Mass Spectroscopy has become the mainstay of most laboratories, particularly those involved in pharmacokinetic investigation, protein identification/quantification and protein and peptide fractionation.
Indeed, the past decade has seen technological improvements in mass spectrometry (MS) explode, boding well for the analysis of small-molecule drugs and biomolecules significantly impacting on drug discovery and development.
The method is featured in the paper: "Accurate Mass Measurements of Product Ions for Metabolite Identification on Unit Mass Resolution Mass Spectrometers," and describes the achievement of high mass accuracy on conventional triple quadrupole mass spectrometers of unit mass resolution running in MS/MS mode.
Using Cerno's MS calibration and data analysis software, MassWorks, which utilises Cerno's MSIntegrity technology, to improve mass spectral measurements.
The level of accuracy required for metabolite identification can normally only be performed on high resolution mass spectrometers, but the results of this research prove that MassWorks can achieve mass measurements of product ions with 5 ppm accuracy on a unit mass resolution instrument.
The method was demonstrated for a set of small-molecule pharmaceuticals from an ABI/Sciex 4000 Q Trap by infusion as well as by LC/MS/MS measurements of rat liver microsomal incubation of verapamil on an ABI/Sciex 3200 Q Trap.
All the mass spectral data were collected in profile mode and processed using MassWorks software.
For the infusion, a few or a single known fragment ion(s) from the MS/MS spectra were selected as calibration standards in order to internally calibrate the spectra.
Other fragment ions in the spectra were tested for mass accuracy resulting in mass errors of less then a few mDa in most cases.
The LC/MS/MS fragment ions were generated by information dependent scans.
Accurate mass measurements of about 5 mDa for demethylated verapamil and its fragments were achieved by applying an external calibration generated by the known fragments of the parent drug verapamil.
Interestingly, the research also found that mass spectrometry calibration, including both mass and peak shape, is critical for high mass accuracy and that internal calibration aids the achievement of the highest possible mass accuracy.
Peak saturation is a key factor causing poor mass accuracy in a quadrupole system.
MassWorks utilises Cerno's DirectRead technology to read most instrument data formats directly, eliminating the need for importing or exporting MS data to the clipboard or utilising intermediate exchange formats.
This saves time, reduces transcription errors, simplifies file management, and saves substantial disk space.
As DirectRead doesn't alter the original data, it assists compliance with common regulatory requirements such as GLP and 21 CFR Part 11.