Inductively coupled plasma-mass spectrometry (ICP-MS) was introduced commercially in 1983 as a very sensitive analytical technique to be deployed for (ultra)trace element analysis. Compared to the previously existing techniques of atomic absorption spectrometry (AAS) and ICP-optical emission spectrometry (ICP-OES), the main advantages offered by ICP-MS over these techniques were its pronounced multi-element capabilities and substantially higher detection power, respectively.
During the last few decades, solution and solid state techniques have been utilised to obtain information about the properties of supramolecular host–guest complexes. Mass spectrometric analysis of these fragile non-covalent complexes has been focused on the determination of the molecular mass of the interacting molecules and the analysis has concentrated on the characterisation of covalent compounds. Since the invention of the soft ionisation techniques [namely ESI (electospray ionisation) and MALDI (matrix-assisted laser desorption/ionisation)] and their development for mass spectrometry (MS) instruments, the area and way that MS analysis is used have greatly changed and expanded. In particular, ESI has attained a steady position for the analysis of biomolecules, their non-covalent complexes and other rather fragile systems, which were earlier impossible to study by mass spectrometric methods. Today, MS can be employed not only for molecular weight identification purposes but also for sophisticated analyses on versatile properties of compounds. In the area of supramolecular chemistry, MS studies are becoming more and more general, although MS utilisation is still quite limited.
Over the last two decades therapeutic antibodies have become the fastest growing area in pharmaceutical biotechnology. The medical significance of these therapeutic entities is highlighted by the commercial availability of about 20 products on the market with more than 160 candidates evaluated in different clinical trials. One reason for the success of antibodies as therapeutic agents is related to the large advancement in their biotechnological production via fermentation. Nowadays titers of about 4 g L–1 in 11-day fed-batch mode using the CHO BI HEX process are achievable using CHO-cells (CHO: chinese hamster ovary).
The ultimate use of XRF for medical analysis is in vivo measurements made directly in the living patient or volunteer. It started with quantitative analysis of iodine in the human thyroid. The idea sprang from the pioneering work by Jacobsson, who developed a technique for subtraction radiology of iodine using two x-ray energies, one above and one below the K-absorption edge of iodine. Hoffer et al. realised that if that technology worked, there should be a chance to see the emitted characteristic x-rays from iodine using the semiconductor detectors, which at that time had been developed for nuclear and particle physics. In this way the first in vivo XRF analysis was done, quantifying the iodine concentration in human thyroid, typically around 400 µg g–1. The further development of the in vivo XRF technique was related to the analysis of heavy elements, first covering lead and later cadmium and to some extent also mercury in occupationally exposed workers. Platinum was also analysed to investigate uptake and kinetics of the cytostatic agent cis-platinum in tumour patients. The following section describes efforts made to study various toxic elements in vivo in occupationally exposed workers and in patients.
This article will demonstrate the use of Raman spectroscopy as a fast and easy detection system for different counterfeit erectile dysfunction drugs. The possible counterfeits analysed consisted of two Viagra® tablets, SEYAGRA-GEL containing the same active ingredient as Viagra® and two tablets claiming to contain the same active ingredient as Cialis®.
The effectiveness of these new reagents in quantitating eight states simultaneously has been determined against a set of known peptides and proteins, and is outlined in this article. The reagents were evaluated for label efficiency, fragmentation efficiency and precision and accuracy of quantitation.
Since the first experiment was performed nearly a decade ago, ultrafast two-dimensional infrared (2D-IR) spectroscopy has emerged as an exciting non-linear ultrafast laser technique for probing molecular structure and solute–solvent interaction dynamics in a range of systems of chemical and biological relevance.
Analysis of used lubrication oil for metals is commonplace in many industries. The metals analysed fall into three categories: wear metals, contaminants and additive elements. The concentration of these metals and elements can then be interpreted to schedule maintenance of engines and machinery such as construction machinery and aeroplanes. The cost of unscheduled maintenance can be high, not only in materials and parts, but also in lost profits due to downtime. Once the oil has been sampled, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis is a very useful tool for this application.
(Image courtesy Shell Motorsport)
One of the dangerous kinds of pollution in aquatic systems is due to the dumping of materials containing heavy metals. Hence, the monitoring of heavy metals in aqueous samples is becoming increasingly important. Normally, metal concentrations in water are in the ng L–1 range, and the analytical procedures used for their determination are usually based on Anodic Stripping Voltametry (ASV) and Atomic Spectrometry, including Electrothermal Atomic Absorption Spectrometry (ETAAS), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). However, the direct analysis of some complex environmental samples like seawater presents some difficulties, mainly due to the high salinity of the matrix. Therefore, in such cases, a dilution of the sample may be necessary before the analysis, or a preliminary separation and/or preconcentration step may be required to eliminate interferences and/or to improve detection limits for metals in the low µg L–1 range. Moreover, when the analysis is performed by using solid sorbents followed by spectrophotometric techniques, an additional elution step after the preconcentration procedure is necessary to recover the species in an appropriate medium.
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.