Searching for Markers in GC-MS Analysis Results with pyAIR

Nitzan Tzanani, Analytica Chemistry, Israel Institute for Biological Research, Ness Ziona, Israel (nitzant@iibr.gov.il)

Marker search is a non-targeted screening approach, focused on sorting through analysis results of samples, searching for compounds that characterize specific group. Breathomics is focused on the search of biomarkers in breath samples – volatile organic compounds (VOCs) that have a clinical significance in diagnosis and treatment of pathologies.

pyAIR was developed as a data processing software tool in the field of breathomics. It was design to read GC-MS analysis results, searching for VOCs biomarkers in multi-group datasets. pyAIR combines retention time (RT) coupled with spectral similarity to align compounds across samples, and statistically compares the groups for compounds that differ by intensity. The reliance on whole spectrum comparison circumvents the ambiguity of GC-MS analysis of low concentration low molecular mass VOCs.

pyAIR was successfully tested and evaluated on gaseous samples spiked with 27 model VOCs at six concentrations, divided into three groups, down to 0.3 nL/L. All analytes were correctly detected and aligned. More than 80% were found to be significant markers with a p-value < 0.05, while low rates of false markers were found. These results demonstrate the potential of pyAIR in the field of breathomics, with capability to differentially examine several groups, such as stages of illness.

The capability of pyAIR to search for similarities and irregularities in GC-MS analysis results of complex mixtures has the potential to apply to various fields. These application may vary from xenobiotics in clinical samples to aroma constituents in food products.