Normalized mass mapping of Orbitrap data to define complex, polyglycerol‐based raw material compositions

Abstract

Kendrick Mass Mapping of complex sample compositions, via data derived by Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) at 1,000,000 resolution, is becoming more common. The Orbitrap mass spectrometer (Fourier Transform Axially Harmonic Orbital Trapping) also uses FT methods and indirect detection, though operating at a maximum resolution of 100,000. We define the more general case of Normalized Mass Mapping to any repeating oligomer unit (e.g., C(3)H(6)O(2)) and apply it to Orbitrap-based mapping of a complex polyglycerol ester, 'green' raw material. Mass measurement errors showed sub-ppm precision and accuracy in many cases, parameters that are critical to obtaining well-defined maps. Map-derived, raw-material-characterization parameters such as iodine value are compared with wet-chemical results and show reasonable agreement for our purposes. The methodology appears applicable to raw material control and eliminates wet chemical methods.

Normalized Mass Maps in Three-Dimensional Space Combining Kendrick-like Values with Chromatographic Separation for Enhanced Data Deconvolution

“…Previously, Strife and Mangels reported the following key concepts for uncluttered, well-aligned normalized mass maps: 6 (1) Using Fourier transform mass spectrometry, the highestresolution method available today, all m/z signals associated with a particular neutral molecular formula are identified and combined to produce a single (2) In order to obtain very well-defined maps, with "sharp" linearity and alignment of map glyphs, one must achieve high-precision mass measurements at the highest resolution possible. The previously reported figure of merit was sub-ppm.…”

“…Accuracy is important as well, but it had been reported many years ago that in the case of the Orbitrap, mass errors were highly systematic, which practically means glyphs tend to stay aligned. 6,7 Nevertheless, a simple internal recalibration following the principle in the original mapping work of Hughey et al 1 was applied successfully. In contrast to the Orbitrap, in those early studies using timeof-flight mass spectrometry, it was found that random massaccuracy errors led to dispersion of glyphs and poor linearity in maps.…”

“…3,4 A variation on Hatcher's mapping work was reported by McCarry et al, in 2010, examining chlorine-substitution reactions by using a mass normalization value based on the accurate mass of Cl minus that of H. 5 The sample extracts were derived from soil proximate to the site of an industrial-plasticsplant fire (polyvinyl chloride products manufacturing) that caused soil contamination with complex, chlorinated-polyaromatic hydrocarbons. Earlier that same year, Strife and Mangels 6 had introduced a further extension of mass mapping. A general renormalization was suggested for oligomers with repeating organic entities like polyethoxylate and was demonstrated particularly for the co-oligomer polyglycerol ( accurate m/z differences 6,7 to discover the origins and relationships of m/z signals.…”

“…Earlier that same year, Strife and Mangels 6 had introduced a further extension of mass mapping. A general renormalization was suggested for oligomers with repeating organic entities like polyethoxylate and was demonstrated particularly for the co-oligomer polyglycerol ( accurate m/z differences 6,7 to discover the origins and relationships of m/z signals. They named this general approach normalized-mass-mapping since "Kendrick" refers specifically to normalization of the periodic table to CH 2 = 14.0000 vs IUPAC C = 12.0000.…”

“…Sato and Fouquet subsequently introduced a series of papers discussing postacquisition processing methods (e.g., fractional base units) to enable spreading of the glyphs in the map and to facilitate the interpretation of these more complex maps, extending the range of instruments applied to oligomer problem solving. 9,10 In the case of polyglycerol polyesters, 6 which utilized the parsing and recombining of the FTMS data to neutral mass, monoisotopic peaks, and single representations of molecular entities, high-resolution maps were created. The calculation of raw-material control parameters for PGE (like average glycerol number, average ester chain length, iodine value, etc.)…”