Application of hydroxylated multi-walled carbon nanotubes as depigmentation agent in the determination of multiple pesticide residues in Lonicerae japonicae flower buds

Lonicerae japonicae flower buds have been used as functional foods for many years, however, the problem of pesticide residues has attracted extensive attention in recent years. In this study, a sorbent package consisting of a combination of hydroxylated multi-walled carbon nanotubes (MWNTs-OH), primary secondary amine, and MgSO4 was developed for modified solid-phase extraction of 57 easily contaminated pesticides residues from Lonicerae japonicae flower bud samples. The pesticides were then detected by gas chromatography coupled to an electron impact ionization triple quadrupole mass spectrometer. Six multi-walled carbon nanotubes were compared for purification efficiency and recovery and found that the best results were achieved with MWNTs-OH (20–50 nm in diameter and 10–30 μm in length). Under optimized conditions, good linearities were obtained in the 1–100 ng·mL−1 range. The average recoveries at three spiked levels were in the 80.4–118.5% range, with relative standard deviations (RSDs) ≤ 20%. The quantification limits were 0.4–5.0 μg·kg−1. Compared with QuEChERS and traditional HLB purification methods, the application of MWNTs-OH could better remove the pigment from a complex sample matrix, as well retain the target analytes as much as possible. Advantages of this newly established method include less analytical time, less solvent consumption and good recovery.