Direct solidification of switchable-hydrophilicity salicylic acid: A design for the on-site dispersive liquid-liquid microextraction of benzoylurea insecticides in water and honey samples

• Published in: Journal of Chromatography A 2023-01, Vol.1688, p.463710, Article 463710
• Main Authors: Wang, Huazi, Wang, Tiantian, Hong, MingXiu, Wang, Ziyang, Jin, Xiaoyan, Wu, Hai
• Format: Article
• Language: English
• Subjects: Benzoylurea insecticides; Direct solidification; On-site dispersive liquid-liquid microextraction; Salicylic acid; Switchable-hydrophilicity solvents
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2022.463710

•SA, a switchable-hydrophilicity aromatic acid, was first introduced to on-site DLLME as the extractant.•The facile and effective dispersion and phase separation were achieved by changing solution pH.•The melting point of SA led to direct solidification and simple collection.•The developed on-site DLLME could be operated manually in the entire process.•The extraction mechanism was well demonstrated by DFT calculations. This study describes the development of a fully manual method for on-site dispersive liquid-liquid microextraction based on the direct solidification of switchable-hydrophilicity salicylic acid (on-site DLLME-DSSA) coupled with high-performance liquid chromatography with an ultraviolet detector (HPLC-UVD) and its utilization for the detection of benzoylurea insecticides (BUs) in water and honey samples. Salicylic acid (SA), a switchable hydrophilic aromatic acid, was used as an extraction solvent. It can be converted into the hydrophobic/hydrophilic forms in pH-changeable solutions, facilitating facile and effective dispersion and phase separation. Moreover, the melting point of SA (significantly higher than room temperature) enables its direct solidification without an ice-water bath, facilitating its collection by filtration. The dispersion, separation, and collection of the extraction solvent were carried out entirely in a plastic syringe without requiring special apparatus or additional energy. Univariate and response surface analyses were used to optimize various parameters of the on-site DLLME-DSSA method. Under optimal conditions, the limits of determination (LODs) were 1.50 µg L−1 and 0.03–0.09 mg kg−1 in water and honey, respectively. The relative standard deviations (RSDs) for inter-day (n = 5) and intra-day (n = 5) precision were ≤8.4%, whereas the extraction recoveries and enrichment factors for the BUs ranged from 67.0 to 97.1% and 29 to 34, respectively. Furthermore, the proposed method was used for the on-site extraction and laboratory detection of BUs from real water and honey samples. Theoretical analyses indicated non-covalent interactions (such as hydrogen bonds, electrostatic interactions, van der Waals forces, and π-π interactions) to be the main driving force for extraction. This study introduces a switchable hydrophilic aromatic acid capable of direct solidification into on-site DLLME for the first time, opening new frontiers in the development of on-site sample pretreatment methods.