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Hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of hydrophilic ion-pairing reagents for the separation of nucleosides and nucleotide mono-, di- and triphosphates A

Mateos-Vivas, María, Rodríguez-Gonzalo, Encarnación, García-Gómez, Diego, Carabias-Martínez, Rita
Journal of chromatography 2015 v.1414 pp. 129-137
adsorption, ammonium, hydrophilic interaction chromatography, hydrophilicity, nucleosides, nucleotides, polar compounds, salts, tandem mass spectrometry, tetrabutylammonium compounds
A fast and efficient method for the simultaneous separation of highly polar compounds, in this case nucleosides and nucleotide mono-, di- and triphosphates, using hydrophilic interaction chromatography coupled with tandem mass spectrometry (HILIC–MS/MS) is proposed. This new separation method revealed the possibilities of the formation of hydrophilic ion-pairing compounds.Three stationary phases (HILIC XBridge-Amide, HILIC-CoreShell and ZIC-HILIC) were assayed for the separation of 20 target analytes, and a detailed study of the composition of the mobile phase was made using different salts at different concentrations in a organic-rich mobile phase. We report that in order to prevent the adsorption of nucleotides on the LC–MS setup and to enhance their retention on the HILIC stationary phase, a mobile phase containing hexafluoro-2-propanol and different cations should be used. Four cations were evaluated: ammonium, diethylammonium, triethylammonium and tetrabutylammonium. The results revealed the formation of an ionic-association compound between the phosphorylated analytes and the cationic ion-pairing reagents, whose retention increased with the polarity of the cationic ion-pairing reagent.HILIC XBridge-Amide was found to be the most suitable column for the separation of these analytes, and the optimized mobile phase consisted of an ACN/UHQ water mixture (3min of isocratic elution using 82:18%, v/v and then a fast gradient from 18% to 22% of water) with 100mM hexafluoro-2-propanol and 50mM diethylamine (wʷpH 9–wˢpH 10). In a total analysis time of 8min, good results were achieved in terms of resolution. Under these optimum conditions, a further comprehensive study of the retention mechanism was carried out.