Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 degrees C for 25-40min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434nm (excitation at 389nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 mu g ml(-1) for tramadol, dothiepin and 5-25 mu g ml(-1) for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 mu g ml(-1) for tramadol, dothiepin and 1-5 mu g ml(-1) for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68 +/- 1.00, 99.95 +/- 1.11 and 99.72 +/- 1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5 +/- 0.844, 100.32 +/- 0.969 and 99.82 +/- 1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application. (c) 2006 Elsevier B.V. All rights reserved.