DOI: https://doi.org/10.55373/mjchem.v25i3.107

Keywords: External standard calibration curve; internal standard calibration curve; standard addition calibration curve; diclofenac sodium

Abstract

Overdoses of diclofenac sodium can be life threatening particularly to the elderly with cardio-vascular diseases. This drug is usually prescribed in high doses and must be consumed over a long period for effective treatment. Hence, quality control of the drug content in pharmaceutical products is essential to avoid overdosage. In this study, the diclofenac sodium content in three tablet brands were separated using RPHPLC-DAD and quantified using external standard calibration curve, internal standard calibration curve and standard addition calibration curve. The external standard method accurately quantified the diclofenac sodium in Voren® (error ≈ 4 %) and Remafen® (error ≈ 9 %) but not in Remethan® (error ≈ 27 %). The internal standard method was used to explore the possibility of volume error that may contribute to the discrepancies of accuracy in the sample brands. It was found that there was no improvement in the accuracy as no volume error was indicated, either in the sample preparation or in the volume injected to the RPHPLC-DAD. The discrepancies of accuracy for Remafen® and Remethan® due to matrix interferences were explored using the standard addition calibration curve. The accuracy of Remafen® (error ≈ 4 %) and Remethan® (error ≈ 2 %) was improved with this method. This suggests that the matrix interference in the two brands probably resulted from excipients used in the drug formulation. The excipient is unlikely to be present in Voren® considering that the diclofenac sodium content can be accurately estimated by merely using external standard method.