Rapid analysis of chemical warfare agents by metal needle-enhanced low-temperature plasma mass spectrometry
Chemical warfare agents (CWAs) are highly toxic compounds that have been used in wars or terrorist attacks. There is an urgent need to develop fast, inexpensive and sensitive on-site CWA inspection techniques. In this study, a low-temperature plasma (LTP) probe was directly coupled with a metal needle tip where sample molecules were desorbed and ionized in the ambient environment for subsequent analysis using mass spectrometry (MS). We found that metal needles greatly increased the ionization efficiencies compared with non-conductive sample substrates. Based on this finding, a method for rapid and highly sensitive detection and quantification of CWA-related compounds, including dimethyl methylphosphonate (DMMP), isopropyl methylphosphonic acid (IMPA), methylphosphonic acid (MPA) and thiodiglycol (TDG) was established. The whole workflow was completed in 10 s with a dynamic range of 1–500 μg L−1, and the limit of detection (LOD) was 500–980 ng L−1. Analytes were spiked in real-world water samples and quantified using this approach with satisfactory recoveries. Our results indicated that metal needle-enhanced LTP-MS will be a useful technique for the highly sensitive detection of CWAs.