Molecularly imprinted polymers (MIPs) are functional materials capable of molecular recognition and other biorelevant functions and can be prepared with ease in a tailor-made fashion by copolymerization in the presence of a crosslinker and a template molecule (the target molecule or its analog) conjugated with a functional monomer(s). These robust and affordable synthetic polymer receptors are highly accepted as favorable alternatives to biomacromolecules such as antibodies and enzymes. This article provides a critical review of the present state of MIPs to establish perspectives on this technique via a survey of early to contemporary work, mainly conducted by the authors, covering new principles and methodology to generate MIPs. These include the design and synthesis of new functional monomers and crosslinkers to develop and/or introduce new functionalities, new polymerization methods to improve the imprint effect, and highly sensitive MIP-based assays and sensors.
Enantiomeric separation ability on high-performance liquid chromatography (HPLC) was compared between native and acetylated β-cyclodextrin stationary phases. In the chiral stationary phases (CSP) used in this work, β-cyclodextrin is chemically bonded to aminopropyl silica gel via sugar chain spacer. The acetylated β-cyclodextrin phase (SUMICHIRALTM OA-7700) exhibits excellent performance for the separation of chiral amines and amino alcohols in reversed phase mode. Conventional phosphate buffer can be used in mobile phase without special modifier and the analytical method is easy to develop. OA-7700 is very useful practically for the determination of optical purity of many important chiral amines. It can separate enantiomers of 1-phenyl-2-(p-tolyl)ethylamine (PTE) which is used for industrial scale resolution of chrysanthemic acids and norephedrin (phenylpropanolamine) which is regulated as stimulant raw material.
Fabrication of a monolithic polymer layer, as the stationary phase, equipped with two electrodes was studied for simultaneous two-dimensional separation, combining high performance liquid chromatography and orthogonal electrophoresis. The monolithic polymer layer was prepared between a pair of glass plates by a two-step UV-initiated photo-polymerization. Prior to preparation of the monolithic polymer layer for separation, high-density monolith bars were prepared along the electrodes to suppress the penetration of bubbles formed at the electrodes into the separation monolith. Using the monolithic polymer layer, 2D separation of colored-dyes was successfully achieved by combining gradient HPLC and orthogonal electrophoresis. The 2D separation of proteins was also demonstrated.
An analytical method for the simultaneous detection of five types of Fusarium toxins (nivalenol (NIV), deoxynivalenol (DON), HT-2 toxin (HT-2), T-2 toxin (T-2), and zearalenone (ZEN)) in processed grains has been developed. Mycotoxins in the sample were extracted using acetonitrile-water (85:15 v/v), purified using MultiSep 226 AflaZon+ multi-functional cartridge columns, and quantified using high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS). With wheat flour, the proposed method showed good linearity (r > 0.999), and the accuracy was 85 - 97%. The RSD values of the intra-day precision were 1.9 - 13.3% and those of the inter-day precision were 10.2 - 19.6%. In a study of commercial foodstuffs, the limit of quantification was 15 μg/kg for NIV and DON, and 5 μg/kg for HT-2, T-2, and ZEN. Using the validated method, we conducted a contamination study of 55 processed food samples, including a variety of wheat and corn products. DON was detected in 36 samples, with a maximum concentration of 238 μg/kg in corn grits. In addition, HT-2 was detected in six samples, and T-2 was detected in two samples, in products that contained wheat as the raw material, with concentrations of less than 20 μg/kg.
The titania that was prepared as a packing material in our laboratory, which changed its color on heating, microwave irradiation, and heating under vacuum during nitrogen adsorption. We assumed that the compound adsorbed on titania was oxidized or oxidatively polymerized on heating, leading to the color change. The color faded on heating the sample at 270°C. The catalytic ability of titania is assumed to accelerate its coloration and decoloration. We demonstrated the catalytic ability of titania using glycerol as an adsorbate; silica gel was used as an adsorbent for comparison with titania. Titania accelerated the oxidation or oxidative polymerization of the adsorbate and the decomposition of the oxidized or polymeric compound obtained. Furthermore, the catalysis of titania led to the modification of its surface by adsorbate oxidation or oxidative polymerization; also, surface modification was demonstrated by using glycerol as the adsorbate. Two different modified titania were prepared as packing material by heating the mixture of titania and glycerol at 120°C and 200°C for up to 2 h after coloration. The retention behavior of purine, allopurinol, hypoxanthine, and oxypurinol on these two modified titania and non-modified one was investigated. Oxypurinol eluted faster than hypoxanthine on titania modified at 120°C although it was more strongly retained on non-modified titania than hypoxanthine. Thus, the retention site of oxypurinol is similar to that of glycerol on non-modified titania, that is, the surface modification by glycerol oxidation or oxidative polymerization blocked the site and accelerated its elution. The results could be used for explaining not only the modification of the surface but also the retention mechanism on titania.
Plasma amino acid concentrations have been analyzed by high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS) after precolumn derivatization. However, it is still unknown whether chyle and bilirubin, which are known to interfere with quantifications of some clinical biomarkers, have any influence on plasma amino acid measurement. In this study, we investigated the effects of those interference substances on amino acid concentrations determined by HPLC-ESI/MS. A total of 20 Japanese subjects (volunteers working for Ajinomoto Co., Inc.) were enrolled in this study. Twenty-one amino acid concentrations in plasma were measured with HPLCESI/MS after addition of each interference substances (a soy bean oil-egg yolk lecithin for the evaluation of chyle and total bilirubin). No significant changes of amino acid concentrations were observed by the addition of soybean oil (less than 0.25%) and bilirubin (final concentration: 0.5-2.0 mg/dL). Although the addition of 0.5% of soybean oil increased proline and phenylalanine levels significantly, the changes were less than ± 5% compared with blank samples. These results suggest that there would be little effects of chyle and bilirubin on the measurement of amino acid concentrations determined by the present HPLC-ESI/MS system.
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