10.1371/journal.pone.0079736.g002
Peter Husen
Peter
Husen
Kirill Tarasov
Kirill
Tarasov
Maciej Katafiasz
Maciej
Katafiasz
Elena Sokol
Elena
Sokol
Johannes Vogt
Johannes
Vogt
Jan Baumgart
Jan
Baumgart
Robert Nitsch
Robert
Nitsch
Kim Ekroos
Kim
Ekroos
Christer S. Ejsing
Christer S.
Ejsing
The ALEX lipid calculator.
Public Library of Science
2013
alex
lipid
2013-11-07 07:13:50
Figure
https://plos.figshare.com/articles/figure/_The_ALEX_lipid_calculator_/943433
<p>(<b>A</b>) Representative positive ion mode FT MS spectrum of a 10:1-phase lipid extract of hippocampus from a PRG-1 knockout mouse. Note that the detection of selected lock mass ions tris(ditert-butylphenyl) phosphate (chemical background, [M+NH<sub>4</sub>]<sup>+</sup>, calculated <i>m/z</i> 680.48022, measured <i>m</i>/<i>z</i> 680.47945, <i>m</i>/<i>z</i> offset = -0.00077) and TAG 17:1/17:1/17:1 (internal standard (IS), [M+NH<sub>4</sub>]<sup>+</sup>, calculated <i>m/z</i> 860.77017, measured <i>m</i>/<i>z</i> 860.76889 and <i>m</i>/<i>z</i> offset = -0.00128). The FT MS calibration offset is estimated as the average of the <i>m/z</i> offset for both lock mass ions, i.e. the FT MS calibration offset = -0.0010. (<b>B</b>) Screenshot of the ALEX lipid calculator showing information for endogenous lipid species PC 32:0 while applying the FT MS calibration offset = -0.0010. Note that the measured <i>m/z</i> of PC 32:0 is 734.56872 and that the calculated <i>m/z</i> adjusted for the calibration offset is 734.56843 which yield a <i>m/z</i> difference of 0.00029 corresponding to a mass error of 0.4 ppm. Without applying lock mass adjustment the mass error would be 1 ppm.</p>