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 microg 1(-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.