Liquid chromatography/mass spectrometry clean

More recently, liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) have been evaluated as possible alternative methods for carfentrazone-ethyl compounds in crop matrices. The LC/MS methods allow the chemical derivatization step for the acid metabolites to be avoided, reducing the analysis time. These new methods provide excellent sensitivity and method recovery for carfentrazone-ethyl. However, the final sample extracts, after being cleaned up extensively using three SPE cartridges, still exhibited ionization suppression due to the matrix background for the acid metabolites. Acceptable method recoveries (70-120%) of carfentrazone-ethyl metabolites have not yet been obtained. 

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... 

OeUig, C. and Schwack, W. 2012, Planar solid phase extraction clean-up for pesticide residue analysis in tea hy liquid chromatography-mass spectrometry, J. Chromatogr. A, 1260 42-53. 

Analysis of pesticides (eight in total, namely, molinate, propanil, fenitrothion, malathion, bentazone, cypermetrine, maloxon, and fenitrothion oxon) in biota was accomplished with a method based on pressurized liquid extraction (ASE), followed by SPE clean-up, and analysis by gas chromatography-mass spectrometry with electron impact ionization (GC/MS-EI). 

Racaityte K, Lutz ESM, Unger KK, Lubda D, Boos KS. 2000. Analysis of neuropeptide Y and its metabolites by high-performance liquid chromatography-electrospray ionization mass spectrometry and integrated sample clean-up with a novel restricted-access sulphonic acid cation exchanger. J Chromatogr A 890 135. 

Ylinen et al. [53] developed an ion-pair extraction procedure employing tetrabutylamonium (TBA) counter ions for determination of PFOA in plasma and urine in combination with gas chromatography (GC) and flame ionisation detection (FID). Later on, Hansen et al. [35] improved the sensitivity of the ion-pair extraction approach using methyl tertiary butyl ether (MTBE) and by the inclusion of a filtration step to remove solids from the extract making it amenable to liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination. Ion-pair extraction procedure has been the basis of several procedures for biota [49,54-58] and food samples [50,59,60]. However, this method has shown to have some limitations, such as (1) co-extraction of lipids and other matrix constituents and the absence of a clean-up step to overcome the effects of matrix compounds and (2) the wide variety of recoveries observed, typically ranging. 

Van Eeckhout, N., Perez, J. C., and Van Peteghem, C. (2000). Determination of eight sulfonamides in bovine kidney by liquid chromatography/tandem mass spectrometry with on-line extraction and sample clean-up. Rapid Commun. Mass Spectrom. 14 2331-2338. 

Chemical analysis of hair samples may also provide a method for examining chronic mycotoxin exposures. In 2003, Sewram et al. (2003) reported that human hair testing could be used to detect fumonisins. After extraction and clean up, high performance liquid chromatography coupled to electrospray ionization-mass spectrometry (HPLC-ESI-MS) was able to detect fumonisin Bi, fumonisin B2, and fumonisin B3 from human hair samples (Sewram et al., 2003). However, these were... 

High-performance liquid chromatography-tandem mass spectrometry method for the determination of gemifloxacin in human plasma was based on the protein precipitation of plasma samples with acetonitrile containing [ C Ha] gemifloxacin as an internal standard. The supernatant was injected onto a PLRP-S column without any further clean-up. The mass spectrometer was operated in positive ion mode, and the ions were detected in multiple reaction-monitoring (MRM) mode. The assay requires 50 gl of plasma and is precise and accurate within the range 10-5000 ng/ml [15]. 

Koch, H. M., Gonzalez-Reche, L. M., and Angerer, J., Online clean-up by multidimensional liquid chromatography-electrospray ionization tandem mass spectrometry for high throughput quantification of primary and secondary phthalate metabolites in human urine, J. Chromatogr. B, 748, 169-182, 2003. 

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