Investigation of porous graphitic carbon at high-temperature liquid chromatography with evaporative light scattering detection for the analysis of the drug combination artesunate—Azithromycin for the treatment of severe malaria

Artesunate combined therapies represent the best option for the treatment of malaria and require the development of new methods of analysis. Retention, selectivity and detection with high-temperature liquid chromatography-porous graphitic carbon-evaporative light scattering detection was studied for artesunate and azithromycin separation. Organic solvent, concentration of organic modifiers, temperature and flow rate were all relevant parameters to optimize this separation. The behaviour of artesunate in the tested conditions appeared close to a neutral compound. In CH₃OH, only azithromycin retention was dramatically altered depending on the triethylamine]/formic acid] ratio and on the temperature, whereas in CH₃CN, azithromycin, artesunate, artemisinin and dihydroartemisinin retentions decreased with the temperature increase whatever the organic modifier ratio. The best efficiency was obtained with CH₃CN. 25% variation of the concentration values of the organic modifiers did not significantly influenced the retention. The sensitivity of ELSD increased with the flow rate decrease. Peak area and S/N ratio dramatically decreased with the flow rate increase by 10- and 5-fold for artesunate and azithromycin, respectively. Non-linear calibration curves were obtained for both artesunate and azithromycin.