Greetings from new friends, lovers of science, where on this occasion I present my third part of the series of mass spectroscopy, one of the oldest techniques and that is still part of science in general, despite the great technological advances that have been presented in recent years.
Let's recap a bit.....
In my two previous publications, we mentioned that the technique is responsible for grouping different materials or compounds of the organic, inorganic and biological nature, by means of which we can obtain both qualitative and quantitative information through the distribution of the characteristics of various materials. a Substance always depending on its mass. At the same time, there is also the possibility of obtaining very effective information on the molecular mass of the analyzed material and from this information can be extracted from the atomic structure of the material, provided only its presence or quantify its chemical concentration.
Mass spectroscopy focuses on the obtaining of ions from the different forms within the material which we are going to characterize, the same ones mostly organic in the phase of the gaseous state that move in the presence of a magnetic field after obtain the ions In this way, within the matter, it will proceed to separate its mass and elemental charge, where finally a detection equipment will be obtained.
Now, we will continue the sequence of the two publications prior to this where in the following diagram shows the composition of the mass spectrometer. We already explained the input system, ion source and analyzer. Now let's explain what the mass detector consists of.
Diagram of a mass spectrometer
Remember the following:
The main purpose of the sample entry system is to enter a certain amount of sample of the material in the spectrometer. This amount must be very small in the order of a micro or perhaps less. This system uses 3 methods to introduce samples that are: Direct, indirect and from a chromatograph.
The ion source is in charge of converting the sample into ions and through the bombardment of electrons or photons towards the material. Another option that is used a lot for the transformation of thermal or electrical energy. We have different sources of ions that are: ionization through electronic impact and chemical ionization.
Analyzer This component has the function of separating the ions of the material from its mass and charge, and is expressed through the following equation:
There are several types of analyzers which are: Analyzer that uses magnetic field, quadrupole analyzer, flight time analyzer and ion trap analyzer.
All this information has been explained in detail in the two previous versions:
Detectors
At present we have a great variety of detectors. The first ones that were used were the multipliers of the electrons of the masses that operated at a rather high vacuum inside the spectrometer chamber. Later, as new detectors developed, "Channeltron" detectors and more sophisticated, sensitive and durable conversion systems appeared. All these low cost detectors and easy commercial access. The most advanced devices in the area were incorporated into the function of other detectors, as have simultaneous detection systems, such as the multichannel micro multipliers (Multichannel multiplanar array detector of microchannel plates).
When the current is transmitted specifically in the source, the outputs, the analyzers, the indications and the detectors, the results are explained in lowercase. and the detection of the sample.
Currently there are three types of detectors used in the mass spectrometer that are:
Electron multiplier
For more information, click here. Emit current to go to another plate and repeat this procedure repeatedly.
This type of detector is very sensitive, however, a small signal can be useful easily. It must also be borne in mind that this detector has a very short life, a measurement made by a system of different samples is going to wear out very quickly, which results in a loss in its operation and a new sweep must be calibrated again . Great care must be taken in its use, since it is a detection system.
Faraday Cup
This is a detector in the form of a box or cup made by an electrode, the main idea of this detector is the impact of what the analyzer generated to detect them, they will be neutralized by the action of electron transfer where a signal is emitted from the form of the electrode, this is the current of the original current of the ions.
It is used for the analysis of gases, rectors, samples of the environment, other types of gases such as permanent and residual, among others. It is also used in the scanning electron microscope.
It presents interesting applications for the relationship of isotopic measurements within some chemical compounds. In these equipments multiple manifolds are used, formed by a battery of Faraday copies, each time one is dedicated to the detection of a single mass.
Detector "Channeltron"
It is undoubtedly the best known therefore the most used by most operators of the mass spectrometer. Its design is very similar to the electron multiplier, it only presents the small differences as the example, the fact that I do not have discrete dinos, but in this case it is formed by a glass tube in the form of a cornet or some shaped of spiral. The interior of this detector is covered by a lead oxide material, this material has to present the characteristics of a semiconductor for the current conduction and resistance of it.
When detecting positive ions, you should of course apply a negative potential in the upper part of the tube, this has the purpose that the ions can be diverted from their path to a plate that ejects the positive potential and then can be attracted to the inside the tube to then interact internally and thus produce an emission of electrons that goes to the end of the tube, where there is a potential close to the earth with a continuous gradient that comes from the top to the bottom of the tube.
Then, as a result of there being no potential, a large number of shocks occur until the end of the trajectory until the electrons multiply. Where finally at the bottom of the tube we will find a collector of the emission signal that will then amplify it so that it can be easily appreciated.
A considerable advantage that this detector presents with respect to the previous ones has been a great atmospheric pressure. Another advantage is that a minimum vacuum is needed to perform the measurements.
Multi-channel detector
Partial cross-section of Orbitrap mass analyzer... Autor: Mkotl in Wiki. Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)
They are varied, they are integrated with batteries that are formed in several layers, each one contains at least two batteries that multiply the frequency signal, they are also made up of a very efficient and very advanced small detection system that is responsible for detecting all The signals emitted by the ions.
Multichannel detectors provide a great advantage over older ones and as a name implies. Spectral line, with an extraordinary capacity that increases in several proportions the signal of amplification.
Thank you for your attention, soon I will be publishing more topics about the interesting world of spectroscopy.
You want to know more about my spectroscopy series visit the following links:
If you want more information about the subject you can visit the following links:
Mass Spectrometry/ Prem,ier Biosoft
Analytical chemistry/ New world enciclopedy
How Does Mass Spectroscopy Work?
Plasma Atomic Emission Spectroscopy
Chemical ionization/ Wikipedia
The Ionization of Atoms by Electron Impact
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Video credits @gtg