Vortex-ultrasonic assisted dispersive liquid-liquid microextraction for seven sulfonamides of fish samples based on hydrophobic deep eutectic solvent and simultaneous detecting with HPLC-PDA

In this work, a simple, rapid, eco-friendly vortex-ultrasonic assisted dispersive liquid-liquid microextraction sample pretreatment method based on hydrophobic deep eutectic solvent was developed for the extraction of seven sulfonamides (sulfadiazine, sulfamerazine, sulfamethazine, sulfacholrpyridazine, sulfamethoxazole, sulfisoxazole, sulfadimethoxine) in fish samples. The hydrophobic deep eutectic solvent was prepared by mixing methyltrioctylammonium chloride as a hydrogen bond acceptor and capric acid as a hydrogen bond donor. The procedure of sulfonamides extraction included mixing solid food samples with 0.6 mL deep eutectic solvent, followed by extraction of sulfonamides into the solvent phase. Then, 3 mL deionized water was injected into the hydrophobic deep eutectic solvent to promote phase separation, resulting in its dissolution and the formation of capric acid dispersed in an aqueous phase. After the phases were separated by centrifugation, the capric acid phase containing sulfonamides was determined by high performance liquid chromatography coupled with photo-diode array detector analysis. Under optimal conditions (0.6 mL of deep eutectic solvent, methyltrioctylammonium chloride: capric acid = 1:1, 3 mL of deionized water, pH = 6), the synthesized DES had excellent extraction and separation effects for four sulfonamides (SPZ, SMZ, SIZ, and SDM) with recoveries ranged from 96.6 to 113.5 %, while the extraction efficiency of the other three sulfonamides (SPD, SM1, and SM2) was slightly lower, and the recovery rate was in the range of 61.6–72.2 %. The proposed method exhibits a wide linear range of 0.02–10 mg kg−1 (r2 ≥ 0.9998). The limit of detection was 0.0053–0.009 mg kg−1 and the limit of quantitation was 0.017–0.03 mg kg−1. Good precision and accuracy (n = 6) of the proposed method were 0.7–3.7 % and 1.4–7.1 % at concentration of 0.5, 1 and 5 mg kg−1, respectively. The proposed method was successfully applied to determine of four kinds of sulfonamides in fish samples with excellent average recoveries in the range of 96.6–113.5 % (SPZ, SMZ, SIZ, and SDM).