Mass
spectrometer is an equipment that can be used to find out the chemical
composition of substances and that too with high accuracy. Mass spectrometer
can measure the masses and relative concentrations of atoms and molecules.
It makes use of the basic magnetic force on a moving charged particle. This
technique of finding masses of individual molecules were developed early in
the 20th century by a number of scientists. Mass spectrometers are used by a
number of researchers in labs and universities worldwide.
Principle of Working
The mass spectrometers measure the characteristics of individual molecules.
They work on the principle that different chemicals have different masses.
To evaluate the mass of chemicals in a sample, first the sample is
vaporized, and then ionized. The resulting ionized gas is accelerated
through a chamber where it is manipulated by external electric and magnetic
fields.
The three essential functions of a mass spectrometer are:
- A small sample of compound is ionized (mainly to cations) by loss of
an electron.
- According to the mass and charge, the ions are sorted and separated.
- The separated ions are then detected and tallied, and the results are
displayed on a chart.
Ionized gases respond to magnetic fields, so a magnet on the wall of the
chamber is used to bend the ions towards a detector. The lighter ions bent
towards the detector at a quick pace, while heavier ions bent at a slower
rate. The resulting distribution of ions, called a mass spectra, can be used
to determine the content of the original sample.
Types of Ionization
There are various types of ionization used for the mass spectrometer. It
include :
- Electron Ionization
- Chemical Ionization
- Electro-spray Ionization
- Matrix-assisted Laser Desorption/Ionization
- Fast Atom Bombardment (FAB)
- Thermo-spray
- Atmospheric Pressure Chemical Ionization (APCI)
- Secondary Ion Mass Spectrometry (SIMS)
- Thermal Ionization
Applications of Mass Spectrometers
- Mass spectrometer is used in carbon dating and other radioactive
dating processes.
- Mass spectrometers are used to detect isotopes. The combination of a
gas chromatograph and a mass spectrometer makes a powerful tool for the
detection of trace quantities of contaminants or toxins.
- Mass spectrometers are used for the analysis of residual gases in
high vacuum systems.
- Mass spectrometers are used in a number of satellites and spacecraft,
for the identification of small numbers of particles intercepted in
space.
