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[Display omitted] • MSU-1, synthesized by us, was used for the first time to pre-concentrate 218 multiclass pesticdes. • The factors which are related in the sorption/desorption were optimized by multi-response surface. • Determination was carried out by UPLC-MS/MS and matrix effect was noted in 20% of pesticides. • Standard addition before SPE performed better that after SPE to correct matrix effect. A mesoporous material (MSU-1), prepared in the laboratory, was applied as a solid phase sorbent to pre-concentrate 218 multiclass pesticides in environmental waters. The pesticides present in the sample extracts were determined by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. The most intense ion was selected as precursor ion. After fragmentation in the collision chamber, the most intense transition (SRM1) was used for quantification and three points were used for identification and confirmation, as established by Directive 96/23/EC. A comprehensive study of the main variables affecting the sorption/desorption of pesticides in the MSU-1 was performed using step-by-step (elution solvent, sample pH and salt content) and multi-response surface (sorbent amount, water volume and solvent elution volume) methodologies, with the optimal values being no addition of NaCl, 100 mg MSU-1 sorbent, 50 mL water sample at pH = 6 and elution of pesticides with 5 mL of acetonitrile. The matrix effect was tested by comparing the slopes of solvent-based and matrix-matched calibration graphs. 80 % of pesticides showed a low matrix effect, and 20 % showed a medium or high matrix effect. Two calibration strategies were tested to correct the matrix effect by adding the pesticide standards before or after the pre-concentration step. The first one corrected for systematic errors due to the low adsorption of pesticides in the MSU-1 and corrected for the matrix effect. The method was validated using blank groundwater samples spiked with 0.1, 0.25 and 0.5 μg/L of all pesticides. Recoveries between 54 and 130 % (RSD ≤ 20 %) were obtained for most pesticides (90 %), while recoveries ≥ 130 % were obtained for 22, 10 and 5 pesticides at 0.1, 0.25 μg/L and 0.5 μg/L, respectively. A monitoring study of thirteen groundwater samples collected in Almería (South of Spain) was performed applying the proposed methodology. Thirty-eight different pesticides were found in the groundwater samples analyzed. However, most of them were found in concentrations below 0.1 µg/L, with imidacloprid, hexaflumuron and oxadixyl being the most frequently detected in 7, 6 and 5 samples, respectively. Only in 5 samples, methiocarb (three samples), pyrethrin I and pytethrin II (one sample) and hezaflumuron (one sample) were found at levels higher than 0.1 μg/L. The method green profile was evaluated using National Environmental Methods Index and analytical Eco-scale assessment tools. [ABSTRACT FROM AUTHOR]

Abstract This paper describes the synthesis of a silica based MSU-1 mesoporous solid and its application as sorbent in solid-phase extraction to pre-concentrate thirteen pesticides of low-high polarity (methomyl, cymoxanil, carbofuran, monolinuron, isoproturon, methidathion, methiocarb, malathion, phosalone, diazinon, penconazole, neburon and chlorotoluron) in ground and river water. The synthesis was based in an H-bonding interaction assembling (I0N0) between two non-ionic components (the inorganic silica surface, I0 and the polyethylene oxide template, N0) by adding tetraethoxysilane to the non-ionic surfactant Brij®100, the latter previously dissolved in HCl 1 M. 50 mL water samples adjusted at pH= 3.5 were passed, at a flow rate of 5 mL/min, through a home-made cartridge containing 50 mg of MSU-1 sorbent, pre-conditioned with 5 mL of ultrapure water; then, the cartridge was washed with 5 mL of ultrapure water. Following elution with 5 mL of acetonitrile, the pesticides were determined by ultra performance liquid chromatography coupled to triple quadrupole-mass spectrometry. Two selected reaction monitoring transitions were monitored per compound, the most intense one being used for quantification and the second one for confirmation. Three points were used for identification, as established in the Directive 96/23/EC for LC-MS/MS analysis, which deals with confirmatory methods for organic residues and contaminants listed in the Group B (veterinary drugs and contaminants). Medium matrix effect (|20%| |50%|). Therefore, the standard addition methodology was applied by adding an adequate amount of the pesticide standard mixture to the final sample extract. All pesticides were quantified using this approach for practical reasons, thus avoiding two different calibrations. The method quantification limit (MQL) of pesticides was 0.01 μg/L for all of them, except for diazinon (0.1 μg/L). Recoveries of the target pesticides at MQL and 0.25 µg/L concentration levels in blank river water were in the range 70.1–113.5% and 86.7–107.3%, respectively, with RSDs lower than 16.3% and 15.7%, respectively. Four ground water samples and three river water samples, taken from Almería (Spain), were analyzed by the proposed method and only phosalone at a concentration level of 0.05 µg/L was found in one river water sample. Graphical abstract fx1 Highlights • Thirteen pesticides were determined in surface waters at trace levels. • The packed MSU-1 silica based sorbent was efficiently used for enrichment and clean-up. • The pesticides were determined by UPLC with MS/MS detection. • The recoveries of some pesticides were better than those obtained using Oasis HLB. [ABSTRACT FROM AUTHOR]