Dispersive liquid‐liquid microextraction based on the solidification of floating organic droplets for preconcentration of amino acids in human plasma samples

Abstract

In this research, dispersive liquid‐liquid microextraction was established based on the solidification of floating organic droplets. This simple, fast, and eco‐friendly sample extraction method allows preconcentration and identification of amino acids in plasma samples through the use of high‐performance liquid chromatography with fluorescence detection. By application of central composite design, the main factors in the microextraction procedure were optimized. The optimal experimental parameters were: 330 μL of 1‐dodecanol as an extraction solvent, 340 μL of acetone as disperser solvent, 140 μL of methanol as diluent at 6.8 min of ultrasonic time, and finally cooling in an ice bath for 3 min. Under these optimal conditions, good responses for 19 amino acids were obtained in the concentration ranges of 0.5–400 μmol L−1, with coefficients of determination higher than 0.9993. Limits of detection were based on a signal‐to‐noise ratio of 3, and ranged from 0.09 to 0.85 μmol L−1. In conclusion, the results demonstrate that this method was successfully applied to determine the amino acids in plasma samples. The relative recoveries of the 19 amino acids ranged from 81 to 103%, with relative standard deviations ranging from 1 to 4%.