Abstract

NOVEL TITRIMETRIC AND SPECTROPHOTOMETRIC DETERMINATION OF DIHYDROARTEMISIN IN PHARMACEUTICALS USING N-BROMOSUCCINIMIDE

Emmanuel Attih* and Daniel A. Ambe

ABSTRACT

The influx of counterfeit artemisinin derivatives into Sub Sahara Africa largely from Southeast Asia is putting the global fight agains malaria in jeopardy. Two methods for the assay of dihydroartemisin, one titrimetric and one spectrophotometric method are developed. The methods are based on the use of N-Bromosuccinimide (NBS) as oxidimetric agent. In the titrimetric method NBS was titrated directly with dihydroartemisinin using methyl orange. In the spectrophotometric method a known excess of NBS is reacted with the drug; the unreacted NBS is determined using fixed amount of methyl orange. In both methods the amount of NBS reacted is proportional to the drug concentration. In the titrimetric method the range was between 1-10mg/ml and with the stoichiometry of 1:2 (drug:NBS). In the spectrophotometric method Beer’s law was obeyed in the range of 0.2-80μg/ml. The molar absorptivity was 3.0 x 104L/mol/cm and the Sandell sensitivity of 0.0095μg/cm. The limit of detection (LOD) and limit of quantification were 0.05 and 0.15. The inter-day and intra-day accuracy and precision were ≥3.0.The methods developed were used to assay drug procured locally and statistically compared with an official method. The accuracy and applicability of the methods were tested further by performing recovery study using standard additive method; with the result showing good recoveries, with no interference from pharmaceutical excipients.

Keywords: counterfeit drugs, dihydroartemisinin, malaria, resistance, Spectrophotometry, Titrimetry.