Stir bar sorptive extraction of propranolol from plasma samples using a steel pin coated with a polyaniline and multiwall carbon nanotube composite

We have developed a simple and sensitive method for the determination of propranolol in plasma samples. It is based on stir-bar sorptive extraction and HPLC with fluorescence detection. Extraction is accomplished with a nanocomposite consisting of polyaniline and multiwall carbon nanotubes that was electrochemically prepared on a steel pin. The extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were optimized. The method has a linear (r = 0.9917) response to propranolol in the 0.1-15 ng mL(-1) concentration range. Relative standard deviations of intra-day (n = 5) and inter-day (n = 3) assay precision are < 8.3 % and 10.4 %, respectively. The enrichment factor for plasma is 8.5, and the limit of detection is as low as 30 pg mL(-1). Obviously, the use of nanotubes can largely improve the extraction efficiencies when compared to the performance of a plain polyaniline coating. The method was successfully applied to the determination of propranolol in spiked human plasma samples.