Liquid chromatography-mass process

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

Im HW, Suh BS, Lee SU, Kozukue N, Ohnisi-Kameyama M, Levin CE and Friedman M. 2008. Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes. J Agric Food Chem 56(9) 3341-3349. 

Internal reflection spectroscopy is widely applied for on-line process control. In this type of application, the chemical reactor is equipped with an internal reflection probe or an IRE. The goal of this type of application is the quantification of reactant and/or product concentrations to provide real-time information about the conversion within the reactor. In comparison with other analytical methods such as gas chromatography, high-pressure liquid chromatography, mass spectrometry, and NMR spectroscopy, ATR spectroscopy is considerably faster and does not require withdrawal of sample, which can be detrimental for monitoring of labile compounds and for some other applications. 

Hong YJ, Barrett DM, Mitchell AE. 2004. Liquid chromatography/mass spectrometry investigation of the impact of thermal processing and storage on peach procyanidins. J Agric Food Chem 52 2366-2371. 

Li H.Q., F. Jiku, and H.F. Schroder. 2000. Assessment of the pollutant elimination efficiency by gas chromatography/mass spectrometry, liquid chromatography-mass spectrometry and—tandem mass spectrometry comparison of conventional and membrane-assisted biological wastewater treatment processes. J. Chromatogr. A 889 155-176. 

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... 

XCMS Scripps Center for Metabolomics Software for processing liquid chromatography-mass spectrometry-based metabolomics data (http //medin.scripps.edu/... 

To investigate the complex metabolic consequences of disease processes, toxic reactions, and genetic manipulation, nonselective but specific analytical approaches are required. Several spectroscopic methods in addition to nuclear magnetic resonance (NMR) can produce metabolic signatures of biomaterials, including mass spectrometry (MS), gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid... 

Lehr, G. J., Barry, T. L., Petzinger, G., Hanna, G. M. and Zito, S. W. Isolation and identification of process impurities in trimethoprim drug substance by high-performance liquid chromatography, atmospheric pressure chemical ionization liquid chromatography/ mass spectrometry and nuclear magnetic resonance spectroscopy. J. Pharm. Biomed. Anal. 19 373-389, 1999. 

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. 

Drexler, D.M. et al., An automated high throughput liquid chromatography-mass spectrometry process to assess the metabolic stability of drug candidates, Assay Drug Dev. Technol., 5(2), 247, 2007. 

A point that may seem fairly obvious, but worth reiterating, is that, with a complex mixture from which one or a few specific compounds are to be isolated, a means of keeping track of the compound through the extraction process is needed. There are two main ways to follow a compound (1) physical assay (for example, HPLC, thin-layer chromatography [TLC], liquid chromatography-mass spectometry [LC-MS], and perhaps involving comparison with a standard), or (2) bioactivity assay. 

Liquid chromatography-mass spectrometry (LC-MS) ideally combines advantages of the gentle separation of HPLC with high sensitivity and selectivity of mass spectrometry. There are two methods of ionization. The electrospray LC-MS ionization process can effectively transform the heterocychc amines from solution to protonated ions in the gas phase. The thermospray LC-MS ionization process produces abundant pseudo-molecular ions for this class of compounds. As a result, in both ionization processes the base peaks in the mass spectra are... 

Kostiainen R, Kauppila TJ, Effect of eluent on the ionization process in liquid chromatography-mass spectrometry, J. Chromatogr. A 2009 1216(4) 685-699. 

McNaney CA, Drexler DM, Hnatyshyn SY, Zvyaga TA, Knipe JO, Belcastro JV, Sanders M. An automated liquid chromatography—mass spectrometry process to determine metabolic stability half-life and intrinsic clearance of drug candidates by substrate depletion. Assay Drug Dev Technol 2008 6(1) 121—129. 

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