Microextraction based on liquid-solid phase transition of benzoic acid: Extraction of statins from human urine...

Herein, a microextraction method was reported based on the liquid-solid phase transition of benzoic acid to quantify two statins, namely lovastatin and simvastatin in authentic human urine. The principle of the method is based on the phase transition of benzoic acid by altering the pH of the sample solution enabling efficient dispersion and phase separation in one step. Due to the moderate melting point of benzoic acid, its solidification is performed at ambient temperature without the need for sample cooling. Various experimental parameters that affect the performance of the analytes (i.e. extractant type and its concentration, acid type and concentration, and sample volume) have been examined and optimized. The method was validated based on the total error concept. For this purpose, accuracy profiles were constructed in the concentration range of 100-5000 ng mL^-1 while β-expectation tolerance intervals fell within ±15% demonstrating that 95% of future results will not exceed the defined bias limits. The intra-day and inter-day method precision was less than 4.7% and 4.3% for both analytes, while the limit of detection was 15 ng mL^-1 for both analytes. It was also proved that the usage of benzoic acid is advantageous in minimizing the potential inter-conversion of the analytes during the acidification step of the extraction procedure. The green potential of the proposed analytical scheme was examined based on Green Analytical Procedure index. The proposed sample pretreatment technique proved to be a valuable tool offering selectivity and rapidness. The developed method was used for the analysis of real human urine obtained after the administration of statin-based pharmaceutical formulations.