Mass Spectrometry & Purification Techniques
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Instrumentation of a Typical Mass Spectrometer

Darlie Wang^{* *}Correspondence: Darlie Wang, Department of Analytical Chemistry, University of the State of Amazonas, Manaus, Brazil, Email:

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Description

By measuring the mass-to-charge ratio and abundance of gasphase ions, the analytical chemistry technique Mass Spectrometry (MS) aids in determining the quantity and kind of compounds present in a sample. By bombarding the sample with electrons, the material is transformed into quickly moving positive ions, and the charged particles are sorted according on their masses. A relative abundance plotted against the mass/ charge ratio (m/e) is called a mass spectrum. The masses of particles and molecules in a sample, their elemental or isotopic signatures, and the chemical structures of molecules and other chemical compounds can all be learned from these spectra [1].

Instrumentation

A typical mass spectrometer contains:

• Sample handling system

• Ionization chamber

• Ion separator

• Ion collector

• Mass analyzer

• Detector

• Signal processor unit

Sample handling system: A sample is introduced into a gaseous ion source at a low, repeatable pressure using a sample handling system. Heating or vaporisation is required for samples that are less volatile. A sample inlet system with a heater for volatile samples at low pressure can be used to introduce non-volatile and thermally unstable substances into ion sources [2].

Ionization chamber:

• The sample is brought into the ionisation chamber from the inlet system, where the electron beam is directed across the molecules of the samples.

• The molecules undergo ionisation. The collision between electrons and molecules produces well-defined fragments with a clear positive charge after the electron beam is accelerated by a high voltage of up to 100V on the collector.

• The positive ions created in the ionisation chamber are dragged out by the electric field in the electrostatic accelerating system [3].

• The ions of masses m1, m2, m3, etc. are accelerated to their final velocities by a high electrostatic field of 400-4000V.

• The second accelerator is charged to a starting potential of 4000 volts each time the mass spectrometer is turned on to start recording the spectrum.

• Then, over the course of 25 minutes, this charge is allowed to trickle off to ground at a controlled rate.

The ion separator: This is the area of MS where ions are divided based on their masses.The following qualities must be present in an analyzer: high resolution; high ion transmission rate [4].

The ion collectors:

• The range of the ion beam currents is 10-15 to 10-19 ampere.

• Mass spectrometers need to be able to detect this current.

• Electrometers, Faraday cylinders, photographic plates, and electron multipliers are frequently used.

• The readout display typically has a direct writing recording oscillograph with three to five galvanometers, each with a relative sensitivity of one, three, ten, thirty, or one hundred [5].

Mass analyzer: It’s resolved that the ions with various mass to charge ratios using the mass analyzer, a part of the mass spectrometry apparatus. We utilised a variety of mass analyzers in the mass spectrometer.

• Single focusing mass analyzer with magnetic deflection

• Double focusing analyzer

• Time to flight mass analyzer

• Quadrupole mass analyzer

Detector: The type of detector utilised to transform a stream of mass-separated ions into a detectable signal is a crucial component of all MS systems. Depending on variables including dynamic range, spatial information retention, noise, and compatibility for the mass analyzer, different types of detectors are utilised. Commonly used detectors include the: Electron Multiplier (EM) and Faraday Cup (FC) [6].

• An Electron Multiplier (EM) is a device that connects separate metal plates serially to multiply an ion current by 108 to create a detectable current of electrons.

• Faraday Cup (FC) ions strike the collector as a result of an enhanced potential drop across the resistor caused by an electron flow from ground via the resistor [3].

Single processor unit: Conversion using a photomultiplier Ions first strikes a dynode, which causes electron emission. When the generated electrons hit a phosphor screen, photons are then released. The photons then enter the multiplier, where amplification takes place in a cascade-like pattern, much like the Electromagnetic Field (EF).

Array detectors span a wide range of detector types and systems that may integrate numerous detection methods, such as detectors for the simultaneous measurement of multiple ions of various m/z and detectors for position-sensitive ion detection [5].

References

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