Mass spectrometer data system

The tedium of carrying out a number of these calculations each time an electrospray spectrum is acquired has been removed by the provision of transformation software with the mass spectrometer data system. This software not only carries out the calculations automatically, but also plots the mass spectrum on a true mass scale. 

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. 

Example The [M-Cl]" ion, [CHCl2], represents the base peak in the El spectrum of chloroform. The results of three subsequent determinations for the major peaks of the isotopic pattern are listed below (Fig. 3.15). The typical printout of a mass spectrometer data system provides experimental accurate mass and relative intensity of the signal and an error as compared to the calculated exact mass of possible compositions. For the [ CH Cl2] ion, the experimental accurate mass values yield an average of 82.9442 0.0006 u. The comparatively small absolute error of 0.6 mmu corresponds to a relative error of 7.5 ppm. 

Mass Spectrometry (MS), A Hewlett-Packard 5930A mass spectro-meter was interi aced with a Tracor 222 GC. The ionization potential was 70 eV and the scanning limits were 33 to 450 amu. Scanning and data processing were accomplished with a FINNIGAN/INCOS 2300 mass spectrometer data system. A novel injection system (18) was used in place of the standard injection port in conjunction with the GC/MS system. 

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.)...

Gas Chromatography-Mass Spectrometry. A Finnigan MAT 4500 series quadrupole gas chromatograph/mass spectrometer/data system equipped with the same capillary column and using the same temperature program described in the previous section was employed. Helium was used as the carrier gas at an average linear velocity of 47.7 cm/sec (30°C). Injector temperature was 220°C, and the ion source temperature was 180°C. The outlet end of the fused silica column was inserted directly into the ion source block, which was maintained at approximately 180°C. 

Martin, C. L., Lackey, W, W., Conkle, J. P., Miller, R. L. Analysis of Trace Volatiles by Gas Chromatography/Mass Spectrometer Data System, NTIS order no. AD-A050 912, December 1977... 

The 7th Edition contains over 390,000 electron impact mass spectra including the older NIST 98 database. Through use of the AccessPak it may be loaded into many Mass Spectrometer data systems. 

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. 

The preceding discnssion has attempted to snmmarize some general fnndamental concepts nnderlying the practical goal of integrating appropriate chromatographic peak areas (e.g. EIC vs TIC). Modern mass spectrometer data systems inclnde integration rontines and these are briefly discussed in Section 7.4.3 bnt practical issues... 

Fortunately all modem mass spectrometer data systems include algorithms that calculate isotope patterns for ions with any combination of elements, at both unit mass resolution (as above) and at high resolution a brief review (Meija 2006) lists the mathematical approaches that have been applied to devising efficient algorithms for this purpose. A simple example of application of these principles (determination of the cross-over value ) was given in Section 1.5. 

The choice of the chronological sequence should be chosen such that the impact due to positional differences due to carryover. In general, the need to include additional carryover blanks in the run should be assessed during validation and specified in the analytical method. The run list is also used to generate an injection batch sequence, including rack and vial number, for the mass spectrometer data system and autoinjector. 

A mass spectrometer produces an enormous amount of data, especially in combination with chromatographic sample inlets [42]. Over the years, many approaches for analysis of GC-MS data have been proposed using various algorithms, many of which are quite sophisticated, in efforts to detect, identify, and quantify all of the chromatographic peaks. Library search algorithms are com monly provided with mass spectrometer data systems with the purpose to assist in the identi cation of unknown compounds [43]. 

FI analysis. For FI analysis a Varian MAT 731/SS200 mass spectrometer/data system (Wiesbaden) was used. Standard high temperature activated carbon emitters were used with a combined EI/FI/FD ion source. The ion source temperature was 50°C, the accelerating voltage 8 kV, the extraction plate voltage 3 kV, and the resolution M/dM about 2000. A heated direct probe was used for sample introduction. 

Before initiating the calibration procedure, tune the mass spectrometer according to manufacturer s instructions. Set the mass spectrometer data system to acquire data in the full scan (TIC-RIC) mode. 

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