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.