Mass spectrometers data from

This chapter reviews another mass spectrometric method called stress mass spectrometry (stress MS). In stress MS, materials are subjected to mechanical deformation, and the volatile compounds evolved from the sample are analyzed by a mass spectrometer. The entire experiment, including application of stress, is performed directly in the ion-source housing of the mass spectrometer. Data from these experiments provide information on changes in the polymer which produce the evolved volatile compounds. When combined with the results of other spectroscopic experiments, these studies provide a means of investigating the chemical processes which occur when polymers are deformed mechanically. 

Very rarely, however, will a single mass spectrum provide us with complete analytical information for a sample, particularly if mass spectral data from a chromatographic separation, taking perhaps up to an hour, is being acquired. The mass spectrometer is therefore set up to scan, repetitively, over a selected m jz range for an appropriate period of time. At the end of each scan, the mass spectrum obtained is stored for subsequent manipulation before a further spectrum is acquired. 

It has been stated that measured accurate masses when used to assign molecular formulae should always be accompanied by their mass accuracies. [34] Ideally, this can be done by giving the mean mass value and the corresponding error in terms of standard deviation as obtained from several repeated measurements of the same ion. [35] This is definitely not identical to the error which is usually provided with the listing from mass spectrometer data systems, where an error is given as the difference of calculated and measured mass value. 

Analysis of the Mixture of Organic Compounds from the Soil. The crude fractions were analyzed using a LKB-2091 capillary gas chromatograph/mass spectrometer/data analysis system (CGC/MS/DA). The capillary column used was a J W DB-1, 60 m x 0.32 mm, connected directly to Ae ion source of the mass spectrometer. Up to 1.0 tfL of a solution of the sample in an appropriate solvent was injected directly onto the column at 40 °C, whereupon the column temperature was immediately raised to 100 for 4 min, and programmed to 310 °C at a rate of 10°/min. and held there for 30 min. 

The relatively recently discovered compounds of the erstwhile inert gases have already been studied in systems with oxides of nitrogen. Johnston and Woolfolk232 reported the reaction rates of xenon difluoride and xenon tetrafluoride with nitric oxide in the temperature range 300-350°K and at pressures between 0.1 and 30 torr. The reactions were followed by a mass spectrometer, separated from the reaction cell by a pinhole. There were serious problems, both in carrying out the experiment and in analyzing the data, but the results seem reliable. In... 

Figure 6.16 Software packages for data manipulation and processing, using standalone computers and servers that are networked with open-access mass spectrometer data systems. (Reprinted with permission from Tong et al., 1998. Copyright 1998 Elsevier.)...

For the light cycle oil from the base FCC operation, a correlation predicts the component mol fractions based on various properties computed by the FCC simulator. These properties include density, molecular weight, and percent carbon as aromatic ring and cycloparaffin ring. The correlation is based on mass spectrometer data on FCC cycle oils. 

If you obtain the isotopic abundance of an element from mass spectrometer data or a table, you can calculate the average atomic mass of the element. You do this by calculating the weighted average of each isotope s mass. A weighted average takes into account not only the values associated with a set of data, but also the abundance or importance of each value. 

Meteor can be interfaced with the MetaboLynx mass spectrometer software from Waters Corporation to integrate mass spectrometry data from metabolism studies directly. MetaboLynx is part of the Waters MassLynx Application Managers, a suite of mass spectrometry instrument software [16]. It is designed for automated metabolism studies with data from LC/MS or LC/MS/MS time-of-flight (TOP) experiments. MetaboLynx is able to detect peaks in an LC/MS data file resulting from in vitro or in vivo biotransformation and provides a list of elemental formulae for unidentified components in a mass spectrum. Meteor uses these data to filter the list of predicted metabolites. System requirements are similar to DEREK for Windows. 

Tiller et al. [289] reported the use of accurate LC-MS/MS data from a Q-TOF system as a first-line approach for metabolite identification studies in the discovery phase of the drug development. In this approach, first, the MS/MS spectrum of the parent compound under conditions of high mass resolution is obtained in order to support the proposed fragmentation pattern by elemental composition data. In the next step of the accurate mass approach to metabolite identification, the in vitro samples of drug candidates from incubations in liver microsomal preparations or hepatocytes are analyzed by LC-MSE on the Q-TOF mass spectrometer. Data are... 

A striking feature of the ionic reaction scheme for ethyl chloride which is evident from examining the reactions above is the fact that virtually all of these processes lead either to the protonated molecule ion or to other precursors of this product. In addition, the protonated species is efficiently converted to the C4Hi0C1+ ion hence, one expects that at higher pressures there will be essentially only this one ionic species present in any appreciable quantity. This conclusion is also supported by the high pressure mass spectrometer data discussed below. 

Case 2. Outlet partial pressures are derived from mass spectrometer data... 

Then the number of charges and the molecular mass can be calculated from these two equations with two unknowns. This takes account of the charging species, usually protons. The system is self-checking as several charge states are observed and each adjacent pair will produce a mass measurement. The complete mass calculation process is normally performed by the mass spectrometer data system. Contamination of a protein with buffer salts or with detergents is a serious problem in electrospray. MALDI is more flexible in this respect. 

Although not stated as such, the discussion thus far has implicitly concerned univariate data, i.e., replicate measurements of a single parameter under closely controlled conditions. A simple example might be a series of weighings to determine the mass of an object. Of course, the fact that a spread of experimental values is always obtained indicates that some of the experimental conditions are not completely under control. However, this class of measurements is usefully contrasted with bivariate and multivariate data (we shall be mainly concerned with the bivariate case. Section 8.3). Experimental measurements become two-dimensional under various sets of circumstances (Meier 2000). The case of main interest in this book corresponds to cases in which measured values (e.g., mass spectrometric signal intensities) are considered as functions of an experimental parameter (e.g., concentration or amount of a specified analyte injected into the instrument), as in acquisition of a calibration determination of the functional relationship between the two parameters is called regression. A related but somewhat different case concerns correlation analysis between two experimentally observable quantities (e.g., signals from a mass spectrometer and from a UV absorbance detector). The correlation behaviour is tested... 

Grieshop AP, Donahue NM, Robinson AL (2009) Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 2 analysis of aerosol mass spectrometer data. Atmos Chem Phys 9(6) 2227-2240... 

Mass spectrometer data Computation of fractional extent parameter a from MS data is explained with the help of a theoretical evolved gas profile shown in Figure 15.20a and b. In this case, the fractional extent of reaction a can be defined as... 

Figure 1. Comparison of analytical results obtained on an industrial polymer by gel permeation chromatography (top) and matrix-assisted laser desorption ionization mass spectrometry (linear time-of-flight mass spectrometer [center] and Fourier transform mass spectrometer [bottom]). From the FT/MS data the polymer can be identified as a substituted polyethylene glycol.

As mentioned previously, FT/MS is capable of providing more detailed structural information compared to most any other analytical technique. For example, it is possible to measure the absolute mass of an oligomer or a polymer fragment ion, and from that mass measurement the most probable elements composition can be computed by the mass spectrometer data station. A more accurate mass measurement (i.e. a lower error on the measurement) limits the chemical formulas that can be computed. Generally this elemental composition information is all that is needed to confirm a suspected molecular structure or substructure. However, if this is not sufficient, mass spectrometry/mass spectrometry (MS/MS) techniques (24) can be applied. 

The ratio of the various U Isotopes to U-233 from the mass spectrometer data Is multiplied by the amount of U-233 spike originally added to the sample to obtain the amount of each uranium Isotope present In the original sample. 

An ion beam causes secondary electrons to be ejected from a metal surface. These secondaries can be measured as an electric current directly through a Faraday cup or indirectly after amplification, as with an electron multiplier or a scintillation device. These ion collectors are located at a fixed point in a mass spectrometer, and all ions are focused on that point — hence the name, point ion collector. In all cases, the resultant flow of an electric current is used to drive some form of recorder or is passed to an information storage device (data system). 

This chapter briefly discusses the advantages to be gained from the use of transputers in acquiring and processing data from an instrument like a mass spectrometer, which routinely deals with large-scale input and output at high speed. 

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