| In this section |
| What is Mass Spectrometry? |
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Mass spectrometry is concerned with the separation of matter according to atomic and molecular mass. It is most often used in the analysis of organic compounds of molecular mass up to as high as 200,000 Daltons, and until recent years was largely restricted to relatively volatile compounds. Continuous development and improvement of instrumentation and techniques have made mass spectrometry the most versatile, sensitive and widely used analytical method available today.
Today techniques such as the following are commonly used:
- GC/MS
- GC/MS/MS
- LC/MS
- FAB
- Electrospray MS
- MALDI TOF MS
- FTMS
- ICPMS
The mass spectrometer can be broken down into four basic components, the functions of which are as follows:
Mass spectrometry is nothing other than the study in the gas phase of ionized molecules with the aim of one or more of the following:
- Molecular weight determination
- Structural characterization
- Gas phase reactivity study
- Qualitative and quantitative analysis of components in a mixture.
Mass spectrometry is an analytical technique used to separate and measure the mass-to-charge ratios (m/z) of ionized molecules and/or atoms. The instruments employed to carry out such measurements are called mass spectrometers (MS). Mass spectrometry consists basically of weighing ions in the gas phase.
The instrument used could be considered as a sophisticated balance, which determines with high precision the masses of individual atoms and molecules. Depending on the samples chemical and physical properties, different ionization techniques can be used. One of the main factor in choosing which ionization technique to be used is thermolability.
For samples that are not themolabile and relatively volatile, ionization such as Electron Impact and/or Chemical Ionization can be effectively used. For samples that are thermolabile such as peptides, proteins and other samples of biological interest, soft ionization techniques are to be considered.
Among the most used soft ionization techniques are Electrospray (ESI) and Matrix Assisted Laser Desorption (MALDI). The name given to a particular mass spec technique is usually pointing to the ionization method being used. In order to detect ionized molecules or atoms, one must first generate them. One of the most powerful of the ionization methods is called electrospray ionization, or ESI. ESI operates by infusing a liquid containing the sample of interest through a channel whose outlet is in an electric field. This causes the liquid to disperse into fine droplets, which are eventually desolvated to release ionized species into the gas-phase.
ESI is a "soft" ionization technique, capable of ionizing and transferring massive biological molecules into the gas-phase for subsequent MS detection. ESI has provided an enormous boost to the field of biomedicine because it provides a mechanism to generate ions of molecules (subsequently detected by MS) that are biomarkers of metabolism and disease.
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