The use of a double coaxial electrospray ionization sprayer improves the peak resolutions of anionic metabolites in capillary ion chromatography-mass spectrometry

Recently, ion chromatography coupled with mass spectrometry has been used for the determination of anionic metabolites. However, connection with a mass spectrometer in this method is not straightforward because backpressure produced by the addition of a make-up solution often affects the peak resolutions of the target metabolites. To overcome this problem, we developed a capillary ion chromatography-mass spectrometry method utilizing a double coaxial electrospray ionization sprayer. This method was not affected by backpressure and the number of theoretical plates was about three times that of a conventional sprayer. Under optimized conditions, 44 anionic metabolites, including organic acids, sugar phosphates, nucleotides, and cofactors, were successfully separated and selectively detected with a Q Exactive mass spectrometer. The calibration curves of the tested metabolites showed excellent linearity within the range of 1–100,000 nmol/L and the correlation coefficient was greater than 0.991. The detection limits for these metabolites were between 1 and 500 nmol/L (0.4 and 200 fmol). The developed method was applied to the quantitation of anionic metabolites in cultured cancer cell samples with tumor necrosis factor (TNF)-α stimulation. This allowed for the successful determination of 105 metabolites. The levels of tricarboxylic acid cycle intermediates changed significantly after TNF-α stimulation. These results demonstrate that the developed method is a promising new tool for comprehensive analysis of anionic metabolites.