Use of switchable hydrophilicity solvents based liquid phase microextraction (SPs-LPME) followed by HPLC-UV for the determination of 17 amino acids in different samples

In the present study,switchable hydrophilicity solvents based liquid phase microextraction (SPs-LPME) followed by HPLC-UV was applied for the simultaneous determination of 17 free amino acids in different samples. Chromatographic procedure for the determination of amino acids as phenylthiocarbamyl derivatives (PTC) is performed. Several variables relating to chromatographic aspects were studied such as the pH and temperature of the mobile phase, buffer and modifier (triethylamine) concentrations in mobile phase and the stability of PTC-derivatives in solution. Dipropylamine was used as extraction solvent with switchable hydrophilicity that can be miscible or immiscible upon the addition or removal of CO2 as a reagent. The major benefits of this technique is mainly the very large surface area between the fine droplets of the extraction solvent and the aqueous sample, and the accordingly fast extraction kinetics that result in the rapid achieving of a state of equilibrium and the high enrichment factors (300–430) usually obtained. Under the optimum conditions, proposed method provided low limits of detection (0.18– 0.97 μg L−1) and acceptable extraction repeatabilities (RSD%= 3.4-5.7). It was linear over two orders of magnitude. Finally, the developed methods were successfully used in determination of the concentrations of 17 free amino acids in differentsamples and acceptable recoveries (> 80%) were obtained