Novel deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase for HPLC-UV determination of aromatic amines in environmental samples

In this study, a green and efficient sample preparation method using a deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase (DES-UA-DLLME-SAP) followed by HPLC-UV was developed for preconcentration and determination of aromatic amines in aqueous environmental samples. In the proposed method, a novel deep eutectic solvent (DES) characterized by low density was prepared by mixing trihexyl(tetradecyl)phosphonium chloride and decanol at a molar ratio of 1:2. Ultrasounds were used to disperse the extractant in the aqueous phase of the sample. Then, the phases were separated by centrifugation, after which the aqueous phase was frozen and the surface DES phase was dissolved in a small volume of methanol before injection into the chromatograph. Various factors, including the selection of extractant and its volume, pH of the sample, duration of ultrasounds treatment, the time and rate of centrifugation and salt addition, were investigated and optimized. Under optimal conditions (40 mu L of DES, pH = 12, 60 s of ultrasound use, 10 min/4500 rpm of centrifugation, 40 mg of NaCl), the proposed method allowed to achieve good precision (n = 6) between 2.9 and 6.2% at 0.4, 5.0 and 40.0 ng mL(-1) levels, respectively. The preconcentration factors were equal to 119, 116 and 121 for 2-chloroaniline, 4-chloroaniline and 1- naphthylamine, respectively. The limits of detection were equal to 0.07 ng mL(-1 )for 2-chloroaniline, 0.11 ng mL(-1) for 4-chloroaniline and 0.08 ng mL(-1) for 1-naphthylamine. The proposed method was successfully applied for determination of aromatic amines in aqueous environmental samples with a good recoveries in the range of 85.1-99.9%