A rapid reversed-phase HPLC method for the simultaneous analysis of olanzapine and simvastatin in dual nanostructured lipid carriers

Abstract

In the present work, a rapid reversed phase high performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of simvastatin, including the lactone prodrug (SV) and the respective active hydroxy acid form, simvastatin acid (SVA) and olanzapine (OL) in a formulation containing co-encapsulating-nanostructured lipid carriers (Combo-NLC). The desired chromatographic separation was achieved on a Phenomenex Luna Phenyl-Hexyl, 5 μm (150 × 3 mm) column at a temperature of 35 °C, under isocratic conditions using UV detection at 230 nm. The optimized mobile phase consisted of a mixture of ammonium acetate aqueous solution (0.02 M), methanol and acetonitrile (30 : 35 : 35, v/v/v) at a flow rate of 0.8 mL min⁻¹. The linear regression analysis for the calibration curves showed a good linear correlation over the concentration range 0.5–100 μg mL⁻¹, with determination coefficients, R², exceeding 0.9994 for all three compounds, SVA, SV and OL. The method was shown to be specific, without the interference of NLC components, precise at the intra-day and inter-day levels, as reflected by the relative standard deviation values, lower than 9.014%, accurate with bias not exceeding 15% and characterized by a recovery rate of 100 ± 8%. The limits of detection and quantification were, respectively, 0.07 and 0.22 μg mL⁻¹ for OL, 0.12 and 0.36 μg mL⁻¹ for SV and 0.09 and 0.27 μg mL⁻¹ for SVA. The method was successfully applied for the determination of Combo-NLC entrapment efficiency.