Abstract
In this paper, a separation procedure combining molecularly imprinted-solid phase extraction (MI-SPE) was developed for the isolation of melamine. The molecularly imprinted polymer (MIP) was prepared using precipitation polymerization method where melamine as template, 9-vinylcarbazole as functional monomer, ethtylene glycol dimethacrylate as a cross-linker and benzoyl peroxide as initiator. An off-line MI-SPE method followed by ultra-performance liquid chromatography detection of melamine was established. MIP showed a better affinity toward melamine compared to non imprinted polymer (NIP) with a maximum binding capacity of 53.01 mg/g MIP. Based on the correlation coefficients, the kinetic study indicated that the adsorption of melamine by MIP fit a pseudo-second order model. From isotherm study, adsorption of melamine by MIP increased when the concentration of melamine increased and followed a Freundlich isotherm model, which indicates the sorption can be described by multilayer sorption. The interference study proved that MIP has better binding capacity towards melamine if compared to NIP due to specific sites of melamine occurred in MIP particles.
Highlights
Melamine, chemically known as 2,4,6-triamino-1,3,5-triazine, is produced in large amounts (1.2 million tons in 2007) primarily for use in the synthesis of melamine formaldehyde resins for the fabrication of laminates, plastics coatings, commercial filters, glues or adhesives, as well as for dishware and kitchenware [1]
Selectivity of the fabricated melamine-molecularly imprinted polymer-9-vinylcarbazole (Mel-MIP-9VC) and non imprinted polymer-9-vinylcarbazole (NIP-9VC) towards melamine was studied by studying the adsorption of the MIP towards cyanuric acid, analogue of melamine
Weak N–H amines can be observed for melamine and Mel-MIP-9VC spectra, at 3413 and 3643 cm−1 but this N–H stretch peak is absence in monomer and NIP-9VC spectra. This peak occurs when melamine is exists. All of these three spectra show a weak band of C–H stretching at 3046 cm−1 for monomer of 9-vinylcarbazole, 2953 cm−1 for Mel-MIP-9VC and 2954 cm−1 for NIP-9VC spectra
Summary
Chemically known as 2,4,6-triamino-1,3,5-triazine, is produced in large amounts (1.2 million tons in 2007) primarily for use in the synthesis of melamine formaldehyde resins for the fabrication of laminates, plastics coatings, commercial filters, glues or adhesives, as well as for dishware and kitchenware [1]. A new type of high efficiency adsorbents, molecularly imprinted polymers (MIPs), due to high sample load capacity, high selectivity, low cost and easy preparation, have been widely applied for preconcentration and high efficient separation of trace analytes in diverse matrices, such as natural, agricultural, food products and environmental samples [7,8]. Due to their favorable molecular recognition capability and stability, potential application of MIPs has been investigated in a broad scientific area, such as ligand binding assays, SPE, sensors and catalysis. The selectivity of the obtained MIP was analyzed by studying the difference in rebinding capabilities towards melamine and structurally related compounds
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