Direct Detection of Benzene, Toluene and Ethylbenzene at Trace Levels in Ambient Air by Atmospheric Pressure Chemical Ionization Using a Handheld Mass Spectrometer
The capabilities of a portable mass spectrometer for real-time monitoring of trace levels of benzene, toluene and ethylbenzene in air are illustrated. An atmospheric pressure interface was built to implement atmospheric pressure chemical ionization for direct analysis of gas-phase samples on a previously described miniature mass spectrometer (Gao, L. et al. Anal. Chem. 2006, 78, 5994-6002). Linear dynamic ranges, limits of detection and other analytical figures of merit were evaluated: for benzene, a limit of detection of 0.2 parts-per-billion was achieved for air samples without any sample preconcentration. The corresponding limits of detection for toluene and ethylbenzene were 0.5 parts-per-billion and 0.7 parts-per-billion, respectively. These detection limits are well below the compounds’ permissible exposure levels, even in the presence of added complex mixtures of organics exceeding the parts-per-million level. The linear dynamic ranges of benzene, toluene and ethylbenzene are limited to ~2 orders of magnitude by saturation of the detection electronics.