Mass Spectroscopy MS

There are several methods of ionizing organic materials such as particle bombardment, chemical and field ionization, electron impact, field desorption, and laser pulse. For example, in the laser micro-mass analysis method, a laser pulse is used to supply the necessary energy to volatilize a sample from the surface for mass spectroscopy. 1 1 Mass spectrometry is often used in conjunction with gas chromatography to identify the separated components. The working technology of mass spectrometry is quite complex. 

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Historically, measurements have classified ambient hydrocarbons in two classes methane (CH4) and all other nonmethane volatile organic compounds (NMVOCs). Analyzing hydrocarbons in the atmosphere involves a three-step process collection, separation, and quantification. Collection involves obtaining an aliquot of air, e.g., with an evacuated canister. The principal separation process is gas chromatography (GC), and the principal quantification technique is wdth a calibrated flame ionization detector (FID). Mass spectroscopy (MS) is used along with GC to identify individual hydrocarbon compounds. 

The predominant method of analyzing environmental samples for methyl parathion is by GC. The detection methods most used are FID, FPD, ECD, and mass spectroscopy (MS). HPLC coupled with ultraviolet spectroscopy (UV) or MS has also been used successfiilly. Sample extraction and cleanup varies widely depending on the sample matrix and method of detection. Several analytical methods used to analyze environmental samples for methyl parathion are summarized in Table 7-2. 

An important breakthrough in HTS ee assays came from the group of Reetz in late 1990, with the introduction of mass spectroscopy (MS)-based procedures [90]. These methods use special asymmetrically isotope-labeled compounds. Enzymatic transformations of these compounds usually lead to two pseudoenantiomeric compounds whose relative concentration can be estimated using MS techniques. 

Computational methods including both metabolism databases and predictive metabolism software can be used to aid bioanalytical groups in suggesting all possible potential metabolite masses before identification by mass spectroscopy (MS) [116,117]. This approach can also combine specialized MS spectra feature prediction software that will use the outputs from databases and prediction software and make comparisons with the molecular masses observed... 

Many techniques for the analysis of anthocyanins have been used for almost a century and are still of importance, along with considerable advances in technologies such as mass spectroscopy (MS) and nuclear magnetic resonance (NMR). This section summarizes the analytical procedures for quantitative and qualitative analyses of anthocyanins, including classical and modem techniques. 

Many methods are currently available for the qualitative analysis of anthocyanins including hydrolysis procedures," evaluation of spectral characteristics, mass spectroscopy (MS), " nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy. - Frequently a multi-step procedure will be used for... 

Knowledge on the plasma species can be obtained by the use of plasma diagnostics techniques, such as optical emission spectroscopy (OES) and mass spectroscopy (MS). Both techniques are able to probe atomic and molecular, neutral or ionized species present in plasmas. OES is based on measuring the light emission spectrum that arises from the relaxation of plasma species in excited energy states. MS, on the other hand, is generally based on the measurement of mass spectra of ground state species. 

There are many references to the speciation of organotin compounds (particularly butyltin compounds) in marine sediments (see below), when compounds Uu Snk4 are separated by GLC or HPLC and analyzed by mass spectroscopy (MS),56 sometimes with isotope dilution.57-59... 

A major consequence of using regulatory limits based on degradant formation, rather than absolute change of the API level in the drug product, is that it necessitates the application and routine use of very sensitive analytical techniques [ 10]. In addition, the need to resolve both structurally similar, as well as structurally diverse degradants of the API, mandates the use of analytical separation techniques, for example, HPLC, CE, often coupled with highly sensitive detection modes, for example, ultraviolet (UV) spectroscopy, fluorescence (F) spectroscopy, electrochemical detection (EC), mass spectroscopy (MS), tandem mass spectroscopy (MS-MS) and so forth. 

Numerous analyses in the quality control of most kinds of samples occurring in the flavour industry are done by different chromatographic procedures, for example gas chromatography (GC), high-pressure liquid chromatography (fiPLC) and capillary electrophoresis (CE). Besides the different IR methods mentioned already, further spectroscopic techniques are used, for example nuclear magnetic resonance, ultraviolet spectroscopy, mass spectroscopy (MS) and atomic absorption spectroscopy. In addition, also in quality control modern coupled techniques like GC-MS, GC-Fourier transform IR spectroscopy, HPLC-MS and CE-MS are gaining more and more importance. 

When exposed to sufficient energy, a molecule may lose an electron to form a cation-radical, which then may undergo fragmentation of bonds. These processes make mass spectroscopy (ms) a useful tool for structure proof. Very small concentrations of the parent molecules (RS), in the vapor state, are ionized by a beam of energetic electrons (e ),... 

In addition, a total of 146 sheep urine and 87 chicken muscle samples from birds sold in local markets and originating from Brazil, Denmark, France, and Turkey were tested for residues of diethylstilbestrol and ethinylestradiol (41). Although some of the samples were positive to both analytes by an immunochemical screening assay, confirmatory analysis by GC-mass spectroscopy (MS) showed that none of the samples contained residues of the examined steroids. 

Although multidimensional separation generally offers enhanced selectivity and discrimination of solutes, application of more than one hyphenated techniques is usually required for complete and unequivocal identification of the analytes. A recent report states that two widespread misconceptions about mass spectroscopy (MS) are that GC-MS is a specific method and tlrat GC-MS is 100% accurate (5). The 1989 Forensic Urine Drug Confirmation Study by the American Association for Clinical Chemistry/College of American Pathologists confirmed this concern about overreliance on GC-MS as a confirmation method (5). 

For complete identification, relevant direct information on the molecular structure of the analyte is always more specific and hence more reliable than indirect information. Analytical steps based on molecular spectroscopy all provide direct more or less detailed information on the structure of the analyte. This is particularly true for fourier-transform infrared (FTIR) and mass spectroscopy (MS), where the spectra have a very high information content. 

The emission levels generated at the processing of HIPS were estimated from static monitors positioned around the engine. In the monitoring positions stainless steel tubes packed with Tenax and Chromosorb as a general purpose adsorbent material were established. After sampling, the adsorbed chemicals were desorbed at 250°C and subsequently analyzed by gas chromatography (GC) coupled with mass spectroscopy (MS). 

We have followed the pathway of TNT degradation in the consortium using reverse phase high performance liquid chromatography (HPLC) and mass spectroscopy (MS). Analysis of the supernatant in the consortium showed sequential reduction of TNT to TAT however, TAT only occasionally accumulated, and even then only in very low concentrations. In addition, methylphloroglucinol (MPG) and />-cresol transiently appeared in the supernatant. All compounds were identified using HPLC by UV spectra and retention times as compared to authentic standards chromatographed under the same conditions. The mono- and diamino intermediates were also confirmed by the MS results. 

The photocatalytic oxidation of alkylbenzenes and alkenylbenzenes has been widely reported. The data concerning alkylbenzenes have shown that the reactivity of toluenes is low when compared to other monosubstituted benzenes (Somarani et al., 1995). The effect of adding a zeolite, which is an acid solid catalyst, by Ti02/UV on various 4-substituted toluenes was studied by Somarani et al. (1995). The compounds of interest were prepared at 0.03 M in solutions containing TiOz. The effect of a zeolite was also studied by adding HY-type zeolites with various Si/Al ratios. The solutions were irradiated with a 125-W mercury lamp emitting light at 330 nm. Samples were taken at 48 hours and analyzed by GC/mass spectroscopy (MS) to determine percent conversions of the toluenes to the desired products. 

Mass spectroscopy (MS) methods can be used to analyze complex mixtures of proteins and peptides in minutes and with mass accuracy several orders of magnitude better than that obtained from electrophoretic methods. For proteins with a known sequence, the mass measurement accuracies are generally sufficient to identify the products resistant to proteolysis precisely and to define compact domains within proteins effectively. 

Sedimentation FFF implies application of the centrifugal field, which is produced by placing the channel in a centrifuge basket. SdFFF instruments can be linked readily to analytical instruments to provide analysis in real time. For the first time, Beckett (1991) introduced FFF-ICP-mass spectroscopy (MS) as a powerful analytical tool for characterizing macromolecules and particles. Taylor et al. (1992) illustrated the characterization of some inorganic colloidal particles and river-borne suspended particulate matter of size range <1 pm using SdFFF and ICP-MS. 

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