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Optimization of ESI Parameters for Comprehensive Lipid Analysis
Author(s) -
Gathungu Rose M,
Larrea Pablo,
Sniatynski Matthew J,
Kristal Bruce S
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.945.2
Subject(s) - lipidome , lipidomics , electrospray ionization , chemistry , fragmentation (computing) , mass spectrometry , ionization , chromatography , extractive electrospray ionization , ion , biochemistry , computer science , protein mass spectrometry , organic chemistry , operating system
Untargeted lipidomics is mainly performed using electrospray ionization mass spectrometry (ESI‐MS) either with or without chromatographic separation. ESI‐MS enables structural annotation and quantitation of lipids, which can then be used to determine the biological relevance of lipids. The use of ESI‐MS requires the optimization of the MS method to ensure detection of as many lipids as possible and the correct annotation of these lipids. Here we look at two factors that affect ESI‐MS that, in turn, influence lipid detection and identification. First, we show that in‐source fragmentation at the ESI source can generate artifacts that can have identical masses to other common lipids leading to the misannotation of the in‐source fragment ions as true lipids. In‐source fragmentation can lead to (i) missing the biologically relevant lipids (i.e., a false negative), and/or; (ii) incorrect assignation of a phenotype to an incorrect lipid (i.e., false positive). To mitigate this problem, we have conducted a systematic evaluation of ESI source parameters with the objective of obtaining uniformly appropriate source conditions for a wide range of lipids, while, at the same time, reducing in‐source fragmentation. Second, since analysis in both the positive and the negative ionization modes is required for a complete coverage of the lipidome, we show that the optimal conditions for analysis of lipids in the positive and negative MS ionization modes are different. We have evaluated the additive effect on ionization of lipids in both the positive and negative ionization modes. Our results indicate that the optimal additives for negative ionization of lipids are 1 mM ammonium acetate with 0.1 acetic acid and the optimal additives for positive analysis are 5 mM ammonium formate with 0.1% formic acid. Support or Funding Information NIH