Liquid chromatography-mass products

Figure 5.55 MS" spectra from rntz 329, the (M + H)+ ion of an hydroxy metabolite of Praziquantel, and the base peaks in subsequent product-ion spectra. Reprinted from J. Chromatogr., B, 708, Lerch, C. and Blaschke, G., Investigation of the stereoselective metabolism of Praziquantel after incubation with rat liver microsomes by capillary electrophoresis and liquid chromatography-mass spectrometry , 267-275, Copyright (1998), with permission from Elsevier Science.

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

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). ... 

Two variations on the analysis of PCR products by ESI mass spectrometry have emerged (1) direct-injection MS and tandem mass spectrometry (MS-MS) and (2) liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS). In the former approach, the sample is cleaned manually, and as noted above, the cleanup is performed as simply and rapidly as possible. In the latter approach, the cleanup is done automatically... 

Sanz-Nebot, V., Benavente, F., Barbosa, J. (2002). Liquid chromatography-mass spectrometry and capillary electrophoresis combined approach for separation and characterization of multicomponent peptide mixtures application to crude products of leuprolide synthesis. J. Chromatogr. A 950, 99-111. 

J. W. Hirschelman, W. H. et ah Increasing the throughput and productivity of Caco-2 cell permeability assays using liquid chromatography-mass spectrometry application to resveratrol absorption and metabolism. Comb Chem High Throughput Screen 2003, 6, 757-767. 

Zwiener C, Glauner T, Frimmel FFl (2003) Liquid chromatography/electrospray ionization tandem mass spectrometry and derivatization for the identification of polar carbonyl disinfection by-products. In Ferrer I, Thurman EM (eds) Liquid chromatography/mass spectrometry, MS/MS and time-of-flight MS, ACS symposium series, vol 850. American Chemical Society, Washington DC, pp 356-375... 

Liquid chromatography-mass spectrometry (LC-MS) or liquid chromatography-tandem-mass spectrometry (LC-MS/MS) has been in general the technique of choice for the analysis of PFCs. Therein detailed information about the main experimental conditions used for analysis, such as LC-MS/MS precursor-product ion transitions, were reported. 

J.D. Vargo, Determination of chloroacetanilide and chloroacetamide herbicides and their polar degradation products in water by LC/MS/MS. In Liquid Chromatography/Mass Spectrometry, MS/MS and Time of Flight MS Analysis of Emerging Contaminants, I. Ferrer, E.M. Thurman (Eds.), American Chemical Society, Washington, DC, 2003. 

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. 

Increased use of liquid chromatography/mass spectrometry (lc/ms) for structural identification and trace analysis has become apparent. Thermo-spray lc/ms has been used to identify by-products in phenyl isocyanate precolumn derivatization reactions Liquid chromatography/thermospray mass spectrometric characterization of chemical adducts of DNA formed during in vitro reaction lias been proposed as an analytical technique to detect and identify those contaminants in aqueous environmental samples which have a propensity to be genotoxic, t.e.. to covalently bond to DNA. 

S Lacorte, D Barcelo. Determination of organophosphorus pesticides and their transformation products in river water by automated on-line solid-phase extraction followed by liquid-chromatography mass spectrometry. J Chromatogr A 712 103—112, 1995. 

Wada, T., Nagasawa, E. and Hanaoka, S. (2006) Simultaneous determination of degradation products related to chemical warfare agents by high-performance liquid chromatography/mass spectrometry. Applied Organometallic Chemistry, 20(9), 573-79. 

Wu Y. The use of liquid chromatography-mass spectrometry for the identification of drug degradation products in pharmaceutical formulations. Biomed Chromatogr 2000 14 384-396. 

R.P. Shah, V. Kumar, S. Singh, Liquid chromatography/mass spectrometric studies on atorvastatin and its stress degradation products, Rapid Commun. Mass Spectrom. 22 (2008) 613-622. 

Liquid chromatography/mass spectrometry (LC/MS)-based techniques provide unique capabilities for pharmaceutical analysis. LC/MS methods are applicable to a wide range of compounds of pharmaceutical interest, and they feature powerful analytical figures of merit (sensitivity, selectivity, speed of analysis, and cost-effectiveness). These analytical features have continually improved, resulting in easier-to-use and more reliable instruments. These developments coincided with the pharmaceutical industry s focus on describing the collective properties of novel compounds in a rapid, precise, and quantitative way. As a result, the predominant pharmaceutical sample type shifted from nontrace/pure samples to trace mixtures (i.e., protein digests, natural products, automated synthesis, bile, plasma, urine). The results of these developments have been sig-... 

Harris, P.G., Carter, J.F., Head, R.N., Harris, R.P., Eglinton, G., and Maxwell, J.R. (1995) Identification of chlorophyll transformation products in zooplankton faecal pellets and marine sediment extracts by liquid chromatography/mass spectrometry atmospheric pressure chemical ionization. Rapid Cornmun. Mass Spectrom. 9, 1177-1183. 

R.M. Black and R.W. Read, Analysis of degradation products of organophosphorus chemical warfare agents and related compounds by liquid chromatography-mass spectrometry using electrospray and atmospheric pressure chemical ionization, J. Chromatogr A, 794, 233-244 (1998). 

R.W. Read and R.M. Black, Rapid screening procedures for the hydrolysis products of chemical warfare agents using positive and negative ion liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization, J. Chromatogr. A, 862, 169-177 (1999). 

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