Mass analyzer general

Metastable Peaks. If the mass spectrometer has a field-free region between the exit of the ion source and the entrance to the mass analyzer, metastable peaks m may appear as a weak, diffuse (often humped-shape) peak, usually at a nonintegral mass. The one-step decomposition process takes the general form ... 

The most common modes of operation for ms/ms systems include daughter scan, parent ion scan, neutral loss scan, and selected reaction monitoring. The mode chosen depends on the information required. Stmctural identification is generally obtained using daughter or parent ion scan. The mass analyzers commonly used in tandem systems include quadmpole, magnetic-sector, electric-sector, time-of-flight, and ion cyclotron resonance. Some instmments add a third analyzer such as the triple quadmpole ms (27). 

The shape of the mass-analyzed gas phase /tot curve is seen to be very similar to that of the capillary current I (Figure 3). An approximate proportionality between the two currents when the concentration is increased is generally observed in this concentration range.45,51 For an analyte concentration above 10 5 M, the intensity of the impurity ions B+ is observed to decrease. This decrease is a consequence of the weak dependence of the capillary current I on the total electrolyte concentration. 

The combination of a mass analyzer with the electron impact apparatus enabled the scope of the pioneer work of Hertz, Lenard, Franck, and Lozier to be greatly extended, and results of less ambiguity were obtainable. Such experiments lead in general to a curve relating the ion current... 

Fig. 1.1. General scheme of a mass spectrometer. Often, several types of sample inlets are attached to the ion source housing. Transfer of the sample from atmospheric pressure to the high vacuum of the ion source and mass analyzer is accomplished by use of a vacuum lock (Chap. 5.3).

Note The numerous ionization methods and mass analyzers in use have created a demand for a large number of calibration compounds to suit their specific needs. Therefore, mass calibration compounds will occasionally be addressed later in the chapters on ionization methods. It is also not possible to specify a general level of mass accuracy with external calibration. Depending on the type of mass analyzer and on the frequency of recalibration, mass accuracy can be as high as 1 mmu or as low as 0.5 u. 

Since the compound(s) you are analyzing are sufficiently volatile to be separated by gas chromatography, I am assuming that you will use a GC for your separations. Here are the detector choices we have to consider a = Mass spectrometer (general purpose)... 

TABLE 5 General Specifications and Features for Mass Analyzers Used in CE/CEC-MS ... 

Quadrupole or radio-frequency mass analyzers have only recently become available with the mass range and resolution 42) to be of general use in inorganic and organometallie mass spectrometry, although they have been popular as small mass spectrometers built into specific systems as reaction monitors. They do have the advantage of essentially linear... 

Selected entries from Methods in Enzymology [vol, page(s)] General Techniques Methods of ionization, 193, 3 mass analyzer, 193, 37 detectors, 193, 61 selected-ion measurements, 193,... 

The general characteristics of a mass analyzer are accuracy, resolving power, mass range, and tandem analysis capabilities. 

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