Molecularly-imprinted microspheres for selective extraction and determination of melamine in milk and feed using gas chromatography-mass spectrometry.

Molecularly-imprinted polymers in the form of microspheres were synthesized using the dispersion polymerization protocol; cyromazine was used as dummy template, while methacrylic acid, ethylene glycol dimethacrylate and acetonitrile (MeCN) were used as functional monomer, cross-linker, and porogen, respectively. When compared with the non-imprinted polymer, the molecularly-imprinted polymers (MIPs) showed outstanding affinity toward melamine in MeCN with a maximum binding concentration (B(max)) of 53.20 nmol mg(-1) MIPs, imprinting effect of 4.6, and a dissociation constant (K(d)) of 90.45 microM. After optimization of the molecularly-imprinted solid-phase extraction conditions, a new method was developed to determine the melamine in milk and feed with gas chromatography-mass spectrometry. The performance of this method has been evaluated in the tainted milk and feed in terms of recovery, precision, linearity, the limit of detection (LOD) and limit of quantitation (LOQ). Recovery ranged in samples from 93.1 to 101.3% with intra-day and inter-day relative standard deviation values below 5.34%. The LOD and LOQ of melamine in milk and feed were 0.01 microg mL(-1) (microg g(-1)) and 0.05 microg mL(-1) (microg g(-1)), respectively.

Li M ，Zhang L ，Meng Z ，Wang Z ，Wu H ... -  《-》

Novel cyromazine imprinted polymer applied to the solid-phase extraction of melamine from feed and milk samples.

He L ，Su Y ，Zheng Y ，Huang X ，Wu L ，Liu Y ，Zeng Z ，Chen Z ... -  《-》

Molecularly imprinted polymer as SPE sorbent for selective extraction of melamine in dairy products.

Yang HH ，Zhou WH ，Guo XC ，Chen FR ，Zhao HQ ，Lin LM ，Wang XR ... -  《-》

The application of pseudo template molecularly imprinted polymer to the solid-phase extraction of cyromazine and its metabolic melamine from egg and milk.

The combination of molecularly imprinted polymer with high performance liquid chromatography has been developed to determine cyromazine and its metabolic melamine in some samples. However, the potential risk of template leakage used in molecularly imprinted polymer is a major disadvantage. To solve this problem, 2-(4,6-diamino-1,3,5-triazin-2-ylamino) ethanethiol disulfide, a molecule that shares the similar imprinting sites with cyromazine and melamine, was selected as pseudo template to prepare molecularly imprinted polymer. Methacrylic acid, ethylene glycol dimethyl acrylate and toluene were selected as functional monomer, crosslinker and porogen, respectively. The molecular recognition property and binding capability of cyromazine and melamine were evaluated by adsorption test and Scatchard analysis. The results showed that the molecularly imprinted polymer based on pseudo template had more excellent affinity and selectivity for cyromazine and melamine. The resulting molecularly imprinted polymer was used as a solid-phase extraction material to enrich cyromazine and melamine in egg and milk samples for high performance liquid chromatography analysis. The solid-phase extraction process was carefully optimized. It was found that when different concentration of cyromazine and melamine standards were spiked into samples, satisfactory recovery rate of cyromazine and melamine were obtained as 85.6-98.8% with relative standard deviation <5.5%.

Wang X ，Fang Q ，Liu S ，Chen L ... -  《-》

Rapid and selective screening of melamine in bovine milk using molecularly imprinted matrix solid-phase dispersion coupled with liquid chromatography-ultraviolet detection.

A simple, convenient and high selective molecularly imprinted matrix solid-phase dispersion (MI-MSPD) using water-compatible cyromazine-imprinted polymer as adsorbent was proposed for the rapid screening of melamine from bovine milk coupled with liquid chromatography-ultraviolet detection. The molecularly imprinted polymers (MIPs) synthesized by cyromazine as dummy template and reformative methanol-water system as reaction medium showed higher affinity and selectivity to melamine, and so they were applied as the specific dispersant of MSPD to extraction of melamine and simultaneously eliminate the effect of template leakage on quantitative analysis. Under the optimized conditions, good linearity was obtained in a range of 0.24-60.0μgg(-1) with the correlation coefficient of 0.9994. The recoveries of melamine at three spiked levels were ranged from 86.0 to 96.2% with the relative standard deviation (RSD)≤4.0%. This proposed MI-MSPD method combined the advantages of MSPD and MIPs, and could be used as an alternative tool for analyzing the residues of melamine in complex milk samples.

Yan H ，Cheng X ，Sun N ，Cai T ，Wu R ，Han K ... -  《-》