Exact mass measurements using a 7 tesla fourier transform ion cyclotron resonance mass spectrometer in a good laboratory practices-regulated environment

Fourier transform ion cyclotron resonance mass spectrometry has been found to produce reliable exact mass measurements using two different internal calibration methods. For these measurements, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) were utilized both individually and in tandem. For internal calibration with a co-dissolved polyethylene glycol standard, measurements of 41 compounds resulted in an average absolute mass determination error of 0.7 ppm, with a standard deviation of 0.9 ppm. For comparison, internal calibration was effected through the simultaneous use of ESI and MALDI, with the former being used for the introduction of analyte ions and the latter for formation of polymethylmethacrylate calibrant ions. This technique led to mass measurements with an average absolute error of 0.8 ppm and a standard deviation of 1.0 ppm. In addition, exact mass measurements of tandem mass spectrometry fragment ions were made for 35 compounds using external calibration with a single internal mass standard. The observed average absolute error was 0.7 ppm with a standard deviation of 1.0 ppm.