Critical assessment of the Kendrick mass defect analysis as an innovative approach to process high resolution mass spectrometry data for environmental applications

The growing application of high resolution mass spectrometry (HRMS) over the last decades has dramatically improved our knowledge about the occurrence of environmental contaminants. However, most of the com-pounds detected remain unknown and the large volume of data generated requires specific processing ap-proaches. Therefore, this study presents the concepts of mass defect (MD), Kendrick mass (KM) and Kendrick mass defect (KMD) to the expert and non-expert reader along with relevant examples of applications in envi-ronmental HRMS data processing. A preliminary bibliometric overview indicates that the potential benefits of KMD analysis are rather overlooked in environmental science. In practice, a simple calculation allows trans-forming a mass from the IUPAC system (normalized so that the mass of 12C is exactly 12) to its corresponding KM normalized on a specific moiety such as CH2 (the mass of CH2 is exactly 14). Then, plotting the KMD according to the nominal KM allows revealing groups of compounds that differ only by their number of CH2 moieties. For instance, data processing using KM and KMD was proven particularly useful to characterize natural organic matter in a sample, to reveal the occurrence of polymers as well as poly/perfluorinated alkylated substances (PFASs), and to search for transformation products (TPs) of a given chemical.

Automated summary

The use of high resolution mass spectrometry (HRMS) has greatly improved our understanding of environmental contaminants, but many detected compounds remain unknown and require specific processing methods. This study introduces the concepts of mass defect (MD), Kendrick mass (KM), and Kendrick mass defect (KMD) and provides examples of their applications in environmental HRMS data processing.