Liquid chromatography/mass spectroscopy

R.P.W. Scott, C.G. Scott, M. Munroe and J. Hess Jr., Interface for on-line liquid chromatography-mass spectroscopy analysis, J. Chromatogr., 99 (1974) 395-405. 

Recently, the word nano has become a trend in science and technology and some of us think that it is the new generation but, as mentioned above, its root is about 22 years old. NLC and NCE are gaining importance day by day. They are very useful and effective tools for samples of low quantities or having low concentrations of the analytes. Columns of low internal diameter are ideal for use in NLC and NCE, especially with detectors requiring very low flow rates, such as electrospray liquid chromatography/mass spectroscopy (LC/MS). Besides, these columns offer high sensitivity due to their low... 

The relative contribution of sample preparation depends on the steps in the measurement process. For instance, typically two-thirds of the time in an analytical chromatographic procedure is spent on sample preparation. An example of the determination of olanzapine in serum by high-performance liquid chromatography/mass spectroscopy (HPLC-MS) illustrates this point [3], Here, samples were mixed with an internal standard and cleaned up in a... 

In the present chapter, various tools such as thin-layer chromatography, high performance liquid chromatography, mass spectroscopy, and NMR used in analysis of flavonoids are discussed. In addition, the relevance and application of such tools in the analysis of flavanones, with emphasis on citrus flavanones, is discussed. 

Vanhoenacker, G., De Villiers, A., Lazou, K., De Keukeleire, D., Sandra, P. (2001). Comparison of High-Performance Liquid Chromatography - Mass Spectroscopy and Capillary Electrophoresis - Mass Spectroscopy for the analysis of phenolic compounds in diethyl ether extracts of red wines. Chromatographia, 54, 309-315. 

Gas Chromatography (or High Pressure Liquid Chromatography) — Mass Spectroscopy. 

Niessen WMA and Vander G., Liquid Chromatography- Mass Spectroscopy, (Marcel Dekker, NY, 1992). 

As part of the specific transfer, the number of lots, replicates, and injections (in the case of HPLC) should be expressly presented. For dissolution transfers, the number of individual dosage forms that will be tested should be stipulated. It is necessary to spell out such details so that small differences in the everyday analytical philosophies do not perturb the transfer process. In the case of new techniques that may not be common to the receiving laboratory (i.e., capillary electrophoresis or liquid chromatography/mass spectroscopy), specific training may be necessary before the execution of a transfer protocol. 

BBB-permeability-liquid chromatography/mass spectroscopy- (LC/MS) Rapid, generic gradient liquid chromatography/ Chu et al. (2002) tandem mass spectroscopy (LC/MS/MS) assays, designed to accelerate sample analyses, have been developed to keep pace with the productivity of advanced synthetic procedures. In this study, LC/MS/MS was combined with an in vitro, cell-based, BBB model to evaluate the potential of new chemical entities (NCEs) to cross the BBB. This in vitro assay provides the permeability of discovery compounds across a monolayer of a primary culture of BBMEC in a fraction of the time that is required for in vivo studies (brain/plasma concentrations), using only 2 mg of the compound. The results are consistent with in vivo brain/plasma concentration ratio data. 

Thin-layer chromatography (TLC) was used to identify safrole, isosafrole, and dihydrosafrole in rat urine and bile (Fishbein et al., 1967). Gas chromatography-mass spectroscopy (GC-MS) and gas liquid chromatography-mass spectroscopy (GLC-MS) were utilized to identify the urinary metabolites of safrole in the rat (Klungsoyr and Scheline, 1983). Plasma and tissue safrole concentrations in rats and humans were measured by GC-MS. Urinary metabolites were identified using TLC and GC-MS (Benedetti et al., 1977). 

Mass spectrometry is also applied in the control of pesticides and other contaminants (e.g., 2,4,6-trichloroanisole), detection of compounds formed by yeast and bacteria, determination of illegal additions to the wine. Liquid chromatography/mass spectroscopy (LC/MS) methods for determination of toxins in the wine (e.g., ochratoxin A) have been proposed (Zollner et al., 2000 Flamini and Panighel, 2006 Flamini et al., 2007). 

Trimethyl-17/,3//,5//-pyrido[3,2,l-jy][3,l]benzoxazines were detected among the reaction products of 2,2,4-trimethyl-l,2-dihydroquinoline with formaldehyde and acetaldehyde by liquid chromatography-mass spectroscopy (LC-MS) investigations (79MI1). 

LC/MS-MS Liquid chromatography/Mass spectroscopy-Mass spectroscopy ... 

Liquid chromatography—mass spectroscopy has become one of the most powerful analytical techniques in the drug discovery and development proeess. LC tandem MS is obviously the technique of choice for the identification of metabolites as illustrated in this chapter. Exact mass measurements and elemental composition assignment are essential for the characterization of the metabolites. Accurate mass measurements of the product ions, formed in an MS/MS experiment, greatly facilitate the structure elucidation of the metabolites. With the ever evolving technological advances in mass spectrometry and separation science, LC MS will continue to play an important role in metabolite identification in the future. 

Rezanka, X, Identification of Very Long Chain Fatty Acids by Atmospheric Pressure Chemical Ionization Liquid Chromatography-Mass Spectroscopy from Green Alga Chlorella Kesslerii. J. of Sep. Set. 25 1332—1336 (2002). 

At first, one may show skepticism at the usefulness of diode-array detection because other analytical systems are more sensitive and offer similar features such as peak identification and purify checks. For these alternatives, one would have to refer to gas chromatography/mass spectroscopy (GC/ MS), liquid chromatography/mass spectroscopy (LC/MS), and tandem mass spectrometry (MS-MS). However, one must keep in mind the significantly higher costs as a tradeoff for enhanced sensitivity. 

M. A. Niessen, J. van der Greef Liquid Chromatography-Mass Spectroscopy, Marcel Dekker, New York 1992. 

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