A method of simultaneous identification of 25 molecules in human urine, bile and gastric contents using liquid-liquid extraction followed by thin layer chromatography (TLC) using multiple screening systems is described. The analytes were extracted at 25°C under isocratic conditions using chloroform after acidification with 1 to 2 drops of HCl 6 N for 10 mL of […]
Category: Analysis
Drugs Toxicological Analysis
Capillary Electrophoresis for Drug Analysis
In the second edition (1986) of this reference work, the index doesn’t even mention electrophoresis. Traditional electrophoretic methodologies, although they used simple and reliable equipment, were always limited by their low resolution of analytes, low throughput, the need to visualise the separated bands and the qualitative nature of the results. They were, in fact, the […]
High Performance Liquid Chromatography (HPLC)
The ability to separate and analyse complex samples is integral to the biological and medical sciences. Classic column chromatography has evolved over the years, with chromatographic innovations introduced at roughly decade intervals. These techniques offered major improvements in speed, resolving power, detection, quantification, convenience and applicability to new sample types. The most notable of these […]
Gas Chromatography
Gas chromatography (GC) is applicable to a wide range of compounds of interest to toxicologists, pharmaceutical and industrial chemists, environmentalists and clinicians. If a compound has sufficient volatility for its molecules to be in the gas or vapour phase at or below 400°, and does not decompose at these temperatures, then the compound can probably […]
Thin–layer Chromatography (TLC)
Introduction Thin–layer chromatography (TLC) is a widely used technique for the separation and identification of drugs. It is equally applicable to drugs in their pure state, to those extracted from pharmaceutical formulations, to illicitly manufactured materials and to biological samples. TLC as we know it today (see Fig 1) was established in the 1950s with […]
Mass Spectrometry
A mass spectrometer works by generating charged molecules or molecular fragments either in a high vacuum or immediately before the sample enters the high–vacuum region. Instruments typically maintain vacuums of about 10–6 mmHg, since ionised molecules have to be generated in the gas phase to be able to manipulate them using magnetic or electrostatic fields. In […]
Nuclear Magnetic Resonance Spectroscopy
Since its first observation in bulk phases in 1945, nuclear magnetic resonance (NMR) spectroscopy, has become one of the foremost methods for molecular identification, for evaluating detailed molecular structures, for understanding conformations and for probing molecular dynamics. If the measurements are carried out under appropriate conditions, NMR spectroscopy can also be used for quantitative analysis. […]
Raman Spectroscopy
Vibrational spectroscopy has been an integral tool for the identification and characterisation of drugs. When one thinks of vibrational spectroscopy, typically infrared (IR) techniques come to mind, not Raman spectroscopy. However, over the past 20 years a renaissance of the Raman technique has occurred, mainly through instrumentation development. These developments have led to unique applications […]
Near–infrared (NIR) Spectroscopy
The near–infrared (NIR) region of the electromagnetic spectrum extends from about 780 to 2500 nm (or 12800 to 4000 cm–1). It is therefore the part of the spectrum that exists between the red end of the visible spectrum and the beginning of the mid-infrared (IR) region. Its discovery by Herschel in 1800 was the first indication that […]
Infra–red Spectroscopy
Infra–red (IR) spectroscopy is the study of the scattering, reflection, absorption or transmission of IR radiation in the spectral range 800 nm to 1 000 000 nm (0.8 to 1000 μm). In older literature (pre–1970), IR radiation was referred to in terms of wavelengths as microns (μm). Nowadays, the wavenumber (ν̃) unit is used almost exclusively. The relationship between wavenumber […]