Methanol and water

All solvents and mobile phase additives were LC-MS-grade. Acetonitrile (CHROMASOLV LC-MS) was purchased from Scientific Laboratory Supplies (Wilford, UK), methanol and water were purchased from Fisher Scientific (Leicestershire, UK), ammonium bicarbonate was obtained from Fluorochem (Hadfield, UK), and ammonium hydroxide was from Sigma-Aldrich (Gillingham, UK). All authentic chemical standards used for the annotation of metabolites were of analytical or higher grade and were obtained from various suppliers (Sigma-Aldrich (Gillingham, UK), VWR (Leicestershire, UK), and Fisher Scientific (Leicestershire, UK)). They were accurately weighed and dissolved in appropriate volumes of LC-MS-grade water to obtain individual stock solutions at concentrations of 1 mg/mL. Appropriate amounts of each stock solution were mixed to obtain four standard mixtures at concentrations of 25 µg/mL in water that were further prepared for HILIC analysis, as described below. Stable isotope-labelled internal standards AMP-¹⁵N₅, ADP-¹⁵N₅, and ATP-¹³C₁₀ were purchased from Sigma-Aldrich (Gillingham, UK) and prepared in a mixture at a concentration of 48 µg/mL.

9-Aminoacridine hydrochloride (9-AA) was purchased from Sigma–Aldrich. Water and Methanol was purchased from Fischer Scientific at the highest purity grade available and used without further purification.