Cyclodextrin-based nanosponges for the dispersive-solid phase extraction of pesticides from environmental waters

Abstract

In this work, harmless, biodegradable, and low-cost cyclodextrin-based nanosponges (CDNS) were synthetized with an optimized green approach based on the use of a natural cyclodextrin (α-CD, β-CD) as the monomer, citric acid as the cross-linker, and NaH2PO4 as the catalyst. The resulting materials were studied using thermal analysis (TGA, DSC), IR spectroscopy, and SEM imaging. For the first time, α-CDNS and β-CDNS were successfully applied for the dispersive-solid phase extraction (d-SPE) from surface waters of eleven pesticides, including achiral compounds (ametocradin, methoxyfenozide, tebufenozide, pyraclostrobin, spiromesifen), optical stereoisomers (mandipropamid, penconazole, difenoconazole, pyriproxyfen, hexythiazox) and geometric stereoisomers (dimetomorph). The extracts were analysed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A cholesteryl-bonded silica column allowed the baseline separation of the geometric stereoisomers of dimethomorph, while a polysaccharide-based column was effective in the separation of the optical stereoisomers. Although no nanosponge displayed stereo-discrimination, all of them provided absolute recoveries depending on the analyte logP, steric hindrance, and spike level. In particular, β-CDNS gave yields between 26 and 93 %, and intra-day and inter-day precision of 2–9 % and 4–18 %. Limits of detection and limits of quantitation were 0.05–40 ng/L and 0.2–120 ng/L, respectively. After validation, the d-SPE-HPLC-MS/MS method was applied to the analysis of water samples from the Tiber River: ametoctradin, mandipropamid, penconazole, pyraclostrobin and pyriproxyfen were detected at concentrations between 16 and 43 ng/L. Last but not least, recycling tests have proved that CDNSs can be reused three times with unvaried extraction yields.