Sequential design of experiments approach for the multiproduct analysis of cholesterol‐lowering drugs by ultra‐high‐performance supercritical fluid chromatography

A multiproduct approach toward method development is presented for a fast and reliable analysis of the eight most important cholesterol‐lowering drugs via ultra‐high‐performance supercritical fluid chromatography. A two‐step approach based on design of experiments was applied: (1) selection of the stationary phase, organic modifier, and diluent in the mobile phase through a multilevel categorical design and (2) optimization of the elution strength by varying the pressure, temperature, and gradient using a central composite design. Finally, the flow rate was adjusted. The first design selected UPC2 Torus 1‐AA as the column, ethanol:water as the organic modifier, and acetonitrile:ethanol 3:2 v/v as the diluent. The results led to a pressure, column temperature, and gradient elution of 14.83 MPa, 42°C, and 5–15.5% of ethanol:water in CO2, respectively. The flow rate was set at 1.8 mL/min, providing a total analysis time of 4 min. This multiproduct method was validated and applied to 11 different commercial products available in the Brazilian market, and it was found to be accurate, with r > 0.990, recoveries between 95 and 105%, and precision not higher than 5.4%. Therefore, this method was shown to be a greener alternative for the analysis of these pharmaceuticals.