PMC

Single quadrupole correlated ion monitoring data of cystine (cell extract), leucine (plasma extract), and isoleucine (plasma extract) correlates the precursor and multiple fragment ions to generate a correlated ion chromatogram. The data was peak picked, aligned and threshold filtered to provide deconvolution of the enhanced in-source multiple fragment ion monitoring data. Correlated ion monitoring also evaluates the ion ratios to monitor if they match the expected (p:f1:f2:f3) ratio, if not the molecule is flagged as being contaminated with co-eluting species. A possible correction for this would be to eliminate the contaminating ion as a quantifier. Additionally, reconstructed fragment spectra are generated allowing for continuous monitoring of ion ratios and matching against genuine standards. p: precursor ion; f1, f2 and f3: fragment ion 1, 2, and 3, respectively.

(a) Single quadrupole MS quantitive analysis general experimental design. (b) Fragment ion intensity ratio for enhanced in-source multiple fragment ion monitoring single quadrupole and MRM triple quadrupole comparison between electrospray ionization positive mode and negative mode. (c) Fragment ion intensity ratio comparison between lipids/fatty acids and other molecules. Log transformed intensity ratio was used in (b) and (c). (d) A typical extracted ion chromatogram of a single quadrupole channel (xanthine in solvent, fragment ion 108 at RT 2.80 min). (e) A typical extracted ion chromatogram of a triple quadrupole transition (xanthine in solvent, transition 151>108 at RT 2.84 min). The number next to the single quadrupole channel or triple quadrupole transition in (d) and (e) represents the maximum intensity of the EIC.

Representative chromatograms and product mass spectra of a meibomian wax ester m/z 620.5, and of its fatty acid product ions m/z 257, 271, 283, and 285. (A) Total ion chromatogram of ion m/z 620.5 (B) and (B') Single reaction monitoring MS chromatogram of ion m/z 257.3 produced in the following automatic experiment: m/z 620.5@cid0.72@cid1.44@cid2.59 → m/z 256, and the mass spectrum of the GLC-ITMS peak with retention time of 41.12 min. Panels (C) and (C') Single reaction monitoring chromatogram of a product ion m/z 620.5 → m/z 271.3, and the mass spectrum of the GLC-ITMS peak with retention time of 41.12 minutes. (D) and (D') Single reaction monitoring chromatogram of a product ion m/z 620.5 → m/z 285.3, and the mass spectrum of the GLC-ITMS peak with retention time of 41.08 minutes. (E) and (E') For comparison purposes, an extracted ion chromatogram of ion m/z 283.3 (a product of spontaneous in-source fragmentation of oleic-acid based WE) is shown. The ion eluted as a GLC-ITMS peak with retention time of 41.7 minutes, and coeluted with another ion (m/z 618.5; not shown). The compound was identified as tertacosanyl oleate.

(a) Example of three Multiple Reaction Monitoring (MRM) extracted ion chromatograms from a single precursor ion (b) Data structure grouped by precursor ion (peptide) [].