[Dispersive solid-phase extraction combined with high-performance liquid chromatography for determination of seven...

Nowadays, anesthetics are widely used in fishery production processes, such as fish breeding, surgery, and fresh aquatic product transportation. Because of the widespread application of anesthetic drugs in aquatic products, there is an increasing demand for the rapid and sensitive detection of anesthetic drugs in aquatic products. The complex aquatic product matrix contains a variety of interfering substances, such as proteins, fats, and phospholipids, along with anesthetic drug residues at very low concentrations; therefore, it is necessary to adopt appropriate pretreatment methods for improving the sensitivity of detection. In this study, a dispersive solid-phase extraction (DSPE) method, combined with high-performance liquid chromatography, was established for the simultaneous detection of seven anesthetic drugs in aquatic products, viz. procaine, oxybuprocaine, tricaine, eugenol, methyl eugenol, isoeugenol, and methyl isoeugenol. For the DSPE step, pretreatment conditions, such as extraction solvent, extraction time, adsorbent amount, and DMSO dosage, were optimized. Sample pretreatment is a three-step process. First, in ultrasound-assisted extraction, 2.0 g samples were extracted using 10.0 mL 1.0% formic acid in acetonitrile under ultrasound conditions for 10 min. Then, DSPE was performed with mixed adsorbents: the solvent extracts were cleaned using 20 mg poly(styrene-glycidylmethacrylate) microspheres (PS-GMA), 50 mg primary secondary amines (PSA), and 10 mg C18, followed by separation by centrifugation. Finally, DMSO-assisted concentration was applied: the organic layer was collected and was dried at 40 ℃ in a N₂ stream with 100 μL DMSO. Water was added to the residue to obtain a final volume of 1.0 mL for HPLC analysis. The seven anesthetic drugs were separated on a Welch welchrom C18 column (250 mm×4.6 mm, 5 μm) by gradient elution using methanol and 0.05% formic acid in 5 mmol/L ammonium acetate aqueous solution as mobile phases. The detection wavelengths were 235, 260, and 290 nm. Two matrix matching standard curves for fish and shrimp were applied for quantitative analysis. Under optimized conditions, the seven target anesthetics showed good linear relationships in their respective concentration ranges (R²>0.999), with the limit of detection (LOD) ranging from 0.011 to 0.043 mg/kg. In fish samples, the mean recoveries obtained at three concentration levels were between 79.7% and 109%, with relative standard deviations (RSDs) being less than 7.2%. In shrimp samples, mean recoveries were 78.0%-99.9%, with RSDs being less than 8.3%. This simple, rapid, accurate, and sensitive method can be applied to the detection of three kinds of aminobenzoic acid esters and four kinds of eugenol anesthetic drugs in aquatic products.