Spectrophotometric and Stability-Indicating High-Performance Liquid Chromatographic Determinations of Terbutaline Sulfate

Spectrophotometric and stability-indicating HPLC procedures are described for determination of terbutaline sulfate in bulk powder and dosage form. The first procedure is based on diazo coupling of the phenolic groups of terbutaline sulfate with fast red B salt in the presence of sodium hydroxide. The colored compound developed in alkaline medium was measured at 475 nm. Different variables affecting the reaction were studied. Beer's Law is obeyed in the concentration range of 1-6 mu g/mL. In the HPLC procedure, the separation was carried out on a Caltrex (R) AIII column, a relatively new packing material consisting of silica-bonded calix([8])arene, using an isocratic binary mobile phase, acetonitrile ammonium acetate (50+50, v/v), at pH 6.2. A diode array detector was used at 280 nm. The method was validated for system suitability, linearity, precision, LOD, LOQ, specificity, stability, and robustness. The LOD and LOQ were 0.196 and 0.781 mu g/mL, respectively. The recovery values of this method were between 98 and 102%, and the reproducibility was within 0.92%. Statistical comparison of the results obtained from the analysis of the studied drug to those of the official British Pharmacopoeia (2007) method using t- and F-tests showed no significant difference between them.