With mass spectrometry

Analytical Approaches. Different analytical techniques have been appHed to each fraction to determine its molecular composition. As the molecular weight increases, complexity increasingly shifts the level of analytical detail from quantification of most individual species in the naphtha to average molecular descriptions in the vacuum residuum. For the naphtha, classical techniques allow the isolation and identification of individual compounds by physical properties. Gas chromatographic (gc) resolution allows almost every compound having less than eight carbon atoms to be measured separately. The combination of gc with mass spectrometry (gc/ms) can be used for quantitation purposes when compounds are not well-resolved by gc. 

Gas Chromatography (gc). A principal advantage of gas chromatography has been the faciUty with which it can be combined with mass spectrometry for amino acid identification and confirmation of purity. The gc-mass spectrometry combination offers the advantage of obtaining stmctural information rather than the identification by retention time in hplc. 

Naiiow-line uv—vis spectia of free atoms, corresponding to transitions ia the outer electron shells, have long been employed for elemental analysis usiag both atomic absorption (AAS) and emission (AES) spectroscopy (159,160). Atomic spectroscopy is sensitive but destmctive, requiring vaporization and decomposition of the sample iato its constituent elements. Some of these techniques are compared, together with mass spectrometry, ia Table 4 (161,162). 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

The recent development and comparative application of modern separation techniques with regard to determination of alkylphosphonic acids and lewisite derivatives have been demonstrated. This report highlights advantages and shortcomings of GC equipped with mass spectrometry detector and HPLC as well as CE with UV-Vis detector. The comparison was made from the sampling point of view and separation/detection ability. The derivatization procedure for GC of main degradation products of nerve agents to determine in water samples was applied. Direct determination of lewisite derivatives by HPLC-UV was shown. Also optimization of indirect determination of alkylphosphonic acids in CE-UV was developed. Finally, the new instrumental development and future trends will be discussed. 

Diethyl sulphate and dimethyl sulphate Lab method using Tenax sorbent tube, thermal desorption and gas chromatography with mass spectrometry 89... 

Sample concentration, and hence enrichment, is certainly a key issue in this area of analysis, since complementary information obtained from NMR or IR spectroscopic detection is often desirable in conjunction with mass spectrometry. Detection methods such as these have far higher concentration thresholds than MS and obtaining adequate quantities of material for detection becomes a significant challenge. 

Authenticity evaluation has recently received increased attention in a number of industries. The complex mixtures involved often require very high resolution analyses and, in the case of determining the authenticity of natural products, very accurate determination of enantiomeric purity. Juchelka et al. have described a method for the authenticity determination of natural products which uses a combination of enantioselective multidimensional gas chromatography with isotope ratio mass spectrometry (28). In isotope ratio mass spectrometry, combustion analysis is combined with mass spectrometry, and the ratio of the analyte is measured versus a... 

The combination of the flash vacuum pyrolysis (FVP) technique169 with mass spectrometry proved to be particularly useful in identification and characterization of both the fragmentation/rearrangement patterns, intermediates and/or final products formed (see Section IV.E.l). Usually, no structures are indicated in the mass spectra, although ionization and appearance potential can, in principle, provide structural information. 

GC-MS gas chromatography coupled with mass spectrometry HDL heavy-duty liquid or laundry liquid... 

Trauger SA, Junker T, Siuzdak G (2003) Investigating Viral Proteins and Intact Viruses with Mass Spectrometry. 225 257-274... 

MS-MS mass spectrometry in combination with mass spectrometry (tandem mass spectrometry)... 

The combination of chromatography and mass spectrometry (MS) is a subject that has attracted much interest over the last forty years or so. The combination of gas chromatography (GC) with mass spectrometry (GC-MS) was first reported in 1958 and made available commercially in 1967. Since then, it has become increasingly utilized and is probably the most widely used hyphenated or tandem technique, as such combinations are often known. The acceptance of GC-MS as a routine technique has in no small part been due to the fact that interfaces have been available for both packed and capillary columns which allow the vast majority of compounds amenable to separation by gas chromatography to be transferred efficiently to the mass spectrometer. Compounds amenable to analysis by GC need to be both volatile, at the temperatures used to achieve separation, and thermally stable, i.e. the same requirements needed to produce mass spectra from an analyte using either electron (El) or chemical ionization (Cl) (see Chapter 3). In simple terms, therefore, virtually all compounds that pass through a GC column can be ionized and the full analytical capabilities of the mass spectrometer utilized. 

What are the Advantages of Linking High Performance Liquid Chromatography with Mass Spectrometry ... 

The combination of HPLC with mass spectrometry therefore allows more definitive identification and the quantitative determination of compounds that are not fully resolved chromatographically. 

Reference has been made to the problems associated with the presence of highly involatile analytes. Many buffers used in HPLC are inorganic and thus involatile and these tend to compromise the use of the interface, in particular with respect to snagging of the belt in the tunnel seals. The problem of inorganic buffers is not one confined to the moving-belt interface and, unless post-column extraction is to be used, those developing HPLC methods for use with mass spectrometry are advised to utilize relatively volatile buffers, such as ammonium acetate, if at all possible. 

The on-line principle has also been extended into the field of detection (Fig. 8). Thus, it is now possible to record FTIR [27-31] and Raman spectra in situ [32, 33], and there have been considerable advances in the on-line coupling of thin-layer chromatography with mass spectrometry. Here it has been, above all, the research groups of Wilson [34-36] and Busch [37-40] that have made the necessary instrumental and methodological advances, so that TLC must no longer be viewed as merely a clean-up method. Rather it forms the essential central point for all these on-line coupling techniques. 

Schultz B, Kjeldsen P. 1986. Screening of organic matter in leachates from sanitary landfills using gas chromatography combined with mass spectrometry. Water Res 20 967-970. 

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

For human studies, the choice of stable isotopes is limited because radioisotopes are associated with ionization radiation and thus with some potential harmful effects for humans. Studying the bioavailability of compounds labeled with stable isotopes requires complex techniques such as gas chromatography coupled with mass spectrometry (GC-MS), liquid chromatography coupled with MS (LC-MS), and atmo-... 

Many methods for determination of cannabinoids in plant material have been developed. Commonly HPLC or GC is used, often in combination with mass spectrometry. Molecular techniques are also available to detect these compounds and will be discussed in this section. 

Microbes of differing physiologic types, acting in consortia, appear to be more destructive than monocultures. Methods for examining consortia are based on the detection of lipid biomarkers that are characteristic for different classes of microbes. These can be analyzed by gas chromatography coupled with mass spectrometry [512]. 

All previous discussion has focused on sample preparation, i.e., removal of the targeted analyte(s) from the sample matrix, isolation of the analyte(s) from other co-extracted, undesirable sample components, and transfer of the analytes into a solvent suitable for final analysis. Over the years, numerous types of analytical instruments have been employed for this final analysis step as noted in the preceding text and Tables 3 and 4. Overall, GC and LC are the most often used analytical techniques, and modern GC and LC instrumentation coupled with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) detection systems are currently the analytical techniques of choice. Methods relying on spectrophotometric detection and thin-layer chromatography (TLC) are now rarely employed, except perhaps for qualitative purposes. 

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