Use of alizarin red S as a chromogenic agent for spectrophotometric determination of loratadine in pharmaceutical formulations
The study involved two simple, rapid, selective and cost-effective spectrophotometric methods for the determination of loratadine in pharmaceutical formulations. Method A was based on the formation of yellow coloured ion-pair complex between loratadine and alizarin red S in acid medium which was extracted into dichloromethane and the absorbance was measured at 425 nm. Method B was based on the breaking of yellow loratadine-alizarin red S ion-pair complex in alkaline medium followed by the measurement of violet colour free dye at 550 nm. Under the optimized conditions, Beer’s law was obeyed over the concentration ranges of 2.5–90.0 and 2.5–30.0 µg/ml loratadine for method A and method B, respectively. The molar absorptivity, Sandell’s sensitivity, detection and quantification limits were calculated. The methods were validated for intra-day and inter-day accuracy, precision, selectivity, robustness and ruggedness. The proposed methods were applied successfully to the determination of LOR in pure drug and commercial formulations. The accuracy and reliability of the proposed methods were further established by reference method and also by recovery studies via standard addition technique.
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