2. Experimental
2.1. Materials and reagents
Analytical grade bentazon was purchased from Sigma-Aldrich. Acetonitrile, methanol, ethanol, chloroform and acetic acid were purchased from Merck and were analytical or HPLC grade. Methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker and α,α′-Azoisobutyronitrile (AIBN) were purchased from Merck (Hohenbrunn, Germany). MAA was distilled under vacuum to remove the inhibitor prior to polymerization. To clean the inhibitor from EDMA, it was washed with 10% aqueous sodium hydroxide three times, followed by washing with pure water, and then dried over anhydrous sodium sulfate. Ultra pure water used for HPLC analysis and MISPE process were obtained from a Direct.Q3 Water Purification System (Millipore Corporation, USA). Bentazon standard solutions were …show more content…
SPE procedure was performed using a Visiprep TM-DL SPE vacuum manifold from Supelco (Bellefonte, PA, USA). Empty SPE tubes were packed with 100 mg of imprinted or non-imprinted polymer using two PTFE frits at each end. SPE cartridges were preconditioned with 2 mL of ultra pure water and 2 mL of methanol to activate the sorbent before the enrichment procedure. 8 mL of bentazon solution were uploaded onto the preconditioned cartridge. After loading, the vacuum was still applied to the cartridges for 5 min in order to remove the residual solvent. 1 mL of ethanol/water (8/2, v/v) were added to the cartridges to eliminate molecules retained by physical adsorption by the polymer. Eluting step was performed using 2 mL of methanol/acetic acid (9/1, v/v) mixture solution. The elution fractions were dried under a gentle nitrogen stream. The residue was dissolved with 1 mL of methanol and filtered through a 0.45µm nylon filter for subsequent HPLC
2.1. Materials and reagents
Analytical grade bentazon was purchased from Sigma-Aldrich. Acetonitrile, methanol, ethanol, chloroform and acetic acid were purchased from Merck and were analytical or HPLC grade. Methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker and α,α′-Azoisobutyronitrile (AIBN) were purchased from Merck (Hohenbrunn, Germany). MAA was distilled under vacuum to remove the inhibitor prior to polymerization. To clean the inhibitor from EDMA, it was washed with 10% aqueous sodium hydroxide three times, followed by washing with pure water, and then dried over anhydrous sodium sulfate. Ultra pure water used for HPLC analysis and MISPE process were obtained from a Direct.Q3 Water Purification System (Millipore Corporation, USA). Bentazon standard solutions were …show more content…
SPE procedure was performed using a Visiprep TM-DL SPE vacuum manifold from Supelco (Bellefonte, PA, USA). Empty SPE tubes were packed with 100 mg of imprinted or non-imprinted polymer using two PTFE frits at each end. SPE cartridges were preconditioned with 2 mL of ultra pure water and 2 mL of methanol to activate the sorbent before the enrichment procedure. 8 mL of bentazon solution were uploaded onto the preconditioned cartridge. After loading, the vacuum was still applied to the cartridges for 5 min in order to remove the residual solvent. 1 mL of ethanol/water (8/2, v/v) were added to the cartridges to eliminate molecules retained by physical adsorption by the polymer. Eluting step was performed using 2 mL of methanol/acetic acid (9/1, v/v) mixture solution. The elution fractions were dried under a gentle nitrogen stream. The residue was dissolved with 1 mL of methanol and filtered through a 0.45µm nylon filter for subsequent HPLC