Miniaturized salting-out liquid–liquid extraction in a coupled-syringe system combined with HPLC–UV for extraction and determination of sulfanilamide

In salting-out liquid–liquid extraction (SALLE) technique, water-miscible organic solvents are used for extraction of polar analytes from saline solutions. In this study, for the first time, a coupled 1-mL syringes system was utilized to perform a miniaturized SALLE method. Sulfanilamide antibiotic was extracted and determined via the developed method followed by high performance liquid chromatography–ultraviolet detection (HPLC–UV). The extraction process was carried out by rapid shooting of acetonitrile as extraction solvent (syringe B) into saline aqueous sample solution (syringe A), and then the shooting was repeated several times at a rate of 1 cycle s−1. Thereby, an extremely large contact surface area was created between phases and led to a rapid equilibrium and mass transfer. In order to improve the efficiency of the method, the effect of extraction solvent (type and volume), shooting times, salt concentration, and pH on the extraction efficiency was investigated. The best performance of the method was achieved with 250 µL of acetonitrile, salt concentration of 250 mg mL−1, pH of 7, and shooting times of 5. The linear dynamic range was 0.001–10 µg mL−1 with the determination coefficient of 0.9999. The relative standard deviation (RSD; n=3, C=5 µg mL−1), and the limit of detection (LOD) were 1.55% and 0.3 ng mL−1, respectively. The developed technique was successfully applied to genuine samples of tea, water, milk, honey, human urine, plasma and blood.