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Abstract
Anti-HIV drug mixtures A and B containing stavudine(d4T)/didanosine (ddI)/saquinavir and stavudine (d4T)/didanosine (ddI)/efavirenz, respectively, were separated and quantitated in human serum using micellar electrokinetic chromatography (MEKC). Serum samples were treated using a solid-phase extraction procedure. The effects of various factors such as buffer type, buffer and surfactant concentration, and pH on the separation of the analytes were investigated. The optimized resolution of both mixtures was achieved with a run buffer containing 18 mM sodium dodecylsulfate (SDS) in 15 mM phosphate and borate buffer (pH 9.0). An uncoated 52 cm (effective length 30 cm) × 50 μm ID fused-silica capillary, operated at 30°C, was used in the analysis with UV detection at 210 nm. Aprobarbital was chosen as the internal standard. All analytes were separated within 15 min with a voltage of +15 kV and a current around 30 μA. The methods were validated over the range of 0.7–35.3 μg/mL for d4T, 0.8–18.5 μg/mL for ddI, 0.5–12.2 μg/mL for saquinavir in mixture A, and 0.7–35.3 μg/mL for d4T, 0.8–18.5 μg/mL for ddI, 0.6–31.9 μg/mL for efavirenz in mixture B. Intra-day and inter-day accuracy were less than 13.7% and intra-day and inter-day precision were less than 14.5% for both mixtures. Extraction recoveries of all analytes from serum were higher than 77.3%. The assay should be applicable for pharmacokinetic studies and routine monitoring of these drugs in serum.