Correction of accurate mass measurement for target compound verification by quadrupole time-of-flight mass spectrometry

Abstract

The aim of this work is to evaluate quadrupole/time-of-flight (QTOF) mass spectrometry for simultaneous measurement of accurate mass and quantification of a target by using a stable isotopically labeled internal standard. Mixtures of caffeine and 13 C 3 -caffeine (internal standard) at different concentration ratios were analyzed by capillary HPLC/QTOF. A calibration plot for quantification is linear over a factor of 20. Without invoking any correction scheme, the mass accuracy seriously degraded when the ratio of the mass standard to the test compound was not unity. The accuracy could be restored to approximately 2 ppm by using a quadratic function to correct the measured mass as a function of the measured signal ratio of target and internal calibrant. (J Am Soc Mass Spectrom 2005, 16, 406 -408)

Accurate mass error correction in liquid chromatography time-of-flight mass spectrometry based metabolomics

“…In addition, a significant improvement in the mass determination was obtained for low intensity signals, as the mass error remained within 1 ppm when mass points with intensities lower than 150 counts were included in the analysis. To our knowledge, the only previous numerical attempt at intensity-dependent error correction was based on using 13 C labeled internal standards (Kofeler and Gross 2005). The method proposed here can be applied using endogenous metabolites and does not require additional measurements and expensive 13 C labeling.…”

“…With the proposed trail-building procedure it was not possible to extract pure components, due to overlap in both (Clauwaert et al 2003;Kofeler and Gross 2005) for obtaining TOF-MS mass accuracy \3 ppm deviation, the proposed method is simpler and does not require additional experiments. For the derivation of the intensity corrected accurate mass using the method of (Kofeler and Gross 2005), 13 C labeled standards are needed. Internal mass calibrants for each mass range can be applied for local mass correction in the mass region of the calibrant (Clauwaert et al 2003).…”

“…In addition, the problem of stochastic noise due to low count rates arises at low signal intensity (Gu et al 2005). To overcome these effects, a correction function can be derived using internal standards measured at different ratio's, which can then be applied to the subsequent analytical runs (Kofeler and Gross 2005). This typically improves accuracy from 5 to 2-3 ppm.…”

Identification of Novel Fluorochemicals in Aqueous Film-Forming Foams Used by the US Military

“…High accuracy masses (to the ten-thousandth of a mass-to-charge unit) were calculated as an average over the entire peak width, which has been reported to give the most reproducible results (Figure S3, S4). 26 Possible elemental compositions of the high-accuracy masses were calculated along with the error, which is reported as the deviation of the detected mass from the calculated elemental composition's mass (in parts-per-million [ppm]). In addition, the elemental composition of the +1 and +2 isotopes were used to rank the likely parent elemental compositions.…”

Automated sub-ppm mass accuracy on an ESI-TOF for use with drug discovery compound libraries

“…Finally, TOF instruments are the most widely available, least expensive, and easily coupled with chromatography, but suffer from the lowest published mass accuracy, usually at or about Ϯ5 ppm [16] with an inter-laboratory comparison showing that 24% of measurements on TOF instruments yielding Ն10 ppm mass accuracy [10]. Further, automation of accurate mass analyses using ESI-TOFMS has been difficult due to dead time effects on the time-to-digital conversion (TDC) circuitry that results in peak shifts to lower masses at high sample concentrations [15,21].…”