Quadrupole instrument manufacturers

With the advent of linear quadrupole analyzers the full width at half maximum (FWHM) definition of resolution became widespread especially among instruments manufacturers. It is also commonly used for time-of-flight and quadrupole ion trap mass analyzers. With Gaussian peak shapes, the ratio of / fwhm to Rio% is 1.8. The practical consequences of resolution for a pair of peaks at different m/z are illustrated below (Fig. 3.17). 

Mass calibration of the quadrupole mass spectrometers, Q1 and Q3, is based on poly(propylene)glycol in methanol as supplied by the instrument manufacturer and following instructions on calibration and tuning provided in the instrument operating manual. 

The most common types of MS/MS instruments available to researchers in food chemistry include triple quadrupole mass spectrometers and ion traps. Less common but commercially produced tandem mass spectrometers include magnetic sector instruments, Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, and quadrupole time-of-flight (QTOF) hybrid instruments (Table A.3A.1). Beginning in 2001, TOF-TOF tandem mass spectrometers became available from instrument manufacturers. These instruments have the potential to deliver high-resolution tandem mass spectra with high speed and should be compatible with the chip-based chromatography systems now under development. 

MBl systems for LC-MS were commercially available from two instmment manufacturers, i.e., Finnigan MAT (currently Thermo Fimugan) and VG (currently Waters, [25]). The Fiimigan system was used in ca. 65% of the application papers. The MBl is about equally used in combination with magnetic sector and with quadrupole instruments. 

Quadrupole mass spectrometers with ranges that extend up to 3000 to 4000 m/z are available from several instrument manufacturers. These instruments easily resolve ions that differ in mass by one unit. Generally, quadrupole instruments are equipped with a circular aperture, rather than a slit (see Figure 11 -6), to introduce the sample into the dispersing region. I hc aperture provides a much greater sample throughput... 

From the standpoint of resolution and reproducibil-ily, instruments equipped with TOF mass analyzers arc nut as satisfactory as those with magnetic or quadru-pole analyzers. ICP-TOF mass spectrometers, for example. typically are an order of magnitude poorer in sensitivity and in detection limits than comparable quadrupole systems. " Several advantages partially offset these limitations, however, including simplicity and ruggedness, ease of accessibility to the ion source, virtually unlimited mass range, and rapid data-acqiiisilion rate. Several instrument manufacturers now offer TOF instruments, but they are less widely used than arc quadrupole mass spectrometers. 

Fl/FD-MS ion sources are available from all major magnetic sector instrument manufacturers. Combination Fl/FD/El/CI sources are common. No specialized mass analyzer, such as time-of-flight (TOF-MS) or Fourier transform (FT-MS), is needed. In short, Fl-MS and FD-MS are quite compatible (and in fact are optimal) for use with the normal types of double-focusing mass spectrometers typically used for analysis of organic compounds. Since high electric fields are required in the ion source, commercial Fl/FD ion sources have not been developed for use with "low voltage" mass spectrometers (such as those with quadrupoles and ion traps). 

Rigorously, the measurand of Fourier transform instruments is the frequency and amplitude of an image current and in quadrupole and time-of-flight instruments it is the ion multiplier ou ut current. In practice, the instrument manufacturer provides die customer die traceable calibration hierarchy information relevant to accounting for the / vs. m/z spectrum. The investigator must verify die claimed traceability of the insttument. The final traceability to the instrument performance (i.e., mass calibration) remains the responsibility of the laboratory operator. 

After the first demonstration of multiply charged gas-phase proteins ions, all major instrument manufacturers developed atmospheric-pressure ion sources, equipped with electrospray interfaces for both protein characterization and LC-MS applications. Within 5 years, electrospray interfacing became the method of choice in LC-MS coupling. It led to a large increase in the use of MS for the characterization and identification of labile and polar analytes as well as to routine quantitative analysis. The advent of electrospray ionization for peptide and protein analysis stimulated further development and analytical application of existing and new mass analysis approaches, such as quadrupole ion traps, Fourier-transform ion-cyclotron resonance MS, and quadru-pole-time-of-flight hybrid instruments. It opened new application areas, such proteomics. LC-MS... 

As we have seen in this book, three developments appear to have provided the necessary momentum, and all three are still works in progress . The first was the development of TOF instruments, which could accomodate electrospray ionization by using orthogonal extraction or combining ion trapping with the TOF analyzer, which led to the possibility of carrying out on-line HPLC analysis. Considerable improvements are required to enable ESI-TOF instruments to be commercially competitive with existing quadrupole (and triple quadrupole) ESI mass spectrometers, but this is sure to be a major focus of development by both University laboratories and instrument manufacturers. 

Two neighboring peaks are assumed to be sufficiently separated when the valley separating their maxima has decreased to 10% of their intensity. Hence, this is known as 10% valley definition of resolution, Rim,- The 10% valley conditions are fulfilled if the peak width at 5% relative height equals the mass difference of the corresponding ions, because then the 5% contribution of each peak to the same point of the m/z axis adds up to 10% (Fig. 3.13). With the advent of linear quadru-pole analyzers the full width at half maximum (FWHM) definition of resolution became widespread especially among instruments manufacturers. It is also commonly used for time-of-flight and quadrupole ion trap mass analyzers. With Gaussian peak shapes, the ratio of / fwhm to Rim, is 1.8. The resolution for a pair of peaks at different m/z and its practical implications are illustrated below (Fig. 3.14). 

In the case of the third requirement, instrument manufacturers have developed highly specialized Magnetic Sector mass filter-based instruments and time-of-flight mass filter-based instruments. Quadrupole mass filter-based SIMS instruments are ineffective in this area because of their inability to provide the high mass resolution required. Fourier Transform Ion Cyclotron Resonance (FT-ICR) as well as Orbitrap mass filter-based instruments, on the other hand, show significant promise. Mass filters are discussed in Section 4.3.2.I. 

The Triple Quadrupole Mass Spectrometer Manufactured by VG Instruments... 

The ICP/MS is an elemental and isotopic analysis method that was first developed in the early 1980s. The ICP had been used only as a source for emission spectroscopy until it was adapted for producing ions for a mass analyzer (Douglas and French, 1981 Houk et al., 1980 Houk et al., 1981 Houk and Thompson, 1982). Since 1983, several manufacturers have sold ICP/MS instruments that incorporate various mass analyzer systems, such as quadrupole mass filter, magnetic sector field, time-of-flight, Paul ion trap, and ion detection systems such as the electron... 

The GC detector is the last major instrument component to discuss. The GC detector appears in Fig. 4.7 as the box to which the column outlet is connected. Evolution in GC detector technology has been as great as any other component of the gas chromatograph during the past 40 years. Among all GC detectors, the photoionization (PID), electrolytic conductivity (EICD), electron-capture (ECD), and mass selective detector (MSD) (or quadrupole mass filter) have been the most important to TEQA. The fact that an environmental contaminant can be measured in some cases down to concentration levels of parts per trillion (ppt) is a direct tribute to the success of these very sensitive GC detectors and to advances in electronic amplifier design. GC detectors manufactured during the packed column era were found to be compatible with WCOTs. In some cases, makeup gas must be introduced, such as for the ECD. Before we discuss these GC detectors and their importance to TEQA, let us list the most common commercially available GC detectors and then classify these detectors from several points of view. 

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