Mass Spectrometers Three Components

Mass spectrometers consist of three components an ionization source, a mass analyzer, and a detector. First, the ionization source adds charge to the proteins or peptides in the sample, typically in the form of a proton to produce positively charged particles, and injects them into a vacuum chamber. Second, a mass analyzer uses an electromagnetic held to separate and sort the ionized peptides. Third, a detector registers the number of ions at each mass-to-charge value. The two most technically demanding components are the ionization sources, which we have discussed in the previous section, and the mass analyzers. 

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We have recently explored the use of an ion mobility spectrometer (IMS) for the study of negative ioinnolecule reactions at atmospheric pressure. This instrument, shown in Figure 6, consists of three major components. They are an ion mobility spectrometer, a mass spectrometer, and a gas-handling plant (GHP). 

Mass spectrometers are used primarily as tools for measuring isotopic compositions, although some kinds can also be used to determine elemental abundances. Mass spectrometers have three basic components (1) a means of ionizing the sample (2) a mass analyzer that separates atoms based on their masses and (3) a detector. Most of the time, the mass spectrometer is identified by its source, although the mass analyzer can also be identified. In the next few paragraphs, we will describe the various sources, the different mass analyzers, and the detectors, and then describe the most common configurations used in cosmochem-istry. For more details, see Gross (2008). 

Mass spectrometry is a very valuable analytical tool based on the simple premise of determining the molecular weight of the compound of interest. In fact, mass spectrometry involves the measurement of the mass (m) of a compound as a function of charge (z), m/z. In most mass spectrometer experiments the charge on an ion is one, such that the molecular weight of the ion is equal in value to m/z. Mass spectrometry can be divided into three steps ionization, mass analysis and detection. Sample introduction is really a distinct component for obtaining quality mass spectra and will be discussed separately. 

In contrast, both gas and liquid chromatography enable the samples of interest to be separated into individual components prior to introduction into the mass spectrometer ion source. Gas chromatography involves sample introduction with the requisite that the sample components must be volatilized prior to separation, and results in a gas sample being introduced to the mass spectrometer (i.e. El, Cl). Figure 5-2 shows the chromatogram obtained after a mixture of three simple phenolic compounds - phenol,... 

Strictly speaking, the term "secondary Ion optics" refers to all those lon-optical components which transmit secondary Ions from the sample surface to the detector. For the sake of this discussion we will limit the scope of the term to those secondary lon-optical components between the sample surface and the mass spectrometer. With this restriction, we see that the purpose of the secondary ion optics is to extract the Ions efficiently from the sample surface and present them to the entrance of the mass spectrometer In a satisfactory manner. Recognition of three Important facts are necessary for such ion optics design ... 

However, a contaminated mass spectrometer may cause various response trends toward different compounds. For example, after a triple quadrupole MS was contaminated with ascorbic acid, different response patterns were observed for levothyroxine (ANA), liothy-ronine (ANB), and their internal standard (thyroxine-13C6) during the repetitive injections of pure reference solutions containing these three components (Fig. 11). The responses of ANA were relatively stable while those of ANB and IS decreased significantly over a time period of about 1 and half hours, which resulted in increasing analyte/IS response ratios for levothyroxine and decreasing ratios for liothyronine. 

The use of tandem mass spectrometers can eliminate the sample preparation steps and provide improved capabilities for MS analysis. One system, the triple quadrupole mass spectrometer, uses a combination of three quadrupoles, or mass analyzers, to ionize, separate, and analyze sample components with minimum sample preparation as shown in Figures 7 and 8. The sample components are ionized and separated according to their mass-to-charge ratio in the first quadrupole. This step corresponds to the GC step in GC/MS. In the second quadrupole these ions collide with an inert gas and fragment (chemical ionization). 

A mass spectrometer has three basic components something to volatilize and ionize the molecule into a beam of charged particles something to focus the beam so that particles of the same mEtssxharge ratio are separated from all others and something to detect the particles. All spectrometers in common use operate in a high vacuum and usually use positive ions. Two methods are used to convert neutral molecules into cations election impact and chemical ionization. 

Fig. 7A-D. SFC/ELSD/CLND/MS analysis of an equimolar mixture of Tolbutamide, Fmoc-Ile-OH, Mebendazole, and Prednisolone. The column flow rate was 5 ml/min. A portion of the column effluent was split to each of the three detectors (CLND, 200 pl/min ELSD,200 pl/min MS, 100 pl/min). A makeup flow of 50/50 MeOH/H20 (300 pl/min) was added to the flow stream diverted to the mass spectrometer ion source. Mass spectra were acquired using electrospray ionization with no special modifications to the ion source A total ion current chromatogram showing two of the four components ionize efficiently under electrospray ionization conditions B ELSD chromatogram of the four components, all showing comparable response C UV chromatogram (254 nm) shows some selectivity in detection as does D D CLND detection. Reprinted from [7] with permission from D.B. Kassel...

A cation exchange clean-up of the method was employed in the examination of samples. Amines were eluted from the clean-up column using 70 vol% O.IM sodium citrate buffer (pH 2.5) -i- 30 vol% methanol. This solution was then injected into the LC-MS. A slow drop-off in MS response was observed using this procedure. In later studies, delaying the introduction of the EC mobile phase into the mass spectrometer for three minutes (i.e. not introducing any ionic non-retained components) overcame this problem. 

Figure 6. Block diagram of the experimental. RB system, vhich consists of three basic components a laser system capable of producing tunable ultraviolet radiation, a magnetic sector mass spectrometer with a suitably modified thermal atomization source, and a detection and measurement circuit capable of quantifying the pulsed ion currents produced in the experiment.

At a fundamental level, mass spectrometers generate ions, separate them according to then-mass to charge ratio, and measure their abundance. Hence, the three main components of mass spectrometers are (i) an ionization source, where samples are ionized, (ii) one or more... 

In a mass spectrometer, instead of an optical spectrum in the spectrometer, we have a mass spectrum of matter radiation. The necessary condition for using a mass spectrometry detection is ionization of components of the analyzed sample. Thus, we can say that mass spectrometry is a destructive method of analysis. There are many techniques and systems for mass spectrometry, but they all have the same three elements source of ions, ion analyzer, and ion detector (Fig. 1). 

As shown in Figure 15.1, there are three main components of every mass spectrometer. The ion source is used to produce gas-phase ions by capture or loss of electrons or protons. In the mass analyzer, the ions are separated according to their mlz ratios ions of a particular mlz value reach the detector, and a current signal is produced. This section describes the soft ionization sources, mass analyzers, and detectors that are used in experiments involving biological macromolecules. 

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