Determination at ppb level of an anti-human immunodeficiency virus nucleoside drug by capillary electrophoresis–electrospray ionization tandem mass spectrometry

Capillary electrophoresis coupled with tandem mass spectrometry was used to indirectly separate and quantify the active metabolite of the anti-human immunodeficiency virus (anti-HIV) didanosine drug. The influence of several parameters (pH and ionic strength of volatile formic acid–ammonia buffer) upon electroosmotic flow, electrophoretic mobility and peak efficiency of several nucleosides (A, dA, ddA, C) has been studied. This paper illustrates the current importance in CE–MS technique as a complementary or substituted method to the known HPLC–radioimmunoassay or HPLC–UV method to measure levels of anti-HIV drugs. The limit of detection for 2′,3′-dideoxyadenosine by this method is 2 μg l−1 in a formic acid–ammonia buffer (pH 2.5, 10 mM ionic strength).This methodology could be used to perform simultaneous detection of two or more anti-HIV nucleosides, such as stavudine or didanosine in combination therapy.