Development and Validation of a RP-HPLC Method for Assay of Atorvastatin and its Application in Dissolution Studies on Thermosensitive Hydrogel-Based Nanocrystals

Purpose: To develop and validate a novel reverse phase high performance liquid chromatographic (RP-HPLC) method for the quantification of atorvastatin in thermosensitive hydrogel-based nanocrystal formulation.
Method: Chromatographic identification was achieved on C18 (5 μm) column using acetonitrile and 0.025 M potassium dihydrogen ortho-phosphate buffer pH 5 (45:55 v/v) as mobile phase, at a flow rate of 1.5 mL/min and using photo diode array detector (PDA) at 246 nm. The developed HPLC method was validated according to International Conference on Harmonisation (ICH) Q2(R1) guidelines and applied to dissolution studies on atorvastatin thermosensitive hydrogel-based nanocrystal formulation, using Lipitor® as standard.
Results: Determination was successfully achieved with good peak resolution from atorvastatin nanocrystals and a commercial formulation brand (Lipitor® tablets) without interference of polymer or excipients. The retention time of atorvastatin was 4.5 min and drug response was linear in the range of 0.1 - 0.5 μg/mL with a correlation coefficient of 0.9995. Precision was determined to be between 0.16 - 0.61 percent relative standard deviation (% RSD) for the analyzed samples. The limit of detection and of quantification was 35.6 and 71.2 ng/mL, respectively, which was 10 times higher than a previously reported method. The assay of atorvastatin nanocrystal and Lipitor® gave 99.37 and 99.12 % recovery, respectively. Dissolution studies showed atorvastatin release of 40 and 65 % at 40 min from thermosensitive hydrogel nanocrystal formulation and Lipitor®, respectively indicating sustained release.
Conclusion: The method is successfully validated and is specific, linear, precise, and accurate with good robustness. It is applicable to atorvastatin nanocrystal dissolution studies and is a promising quality control tool for atorvastatin analysis in nanoformulations and pharmaceutical dosage forms.

Keywords
Atorvastatin; Anticholestermic; Dissolution studies; Hydrogel; Nanocrystal; Thermosensitive