How Mass spectrometry works : Components and Table

Overview

The groundwork for mass spectrometry was laid in 1898 by Wilhelm Wien, a German scientist, demonstrating that a magnetic field may deflect beams of charged particles. J.J. Thomson, a British physicist who had already identified the electron and seen its deflection by an electric field, passed a stream of positive ions through a mixed electrostatic and magnetic field in more detailed research between 1907 and 1913. Thomson’s tube’s two fields were positioned such that the ions were deflected via modest angles in two perpendicular directions.

He examined across a mass spectrum and measured the current proportional to each segregated ion species by adjusting the magnetic field. As a result, he may be attributed to the creation of the first mass spectrograph and first mass spectrometer.

What is Mass Spectrometry?

So what is the mass spectrometry? Well, mass spectrometry is a technique for determining the mass-to-charge ratio (m/z) of one or more than one molecule in a mixture. These data are frequently used to determine the precise molecular mass of the mixture components.

Mass spectrometers are typically used to determine unknown chemicals by molecular weight, measure known compounds or substances, and analyse molecules’ chemical and structural characteristics. The entire procedure entails converting the material into gaseous ions, both with and without fragmentation, which is subsequently classified based on one’s mass to charge ratios (m/z) and relative proportions.

This technique is employed to determine the effects of ionising energy on molecules. It is dependent on chemical events in the gas phase that consume collection molecules during the production of ionic and neutralising species.

How does Mass Spectrometry work?

Magnetic fields can deflect or distort atoms and molecules if they are first converted into an ion. A magnetic field affects electrically charged particles but not electrically neutral particles. Following is the mass spectrometry table in proper sequence.

Ionisation 

Ionisation occurs when an atom or molecule loses one or more electrons, resulting in a positive ion. It is true even for items that expect to create negative ions (such as chlorine) and never really form ions at all (such as argon). The majority of mass spectrometers use positive ions.

Acceleration

The ions are accelerated to have the same amount of kinetic energy.

Deflection

A magnetic field is then used to deflect the ions based on their masses. They are deflected more when they are lighter. The degree of deflection is also determined by the number of positive charges on the ion or even how they pushed off many electrons during the initial step. The more ions are charged, the more it will deflect them.

Detection 

The electrical detection of the ion beam travelling through the equipment.

Mass Spectrometry: Components

How can a mass spectrometer accomplish this? Every mass spectrometer contains at least three of the following components:

Ionisation Source

Molecules are transitioned to gas-phase ions, allowing them to be moved and managed by magnetic and electric fields. In clinical laboratories, scientists employ nanoelectrospray ionisation technology comparable to how automobiles are painted in the industry.

This approach can generate positively and negatively charged ions based on the experimental requirements. The exit of a narrow chromatography column can be directly coupled to the input of a mass spectrometer using nanoelectrospray ionisation. The stream from the column is routed through a needle with a tip diameter of 10-15 um.

Mass Analyser

Ionised ions are sorted and segregated based on mass-to-charge (m/z) ratios. There are several mass analysers on the market today, each with trade-offs regarding operation efficiency, separation resolution, and other standard operating procedures. The next section goes over the specific kinds used by the Broad Institute. The mass analyser is frequently used in conjunction with the ion detection technique.

Ion Detection System

The separated or differentiated ions are then evaluated and transferred to a data system, where the m/z ratios and relative abundance are kept together. A mass spectrum is the m/z ratios of the ions in a material shown against their concentration. Each peak in a mass spectrum represents a distinct m/z component in the material, and the heights of the peaks indicate the relative abundance of the numerous components in the material.

There are various ways to complete each of the three components of mass spectrometry described above. Ionisation is accomplished in one common process by utilising a high-energy electron beam, and ion separation is accomplished by accelerating and focussing the ions in a beam. An externally applied magnetic field would then bend.

The data for these electronically detected ions are properly saved and evaluated on a computer. Students can refer to the diagram (shown below) to analyse the working of mass spectrometers. These ions are sourced at the core of the spectrometer. Electrons (bright blue lines) emitted from heated filaments assault the sample molecules (black dots). The entire process takes place in an EI (electron-impact) device.  

A reservoir of volatile and gaseous liquid mixtures is enabled to drop into the ion source (as shown in the figure). Solids and liquids that are not volatile can be introduced directly. These red dot cations are generated by electron bombardment which is then deflected by a charged repeller plate to attract anions to it. Later on, these electrons are propelled toward additional electrodes with slits through which the ions travel in a stream.

Some of these ions disintegrate into small cations and neutral molecules. The ion beam is deflected in an arc whose radius is proportionate to the mass of each ion by a perpendicular magnetic field. Lighter ions are deflected more often than heavier ions.

The mounted detector can focus on ions of varied masses at the end of a curved tube by adjusting the strength of the magnetic field (also under high vacuum circumstances).

Mass Spectrometry: Applications

Mass spectrometry is a powerful tool for determining the chemical composition of the samples or molecules. It has lately been used to categorise biological products in various species, specifically proteins and associated proteins. Mass spectrometers are typically used to identify unknown chemicals by measuring molecular mass, known compounds or substances and evaluating the structure and morphology of molecules.

• Mass spectrometry is used to identify unknown chemicals due to its ability to differentiate between them.
• It is used to study substances’ various chemical, biological and physical aspects in both analytical and clinical laboratories. Because it is performed in a controlled environment, it has less interference than other analytical procedures.
• It is also used to determine the substance’s isotopes.

Mass Spectrometry Table

The fragmentation of molecular ions into various fragment ions has great bonuses and drawbacks. The nature of the fragments frequently reveals information about the molecular structure. Still, if the molecular ion has a lifespan of less than a few nanoseconds, it will not survive enough to be examined. The difficulty of understanding a mass spectrum increases when there is no molecular ion peak to use as a reference.

Most organic substances, fortunately, have mass spectra that include a molecular ion, which does not favourably respond to the use of softer ionisation conditions. The most persistent molecular ions in simple organic compounds are those derived from methyl groups, other conjugated pi-electron systems, and cycloalkanes. Ethers and alcohols are highly branched alkanes, most prone to fragmentation.

The mass spectrometry table is highlighted below:

Conclusion

Mass spectrometry is a potent quantitative approach that can be even applied to drug monitoring systems. Mass spectrometry has various advantages for clinical laboratories, including accuracy, responsiveness, efficiency, and cost-effective testing. However, in certain cases, mass spectrometry lacks standardisation for drug monitoring tests, creating concerns for future FDA rules.

Despite all this, mass spectrometry is used successfully in many clinical laboratories to analyse various chemical reactions. Finally, mass spectrometry applications are limitless and provide clinical laboratories with a solution to address the requirements of physicians.

Frequently Asked Questions

1. What is a quadrupole?

Mass spectrometry is a process used for measuring chemicals, which calculates the usual mass fragments generated by the ionisation of the substance. An electron beam ionises the test molecules, and the resultant molecular ion and constituent ions are detected in a mass analyser.

Because mass spectrometry is highly specific and sensitive, and mass spectra are easily discoverable against enormous reference databases, it is often regarded as the gold standard for identifying unknown organic compounds.

2. What are the uses of mass spectrometry?

Mass spectrometry is a versatile technology with numerous uses in chemistry, biology, physics, clinical treatment, and space exploration. It is implemented by segregating molecular ions based on their charge and mass to evaluate the molecular weight of the compounds or substances.  

3. What exactly is unit mass resolution?

Unit mass resolution is traditionally described as the smallest distance between two mass spectrometric peaks of identical height and width, with a discernible “valley” between them. The next number mass can be isolated from each volume using unit resolution. The unit mass resolution can differentiate mass 60 from mass 61 and similarly differentiate mass 900 from mass 901. This term is commonly used to characterise quadrupole and ion trap mass spectrometer resolution.