Diagnostic potential of the pulsed discharged helium ionization detector (PDHID) for pathogenic Mycobacterial volatile biomarkers.

Pathogenic Mycobacteria cause diseases in animals and humans with significant economic and societal consequences. Current methods for Mycobacterial detection relies upon time- and labor-intensive techniques such as culturing or DNA analysis. Using gas chromatography and mass spectrometry, four volatile compounds (methyl phenylacetate, methyl p-anisate, methyl nicotinate and o-phenyl anisole) were recently proposed as potential biomarkers for Mycobacteria. We demonstrate for the first time the capabilities of a field-deployable, pulsed discharge helium ionization detector (PDHID) for sensing these volatiles. We determined the analytical performance of the PDHID toward these Mycobacterial volatiles. Detector performance was moderately affected over the temperature range of 150 to 350 °C. The linear dynamic range for all four analytes exceeded three orders of magnitude. The limits of detection (LOD) and quantitation (LOQ) were calculated as 150 and 450 pg respectively, for all compounds, except methyl phenylacetate (LOD and LOQ, 90 and 270 pg, respectively). Control charts revealed that the PDHID detection system was generally stable, and deviations could be traced to common causes and excluded special causes. Grob tests and ionization potential data suggest that the PDHID is capable of detecting Mycobacterial volatiles in a complex milieu such as culture headspace or breath samples from tuberculosis patients. The diagnostic potential of the PDHID is critical to our goal of a handheld, field-deployable 'sniffer' system for biological pathogens and chemical warfare agents.