Metabolic profiling of human urine by CE-MS using a positively charged capillary coating and comparison with UPLC-MS

Abstract

The potential of capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS) using capillaries coated with a triple layer of polybrene–dextran sulfate–polybrene (PB–DS–PB) was evaluated for metabolic profiling of human urine. The method covers various metabolite classes and stable metabolic profiles of urine samples were obtained with favourable migration time repeatability (RSDs <1%). The PB–DS–PB CE-TOF-MS method was used for the analysis of human urine samples from 30 males and 30 females, which had been previously analyzed by reversed-phase UPLC-TOF-MS. Multivariate data analysis of the obtained data provided clear distinction between urine samples from males and females, emphasizing gender differences in metabolic signatures. Nearly all compounds responsible for male–female classification in CE-TOF-MS were different from the classifying compounds in UPLC-TOF-MS. Almost all compounds causing classification in the CE-TOF-MS study were highly polar and did not exhibit retention in the reversed-phase UPLC system. In addition, the CE-TOF-MS classifiers had an m/z value in the range of 50–150, whereas 95% of the classifying features found with UPLC-TOF-MS had an m/z value above 150. The CE-TOF-MS method therefore appears to be highly complementary to the UPLC-TOF-MS method providing classification based on different classes of metabolites.