Simple LC Isocratic Methods Development, Validation, and Application in the Analysis of Poor Quality Antimalarial Medicines

Abstract

Liquid chromatographic methods in isocratic mode for the analysis of poor quality medicines are privileged due to their simplicity and facility in methods development. They are generally fast; do not need to be re-equilibrated between sample injections; have larger flexibility with acceptable changes on different column dimensions; and are applicable to LC systems equipped with simple or high developed pumps. In this study, we focused on developing simple isocratic methods using classical mobile phase composed by methanol and ammonium formate buffer for the analysis of most common antimalarial medicines marketed in malaria endemic countries and susceptible of being counterfeit/falsified, substandard and degraded. The selected medicines were quinine and related cinchona alkaloids in tablets and injectable forms; artemether/lumefantrine tablets; and artemisinin compounds (arteether, artemether, and artesunate) in injectable forms. The current methods were developed thanks to simple methodological approach consisting in sequential isocratic runs through adjustment or adaptation of existing methods to obtain optimal analytical conditions without complex design of experiments that might be long and costly. Then, the new methods presented shorter analysis time; allowed increase of sample analysis throughput; and obviously consumed little mobile phase solvents on classical analytical columns: 50 - 250 mm of length (L), 4.6 mm of internal diameter (I.D.), and 3.5 - 5.0 μm of particle size (dp).