Simple Spectrometric Determination of Artesunate and Dihydroartemisinin in Pharmaceuticals using Potassium Iodate and Indigo Carmine as Reagents

Résumé

The distribution of counterfeit artemisinin derivatives in sub-Saharan has reached a dangerous level. Based on this, a simple sensitive and reproducible method is developed for the assay of artesunate (ART) and dihydroartemisinin (DHA) in tablets. The method is based on the reaction of the drug with a known excess of the antioxidant (potassium iodate) in acid medium and thereafter determination of residual antioxidant by reacting with a fixed amount of indigo carmine n and measuring the absorbance at 610 nm. Absorbance is proportional to increasing drug concentration. The method obeys Beer’s law at the range of 0.5 – 5.0 and 0.5 – 6.0 for ART and DHA respectively. The correlation coefficient of the curve generated by least square method was 0.9989 and 0.9996 for ART and DHA respectively. The molar absorptivities were 2.0 x 104 and 2.1 x 104 L/mol/cm and Sandell sensitivity of 0.0192 and 0.013 ?g/cm2 respectively for ART and DHA. Limit of detection and quantification were 0.48 and 1.58, and 1.48 and 1.58 ?g/mL respectively for ART and DHA. The intraday and inter day accuracy (R.E.%) and precision (RSD%) were ? 1.0 ? 2.6 in all cases. The method was statistically compared with an official method via student t-test and Varian Ratio test F-tests and used successfully to evaluate ART and DHA tablet procured in Uyo metropolis. The accuracy of the method was further tested by performing recovering study via standard addition method with excellent necrosis raging ? 99.9 ? 103 and standard deviation of between 1.07 – 1.86 meaning that the excipients have no effect on the performance of the method.