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

Trace gas emissions from municipal solid waste landfills: A review

“…Compared to ex-situ techniques, on-site practices tend to have higher detection limits (e.g. at ppb or ppm levels) and larger variability (Harshman et al, 2017). Additionally, fewer compounds can be detected and quantified, and their separation is also often poor, due to the short analytical time (Marć et al, 2015).…”

Data quality improvement for field-portable gas chromatography-mass spectrometry through the use of isotopic analogues for in-situ calibration

“…Recently, extensive testing of the HER was performed to identify the limitations of this portable GC-MS system that are problematic during field experiments (Harshman et al 2017). It was observed that a few select units showed extreme variability in the measured response to IS#2, which lead to a greater variability in normalised data when compared with non-normalised data.…”

“…It was observed that a few select units showed extreme variability in the measured response to IS#2, which lead to a greater variability in normalised data when compared with non-normalised data. While those experiments demonstrated the capability of obtaining minimum detection limits (MDLs) comparable to gold-standard (benchtop) instrumentation (Martin et al 2016), issues of interinstrument variability have been observed that suggest the typical practice of applying relative response factors (RRfs) obtained from one or more representative units across a broad swath of deployed field instruments is likely to generate unacceptable errors in quantification (Harshman et al 2017). Thus, the US Environmental Protection Agency (EPA)-prescribed practice of using an internal standard compound for normalising instrument responses is unreliable on this instrumentation because of the lack of on-site calibration (US Environmental Protection Agency 1999).…”

Air2Liquid Method for Selective, Sensitive Detection of Gas-Phase Organophosphates

“…In order to identify and quantify low concentrations of sVOCs, multiple mechanisms can be deployed: (1) deployment of sensitive detection techniques, (2) preconcentration of air samples, and/or (3) assay technologies for signal amplification. Standard high-sensitivity detection systems, such as photoionization detectors (PIDs), are cross-reactive and/or can be confounded by background contaminants, preventing target identification without incorporating chemical separation or orthogonal information. − Since these sensors are often deployed in environments where common interfering compounds are present (i.e., isopropyl alcohol, toluene, hexanes) that have PELs > 100 ppm, >100× higher than toxic compounds of interest, even techniques that can fingerprint the environment, such as ion-mobility spectrometry (IMS) and surface acoustic wave (SAW) lack the resolution needed to identify and discriminate acetylcholinesterase inhibitors. − Preconcentrators using hydrophobic sorbents followed by thermal desorption have been demonstrated for sVOCs using GC-MS, GC-PID, and GC-SAW instruments, where the temperature at which the compound is eluted provides information toward identification. However, both PIDs and SAWs lack the absolute specificity for the analyte of interest, leading to potential false positives.…”

“…4−7 Since these sensors are often deployed in environments where common interfering compounds are present (i.e., isopropyl alcohol, toluene, hexanes) that have PELs > 100 ppm, >100× higher than toxic compounds of interest, even techniques that can fingerprint the environment, such as ion-mobility spectrometry (IMS) and surface acoustic wave (SAW) lack the resolution needed to identify and discriminate acetylcholinesterase inhibitors. 5−7 Preconcentrators using hydrophobic sorbents followed by thermal desorption have been demonstrated for sVOCs using GC-MS, 8 GC-PID, 9 and GC-SAW instruments, where the temperature at which the compound is eluted provides information toward identification. However, both PIDs and SAWs lack the absolute specificity for the analyte of interest, leading to potential false positives.…”