A brief history and personal recollection of the development of magnetic resonance imaging (MRI).
Thin polymer layers on solid substrates are of high technological importance due to their increasing potential for applications in electronics, sensors, nanotechnology and biotechnology. Appropriate characterisation methods are necessary for the design and analysis of devices made using such materials. This review article focuses upon presenting the many analytical possibilities for quantitative evaluation of the optical constants and thickness of polymer layers by combined application of spectroscopic ellipsometry (SE) in the visible (vis) and infrared (IR) spectral range.
Surface Analysis Coordinator, School of Materials, The University of Manchester, PO Box 88, Manchester, M60 1QD, UK. E-mail: [email protected], Web: personalpages.manchester.ac.uk/staff/john.walton
The purpose of this short review article is to highlight some capabilities of qNMR spectroscopic methods in drug quality evaluation, indicating that qNMR spectroscopy should be more often applied when chromatographic methods are not working effectively.
UV/vis reflection spectroscopy is a practical method to investigate pulp ageing, especially when reflectance spectra are converted to absorbance (k/s) spectra. Even if detailed reaction paths cannot be solved with this technique alone, it provides a very fast and simple method to study the changes in the concentrations of certain important pulp components during ageing. In addition, the concentrations of these components have been studied also in other pulp processes, such as mechanical and chemical pulp bleaching.
A number of analytical applications in the area of security screening, medical diagnosis, drug authentication and quality control often require non-invasive probing of diffusely scattering (turbid) media in order to obtain chemical characterisation of deep-lying sample regions. Examples include non-invasive disease diagnosis, the detection of concealed explosives and illicit materials, the identification of counterfeit drugs and quality control applications in the pharmaceutical industry. Raman spectroscopy holds particular promise in this area due to its inherently high chemical specificity [exceeding that of near infrared (NIR) absorption spectroscopy and comparable with mid-infrared and THz methods], the ability to probe samples in the presence of water (the Raman scattering cross-section of water is very low) and its high penetration depth into turbid non-absorbing or weakly absorbing samples. On the downside, the technique is restricted to samples that do not exhibit strong fluorescence emission although this problem can, in the majority of cases, be avoided by using NIR excitation. Until recently, Raman techniques have generally been confined to applications involving surface layers of turbid media due to limitations imposed by the backscattering collection geometry common to the majority of commercial Raman probes. In principle, confocal Raman microscopy can potentially resolve objects to depths of up to several hundred micrometres. Deeper layers cannot be readily resolved and, typically, are overwhelmed by Raman and fluorescence signals emanating from the surface layer.
Knowledge of the absolute configuration of asymmetric, chiral carbon atoms is essential for the understanding of enzyme mechanisms, drug action and structure–function relations, as well as for the determination of biological structure. For example, the right-handed alpha helix in proteins and DNA (both right-handed B and left-handed Z) are all based on the knowledge of the absolute configuration of their building blocks, amino acids and nucleic acids, respectively. Knowledge of the absolute configuration is crucial in the discovery, development and the registration of drugs. The independent determination of the absolute configuration is commonly achieved by single crystal X-ray analysis making use of anomalous dispersion. However, crystals of suitable quality are required for this technique. Moreover, the crystal should preferably contain a heavy atom, such as chlorine or heavier, for the anomalous dispersion technique to work. In this article we describe a technique for determining absolute configurations in solution.
Our focus here is analytical procedures and the role of nuclear magnetic resonance (NMR) in particular. These have, until now, largely relied on conventional chromatography, and vibrational spectroscopy—infrared (IR), Raman and near infrared (NIR) spectroscopy. In spite of inherent difficulties with peak assignment and reliable quantification, vibrational spectroscopy has been used to derive information on reaction progression to impart fundamental understanding. This article sets out a wider scope to show how NMR can play a key role. Furthermore, NMR integrates well with established procedures to provide a suite of useful technologies that make the PAT challenge tractable.
We will consider here the analytical aspects involved in the measurements of illicit drugs and their metabolites in wastewater samples by HPLC-MS/MS.
In the post-genome era, the focus of life science is shifting to proteins. Based on the difference between the various states of the protein, time resolved Fourier transform (tr-FT-IR) spectroscopy can selectively detect, with nanosecond resolution, reactions of the amino acids, the ligands and specific water molecules in the active centre of the protein, thereby providing a detailed understanding of the reaction mechanism. Malfunctioning of proteins is the cause of many diseases. Thus, the understanding of structure, function and interaction of proteins at the molecular level is essential for the development of drugs for a rational molecular therapy.
X-ray fluorescence spectrometry could be a good analytical tool for trace metal analysis of vegetation samples as an alternative to classical destructive methods, given that it provides accuracy and precision fulfilling the requirements for environmental studies.
Raman spectroscopy was used to study the condition of the Victory sail. Molecular spectroscopic analysis of the sail fibres was needed to simulate the aged, degraded material, thereby effecting a better compatibility between the old and replacement materials which would assist in the preservation of this ancient, historic marine textile.
The University of Leicester began an investigation to determine whether useful information on PAN (Peroxyacetyl nitrate) could be obtained from MIPAS data using the MSF absorption cross-sections.
This article focusses on the application of near infrared (NIR) spectroscopy as a potential substitute to the sensory evaluation of tea quality.
The authors show how the use of SIAM method (Species Identification of Animals MALDI-TOF mass spectrometry) is a fast and reliable tool for recognising the origin of mammalian species.
The aim of this study is to compare two of the most applied digestion methods for heavy metals determination in calcareous soils, evaluating the most effective and useful digestion method to be applied to agricultural soils devoted to growing vegetable crops in the Valencian Mediterranean region, a representative area of the European Mediterranean region.
The author looks at the origins and research at the Molecular Spectroscopy Facility (MSF) at the Rutherford Appleton Laboratory (RAL).
The authors report on an analytical technique based on the combination of attenuated total reflection infrared (ATR-IR) spectroscopy and modulation excitation (ME), which enables the investigation of the interactions leading to separation at the selectand—selector interface.
J.I. Baumbacha and M. Westhoffb
aISAS—Institute for Analytical Sciences, Department of Metabolomics, Bunsen-Kirchhoff-Straße 11, 44139 Dortmund, Germany
bLung Hospital Hemer, Theo-Funccius-Str. 1, 58675 Hemer, Germany