LC Determination of Ritonavir, a HIV Protease Inhibitor, in Soft Gelatin Capsules

A rapid, simple and sensitive high-performance liquid chromatographic method (HPLC) has been developed to assay ritonavir in semisolid capsules. The HPLC analysis used a reversed-phase C₈ (125 × 4.0 mm i.d., 5 μm particle size) analytical column and a mobile phase consisting of methanol and water (67:33, v/v), with UV detection at 210 nm. Specificity was evaluated using a photodiode array detector (PDA). The validation data showed that the assay is sensitive, specific and reproducible for determination of ritonavir in this dosage form. Calibration curves were linear from 100–300 μm L^?1 (R² ≥ 0.999). The accuracy of the method ranged from 98.8 to 102.0%. Mean inter- and intra-assay relative standard deviations (RSD) were less than 1.0%. The proposed method provided an accurate and precise analysis of ritonavir in soft capsules, requiring neither the use of a buffered mobile phase, nor the addition of amine modifiers.