Novel spectrophotometric determination of some artemisinin derivatives using alcoholic ammonia solution generated insitu

Background: Dihydroartemisinin (DHA) and Artesunate (ART) are frontline antimalarial drugs for treatment of uncomplicated malaria. A sensitive spectrophotometric method is here developed for the assay of these two antimalarials.

Methods: The reaction is based on the generation of alcohol Ammonia in situ by the action of sodium hydroxide on ammonium Nitrate. The lactone ring of the artemisinin derivatives opens producing a chromogen that can be measured spectrophotometrically; at ?max 350nm and 340nm for DHA and ART respectively.

Results: The absorbance is directly proportional to the drug concentration. Bears law is obey in the range of 5.0-10?g and 5.0 – 80µg/ml for DHA and ART respectively. The correlation coefficient of 0.9997 and 0.9998 respectively. The method was sensitive with molar absorptivity of 2.65 x 103 LMOL-1 and 2.0 x 103 lMOL-CM-1 and Sandell sensitivity of 0.115 and 0.225 ?g/cm2 respectively for DHA and ART. The limit of detection and limit of quantification were determined as per the current ICH guidelines and found to be 0.485 and 0.430/ 1.27 and 1.32µg/ml for DHA and ART respectively. The precision and accuracy are excellent at < 3.00 in all cases.

Conclusion: The method was compared statistically with official pharmacopoeal method via F-test and students T-test and was used to assay DHA and ART tablets procured local which showed good congruence. The aplicability of the method was ascertained by conducting recovery test via standard addition method with results showing no significant interference from excipients.