Effects of sample injection amount and time-of-flight mass spectrometric detection dynamic range on metabolome analysis by high-performance chemical isotope labeling LC-MS

摘要

The effect of sample injection amount on metabolome analysis in a chemical isotope labeling (CIL) liquid chromatography-mass spectrometry (LC-MS) platform was investigated. The performance of time-of-flight (TOE) mass spectrometers with and without a high-dynamic-range (HD) detection system was compared in the analysis of C-12(2)/C-13(2)-dansyl labeled human urine samples. An average of 1635 +/- 21 (n = 3) peak pairs or putative metabolites was detected using the HD-TOF-MS, compared to 1429 +/- 37 peak pairs from a conventional or non-HD TOF-MS. In both instruments, signal saturation was observed. However, in the HD-TOF-MS, signal saturation was mainly caused by the ionization process, while in the non-HD TOF-MS, it was caused by the detection process. To extend the MS detection range in the non-HD TOF-MS, an automated switching from using C-12 to C-13-natural abundance peaks for peak ratio calculation when the C-12 peaks are saturated has been implemented in IsoMS, a software tool for processing CIL LC-MS data. This work illustrates that injecting an optimal sample amount is important to maximize the metabolome coverage while avoiding the sample carryover problem often associated with over-injection. A TOP mass spectrometer with an enhanced detection dynamic range can also significantly increase the number of peak pairs detected.