Method optimisation and robustness testing in HPLC analysis of Angiotensin II receptor blockers (ARB) antagonists

Abstract

The active pharmaceutical ingredients irbesartan, losartan and valsmian are three members of a newer class of antihypertensive agents known as angiotensin II receptor blockers. These agents help the blood vessels to dilate, which consequently lowers the blood pressure allowing the hemi to pump blood easier and without extraneous effort. The objective of this dissertation was to optimise an assay and related substances method for each respective active ingredient. The methods optimised were all perf01med in reverse phase chromatography and required an HPLC system coupled with a UV detector as instrnmentation. The optimisation process required gathering information on the physicochemical parameters of the named components first. The second step was to generate an experimental design in a one-variable-at-a-time (OVAT) set up, where certain parameters such as flow rate, column temperature, mobile phase composition, mobile phase buffer pH and HPLC columns were tested and evaluated using statistical tools. Software simulation was used to scout for the best parameters and obtain the finalized method. The third step was to build the optimised method from the results of the OV AT analysis, test it and fine tune accordingly. Once the optimisation goals were met and the final method confirmed, the fourth step was to perform robustness, testing different pre-defined factors at extreme tolerance. Assay method development was performed on irbesartan, losartan and valsartan in reverse phase mode as part of a secondary objective of this study. The developed HPLC method was planned to be transferred geometrically on UHPLC to increase the efficiency and throughput. Therefore, the method development started with pre-selected columns onto which the rest of the method was developed. The data collected from the previous optimisation stage together with various scouting runs led to the development of a robust method. The development strategy and development goals were key for a successful method outcome. Software simulation was also an integral asset especially in the determination of the pH of the mobile phase, where pH 2.0, 3.0 and 4.0 were tested during scouting and the results achieved inputted into the software to generate a resolution map for the whole range of pH values between pH 2.0 and 4.0. In conclusion it was determined that with the knowledge of the physiochemical parameters of the components of interest one can deduce through limited experimentation an optimised method which is effective and robust. Through the same concept, a method was developed and transferred geometrically from HPLC to UHPLC retaining the same component selectivity and specificity.