Liquid chromatography-mass spectrometry (LC-MS) is an analytical technique that couples high resolution chromatographic separation with sensitive and specific mass spectrometric detection. This includes high performance liquid chromatography (HPLC)-MS, capillary electrophoresis (CE)-MS and more recently capillary electrochromatography (CEC)-MS. The technique is still fast developing, particularly in the mass spectrometry area, with vastly improved sensitivity and resolution. It is probably the most powerful technique currently available for pharmaceutical analysis.This review is intended as a discussion on the current developments of LC-MS in pharmaceutical analysis rather than a review of literature alone. Various LC-MS techniques will be described briefly and the advantages and disadvantages of each will be discussed. DEVELOPMENTS IN LC-MS Brief History of LC-MSThe last twenty years has seen a dramatic increase in the capabilities of MS. At the beginning of this period the invention of fast atom bombardment (FAB), by Barber et al. in 1981, 1) enabled easier analysis of involatile and thermally unstable molecules, especially those of biological interest. It may be argued that this technique acted as a catalyst for the development of other ionization techniques, such as matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), applicable to such molecules.The combination of liquid chromatographic techniques with MS has been an important development. Early interfaces were concerned with coping with the potential of 1 l/min vapour in the MS ionisation source vacuum that would be generated by eluent from typical analytical columns flowing at 1 ml/min. This was achieved by evaporating solvent on a heated moving belt, 2,3) or the use of very low flows, such as direct liquid introduction 4,5) and continuousflow FAB (CF-FAB).6) Thermospray 7) and particle beam 8) interfaces were improved methods during the 1980s.Atmospheric Pressure Ionization (ESI and APCI) Over the last decade, ESI and atmospheric pressure chemical ionization (APCI), have become the dominant techniques superseding thermospray etc. and are likely to remain so for the foreseeable future being inherently the most suitable for analytes in solution presented to the MS. ESI was originally proposed by Dole,9) who suggested using charged droplets as a source of ions for MS and Fenn 10) pioneered its development as an ionization source for MS, leading to the first commercially available instrument in 1989.In essence, the electrospray process involves producing a fine spray of ionized droplets from the outlet of a capillary carrying a liquid stream, which may be eluent from HPLC, CE, CEC or direct infusion of sample solution. This is achieved by applying a high voltage (typically 3-5 kV) to the outlet of the capillary at the spray tip, which creates a high electric potential and causes the production of a fine mist of droplets. This occurs at atmospheric pressure, hence the term atmospheric pressure ionization (API), is used. Thi...

A capillary zone electrophoretic (CZE) method for the rapid analysis of the major alkaloids (arecoline and guavacoline) in areca nut extract is described. Areca nuts were pulverized and then extracted with water by sonication in a water bath. After centrifugation, the supernatant was analysed on a fused-silica capillary with 100 mM ammonium acetate-acetic acid (pH 4.6) as the running buffer at a voltage of 20 kV and temperature of 30 degrees C. The method is applicable to the analysis of alkaloids in the nut, commercial preparations (pan masala) and in the saliva of areca nut chewers.

Substantial evidence points to the presence in human plasma of an inhibitor of the sodium/potassium pump which plays a central role in the pathophysiology of circulatory disorders, including essential hypertension. Studies from the 1980/90s claimed that this inhibitor was identical or very similar in structure to plant-derived ouabain and was synthesized by the adrenal cortex. However, the physical evidence in studies reporting isolation and identification of ouabain in human plasma appears insecure on closer examination. Additionally, reported circulating levels of immunoreactive ouabain in humans vary greatly, the ability of the human adrenal glands to secrete ouabain is questionable and the original commercial assay for measuring immunoreactive ouabain is no longer available. We submit that the position of ouabain as an endogenous, adrenally produced regulator of the sodium pump is of such importance that the current evidence needs either to put on a more secure footing or to lose its current status.

Introduction Acute metabolic acidosis of non-renal origin is usually a result of either lactic or ketoacidosis, both of which are associated with a high anion gap. There is increasing recognition, however, of a group of acidotic patients who have a large anion gap that is not explained by either keto-or lactic acidosis nor, in most cases, is inappropriate fluid resuscitation or ingestion of exogenous agents the cause.