Abstract
A stability-indicating capillary electrophoresis method coupled to a diode array detector (DAD) was developed and validated for the simultaneous determination of emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) in combined tablets. This proposed method utilized a fused silica capillary (effective length, 62 cm; internal diameter [ID], 75 mu m) and a background electrolyte (BGE) consisting of phosphate solution (pH 9.5, 50 mM). The separation was achieved at a voltage of 25 kV and a temperature of 21 degrees C using paracetamol as an internal standard. The described method was linear over the range of 5-200 mu g/mL for both drugs (r = 0.9992). Intra-and inter-day relative standard deviation (RSD) (n = 9) was 0.41%. The limits of detection for FTC and TDF were 1.25 and 1.00 mu g/mL, respectively. The average percentage recoveries of FTC and TDF from their tablet formulations were 99.66 +/- 0.73 and 99.48 +/- 0.33, respectively. The two drugs were subjected to thermal, photolytic, hydrolytic, and oxidative stress conditions, and then the stressed samples were analyzed by the proposed method. Degradation products produced as a result of stress studies did not interfere with the detection of FTC and TDF. The assay can thus be considered stability indicating.