Non-target Environmental Forensics Using GC×GC–TOF MS and Automated Chromatographic SubtractionEnvironmental Forensics
Oral Presentation
Presented by C. Widdowson
Prepared by L. McGregor1, S. Smith1, M. Edwards2, J. Grandy2, K. Murtada2
1 - SepSolve, 4 Swan Court, Peterborough, Other, PE78GX, United Kingdom
2 - SepSolve, 1060 Guelph Street, Kitchener, Ontario, N2B 2E3, Canada
Contact Information: [email protected]; 01733669222
ABSTRACT
Environmental forensics relies on the ability to detect and characterize unknown or unexpected chemical pollutants in complex matrices. Conventional one-dimensional gas chromatography–mass spectrometry (GC–MS) often lacks the resolving power to separate the thousands of compounds present in environmental samples, meaning important details can be missed.
Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOF MS) overcomes these limitations by providing vastly expanded separation space and highly sensitive detection, enabling confident non-target screening. This approach allows the identification of a wide range of organic pollutants, including pesticides, pharmaceuticals, and emerging contaminants, even at trace levels.
To efficiently interrogate these complex datasets, we applied probability-based subtraction of the raw chromatographic data. Unlike conventional subtraction, where minor variations between high-intensity peaks can dominate and obscure meaningful differences, probability-based subtraction suppresses these small variations, generating a clean background that highlights compounds of interest. The resulting subtracted data can be processed using standard workflows for automated integration, library searching, and rapid reporting, allowing key chemical differences between sampling sites to be identified in minutes without advanced statistical expertise.
This workflow is demonstrated using river water extracts from two sampling sites, illustrating its capability for rapid, reliable non-target environmental forensics and providing insights into pollutant sources and trends.
