The development of micellar electrokinetic chromatographic method for the simultaneous determination of codeine phosphate and promethazine hydrochloride in cough solutions

Abstract

The developed micellar electrokinetic chromatographic (MEKC) method for the simultaneous analysis of codeine phosphate and promethazine hydrochloride in cough solutions was performed on a fused silica capillary (37cm x 75 um I.D.) at 20 ํC with background electrolyte consisting of 50 mM sodium dodecyl sulfate in 25 mM borate buffer pH 10.0 and 10% acetonitrile. UV detection was performed at 214 nm. Guaifenesin was used as an internal standard. Codeine phosphate and promethazine hydrochloride were well separated from inactive ingredients and photodegradation products. The relationship between concentration and peak area ratio was linear in the range of 45 - 135 ug/ml of codeine phosphate and 18 - 54 ug/ml of promethazine hydrochloride. The relative standard deviation of the intra - day precision (n=6) and inter - day precision (n=3) were 1.14 and 1.45 % for codeine phosphate and were 1.12 and 2.15 % for promethazine hydrochloride. Accuracy of the method expressed as mean recovery at three concentration levels were 99.2% for codeine phosphate and 98.2% for promethazine hydrochloride. The content of codeine phosphate and promethazine hydrochloride which were analysed by MEKC method was not significantly different from the one obtained from high performance liquid chromatographic method at 95% confidence level. The developed MEKC method was rapid, specific, precise, accurate, no sample pretreatment required and no interference from photodegradation products of promethazine hydrochloride.