Liquid chromatography/mass weights

The ion spray liquid chromatography/mass spectrometry (LC-MS) interface coupled via a postsuppressor split with an ion chromatography (IC) has been used in the analysis of alcohol sulfates. The IC-MS readily produces the molecular weight while the tandem mass spectrometric detection IC-MS-MS provides structural information [305]. 

GC Galletti, J Eagles, FA Mellon. Analysis of low molecular weight plant phenolics by thermospray liquid chromatography/mass spectrometry. J Sci Food Agric 59 401-404, 1992. 

LC/MS (Liquid Chromatography/Mass Spectrometry)—Chromatography system in which an HPLC is married to a mass spectrometric detector through an evaporated, ionizing interface. A variety of mass spectrometers are used to produce various LC/MS and LC/MS/MS configurations. MS detectors are universal, mass detectors that provide molecular weight information and can give a definitive identification of separated compounds. 

Niemela K, Sjostrom E (1986) Simultaneous identification of aromatic and aliphatic low molecular weight compounds from alkali pulp liquor by capillary gas-liquid chromatography-mass spectrometry Holzforschung 40 361-368... 

Identification and quantification of low molecular weight and volatile phenols is usually performed by Gas Chromatography and Mass Spectrometry (GC-MS). For analysis and structural characterization of more polar compounds such as polyphenols, liquid-phase and Liquid Chromatography Mass Spectrometry (LC-MS) and Multiple Mass Spectrometry (MS/MS and MSn) techniques are used (Niessen and Tinke, 1995 de Hoffmann, 1996 Abian, 1999 Flamini et al., 2007). 

Mass spectrum interpretation is essential to solve one or more of the following problems establishment of molecular weight and of empirical formula detection of functional groups and other substituents determination of molecular skeleton (atom connectivity) elucidation of precise structure and, even in favorable cases, certain stereochemical features. As discussed in the previous chapters, electrospray (ESI) and atmospheric pressure chemical ionization (APCI) are two of the most effective and successful interfaces for the liquid chromatography—mass spectrometry (LC—MS) that have been developed. Thus, we will focus on how to interpret the mass spectral data generated by either ESI or APCI in this section. 

See also Capillary Electrochromatography. Capillary Electrophoresis Pharmaceutical Applications Low-Molecular-Weight Ions Food Chemistry Applications Clinical Applications. Extraction Solid-Phase Extraction Solid-Phase Microextraction. Gas Chromatography Mass Spectrometry. Liquid Chromatography Overview Liquid Chromatography-Mass Spectrometry. 

When less thermally labile compounds require separation prior to analysis, in-line liquid chromatography-mass spectrometry (LC-MS) can be used. Even where liquid chromatographic separation is not required LC-MS interfaces may be used as a convenient method of sample introduction, e.g. for polar, ionic, thermally labile, involatile or high-molecular-weight species. There are several different types of LC-MS interface each with its own characteristics in terms of the solvent systems and sample types that it can handle and the appropriate solvent flow rates no one interface is applicable to all solvent-solute combinations. 

The capability of HPLC has been greatly extended by the commercialisation of affordable liquid chromatography-mass spectroscopy (LC-MS) instruments. The mass selective detector enables unknown samples to be analysed and the antioxidants present to be identified. The LC-MS technique therefore compliments GC-MS and, with it, enables the complete molecular weight/volatility/polarity range to be covered. 

For mixture.s the picture is different. Unless the mixture is to be examined by MS/MS methods, usually it will be necessary to separate it into its individual components. This separation is most often done by gas or liquid chromatography. In the latter, small quantities of emerging mixture components dissolved in elution solvent would be laborious to deal with if each component had to be first isolated by evaporation of solvent before its introduction into the mass spectrometer. In such circumstances, the direct introduction, removal of solvent, and ionization provided by electrospray is a boon and puts LC/MS on a level with GC/MS for mixture analysis. Further, GC is normally concerned with volatile, relatively low-molecular-weight compounds and is of little or no use for the many polar, water soluble, high-molecular-mass substances such as the peptides, proteins, carbohydrates, nucleotides, and similar substances found in biological systems. LC/MS with an electrospray interface is frequently used in biochemical research and medical analysis. 

High performance liquid chromatography is an effective technique for the separation of compounds of high molecular weight. There are, however, two major problems with the use of mass spectrometry for the study of this type of molecule... 

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