Quantitative Fourier transform ion cyclotron resonance mass spectrometry—the determination of creatinine by isotope dilution mass spectrometry

Abstract

Accurate quantitation has been demonstrated on many different types of mass spectrometer. However, quantitative applications of Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) have been limited. In this study, the quantitative potential of FTICRMS has been investigated using an exact matching isotope dilution method for the determination of creatinine in serum. Creatinine is an important clinical biomarker and its measurement is used as an assessment of renal function. The quantitation of creatinine was selected because a high-accuracy high-performance liquid chromatography/mass spectrometry (HPLC/MS) determination using a triple quadrupole mass spectrometer has already been successfully developed in-house. Therefore, a direct comparison of the quantitative capability of FTICRMS could be made against an established method. The accuracy of the quantitation of creatinine was found to be equivalent to that obtained using LC/MS. However, the expanded measurement uncertainty (k = 2) was larger, at 6%, when using FTICRMS compared with 1% when using HPLC/MS with the triple quadrupole mass spectrometer.

Precision mapping of the metabolome

“…Ions injected off-centre will thus begin harmonic (pendulum) oscillations around the equator, superimposed on their circular motion. The frequency of this oscillation is proportional to the mass-over-charge ratio and is detected and processed by fast Fourier transform, as in FTICR-MS. measurements (intensity accuracies of only 5-10% have been reported [19]) but improvements in time-of-flight mass spectrometers are showing great promise in this area. However, the high resolving power of top-end FTICR machines enables the discrimination of minor isotope peaks, for example, a compound containing one 34 S atom can be resolved from a molecule containing two 13 C atoms [20].…”