Articles
During the last decade, the amount of counterfeit drugs on the worldwide market has rapidly increased. It is difficult to determine the exact scale of this problem, since not all counterfeit drugs are reported or even detected. The drugs that are often counterfeited can be divided into two groups, depending on the region where they are brought onto the market. The use of Raman spectroscopy in the pharmaceutical field has been increasing over the last few years. Raman spectroscopy has some specific benefits, which can be very useful for the detection of counterfeit drugs: a Raman spectrum can be recorded rapidly without any sample preparation. Moreover, not only does a Raman spectrum provide information about the active ingredient present in the drug, but also a Raman spectrum contains information on its concentration and allows identification of excipients present in the drug. So far, this technique has been used for the detection of different kinds of illicit drugs, such as cocaine, heroin and ecstasy, and also for the detection of counterfeit antimalarial and Viagra® tablets. This article will demonstrate the use of Raman spectroscopy as a fast and easy detection system for different counterfeit erectile dysfunction drugs. Three different genuine erectile dysfunction drugs are available on the market: Viagra®, Cialis® and Levitra®. Viagra® is the most commonly counterfeited drug, but the amount of counterfeit Cialis® has rapidly increased over the last few years. 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®.
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.
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.
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.
Peter A. Rinck
European Magnetic Resonance Forum (EMRF) Foundation, WTC, BP 255, F-06905 Sophia Antipolis Cedex, France
In 1946, two scientists in the United States, independently of each other, described a physicochemical phenomenon that was based upon the magnetic properties of certain nuclei in the periodic system. This was “nuclear magnetic resonance”, for short “NMR”. The two scientists, Felix Bloch and Edward M. Purcell were awarded the Nobel Prize in Physics in 1952.
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 down time. Once the oil has been sampled, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis is a very useful tool for this application. The high temperature source allows for full dissociation of organo-metallic compounds and also has the ability to handle the complex organic matrix. This allows for the oil to be directly aspirated into the ICP after a simple dilution, negating the need for any time consuming sample preparation technique and enabling a fast turnaround time.
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.
John Walton
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
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.
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.
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.
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.
Concentrations of therapeutic drugs and their metabolites in waste and surface water are measured by highly selective and sensitive mass spectrometric techniques, such as gas chromatography-mass spectrometry (GC-MS) or high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Using data obtained in this way, information about human metabolism of single active principles, and WWTPs characteristics (e.g., flow rate, population served), it is possible to calculate the environmental loads of therapeutic drugs and correlate them to their effective use (known from sales or production data). 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.
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 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.
