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

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).