Ultrasensitive detection of trace chemical warfare agent-related compounds by thermal desorption associative ionization time-of-flight mass spectrometry.

Abstract A thermal desorption associative ionization time-of-flight mass spectrometer was developed for ultrasensitive detection of semi-volatile chemical warfare agents (CWAs). The excited-state CH2Cl2-induced associative ionization method presented a soft ionization characterization and an excellent sensitivity towards CWAs. The detection sensitivities of the investigated nine CWA-related substances were 2.56 × 105–5.01 × 106 counts ng−1 in a detection cycle (30 s or 100 s). The corresponding 3σ limits of detection (LODs) were 0.08–3.90 pg. Compared with the best-documented LODs via the dielectric barrier discharge ionization (DBDI) and secondary electrospray ionization (SESI), the obtained LODs of the investigated compounds were improved by 2–76 times. Additionally, the measured sensitivity of 2-Chloroethyl ethyl, a proxy for mustard gas, is 550 counts pptv−1, which exceeds the DBDI and SESI's corresponding values (4.4 counts pptv−1 and 6.5 counts pptv−1) nearly by two orders of magnitude. A field application simulation was conducted by putting a strip of PTFE film contaminated with the CWA-related agent into the thermal desorption unit. The simulation showed that the sensitivities of the instrument via swipe surveying could achieve 2.19 × 105 to 5.23 × 106 counts ng−1. The experimental results demonstrate that the excited-state CH2Cl2-induced associative ionization is an ultrasensitive ionization method for CWAs and reveal a prospect for improving the detection of CWA species future.