Ultrasound-assisted dispersive micro-solid-phase extraction using hydrophobic thiolated ionic liquids immobilized on gold nanoparticles for the preconcentration and determination of amino acids in human plasma samples

We describe the pre-column derivatization of 19 amino acids with o-phthalaldehyde/2-mercaptopropionic acid. The derivatives were extracted using an ultrasound-assisted dispersive micro-solid-phase extraction based on hydrophobic thiolated ionic liquids immobilized on gold nanoparticles. For this purpose, 10 mg of adsorbent was added to 10 mL of aqueous sample in the absence of any electrolyte and was inserted in ultrasound bath, which led to the efficient dispersion of adsorbent. The correlation between the extraction efficiency and parameters were optimized using experimental design and response surface methodology. The effects of alkyl-chain length and anion of hydrophobic thiolated ionic liquids on the surface water wettability of gold nanoparticles were measured. Also, NMR spectroscopy and BET analysis were performed to recognize the formation of thiolated ionic liquids. Transmission electron microscopy, FTIR spectroscopy and X-ray diffraction were conducted to characterize the gold nanoparticles. The suggested method shows a linear range (0.5-500 mu mol L-1) under the optimized conditions with limits of detection in the range of 0.11-0.98 mu mol L-1 for analytes. The validated method was successfully used for the quantification of nineteen amino acid derivatives with relative recoveries in the acceptable range of 81.1-104.4% and relative standard deviation less than 4.2%.