Microemulsion high performance liquid chromatography (MELC) method for the determination of terbutaline in pharmaceutical preparation

A robust and sensitive microemulsion HPLC (MELC) method using oil-in-water microemulsion mobile phase was developed and used for the determination of terbutaline in Bricanyl® Turbuhaler. The applicability of microemulsion as an eluent for reversed phase HPLC was examined. In addition, the effect of operating parameters on the separation behaviour was studied.The samples were injected into C18 Spherisorb (250 mm × 4.6 mm × 5 μm) columns at 25 °C using a flow rate of 1 ml/min. The mobile phase was 95.5% aqueous orthophosphate buffer (adjusted to pH 3 with orthophosphoric acid), 0.5% ethyl acetate, 1.5% Brij35, and 2.5% 1-butanol, all w/w. The terbutaline peak was detected by fluorescence, using excitation and emission wavelengths of 267 and 313 nm, respectively.The accuracy of method was >99% and the calibration curve was linear (r2 = 0.99). The limit of detection (LOD) and limit of quantitation (LOQ) were 8 μg/L and 26 μg/L, respectively. The intra-day and inter-day precisions (in term of % coefficient of variation) were < 1.46% and <0.97%, respectively. The influence of the composition of the microemulsion system was also studied and the method was found to be robust with respect to some changes of the microemulsion components. The microemulsion HPLC method has been applied to determine the content of the emitted dose and the fine particle dose of terbutaline in a Bricanyl® Turbuhaler.