Methyl-Orange Complexation Method For Field Determination Of Chloroquine Base: Suitability For Tablet And Urine Samples
A simple colorimetric assay for field estimation of chloroquine in tablet dosage forms and biological fluids would be useful, given that the high prevalence of substandard brands may have been a factor in the development of drug resistance. Chloroquine base was liberated from chloroquine phosphate tablets and extracted with chloroform. Methyl orange was then used to complex the base and the absorbance of the complex was determined in a colorimeter. This method was used in determining the amount of drug in tablet brands and urine samples of volunteer human subjects. It was able to determine the amounts of chloroquine in the tablets, with only two tablet brands out of 5 passing the test for content of active ingredient. Statistical analyses of the results show that there are significant differences in chloroquine elimination in the volunteers in each group (p = 0.005 and 0.004 for groups 1 and 2 respectively). An initial (36 h) elimination half life of 22.88 ± 6.93 was obtained. This value agrees significantly with initial plasma elimination half life of chloroquine reported in literature. This test may therefore be a good quality-indicating assay for resource limited or field conditions.
Keywords: chloroquine, colorimetry, methyl orange, complexation, assay