Real-time monitoring of the work environment using ion-mobility spectrometry

Ion-mobility spectrometry (IMS) is a promising system for on-site real-time monitoring of volatile organic compounds (VOCs). Calibration curves derived from shifts in nominal arrival-time spectra of chemical substances relative to those of water clusters enable quantitative analysis at high concentrations.

This study investigated the adaptability of IMS to real-time monitoring of VOCs in the work environment, using toluene as a test case. Toluene concentrations were measured by IMS at one-minute intervals during a ten-minute simulated cleaning operation.

The arrival-time shift was lower at high concentrations because ion production saturates as the toluene concentration approaches the limit of ionizability, with a resulting decrease in slope of the calibration curve. The lower limit of quantification for toluene was assumed to be 13.3 ppm because no arrival-time shift was observed at lower concentrations. The time-averaged toluene concentration measured by IMS for 10 minutes of operation was 45.8 ppm, which is comparable to that measured by gas chromatography-mass spectrometry (GC-MS; 44.3 ppm) within ~3%.

Our results indicate that the measurement of toluene concentrations is possible at one-minute intervals by IMS, making it possible to track rapid changes in workplace conditions. Therefore, IMS can measure exposure to VOCs in real-time with an accuracy similar to that of GC-MS.