Data system

Major advancements in mass spectrometric instrumentation (e.g., ESI and MALDI) and electronics (e.g., TOE data handling) have been accompanied by rapid progress in computerization. Older mass spectrometrists may still remember when hand-adjusted potentiometers were used to manipulate the ion beam, and spectra were collected on photographic paper where the peaks had to be counted by hand (using 

The operation control functions range from relatively simple tasks, such as instrument tuning (e.g., automatic control of the ion beam and mass calibration), to highly sophisticated automatic switching from one mode of operation to another, such as data-dependent acquisition in the MS/MS mode triggered by ions (obtained 

Data processing for small molecules and library matching, usuaUy in-house. 

Post-acquisition data processing need not be on a separate computer, particularly for data on small molecules. Large sets of biopolymer and metabolomic data, often on the gigabyte scale, are processed separately. 

Protein, genomic, and metabolomic data are matched with Web-based libraries using software from instrument manufacturers or independant developers. 

One may lose the use of a valuable commercial product or one may waste precious resources in needless testing. In any event, a competent scientist should review computer generated information before it is used as a basis for Hazard Communication. 

Federal Index This data base covers virtually all federal documents issued between October 1976 and the present. Available from Capitol Services, Inc., Washington, D.C., the Federal Index covers proposed rules, regulations, speeches, bill introductions, congressional hearings, court decisions, executive orders, Washington Post articles, as well as all Federal Register documents. The cost for one hour of on-line connect time is 90.00 for subscribers to Lockheed s Dialog Information Retrieval Service. 

Suppose one wanted to search for cases of product liability regarding hazards of chemical products. Once one enters the request, e.g. Product Liability and Chemicals on the termined and the computer has done its search, the number of cases found with the search request appears on the screen. Since this number may be large, one may want to narrow the request further (hazards of corrosive chemical products flammable chemical products, toxic chemical products, etc.). The computer indicates how many headnotes and/or cases have been retrieved and will be displayed. Once promising headnotes are found in a search, the searcher may ask to have the full text displayed. If it is not available on line, it s possible to find the case in its bound form. 

Millipore/Waters Hewlett-Packard Spectra Physics Trivector 

The above comments apply generally to chromatographic data systems, and many are available commercially, based on a wide variety of microcomputers. Data systems for use in SEC are basically the same as those already described, but utilize additional software for calculation of the average molecular masses. This capability is only available from a limited number of manufacturers (see Table 2.1). 

Data handling will be discussed in detail in Chapter 3 and will be described only briefly here. Most software operates on the digitized data in a similar fashion. A baseline under the peak of interest is selected and the peak divided into slices. The area (/ij) of these slices is measured and their corresponding molecular masses (Mj) obtained from the calibration curve. The average molecular masses are then calculated as follows  

The chromatograph is usually calibrated with polystyrene standards, although a limited range of other polymer standards is available (see Appendix 2). If standards are not available for the polymer of interest, and if the Mark-Houwink constants K and a are known, then the universal calibration procedure can be employed, making use of the following equation  

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Mukeqee P and Mysels K J 1970 Critical Micelle Concentrations of Aqueous Surfactant Systems (National Standard Reference Data System, National Bureau of Standards Circular No 36) (Springfield, VA National Teehnieal Information Serviee)... 

The network model of a database system is an improvement over the hierarchical model. This model was developed in 1969 by the Data Base Task Group (DBTG) of CODASYL (Conference on Data System Languages) [8, because sometimes the re-... 

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). 

By connecting a gas chromatograph to a suitable mass spectrometer and including a data system, the combined method of GC/MS can be used routinely to separate complex mixtures into theii individual components, identify the components, and estimate their amounts. The technique is widely used. 

Chromatographic peak areas are calculated automatically by the data system by reference to the response obtained from certain specified, compound-dependent ions. From the peak areas of the target compounds, quantification is achieved by comparison with the internal standards, which are present in known concentration. The laboratory responsible for the analysis must report the target compounds and all tentatively identified (nontarget) compounds. Standard EPA forms must be completed and submitted. A laboratory is said to be in compliance when it has satisfied all aspects of its CLP contract. 

More likely now, the analog electrical signal will be digitized and processed by a computer (data) system. Alternatively, a time-to-digital converter can be used as an ion collector (see Chapter 31). 

A data system stores the mass spectrum until required, when it can be printed at leisure or viewed immediately on the computer screen. 

The amplified signal can be recorded directly by analog means but, more likely, the signal is digitized and processed by a computer (data system). 

Data processing. Once information is obtained with an appropriate data system, the information must be interpreted appropriately for the end use. Data processing involves the steps leading to this end use data processing does not necessarily imply application of modem computer techniques. 

Data system. Components used to record and process information during the analysis of a sample. The system includes a computer and an analog-to-digital conversion module as well as other control devices for data recording, storage, and manipulation. 

Tables of Stored Parameters, from Computer Stored Thermophysical Data System, Management Information Control, Phillips Petroleum Co., BartiesviUe, OHa., 1976.

Material Properties Numerical Data System Purdue University Purdue University (CINDAS) evaluated data compiled, correlated, analyzed, and synthesized to generate values for the thermophysical, mechanical, and electrical properties of materials... 

OHS MSDS Summary Sheet Oil and Ha2ardous Materials Technical Assistance Data System (OHM-TADS) Radioactivity Environ-mental Monitoring... 

A mass spectrometer consists of four basic parts a sample inlet system, an ion source, a means of separating ions according to the mass-to-charge ratios, ie, a mass analyzer, and an ion detection system. AdditionaUy, modem instmments are usuaUy suppUed with a data system for instmment control, data acquisition, and data processing. Only a limited number of combinations of these four parts are compatible and thus available commercially (Table 1). 

Because of the large number of samples and repetitive nature of environmental analysis, automation is very important. Autosamplers are used for sample injection with gc and Ic systems, and data analysis is often handled automatically by user-defined macros in the data system. The high demand for the analysis of environmental samples has led to the estabUshment of contract laboratories which are supported purely by profits from the analysis. On-site monitoring of pollutants is also possible using small quadmpole ms systems fitted into mobile laboratories. 

Economic Aspects. The Ic interface to a mass spectrometer is usually provided as an option to the more sophisticated, full capabiHty instmments. Some systems can have both Ic and gc interfaces and can conveniently switch between the two modes. Lc interfaces are approximately 30,000 bringing a Ic/ms that includes a data system into the 130,000—180,000 range. 

Tandem mass spectrometry or ms/ms was first introduced in the 1970s and gained rapid acceptance in the analytical community. The technique has been used for stmcture elucidation of unknowns (26) and has the abiUty to provide sensitive and selective analysis of complex mixtures with minimal sample clean-up (27). Developments in the mid-1980s advancing the popularity of ms/ms included the availabiUty of powerhil data systems capable of controlling the ms/ms experiment and the viabiUty of soft ionisation techniques which essentially yield only molecular ion species. 

Sodium Silicate-Oil and Hac rdous Materials—Technical Assistance Data System, National Institute of Health, Washington, D.C. (an on-line database). 

Use of such a data system is easy, provided that the permanent system data bank has entries for the components of interest. Thus it is often important to the user that the data bank is extensive and not restricted to a small class of compounds. However, the number of chemical species is enormous and expanding at a rapid rate. Accordingly, for wide appHcation it is necessary that the physical property system embodies faciUties for the use of user-supphed data. 

Figure 8-5 illustrates the concept of samphng a continuous function. At integer values of the saiTmling rate. At, the value of the variable to be sampled is measured and held until the next sampling instant. To deal with sampled data systems, the z transform has been developed. The z transform of the function given in Fig. 8-5 is defined as... 

Nuclear Plant Reliability Data System Annual Reports of Cumulative System and Component Reliability for Period from July 1, 1974, through December 31, 1982, NPRD A02/A03 (INPO 83-034), Institute of Nuclear Power Operations, Atlanta, GA, October 1983. 

The real-time analyzer plays a very important role in presenting vibratory data in a manner that ean lend itself to a trending data system. This important role of the speetrum analyzer will be explored in detail in this ehapter. Also, the role of the speetrum analyzer will inerease with a better understanding of statistieal teehniques in vibration analysis. 

A first-order sampled-data system is shown in Figure 7.10. 

Consider the characteristic equation of a sampled-data system... 

To obtain the z-transform of a first-order sampled data system in cascade with a zero-order hold (zoh), as shown in Figure 7.10. 

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