Environmental pollutants and toxicants degrade due to environmental fate mechanisms and biological xenobiotic metabolism. Some of these degradation products are more toxic than their parent compounds. High resolution mass spectrometry based non-targeted analysis can be used to screen for suspected metabolites in samples as well as identify new degradation products. However, each sample usually contains thousands of peaks that may require extensive time to fully annotate.  In this work, we propose an alternate approach called structure/reaction directed analysis for screening metabolites. We use specific paired mass distances (pmd) as a filter to screen the untargeted peak profiles. For example, a pmd of 15.99 could be a marker for xenbiotics phase I reactions for a hydrolysis, reduction or oxidation process. To this end, we have developed an automatic algorithm that can directly screen all of the compounds involved in such structures or reactions and visulize the results on mass to charge ratio and retention time profiles. Coupled with a GlobalStd algorithm which could reduce the redundant adducts, neutral losses, isotopologues or fragment ions to a single representative peak, our method can be used to investigate both known and unknown biotic or abiotic environmental process.<br/>Here we use NIST plasma standard referece matrials 1950 in a demonstration of our workflow. Among 2532 features from NIST samples, we found 527 independant peaks by the GlobalStd algorithm. For those peaks, we found 98 peaks involved in pmd 14.02(-CH<sub>2</sub>-), 84 peaks involved in pmd 15.99(O) and 205 peaks involved in pmd 2.02(break of doulble bonds). By overlapping the three pmd groups and combine the sub-structures, we could screen thirteen potential pollution metabolites involved in the serious of those three reactions.

Structure/reaction directed analysis for environmental metabolites

2019 Fall National Meeting

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