Ultraviolet spectrophotometry with high-performance liquid

Chemicals that have been prepared for a specific application are also available. Included among these are solvents for spectrophotometry and high-performance liquid chromatography. Information pertinent to the intended use is supplied with these reagents. Data provided with a spectrophotometric solvent, for example, might include its absorbance at selected wavelengths and its ultraviolet cutoff wavelength. 

Triethanolamine can be determined in metalworking and cutting fluids by gas chromatography-mass selective detection of silylated derivatives, by isotachophoresis, by capillary zone electrophoresis with indirect ultraviolet detection, and by spectrophotometry (Kenyon et al, 1993 Fernando, 1995 Schubert et al, 1996 Sollenberg, 1997) and in cosmetics and pharmaceuticals by ion-exclusion chromatography and by reversed-phase high performance liquid chromatography (Fukui et al, 1992 Maurer etal, 1996). 

API-related organic impurities usually involves high performance liquid chromatography (HPLC)-based analytical methods, with relatively non-specific detection techniques such as Ultraviolet/Visible (UV/Vis) Spectrophotometry. Residual solvents analysis usually involves gas chromatography (GC)-based analytical methods, again with relatively non-specific detection techniques such as flame ionization (FID). GC-based methods are most appropriate for volatile analytes such as residual solvents, whereas HPLC-based methods are more appropriate for the relatively non-volatile and polar API-related analytes. 

Other methods for nitrates and nitrites include the AOAC procedure in which w-xylenol is nitrated and the nitro-xylenol is distilled into sodium hydroxide solution to form a colored sodium salt that is determined with ultraviolet spectrophotometry at 450 mn. Gas chromatography with electron capture detection and high-performance liquid chromatography have been used for determination of nitrate and nitrite derivatives. 

Caffeine has traditionally been identified in foods by ultraviolet spectrophotometry of an organic solvent extract after suitable cleanup by column chromatography. Such methods tend to be laborious and may be subject to interference from other ultravioletabsorbing compounds. Recently, high-performance liquid chromatography has been more extensively used. This technique, often in conjunction with solid phase extraction, can provide accurate data for the determination of caffeine in foods and physiological samples. 

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