Molecular Imprinting in Sol-Gel Materials: Recent Developments and Applications

Since its inception five decades ago, imprinted sol-gel materials went practically unnoticed, until in the 1970s the conceptual introduction of molecular imprinting in synthetic polymers triggered a new interest in this field. The recent growth in interest in organic–inorganic hybrid materials prepared by sol-gel chemistry and the development of a variety of new strategies for imprinting polymeric matrices have led to a growing activity in what became known as molecularly imprinted sol-gel materials. This paper intends to give an overview of recent progress in molecular imprinting in sol-gel matrices, the potential analytical applications of these tailor-made materials and their limitations, with the aim of drawing attention to useful information and to enhancing interest in this practically unexplored but promising field.     

Determination of the amino acid tryptophan and the biogenic amine tryptamine in foods by the heavy atom induced-room temperature phosphorescence methodology

Very simple and selective methods are presented to determine the amino acid tryptophan (Trp) and the biogenic amine tryptamine (Tryp), both compounds with an indole-type molecular structure by the methodology named Heavy Atom Induced-Room Temperature Phosphorescence (HAI-RTP) which constitutes the first time that HAI-RTP has been used to detect compounds with non-naphthalenic structures in their molecules. Different variables affecting the phosphorescence signal (heavy atom perturber and sodium sulfite concentration) were carefully studied. The analytical curves give a linear dynamic range of 15-100 ng ml(-1) and a detection limit of 4 ng ml(-1) for Trp and 94-400 ng ml(-1) and 28 ng ml(-1) for Tryp. The methods have been successfully applied to the analysis of complex food matrices such as the presence of tryptophan in yoghurt and tryptamine in bottled beer. A single alkaline hydrolysis to release Trp from yoghurt proteins and two methods for extracting Tryp from beer samples are proposed and optimised. A total Trp content of 374 mg of Trp per kg of yoghurt was quantified by the standard addition method of calibration and a recovery of 90% was obtained for 250 ng ml(-1) of Tryp in spiked non-alcoholic beer samples.     

高固含量聚合物乳液制备方法新进展

高固含量一直是聚合物乳液制备追求的目标 ,本文将高固含量 (>6 0 % )聚合物乳液的制备方法按机理分为控制乳胶粒直径分布 ,增大乳胶粒直径和使乳胶粒发生形变三类 ,详细评述了各种制备方法的研究进展 ,并对高固含量乳液制备的发展进行了展望。     

The modulating possibilities of dicarbollide clusters: optimizing the Kharasch catalysts

exo-Cluster dicarbollides substitution has allowed tuning of the E degrees (Ru(II)/Ru(III)) potential to obtain the best-performing Kharasch catalyst. We postulate that this is possible through the to-and-fro electron movement between the boron cluster and the sulfonium moieties.     

High performance liquid chromatography post-column chemiluminescence determination of sulfonamide residues in milk at low concentration levels using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate as chemiluminescent reagent

The determination of seven sulfonamides by means of HPLC with chemiluminescence detection is proposed for the first time. The analytes are derivatized with fluorescamine, separated and subsequently they participate in the post-column chemiluminescence (CL) peroxyoxalate system using imidazole as a catalyst. Among the different peroxyoxalates tested, bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate provides higher sensitivities and stabilities, avoiding precipitation problems. A rigorous optimization of the significant variables by means of experimental designs has been developed in order to reconcile the chromatographic conditions with the CL reaction. The method provides detection limits in the low microgl(-1) range and has been satisfactorily applied to the analysis of spiked raw milk samples.     

Simultaneous determination of propacetamol and paracetamol by derivative spectrophotometry

The present paper describes a procedure that phenols in air were preconcentrated in a membrane cell and their content was determined by adsorptive polarography. First, the phenols in air samples were preconcentrated in a membrane cell using 2.0 M NaOH solution, then in a pH 1.3 buffer solution p-bromophenylamine forms a diazoate with NaNO(2), and into the mixture the collected phenols were added to form azo-compound in a pH 13 buffer solution. The azo-compound can be adsorbed at the mercury electrode and yields a sensitive oscillopolarographic wave. Over the range 2.0x10(-8)-2.0x10(-5) M, the peak currents are linearly proportional to the concentration of phenols. The detection limit is 5.0x10(-9) M.     

Pyrylium-containing polymers as sensory materials for the colorimetric sensing of cyanide in water

A sensory polymeric material for the colorimetric sensing of cyanide in water has been developed based on the reactivity of this anion with the pyrylium cation.     

Size evolution of the vibrational predissociation process in Br2...Nen clusters: simulation and kinetic study

A hybrid quantum-classical simulation of the vibrational predissociation of Br2...Nen, (n = 2-11) clusters in the B electronic state is carried out. The time-evolution of the reactants, products, and intermediates is analyzed by a kinetic mechanism consisting of three elementary steps: direct vibrational predissociation (VP), intramolecular vibrational redistribution (IVR), and evaporative cooling (EC). The importance of intramolecular vibrational redistribution followed by evaporative cooling relative to direct vibrational predissociation is shown to increase rapidly with increasing cluster size. Final product state distributions reveal that only one or less Br2 stretching quantum per neon atom is required in order to achieve complete dissociation (n quanta for n < or = 9 and n - 1 for n = 10 and 11). The proportion of available energy going into translation is proposed as a parameter to study the statistical behavior of the Van der Waals clusters. It is shown to depend only on the number of remaining degrees of freedom, a characteristic of a statistical behavior, for n > or = 3.     

Developing an on-line derivatization of FAs by microwave irradiation coupled to HPLC separation with UV detection

The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water–microemulsion–oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet–violet (UV–Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV–Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW–HPLC–UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water–microemulsion–oil systems, to quantify the total acid fraction in each phase.     

血橙中微量元素的测定

采用电感耦合等离子体原子发射光谱仪(ICP-AES),对血橙果肉汁、皮、籽中10种微量元素进行了测定。结果表明,血橙果肉汁、皮、籽中含有Ca、Mg、Fe、Zn、Mn、Cu、Ni等丰富的人体必需微量元素,且血橙果皮、籽中的微量元素含量普遍高于果肉汁中的微量元素的含量,这为血橙药效功能的进一步研究和资源综合开发利用提供一定的科学依据。