Sector mass spectrometer

Sector mass spectrometer is an analytical instrument used for the separation and analysis of ions based on their mass-to-charge ratio (m/z). It employs magnetic and/or electric fields to manipulate the path of ions. The sector mass spectrometer has been instrumental in the fields of Analytical Chemistry, Biophysics, and Environmental Science, among others, for identifying the composition of chemical substances and measuring isotopic ratios.

Principle of Operation

The operation of a sector mass spectrometer involves ionizing the sample to be analyzed, accelerating the ions into a beam, and then passing this beam through magnetic and/or electric fields. The fields act as a filter, deflecting ions at different angles based on their mass-to-charge ratio. By measuring the deflection, the mass-to-charge ratio of the ions can be determined, allowing for the identification and quantification of the components of the sample.

Ionization

Ionization is the first step in the mass spectrometric analysis where the sample molecules are ionized to form ions. This can be achieved through various methods such as Electron Ionization (EI), Chemical Ionization (CI), or Matrix-Assisted Laser Desorption/Ionization (MALDI).

Acceleration and Deflection

After ionization, the ions are accelerated by an electric field to a uniform kinetic energy. The accelerated ions then enter a region where they are subjected to magnetic and/or electric fields. In a magnetic sector, ions are deflected in a circular path, while in an electric sector, the path is parabolic. The radius of the path in a magnetic field is dependent on the mass-to-charge ratio of the ions, allowing for their separation.

Detection

The separated ions are detected by an ion detector, such as an Electron Multiplier or a Faraday Cup, which converts the ions into an electrical signal. The intensity of this signal is proportional to the abundance of the ions, providing quantitative information about the sample.

Applications

Sector mass spectrometers are used in a wide range of applications, including:

• Isotope Ratio Mass Spectrometry (IRMS) for determining the isotopic composition of elements.
• Residue Analysis in food safety and environmental monitoring.
• Structural elucidation of organic compounds in Organic Chemistry.
• Analysis of complex biological molecules in Proteomics and Metabolomics.

Advantages and Limitations

The main advantages of sector mass spectrometers include high mass resolution and accuracy, making them suitable for precise isotopic measurements and the analysis of complex mixtures. However, they are generally more expensive and have a larger footprint compared to other types of mass spectrometers, such as Time-of-Flight Mass Spectrometry (TOF-MS) and Quadrupole Mass Spectrometry (QMS).

See Also

• Mass Spectrometry
• Time-of-Flight Mass Spectrometry (TOF-MS)
• Quadrupole Mass Spectrometry (QMS)
• Ionization Techniques in Mass Spectrometry