungicides (such as chlorothalonil) in agricultural production have caused various adverse effects on the environment, especially on the soil. Herein, a novel laser desorption VUV single photon postionization mass spectrometry (LDPI-MS) has been firstly applied to 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 in 118 nm ionization was determined to be 0.5 pmol per spot, ca. 1 mg/kg of chlorothalonil in soil. Moreover, no other additives were needed to assistant desorption/evaporation of chlorothalonil from soil samples and the detecting process could be rapidly completed on the basis of a time-saving sample pretreatment. The results demonstrated that LDPI-MS method held a great potential for detecting real natural soil contaminated with chlorothalonil.

Deep Ultraviolet Single‐Photon Ionization Mass Spectrometry

“…Simply by measuring the ions abundance relating to their mass-to-charge ratios, mass spectrometry is known as the most powerful tool for identifying the quantity and type of chemicals present in a sample. According to the ionization strategies, mass spectrometry can be classified into hard ionization techniques (typically by direct electron impact, i.e., EI method) [1] and soft ionization techniques which usually include photoionization (PI) [2][3][4][5][6][7][8], chemical ionization (CI) [9,10], matrix-assisted laser desorption/ionization (MALDI) [11], and electrospray ionization (ESI) [12]. Comparing with the EI technique which readily brings rigorous fragmentation for organic compounds, soft ionization techniques find their own advantages of maximal ionization efficiency without using high-energy electron impact.…”

“…Single-photon ionization mass spectrometry (SPI-MS) is known as an attractive soft-ionization technique resulting in simple mass identification neither utilizing matrix assistance nor rendering interference of multiple-charge ions [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Reasonable research interest has been attracted to SPI-MS due to the interference-free and fragmentation-free mass spectra, which is especially helpful for complex contaminant detection and mixed sample identification [7], for example, gasoline and diesel, cigarette smoke, and volatile organic compounds (VOCs) . The accurate measurements of molecular weight also enable promising applications in conformational analysis [49,50], real-time process monitoring [51], online characterization of aerosols [52,53], and pyrolysis and combustion chemistry [54].…”