20 February / March 2018
Comprehensive, Non-Target Characterisation of Blinded Environmental Exposome Standards Using GCxGC and High Resolution Time-of-Flight Mass Spectrometry
by Lorne Fell*, Todd Richards and Joe Binkley LECO, Saint Joseph, Michigan, USA *Corresponding Author:
lorne_fell@leco.com
The importance of non-targeted analysis (NTA) methods has been steadily growing over the last several years as witnessed by an increase in publications demonstrating their utility. Several of these papers have outlined a standard protocol for the NTA portion of environmental analysis [1-3]. However most of these publications or methods have not quantifiably examined the ability to identify unknown chemicals in a sample. The purpose of the present investigation is to apply new technologies to this field of study, evaluate its ability to identify known unknowns and in so doing propose an appropriate quantifiable paradigm for identification.
There exists much precedence on identification with GC/ MS from the early studies of the NIST library [4-8] and previously established United States Environmental Protection Agency (EPA) and European Union methodologies. However, many of these methods were specific to certain (classes of) compounds or did not fully embrace new technologies such as GCxGC. These procedures left gaps in quantifying the certainty of identification, which has led to several additional proposals for systematic identification [3, 9]. The Norman Association conducted the first major
Figure 1: Number of identified hits per sample (Total A+B versus # expected). The hits are broken out into 4 separate sections, total A level matches/sample, total B level matches/sample, the combine total of A+B matches and the actual number of components added by the EPA.
attempt to evaluate the methods; publishing a critical review on water analysis using high resolution mass spectrometry [3]. A total of 18 institutes in 12 countries analysed an extract of the same water sample from the River Danube and the recommendation was to produce a more comprehensive sample set for future work. Subsequently the EPA has proposed and launched a collaborative project with that goal in mind; utilising researchers who can investigate practical
means to achieve confident identifications of the xenobiotic profiles within environmental samples. A round robin trial of increasing experimental complexity was designed and samples delivered to academic and industrial researchers; called the EPA’s Non-Targeted Analysis Collaborative Trial (ENTACT).
The EPA’s goals are to produce benchmark methods for analysis and reporting of non-target analysis results, standardise and facilitate future analyses, and identify areas of
improvement. The project includes 3 phases;
Phase 1: Identification of chemicals within ten mixtures which were blinded to the study participants. These blinded mixtures contained chemicals from the EPA CompTox Chemistry Dashboard [10].
Phase 2 included analysing individual standards to confirm the results from the first phase.
Phase 3 is to analyse standard references
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