Liquid chromatography–tandem mass spectrometry assays for intracellular deoxyribonucleotide triphosphate competitors of nucleoside antiretrovirals

This study was aimed to apply an LC–MS–MS method previously developed for intracellular nucleoside reverse transcriptase inhibitors-triphosphate (NRTI-TPs) to the determination of natural deoxyribonucleotides (dNTPs) in human peripheral blood mononuclear cells. The LC–MS–MS method was directly used in assay of dATP and dTTP. Interferences by ribonucleotides (rNTPs) prevented direct application to the two other analytes: dGTP and dCTP. A periodate oxidation procedure was therefore optimized to remove rNTPs from the cell medium in order to quantitate dCTP and dGTP. The determination of the intracellular ratio of NRTI-TP/dNTP in HIV-infected patients now involves use of the same chromatographic system for simultaneous assay of several analytes.