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Selective Identification (selective + identification)
Selected AbstractsSelective Analysis of Secondary Amines Using Liquid Chromatography with Electrochemical Detection (LC-EC)ELECTROANALYSIS, Issue 21 2006Celia Abstract In a mixture of primary and secondary aliphatic amines, the primary amines were derivatized (masked) with o -phthalaldehyde (OPA) followed by derivatization of the remaining secondary amines with ferrocenecarboxylic acid chloride (FAC). The "tagged" amines were analyzed by LC-EC (liquid chromatography with electrochemical detection) using in-series dual electrode detection. Chemically-reversible oxidation of the FAC tagged secondary amines and their subsequent complementary oxidation and reduction signals coupled with chemically-irreversible oxidation of OPA tagged primary amines provided the selectivity for quantitative secondary amine analysis. The procedure was also applied for the selective identification of fragment 4,11 (N -terminus-proline) of Substance P in the presence of other Substance P fragments with primary amino acids as their N -termini. [source] CE coupled to MALDI with novel covalently coated capillariesELECTROPHORESIS, Issue 4 2010Stefan Bachmann Abstract CE offers the advantage of flexibility and method development options. It excels in the area of separation of ions, chiral, polar and biological compounds (especially proteins and peptides). Masking the active sites on the inner surface of a bare fused silica capillary wall is often necessary for CE separations of basic compounds, proteins and peptides. The use of capillary surface coating is one of the approaches to prevent the adsorption phenomena and improve the repeatability of migration times and peak areas of these analytes. In this study, new capillary coatings consisting of (i) derivatized polystyrene nanoparticles and (ii) derivatized fullerenes were investigated for the analysis of peptides and protein digest by CE. The coated capillaries showed excellent run-to-run and batch-to-batch reproducibility (RSD of migration time ,0.5% for run-to-run and ,9.5% for batch-to-batch experiments). Furthermore, the capillaries offer high stability from pH 2.0 to 10.0. The actual potential of the coated capillaries was tested by combining CE with MALDI-MS for analysing complex samples, such as peptides, whereas the overall performance of the CE-MALDI-MS system was investigated by analysing a five-protein digest mixture. Subsequently, the peak list (peptide mass fingerprint) generated from the mass spectra of each fraction was entered into the Swiss-Prot database in order to search for matching tryptic fragments using the MASCOT software. The sequence coverage of analysed proteins was between 36 and 68%. The established technology benefits from the synergism of high separation efficiency and the structure selective identification via MS. [source] Liquid chromatography/triple quadrupole tandem mass spectrometry with multiple reaction monitoring for optimal selection of transitions to evaluate nutraceuticals from olive-tree materialsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2008Rafael Japón Luján Optimal transitions have been selected for the identification and quantitation of the most interesting hydrophilic biophenols in extracts from olive-tree materials, which are of interest because of their nutraceutical properties. The tested materials were extra virgin olive oil, waste from oil production (known as alperujo), and olive-tree materials such as leaves, small branches and fruit stones. The identification and determination steps of the target biophenols are based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) with a triple quadrupole (QQQ) mass detector. The interface between the chromatograph and the QQQ was an electrospray ionization source operated in the negative ion mode. Highly selective identification of the biophenols was confirmed by multiple reaction monitoring (MRM) using the most representative transitions from the precursor ion to the different product ions. Quantitative MS/MS analysis was carried out by optimization and selection of the most sensitive transition for each analyte, which resulted in estimated detection limits of 5.10 to 11.65,ng/mL for the extracts. The biophenols were extracted from the tested samples by different methods: liquid-liquid extraction for virgin olive oil, microwave-assisted leaching for olive leaves, branches and stones, and pressurized liquid leaching for alperujo. This study provides valuable information about the most suitable source for the isolation of each nutraceutical biophenol and enables us to obtain a complete profile of them in Olea Europaea. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simultaneous clinical monitoring of lactic acid, pyruvic acid and ketone bodies in plasma as methoxime/tert-butyldimethylsilyl derivatives by gas chromatography,mass spectrometry in selected ion monitoring modeBIOMEDICAL CHROMATOGRAPHY, Issue 5 2008Man-Jeong Paik Abstract Simultaneous determination of lactic acid, pyruvic acid, 3-hydroxybutyric acid and acetoacetic acid for clinical monitoring of lactic acidosis and ketone body formation in human plasma (20 µL) was performed by gas chromatography,mass spectrometry in selected ion monitoring (SIM) mode after generating methoxime/tert-butyldimethylsilyl derivatives. All of the targeted carboxylic acids were detected by characteristic fragment ions, which permitted sensitive and selective identification in the presence of co-extracted free fatty acids and other acidic metabolites at much higher levels. The method was linear (r , 0.9991), reproducible (% relative standard deviation = 1.2,5.8), and accurate (% relative error = ,7.2,7.6), with detection limits of 0.05,1.7 ng/mL. This rapid, accurate and selective method using minimal plasma samples (20 µL) is useful in the clinical monitoring of lactic acidosis and ketone body formation in plasma. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||