Molecularly imprinted polymers—potential and challenges in analytical chemistry

Among the variety of biomimetic recognition schemes utilizing supramolecular approaches molecularly imprinted polymers (MIPs) have proven their potential as synthetic receptors in numerous applications ranging from liquid chromatography to assays and sensor technology. Their inherent advantages compared to biochemical/biological recognition systems include robustness, storage endurance and lower costs. However, until recently only few contributions throughout the relevant literature describe quantitative analytical applications of MIPs for practically relevant analyte molecules and real-world samples. Increased motivation to thoroughly evaluate the true potential of MIP technology is clearly attributed to the demands of modern analytical chemistry, which include enhanced sensitivity, selectivity and applicability of molecular recognition building blocks at decreasing costs. In particular, the areas of environmental monitoring, food and beverage analysis and industrial process surveillance require analytical tools capable of discriminating chemicals with high molecular specificity considering increasing numbers of complex environmental contaminants, pollution of raw products and rigorous quality control requested by legislation and consumer protection. Furthermore, efficient product improvement and development of new products requires precise qualitative and quantitative analytical methods. Finally, environmental, food and process safety control issues favor the application of on-line in situ analytical methods with high molecular selectivity. While biorecognition schemes frequently suffer from degrading bioactivity and long-term stability when applied in real-world sample environments, MIPs serving as synthetic antibodies have successfully been applied as stationary phase separation matrix (e.g. HPLC and SPE), recognition component in bioassays (e.g. ELISA) or biomimetic recognition layer in chemical sensor systems. Examples such as MIP-based selective analysis of flavones/flavonoids in wine, the determination of mycotoxins in beverages and analysis of organic contaminants in environment samples will elucidate the perspectives of this technology and will be contrasted with the challenges of rational MIP design providing control on binding site density, receptor capacity and selectivity.     

Infrared Spectroscopic Study of the Solvation of Tetramethylurea in Protic + Aprotic Mixed Solvents

The infrared spectra of tetramethylurea have been measured in mixtures of dimethylsulfoxide or acetonitrile with D₂O or deuterated methanol (CH₃OD). Marked solvatochroism is observed for bands associated with the C=O and C–N stretches of tetramethylurea, with the former moving to lower wavenumber, and the latter to higher, as the concentration of the protic component is increased. The C=O band shows four distinct absorbances, which are attributed to non-, mono, di-, and trihydrogen bonded tetramethylurea. The relative populations of the different hydrogen bonded species were determined from analyses of the C=O band shapes. It is found that the variations in the populations of the different hydrogen bonded species can be accounted for by a simple mass action treatment.     

A spectral and polarographic study of potassium chlorazepate.

Two new types of solid standards are described for the direct determination of trace impurities in metals by flameless atomic absorption. One of these, a primary standard, has a metal matrix and can be tailor-made to the required size and concentration by the technique of ion implantation. The other, a secondary standard, has a urea matrix into which trace elements are introduced by dissolution. Upper concentration limits are in the 100–1000 p.p.m. range. Both types of standard, the secondary in particular, are suitable for application in other methods of trace analysis.     

An introduction to bismuth film electrode for use in cathodic electrochemical detection

A new electrode surface design, the bismuth film electrode (BiFE), is presented as a promising alternative to mercury and other solid electrodes for direct cathodic electrochemical detection of organic compounds. The preparation of the BiFE, involving an ex situ electroplating of metallic bismuth onto a glassy carbon (GC) substrate electrode, was optimised. The useful negative potential windows of the BiFE in the pH range 1 (−0.2 to −0.8 V vs Ag/AgCl) to 10 (−0.2 to −1.5 V) were determined. The reproducibility of measuring 2-nitrophenol as a model compound (relative standard deviation, r.s.d., n=10) was found to be 0.5% at the same BiFE, and 1.0% at successive newly prepared BiFEs. No polishing or any other pre-treatment of the substrate GC surface was required prior to re-plating of a new Bi film. The BiFE showed similar or even favourable voltammetric behaviour when compared to mercury and bare GC electrodes, and was successfully tested for amperometric detection under hydrodynamic conditions. The results revealed that BiFE is an attractive new non-mercury metallic electrode particularly suitable for cathodic electrochemical detection in flow analytical systems.     

On some Banach space properties sufficient for weak normal structure and their permanence properties

We consider Banach space properties that lie between conditions introduced by Bynum and Landes. These properties depend on the metric behavior of weakly convergent sequences. We also investigate the permanence properties of these conditions.

     

Development of an amperometric immunosensor based on flow injection analysis for the detection of red blood cells

An amperometric immunosensor, based on a non-competitive sandwich assay and flow injection analysis (FIA), was developed for the detection of human red blood cells (RBCs). A dual working electrode, on which specific IgM and nonspecific IgM were chemically immobilised to form sensing and blank electrodes, respectively, was employed to determine the binding of specific blood cells and non-specific adsorption in one determination. Horseradish peroxidase (HRP)-labelled antiblood group A IgM was used in the assay. Sensor preparation involved chemical immobilisation of the IgMs on glassy carbon electrodes using l-ethyl-3(3-dimethyl aminopropyl)carbodiimide (EDC) as a coupling reagent in the presence of N-hydroxysuccinimide (NHS). The interference contributions, such as the non-specific adsorption of the enzyme conjugate and the blood cells, were determined and removed. A quantitative relationship between the cell binding response and its concentration was obtained in the region 1 − 30 × 10⁸ cells ml⁻¹.     

Approximate solutions for magmon propagation from a reservoir

^** Email: tim_marchant{at}uow.edu.au^*** Email: n.smyth{at}ed.ac.uk A 1D partial differential equation (pde) describing the flowof magma in the Earth's mantle is considered, this equationallowing for compaction and distension of the surrounding matrixdue to the magma. The equation has periodic travelling wavesolutions, one limit of which is a solitary wave, called a magmon.Modulation equations for the magma equation are derived andare found to be either hyperbolic or of mixed hyperbolic/elliptictype, depending on the specific values of the wave number, meanheight and amplitude of the underlying modulated wave. The periodicwave train is stable in the hyperbolic case and unstable inthe mixed case. Solutions of the modulation equations are foundfor an initial-boundary value problem on the semi-infinite line,these solutions representing the influx of magma from a largereservoir. The modulation solutions are found to consist ofa full or partial undular bore. Excellent agreement with numericalsolutions of the governing pde is obtained, except in the limitwhere the wave train becomes a train of magmons. An alternativeapproximation based on the assumption that the wave train isa series of uniform magmons is also derived and is found tobe superior to modulation theory in this limit.