Abstract:

The complex composition of aquatic products, with high levels of protein and fat, significantly impacts the accuracy of liquid chromatography-mass spectrometry analysis for pesticide residue detection. Hence, developing effective purification materials is essential to mitigate these matrix interferences. To address strong matrix interference in pesticide residue analysis, a composite material, multi-walled carbon nanotubes (MWCNTs)-sodium alginate (SAL) (MWCNTs-SAL), was developed and used as purification material in a push-rod oscillation purification column to establish a rapid method for analyzing 66 pesticide residues in Litopenaeus vannamei. The composite solution of MWCNTs and SAL was quickly sprayed into CaCl₂ solution by electrospray device for crosslinking, and MWCNTs-SAL materials were prepared. The results of scanning electron microscopy image proved the successful preparation of the MWCNTs-SAL. Acetonitrile, as the extraction solvent, was modified with acetic acid to augment the extraction efficiency of acidic pesticides, and anhydrous sodium sulfate was utilized to remove water from the matrix. Push-rod oscillation purification technology was used for purification of the post-centrifugation extract. The target compounds were separated using C₁₈ RRHD column (150 mm×3.0 mm, 1.8 μm) and the mobile phases were consisted of 0.2% formic acid aqueous solution (containing 5 mmol/L ammonium acetate) and 0.2% formic acid methanol. The high performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry (HPLC-QTRAP-MS/MS) was used for separation and determination, and the data was collected through the multiple reaction monitoring (MRM) mode. Due to the different properties of the target compounds, positive and negative ion acquisition scan modes were employed for mass spectrometry analysis. The quantitative analyses of the 66 pesticides were achieved by matrix-matched standard curves. The purification effects of MWCNTs-SAL and commercial sorbents on the extraction of the 66 pesticides were compared. The pretreatment parameters, such as the optimal dosage of MWCNTs-SAL and anhydrous sodium sulfate on the purification effects of the 66 pesticides were also assessed. When using 50 mg MWCNTs-SAL and 100 mg anhydrous sodium sulfate as the purification materials, the purification effect of aquatic products was the best. The 66 pesticides demonstrated good linearities in the range of 0.5-50 μg/L, with correlation coefficients of greater than 0.99. The limits of detection and quantification for the 66 pesticides were 0.5-1 μg/kg and 1-2 μg/kg, respectively. The recoveries of the 66 pesticides under three spiked levels (low, medium, high) were 64.1%-107.3%. The intra- and inter-day precisions were both less than 20.4%. This study provides an economical, quick, efficient, and sensitive approach for pesticide residue detection in aquatic products.

Key words: multi-walled carbon nanotubes (MWCNTs), high performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry (HPLC-QTRAP-MS/MS), aquatic products, pesticide residues