Flat membrane-based liquid-phase microextraction for the determination of basic and acidic pesticide residues in water samples.

A flat membrane-based liquid-phase microextraction (FM-LPME) method was developed for the first time to simultaneously separate and extract basic and acidic pesticide analytes from the same sample. Using carbendazim and pirimicarb as representative basic pesticides, along with bromacil, diflubenzuron and 1,2-dibenzoyl-1‑tert-butylhydrazine (RH-5849) as representative acidic pesticides, the performance of FM-LPME for the extraction of these model pesticides has been optimised individually. Under optimal extraction conditions, the developed FM-LPME-LC-MS/MS method exhibited excellent linearity, with R² values exceeding 0.9903 in concentration ranges of 0.1-1400 ng mL^-1 for carbendazim and pirimicarb, and 1-1400 ng mL^-1 for bromacil, diflubenzuron and RH-5849. The limits of detection ranged from 0.01 to 0.09 ng mL^-1. The recoveries and relative standard deviations of all the tested pesticides at three spiked concentrations (100, 500 and 1200 ng mL^-1) were in the ranges of 80.0 %-125.0 % and 0.3 %-9.3 %, respectively. The FM-LPME-LC-MS/MS method demonstrated advantages in terms of being environmentally friendly, possessing a wide linear range, high sensitivity, high precision and satisfactory recoveries, thus highlighting its notable potential for the separation and extraction of basic and acidic pesticide residues in water samples.