Evaluation of Molecularly Imprinted Polymers for the Simultaneous SPE of Six Corticosteroids in Milk
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A molecularly imprinted solid-phase extraction procedure was optimized for the simultaneous extraction of six corticosteroids commonly employed in animal husbandry. Two different molecularly imprinted polymers (MIPs) were synthetized by precipitation polymerization, using dexamethasone (DM) and flumethasone (FLU) as template molecules. Methacrylic acid was used as functional monomer and divinylbenzene as cross-linker, and the selected porogen was a solution of acetonitrile and toluene (3:1). After removal of the template, both molecularly imprinted and non-imprinted polymers were placed into glass cartridges to perform solid-phase extraction experiments. Loading, washing and elution steps were optimized for each MIP in order to test the suitability of the selected template molecules DM and FLU to provide selective polymeric sites for corticosteroids. Recovery measurements were performed by HPLC–MS/MS. The maximum recovery for all corticosteroids was achieved with DM-based MIP when loading with toluene and washing with 5% acetonitrile in toluene, and eluting with 1% acetic acid in methanol. When cleaning-up milk samples spiked with corticosteroids, the recovery of DM-based polymer decreased. However, the efficiency of FLU-based polymer clearly improved even when a strong matrix effect was observed. Additionally, two frequently used commercial solid-phase extraction (SPE) cartridges were compared with imprinted polymers. The commercial SPE cartridges gave good recoveries only for specific analytes while MIPs provided good recoveries for all analyzed corticosteroids.
KeywordsMIP Corticosteroids Methacrylic acid Divinylbenzene Milk SPE
This work was supported by the project with reference AGL2009-14707 from the Spanish Ministry of Science and Innovation.
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