Separation technique, coupling

The choice of the method of analysis depends on the question to address. Spectrophotometry is sufficient for total curcuminoid content determination in a turmeric extract. Separation techniques coupled to mass spectrometry detection and MALDl-TOF are highly sensitive techniques that are more adapted to the identification of metabolites in biological fluids such as urine or plasma. ... 

Principles and Characteristics The main reasons for hyphenating MS to CE are the almost universal nature of the detector, its sensitivity and the structural information obtainable, including assessment of peak purity and identity. As CE is a liquid-phase separation technique, coupling to the mass spectrometer can be achieved by means of (modified) LC-MS interfaces. Because of the low flow-rates applied in CE, i.e. typically below lOOnLmin-1, a special coupling device is required to couple CE and the LC-MS interface. Three such devices have been developed, namely a... 

Either gas chromatography (GC) or liquid chromatography (LC) can be used as a separation technique coupled with a variety of detection methods. Mass spectrometry (MS) is one of the most popular means of detection. When using GC-MS, a capillary column should be used, while any suitable LC column can be used for LC-MS. It is advisable to obtain a print-out of the chromatogram so that the shapes of individual peaks can be assessed. Electronically produced data using integrators should be treated with some suspicion and always examined visually to check the selected baseline, start- and end-points of peak integration, etc. 

Whilst these methods are informative for the characterisation of synthetic mixtures, the information gained and the nature of these techniques precludes their use in routine quantitative analysis of environmental samples, which requires methods amenable to the direct introduction of aqueous samples and in particular selective and sensitive detection. Conventionally, online separation techniques coupled to mass spectrometric detection are used for this, namely gas (GC) and liquid chromatography (LC). As a technique for agrochemical and environmental analyses, high performance liquid chromatography (HPLC) coupled to atmospheric pressure ionisation-mass spectrometry (API-MS) is extremely attractive, with the ability to analyse relatively polar compounds and provide detection to very low levels. 

Erny, G. L., and Cifuentes, A. (2006). Liquid separation techniques coupled with mass spectrometry for chiral analysis of pharmaceuticals compounds and their metabolites in biological fluids. ]. Pharm. Biomed. Anal. 40, 509—515. 

Merino, F., S. Rubio, and D. Perez-Bendito. 2005. Supramolecular systems-based extraction-separation techniques coupled to mass spectrometry. J. Sep. Sci. 28 1613-1627. 

Sample Preparation for Speciation Analysis by Liquid-Phase Separation Techniques Coupled with ICP-MS... 

Table 8.2 lists common sample preparation techniques for extraction and enrichment of analytes before HPLC analysis. More detailed discussion on sample preparation procedures is available elsewhere.6,7 A modern method trend is the use of higher-resolution separation techniques coupled with specific detectors (e.g., LC/MS/MS) to eliminate or minimize the time-consuming... 

Improvements in the sample pretreatment procedures. Sample cleanup, preconcentration, and preservation procedures of natural species are urgently needed. There is no guarantee that transformation of elemental speciation along the whole analytical procedure does not take place. In this sense, the use of isotopically labeled compounds using an adequate separation technique coupled to ICP-MS is being established. It seems clear that the use of isotopically enriched species, synthesized for the purpose, will became an important tool for validation of speciation results. 

Abstract In the past years, elucidation of transformation products of per- and polyfluorinated chemicals (PFC) has been a task frequently approached by analytical chemists. PCT, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are persistent and thus, the analytical quest to detect transformation products has failed so far. Their prominence as contaminants is mainly due to their extreme persistence, which is linked to their perfluoroalkyl chain length. Molecules that are less heavily fluorinated can show very complex metabolic behavior, as is the case for fluorotelomer alcohols. These compounds are degraded via different but simultaneous pathways, which produce different stable metabolites. Biotransformation processes of PFC may occur when these compounds enter the environment, and thus known and unknown PFC may be generated in these compartments. Therefore, it is essential to determine metabolic pathways of such compounds in order to entirely understand their fate in the environment. This chapter summarizes methodological approaches and instmmental setups which have been implemented in biotransformation studies of PFC and focuses on mass spectrometric methods and the separation techniques coupled to the mass spectrometer (MS). Valuable MS approaches that have not been frequently used in studies on PFC are presented as well. Since compounds carrying C-F bonds exhibit unique properties, these will be initially presented to address the meaning of these properties both for analytical tasks and for the setup of biotransformation experiments. 

This article summarizes methodological approaches and instmmental setups which have been implemented in biotransformation studies of PFC and focuses on mass spectrometric methods (MS, will be used for mass spectrometer, mass spectrometry and mass spectrometric) and the separation techniques coupled to the MS. Valuable MS approaches that have not been frequently used in studies on PFC are presented as well. Since compounds carrying C-F bonds exhibit unique properties, these will be initially presented to address the meaning of these properties both for analytical tasks and for the setup of biotransformation experiments. 

Separation Techniques Coupled with Mass Spectrometry... 

However, full characterization of functionalized siloxanes, particularly those containing high degrees of polymerization, can be difficult. Therefore, separation techniques coupled with various detection devices are typically employed. Supercritical fluid chromatography is effective for the separation of silicone oligomers that have molecular weights less than 3000 Da (688,689). Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is applicable up to 10,000 Da (660). 

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