A simple colorimetric method for estimation of tramadol hydrochloride in pure and tablet dosage forms

OBJECTIVE: The objective of this study was to develop and validate a simple method for estimation of tramadol hydrochloride (TH) in pure and pharmaceutical dosage forms using a colorimeter. MATERIALS AND METHODS: TH on reaction with Eriochrome Black T in the presence of acetate buffer at pH 3.5 forms a colored complex. This complex was extracted with a fixed volume of chloroform. The optical density of this colored complex was measured against reagent blank using a colorimeter at 520 nm. RESULTS: Beer's law was obeyed with a good correlation coefficient (0.999) in the concentration range of 2.5 μg/ml to 10 μg/ml. Drug content estimation and recovery studies carried out on commercial tablet dosage forms demonstrated the accuracy of the method and that excipients do not cause interference. Precision and robustness were measured and found to be acceptable (% relative standard deviation <2%). CONCLUSION: The proposed method can be used for the rapid determination of TH content in tablets at a health-care provider level using already available staff and equipment.