Capillary liquid chromatography derivatization with

Song Y, Quan Z, Evans JL, Byrd EA, Liu YM. 2004. Enhancing capillary liquid chromatography/tandem mass spectrometry of biogenic amines by pre-column derivatization with 7-fLuoro-4-nitrobenzoxadiazole. Rapid Commun Mass Spectrom 18 989. 

Song, Y, Shenwu, M., Zhao, S., Hou, D., and Liu, Y. M., Enantiomeric separation of amino acids derivatized with 7-fluoro-4-nitrobenzoxadiazole by capillary liquid chromatography/tandem mass spectrometry,/owmaZ o/Chroma/ograp/jy 4 1091(1-2), 102-109,2005. 

As described in more detail in Section 13.3.2, the main analytical techniques that are employed for metabonomic studies are based on nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The latter technique requires a preseparation of the metabolic components using either gas chromatography (GC) after chemical derivatization or liquid chromatography (LC), with the newer method of ultra-high-pressure LC (UPLC) being used increasingly. The use of capillary electrophoresis (CE) coupled to MS has also shown promise. Other more specialized techniques such as Fourier transform infrared spectroscopy and arrayed electrochemical detection have been used in some cases. 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

Following extraction/cleanup, quinoxaline-2-carboxylic acid can be detected by electron capture, or mass spectrometric techniques, after gas chromatographic separation on capillary or conventional columns. A prerequisite of quin-oxaline-2-carboxylic acid analysis by gas chromatography is the derivatization of the molecule by means of esterification. Esterification has been accomplished with methanol (419, 420, 422), ethanol (421), or propanol (423) under sulfuric acid catalysis. Further purification of the alkyl ester derivative with solid-phase extraction on a silica gel column (422), thin-layer chromatography on silica gel plate (420), or liquid chromatography on Hypersil-ODS, 3 m, column (423), has been reported. 

Creatinine can be analyzed in automatic colorimetric analyzers using the Jaffe method, by gas chromatography-mass spectrometry (GC-MS) after derivatization, or simultaneously with creatine by high-performance liquid chromatography (HPLC) or capillary electrophoresis (CE). Enzyme-based methods for both creatine and creatinine are used for colorimetric analyses as well as in biosensors. Creatine can be converted to creatinine to be analyzed by the Jaffe reaction. Eluorescence analyses and methods involving partial least squares (PLS) with ultraviolet (UV), infrared (IR), or near-infrared (NIR) spectra can also used. 

Despite these difficulties (discussed in Section 5.3.3a) API sources are currently used widely in combination with a wide range of liquid chromatography methods, i.e. normal and reverse phase, isocratic and gradient, normal bore (4.6 mm i.d.) and capillary columns, as well as ESI with capillary electrophoresis and APCI with GC. In the context of trace level quantitation, API techniques are most often used in combination with reverse phase HPLC, and it is this combination that will be the main focus of discussions of matrix effects (Sections 5.1.1 and 5.3.6a) and of the more practical aspects in Sections 9.6 and 10.10.4.1d. In this regard it is worth noting here that in reverse phase chromatography using e.g., a Cjg-derivatized silica... 

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