Evaluation of thermal desorption analysis on a portable GC-MS system

The HAPSITE-ER-TD (Hazardous Air Pollutants on Site Extended Range HAPSITE-ER) portable gas chromatograph-mass spectrometer (GC-MS) combines the sensitivity of a thermal desorption (TD) GC-MS with the advantages of field-portable instrumentation. Though previous iterations of the HAPSITE have been extensively evaluated in the literature, performance assessment of the TD-equipped instrument is lacking. In this manuscript, the variability in the HAPSITE-ER-TD response was established for both internal standards and test compounds across three instruments over a 5-week time course. These data show poor normalised internal standard reproducibility with % RSD values from 17.84% to 49.97% on the HAPSITE-ER-TD when compared to a bench-top instrument (% RSD < 11.6%), suggesting that use of TD tubes preloaded with an internal standard may be valuable for normalisation purposes. Though our determined method detection limit (MDL) values reveal that substantial variabilities exist between separate HAPSITE-ER-TD systems, MDL values comparable to the standard bench-top equipment can be achieved. Additionally, data generated with the TO-15/TO-17 65 component target compound mix and JP-8 jet fuel show statistically significant (p value = 0.0014) compound-dependent system carryover on the HAPSITE-ER-TD, indicating that procedural modifications to eliminate instrumental carryover may be necessary. This study establishes several limitations associated with the use of the HAPSITE-ER TD accessory with suggestions for addressing the shortcomings to allow for reliable field use.