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Simultaneous Determination of Glyphosate and 13 Multiclass Pesticides in Agricultural Soil by Direct-Immersion SPME Followed by Solid–Liquid Extraction
Publication . Brinco, João; Guedes, Paula; Silva, Marco Gomes da; Mateus, Eduardo P.; Ribeiro, Alexandra B.; DCEA - Departamento de Ciências e Engenharia do Ambiente; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
A new method is presented for the simultaneous determination of 13 multiclass pesticides along with glyphosate. The multiclass pesticides were extracted by creating a soil slurry with 2% ethanol in water (v/v), and then, applying direct-immersion solid-phase microextraction (DI-SPME) with a new type of semi-disposable SPME fiber configuration called LC-Tips. The fibers were then retroextracted to ethanol, and aqueous ammonia was added to the slurry to extract glyphosate. Derivatization of the glyphosate extract was accomplished with a mixture of trifluoroacetic anhydride and trifluoroethanol, after which the reaction mixture was dried and resuspended with the SPME ethanol extract. To this, a mixture of analyte protectants was added, and it was analyzed by GC-MS/MS in multiple-reaction-monitoring mode. All analytes showed a coefficient of determination greater than 0.95 in the 0.1–100 µg/kg calibrated range, and the limits of detection were between 0.1 and 1 µg/kg, except for glyphosate, which was 0.01 µg/kg. The method shows relatively high replicate relative standard deviation (as much as 37% for five extractions at 20 µg/kg), but the isotopically labeled internal standard was effective at mitigating this effect for some analytes.
Extraction of pesticides from soil using direct-immersion SPME LC-Tips followed by GC–MS/MS
Publication . Brinco, João; Carvalho, Raquel; Silva, Marco Gomes da; Guedes, Paula; Ribeiro, Alexandra B．; Mateus, Eduardo P．; DCEA - Departamento de Ciências e Engenharia do Ambiente; LAQV@REQUIMTE; DQ - Departamento de Química; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; Elsevier Science B.V., Amsterdam.
A new method was evaluated and developed for the analysis of pesticides in sandy-loam soil by direct-immersion solid phase microextraction (DI-SPME) followed by gas chromatography tandem-mass spectrometry (GC–MS/MS) determination. Ten pesticides were selected based on a literature survey of the compounds reported to be present in EU soils. The extraction was performed using SPME LC-Tips, a new SPME configuration with the coated fibers attached to a disposable and easy-to-handle micropipette tip, which was immersed into a soil slurry made by the addition of an aqueous solution to the soil sample. Ten experimental parameters were evaluated with a Plackett-Burman design, after which the extraction time and percentage of organic solvent in the aqueous extraction were optimized separately. The two fiber chemistries available (PDMS/DVB and C18) were evaluated in parallel for the entire work. In the final method, slurry samples were made by adding an aqueous solution (6 % methanol v/v) to 2 g of soil. The fiber was conditioned and then inserted, for extraction, into the samples, stirred by a magnetic bar. Afterwards, the analytes were desorbed onto 100 µL of methanol. After the addition of analyte protectants (ethylglycerol, gulonolactone, and sorbitol) the extract was injected into the GC–MS/MS system. Isotopically labelled penconazole was used as internal standard. A calibration was performed by extracting spiked soil with analyte concentrations of 0.1–50 µg/kg. Coefficients of determination of the linear calibration were between 0.94–0.98 for the PDMS/DVB and 0.92–0.99 for the C18. Limits of detection range between 0.01–10 µg/kg for the PDMS/DVB and 0.1–10 µg/kg for the C18. Overall, the C18 analytically outperformed the PDMS/DVB but required a longer extraction time (120 min vs 75 min for the PDMS/DVB). This method allows automation and generates low residual toxic waste, having the potential to be introduced as a greener and simpler alternative to currently used sample preparation methodologies.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso para Financiamento de Projetos de Investigação Científica e Desenvolvimento Tecnológico em Todos os Domínios Científicos - 2020
Número da atribuição
PTDC/CTA-AMB/6587/2020