Quadrupole and Magnetic Sector Instruments

There are other characteristics of quadrupoles that make them cheaper for attainment of certain objectives. For example, quadrupoles can easily scan a mass spectrum extremely quickly and are useful for following fast reactions. Moreover, the quadrupole does not operate at the high voltages used for magnetic sector instruments, so coupling to atmospheric-pressure inlet systems becomes that much easier because electrical arcing is much less of a problem. 

Some Factors Important in Choosing between Quadrupole and Magnetic-Sector Mass Spectrometers 

Ultimate resolving power (accurate mass determination) + +++ 

Note The plus (+) signs provide only a qualitative guide and should not be construed as a definitive assessment. The greater the number of plus signs, the more advantageous the system. 

Ultimate resolving power taccurare mass detenmination l + 4-++  

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Performance characteristics for quadrupole and magnetic sector instruments are shown in Table 5.2. 

Selected-ion monitoring (SIM), where the ion abundances of preselected ions are acquired. Selected-ion monitoring is applied in routine quantitative analysis. In quadrupole and magnetic sector instruments, acquisition in SIM mode provides a substantial gain in signal-to-noise ratio (S/N). 

Application of the FTMS to microelectronic laboratory service has proven to be very successful. Instrument stability and resolution are unmatched by conventional instruments. In moisture analysis, comparison of quadrupole and magnetic sector Instruments with FTMS, has, in addition, shown higher sample through-put and data consistency for both known atmospheres and device lot samples. 

Quadrupole and magnetic-sector instruments are the conunon type of mass analyzers for the detection of the GD-formed ions. The use of quadrupole ion traps, FT-ICR, and TOF instruments has also been explored [11-13], Specifically, quadrupole ion traps and FT-ICR mass spectrometers are of particular interest because they can accumulate and store ions for a desired length of time for subsequent CID or ion-molecule reactions that will eliminate isobaric interferences. The fast-scan facility of a TOF mass analyzer has the advantage that it can be used to monitor even short-lived transient signals. 

Performance characteristics for quadrupole and magnetic sector instruments are shown in Table 2 and Figure 6. The main advantages that ICP-MS has over other techniques are low detection limits, in the 0.1-100 pg ml range for quadrupole instruments (Figure 6), with magnetic sector instruments a factor of 10-100 lower large linear dynamic... 

The conditions under which a mass spectrometer operates places certain restraints on on-line chromatographic methods. While ionization can be assumed to be instantaneous, mass analysis is not. As an example, fast-scanning quadrupole and magnetic sector instruments provide scan speeds... 

Vandervorst W, Shepherd FR (1987) Secondary ion mass spectrometry profiling of shallow, implanted layers using quadrupole and magnetic sector instruments. J Vac Sci Technol A... 

Figure 4.15 Pictorial representations of the energy filtering experienced by positive ions passing through (a) Electro Static Analyzers (ESA) used in Quadrupole and Magnetic Sector instruments and TRIFT type Time of Flight analyzers and (b) reflectron type Time of Flight analyzers. For negative secondary ions, the polarities applied are simply reversed.

Quadrupole and Magnetic Sector Instruments To initiate Cl reactions and to guarantee a sufficient conversion rate, an ion source pressure of about 1 Torr in an analyser environment of 10 -10" Torr is necessary for beam instruments. For this, the El ion source is replaced by a special Cl source, which must have a gas-tight connections to the GC column, the electron beam and the ion exit in order to maintain the pressure in these areas. 

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