Normalized liquid chromatography spectrometry

Ramanathan, R., Zhong, R., Blumenkrantz, N., Chowdhury, S. K., and Alton, K. B. (2007c). Response normalized liquid chromatography nanospray ionization mass spectrometry. J. Am. Soc. Mass. Spectrom. 18 1891-1899. 

A liquid chromatography-mass spectrometry (LC-MS) method that can quantitatively analyze urinar y normal and modified nucleosides in less than 30 min with a good resolution and sufficient sensitivity has been developed. Nineteen kinds of normal and modified nucleosides were determined in urine samples from 10 healthy persons and 18 breast cancer patients. Compounds were separ ated on a reverse phase Kromasil C18 column (2.1 mm I.D.) by isocratic elution mode using 20 mg/1 ammonium acetate - acetonitrile (97 3 % v/v) at 200 p.l/min. A higher sensitivity was obtained in positive atmospheric pressure chemical ionization mode APCI(-i-). 

Jandera, P., Holcapek, M., Theodoridis, G. (1998). Investigation of chromatographic behavior of alcohol ethoxylate surfactants in normal-phase and reversed-phase systems using high-performance liquid chromatography-mass spectrometry. J. Chromatogr. A 813(2), 299-311. 

Continuous distribution functions Some experiments, such as liquid chromatography or mass spectrometry, allow for the determination of continuous or quasi-continuous distribution functions, which are readily obtained by a transition from the discrete property variable X to the continuous variable X and the replacement of the discrete statistical weights g, by the continuous probability density g(X). For simplicity, we assume g(X) as being normalized J ° g(X)dX = 1. Averages and moments of a quantity Y(X) are defined by analogy to the discrete case as... 

Kagan M, Chlenov M, Kraml CM. 2004. Normal-phase high-performance liquid chromatographic separations using ethoxynonafluorobutane as hexane alternative. II. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry applications with methanol gradients. J Chromatogr A 1033 321. 

Hyphenated analytical techniques such as LC-MS, which combines liquid chromatography and mass spectrometry, are well-developed laboratory tools that are widely used in the pharmaceutical industry. Eor some compounds, mass spectrometry alone is insufficient for complete structural elucidation of unknown compounds nuclear magnetic resonance spectroscopy (NMR) can help elucidate the structure of these compounds (see Chapter 20). Traditionally, NMR experiments are performed on more or less pure samples, in which the signals of a single component dominate. Therefore, the structural analysis of individual components of complex mixtures is normally time-consuming and less cost-effective. The... 

Jiang H, Jiang J, Hu P et al. Measurement of endogenous uracil and dihydrouracil in plasma and urine of normal subjects by liquid chromatography-tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2002 769 169-176. 

The number of detectors that are sensitive and selective enough to be applied online with LC is limited because the solvents used are not compatible, as in the case of immunochemical detection after reversed- or normal-phase LC. The technology of coupling is still under development and not yet available in a large number of laboratories not specialized in techniques such as LC-MS. Therefore, LC separations are frequently followed by offline detection. Confirmatory analysis of suspected liquid chromatographic peaks can be made possible by coupling liquid chromatography with mass spectrometry. Atmospheric-pressure chemical ionization LC-MS has been employed for the identification of six steroid hormones in bovine tissues (448). 

AA Karlsson, P Michelsen, A Larsen, G Odham. Normal-phase liquid chromatography class separation and species determination of phospholipids utilizing electrospray mass spectrometry/tandem mass spectrometry. Rapid Communications Mass Spectrom 10 775-780, 1996. 

D Barcelo, G Durand, RJ Vreeken, DJ de Jong, UAT Brinkman. A non-polar solvent for normal-phase liquid chromatography and postcolumn extraction in thermospray liquid chromatography/ mass spectrometry. Anal Chem 62 1696-1700, 1990. 

L. G. McLaughlin and J. D. Henion, Determination of dexamethasone in bovine tissues by coupled-column normal-phase high-performance liquid chromatography and capillary gas chromatography-mass spectrometry ,./. Chromatogr. 529 1-19 (1990). 

M. Wuhrer, C. A. M. Koeleman, A. M. Deelder, and C. H. Hokke, Normal-phase nanoscale liquid chromatography-mass spectrometry of underivatized oligosaccharides at low-femtomole sensitivity, Anal. Chem., 76 (2004) 833-838. 

B. Kiister, S. F. Wheeler, A. P. Hunter, R. A. Dwek, and D. J. Harvey, Sequencing of AMinked oligosaccharides directly from protein gels In-gel deglycosylation followed by matrix-assisted laser desorption/ionization mass spectrometry and normal-phase high-performance liquid chromatography, Anal. Biochem., 250 (1997) 82-101. 

Stenhoff et al. [117] determined enantiomers of omeprazole in blood plasma by normal-phase liquid chromatography and detection by atmospheric-pressure ionization tandem mass spectrometry. The enantioselec-tive assay of omeprazole is using normal-phase liquid chromatography on a Chiralpak AD column and detection by mass spectrometry. Omeprazole is extracted by a mixture of dichloromethane and hexane and, after evaporation, redissolution and injection, separated into its enantiomers on the chiral stationary phase. Detection is made by a triple quadrupole mass spectrometer, using deuterated analogs and internal standards. The method enables determination in plasma down to 10 nmol/1 and shows excellent consistency suited for pharmacokinetic studies in man. 

Zavitsanos, A. P. Alebic-Kolbah, T. 1998. Enantioselective determination of terazosin in human plasma by normal phase high-performance liquid chromatography-electrospray mass spectrometry. / Chromatogr. A, 794, 45-56. 

It also was reported by Lagerstroem et al that pantoprazole and its enantiomers can be separated by using normal-phase liquid chromatography, and detection by atmospheric pressure ionization tandem mass spectrometry [13]. 

This paper is the only one in the liquid chromatography portion of this symposium which will attempt to deal with chromatography specifically from the viewpoint of the pesticide metabolism chemist. A residue analyst knows what compound he must analyze for, and develops his method with the properties of that substance in mind. On the other hand, the pesticide metabolism chemist has a different problem. At the conclusion of the treatment, exposure, and harvest phases of a radiolabeled metabolism study, he divides his material into appropriate samples, and extracts each sample with selected solvents to obtain the radioactive materials in soluble form. Typically these extracts consist of low levels (ppm) of carbon-14 labeled metabolites in a complicated mixture of normal natural products from the plant, animal, or soil source. The identity of each metabolite is unknown, and each must be isolated from the natural background and from other labeled metabolites in sufficient quantity and in adequate purity for identification studies, usually by mass spectrometry. The situation is rather like looking for the proverbial "needle in the haystack" when one does not know the size, shape,or composition of the needle, or even how many needles there are in the stack. At this point a separation technique must be selected with certain important requirements in mind. 

Indirect indicators of vitamin B12 deficiency include measurements of the metabolites homocysteine and methylmalonic acid (MMA) in serum and MMA in urine (see the Biochemical Perspectives section). Whereas the serum homocysteine concentration increases during folate or vitamin B12 deficiencies, the serum and urine MMA concentrations increase only in vitamin B12 deficiency. Therefore, MMA determinations can be used to differentiate vitamin B12 deficiency from folate deficiency. The normal concentration of MMA in serum ranges from 0.08 to 0.28 pmol/L. MMA is quantified using gas-liquid chromatography and mass spectrometry. Elevated concentrations of MMA and homocysteine in serum may precede the development of hematological abnormalities and reductions in serum vitamin B12 concentrations. One should be aware that other conditions, including renal in sufficiency and inborn errors of metabolism, can also result in elevated serum levels of MMA. 

In drug analysis, LC-MS usually means reversed phase liquid chromatography coupled to mass spectrometry. Although normal phase LC can be used as well (especially in combination with atmospheric pressure chemical ionization - APCI), predominantly reversed phase LC is used in drug research and drug analysis due to the typical physical and chemical properties of the analytes (e.g. polarity, size). 

The coupling of liquid chromatography is more delicate because gas-phase ions must be produced for mass spectrometry. Liquid chromatography normally is used for compounds that are not volatile and are not suitable for gas chromatography. 

Both variolin B and its 5-deoxy derivative 19 (Scheme 6.1 Part 2) have shown promise in pharmacokinetic and in vivo studies. These compounds have been shown to have long terminal half-lives and low normal cell toxicity, however the 5-deoxy derivative demonstrated better Cmax, plasma clearance and terminal plasma half-life.318,319 Both are effective against human lung carcinoma cell lines in nude mice.104 The deoxy-variolin B showed growth inhibitory activity against human leukemic cell lines.105 A standardised method for liquid chromatography-mass spectrometry (LC-MS)/MS analysis of plasma has been developed to monitor the results of the in vivo studies.320... 

Hao, Z. Parker, B. Knapp, M. Yu, L. 2005. Simultaneous quantification of a-tocopherol and four major carotenoids in botanical materials by normal phase liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry. J. Chromatogr. A. 1094 83-90. 

Smith, J.R. (2004). Analysis of the enantiomers of VX using normal-phase chiral liquid chromatography with atmospheric pressure chemical ionization-mass spectrometry. J. Anal. Toxicol. 28(5) 390-2. 

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