Determination of Free Amino Acids in Fertilizer Samples by Switchable Hydrophilic Solvent-Based Extraction (SHSE) Followed by HPLC-UV

In the present work, switchable hydrophilic solvent-based extraction (SHSE) followed by high performance liquid chromatography with UV detection (HPLC-UV) was used to determine free amino acids in fertilizer samples. During the phase transformation of SHSE, the organic phase appeared to effectively capture the target analytes. In this extraction technique, 200 μL of a water-immiscible solvent (dipropylamine) is used, which can be solubilized in the acidic aqueous phase. Phase separation is then brought about by the addition of sodium hydroxide. The variables affecting this method were optimized to achieve the best extraction efficiency. The optimized conditions included: volume of sample 25 mL, volume of extraction solvent 200 μL, and extraction time 2 min. Under the optimal experimental conditions, good detection limits (0.0006-0.0021 µmol ml-1), linearities (R2 0.997), and precision (relative standard deviation less than 5.0%) were obtained. Finally, the developed method was successfully applied to the determination of target analytes in different types of fertilizer samples and acceptable recoveries ( 97.2%) were obtained.