Preparation of guanidinium terminus-molecularly imprinted polymers for selective recognition and solid-phase extraction (SPE) of [arginine]-microcystins
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About 70 % of microcystin (MC) congeners reported in literature consist of l-arginine amino acid (R) with its guanidinium terminal extending out of the cyclic moiety of these MCs. Molecularly imprinted polymer (MIP) bearing guanidinium terminus cavities was successfully synthesised using l-arginine as a template. Non-imprinted polymer (NIP; without template) was also synthesised for control purposes. The surface area, total pore volume and average pore diameter of MIP and NIP were 267.13 m2/g, 0.63 cm3/g and 88.39 Å; 249.39 m2/g; 0.54 cm3/g and 87.14 Å, respectively. The polymers were investigated for selective recognition and extraction of [arginine]-MCs in water using solid-phase extraction/liquid chromatography-electrospray ionisation–mass spectrometry (SPE/LC-ESI-MS) method. Representative model standard solutions (0.5–10.0 μg/L) of MC-LR and MC-LY were spiked in distilled water, recovered by SPE and quantified by LC-ESI-MS. In this study, Oasis Waters™ HLB cartridges served as positive control SPE sorbents. The MIP recognised MC-LR with high recoveries (70.8–91.4 %; r 2 = 0.9962) comparable to HLB cartridges (71.0–91.85 %; r 2 = 0.9993), whereas the NIP did not recognise or retain MC-LR. Also, neither MIP nor NIP recognised or retained MC-LY. Extracts of environmental toxic Microcystis aeruginosa were subjected to SPE procedure employing MIP, NIP and HLB cartridges. Microcystin-LR, -YR, -RR, -WR, -(H4)YR and (D-Asp3, Dha7)MC-RR were extracted by MIP and HLB cartridges only as confirmed by LC-ESI-MS. This study demonstrated that the prepared MIP have potential applications for the removal in water and LC-ESI-MS identifications of MCs consisting the guanidinium moiety, i.e.[arginine]-MCs, and in particular targeting commonly encountered toxic congeners, MC-LR, -YR and -RR.
KeywordsGuanidinium terminus MIP SPE Selective recognition [arginine]-Microcystins
We acknowledge the World Bank-Science and Technology Higher Education Project (WB-STHE Project, Dar es Salaam, Tanzania) and the Centre for Nano-materials, Department of Applied Chemistry, University of Johannesburg (Republic of South Africa) for financial support.
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