Talk:Mass spectrometry

From Academic Kids

I read the article posted here for Mass spectrometry and use a ESI mass spec, but I am not familiar with the term 'Wilkinson ion'. Could some one please explain what a Wilkinson ion is?

Much cleanup is needed in related topic Gas_chromatography-mass_spectrometry

Russian version

Would someone be so kind as to translate and incorporate the information in the vastly larger Russian version of this article? --Ardonik 08:15, Jul 21, 2004 (UTC)

Well, check out the following link--it's a fairly 'functionalist' translation, that gives you a sense of the russion version: http://www.systranbox.com/systran/box?systran_lp=ru_en&systran_id=SystranSoft-en&systran_url=http://ru.wikipedia.org/wiki/%D0%9C%D0%B0%D1%81%D1%81-%D1%81%D0%BF%D0%B5%D0%BA%D1%82%D1%80%D0%BE%D0%BC%D0%B5%D1%82%D1%80%D0%B8%D1%8F&systran_f=1090404300

While it is longer, it's a bit chatty. I don't think it's vastly superior, oddly. I wrote an article once that I can add a few things from in the future.

--Jvraba 08:49, 21 Jul 2004 (UTC)

• Thanks. (Wikimedia can't handle your URL, so anyone wishing to see the site will have to copy and paste it.) That's really painful reading, and I suspect it would be even if it were translated perfectly. But you have to start somewhere. --Ardonik 10:11, Jul 21, 2004 (UTC)

• Here's a better translation than the link above, because I involved a scientific dictionary --Jvraba 18:14, 21 Jul 2004 (UTC)

English "Translation" of the Russian Version

Mass spectrometry Material from Vikipedii - free encyclopedia.

Mass spectrometry - is physical method, based on mass measurement of the charged particles of the material, used for the analysis of substance for more than 50 years.

This method, today routine used in thousands of laboratories and enterprises of peace, has in its basis the fundamental knowledge of nature of substance and uses the basic physical principles of phenomena. It was before dismantled, why to whom this method was necessary, briefly (how this is possible) and simply let us pause at how it is realized.

Naturally, the instruments, which are used in this method, mass spectrometers or mass-spectrometric detectors are called. These instruments deal concerning the material substance, which as is known, it consists of the smallest particles - molecules and the atoms. Mass spectrometers install that this for the molecules (i.e., they compose their what atoms, which their moleklyarnaya mass, such as the structure of their arrangement) and that this for the atoms (i.e., them изотопный состав). An essential difference in the mass spectrometry from other analytical physico chemical methods lies in the fact that optical, X-ray and some other methods detect emission either energy absorption by molecules or by atoms, and mass spectrometry deals concerning very particles of substance. Mass spectrometry it is measured their mass, is more accurate mass-ratio to the charge. Are used the laws of the motion of the charged particles of the material in the magnetic or the electrical it fell for this. Mass-spectrum - this is simple the sorting of the charged particles throughout their masses (more precise to the mass ratios to the charge).

Consequently, the first, that must it made so that it would obtain the mass-spectrum, would convert neutral molecules and atoms, which compose any organic or inorganic matter, into the charged particles - ions. This process is called ionization and in different ways is achieved for the organic and inorganic matter.

In the organic matter of molecule are the determinate structures, formed by atoms. Nature and man created the truly neischislimoye variety of organic compounds. And we today umeyem practically everything of them converted into the ions.

Ionization

The oldest and most widely used in the contemporary mass spectrometry method of the ionization of the molecules of organic compounds - this the so-called electron collision (Ъ, in English EI - Electron Impact). So that would ionize the organic matter of it necessarily first from the condensed phase (liquid, solid body) would transfer by any means into the gas phase, for example, it heated (this, of course, it did not not necessarily make with the gases). Then, them necessarily introduced in the so-called source of the ions, where they undergo the bombardment with the electron beam, which possible obtained heating, for example, the metallic ribbon (cathode). Possible placed substance in the condensed phase into the source of ions and it there evaporated. Electrons - lungs in comparison with the molecules the negatively charged particles - colliding with molecules pull out from the electron shells electrons and convert molecules into the ions. In this case the molecules frequently are pulled down to the charged fragments by the mechanism specific for each connection. Specifically, as a result of this process in the final analysis mass-spectrum is received - you remember, the collection of rassortirovanykh throughout the masses ions - carrying information about the structure of molecule and, frequently, so characteristic for the defined organic compound, that it is called "it is fingerprint", i.e., this individual as figure on the fingers of man. All this must it occurred in the vacuum, otherwise electrons too rapidly zaryadyat the molecules, which compose the components of air, and the ions, which were formed from that connection, which interests us, too rapidly again tyuey prevratyatsya into the neutral molecules.

Another method of ionization - this is the ionization in ionomolecular reactions, called the chemical ionization (CHI, THE CI - Chemical Ionization). With this method the source of ions is filled up with any gas (for example, by methane, by isobutane, by ammonia), which ionizuyetsya all by the same electron collision, and the molecule of the interesting us substance, falling into the source they are converted into the ions due to vzamodeystviya with the already located there charged ion- reagents or with the "slow" electrons. This ionization in the gas phase is "soft", i.e., the formed ions are not pulled down to the small fragments, but they rather remain large pieces either only less than initial molecule or even it is larger it due to the connection of other ions. This method gives less than the information about how the structure of molecule is arranged, then with its aid its molecular weight more easily was determined.

Unfortunately, very many organic matter impossibly it evaporated without the decomposition, i.e., it transferred into the gas phase. But this it is meant, that them cannot it ionized with electron collision. But among such substances almost everything which composes the living tissue (proteins, DNA, etc.), physiologically active materials, polymers, i.e., all that which is today of special interest. Mass spectrometry did not stand on the spot and last years was developed the special methods of the ionization of such organic compounds. Today are used, in essence, two of them - ionization into the the elektrospreye (ESI) or its subtype - chemical ionization for the atmospheric pressure, and also ionization by laser desorption with the assistance of matrix (MALDI). In the first case the liquid (interesting us connections with the solvent) escapes under the pressure from the narrow capillary with the enormous speed and directly in this jet from the shells of molecules electrons are torn away, converting them into the ions. In method MALDI laser beam pulls out from the surface of target, to which it is substituted model with the specially selected matrix, ions.

Until now we described the methods, used for the ionization of relatively "myakikh" connections, that compose organic material. "soft" it means that so that it would transfer the molecules of organic matter into the ions they were necessary to relatively low energy. For the ionization of inorganic materials (metals, alloys, the rocks so forth.) the use of other methods is required. Of energies of atomic bond in the solid tele- much more and considerably more rigid methods necessarily used so that it would tear these connections and ions were obtained. Many methods of ionization was tested and today only several of them adapt in the analytical mass-spectral practice.

First method, most common, ionization in the so-called inductively connected plasma. The inductively connected plasma (ISP [SINGLE-OWNER COMPANY], ICP) it is formed inside the burner, in which burns, usually, argon. Argon, generally speaking, non-burning gas; therefore so that it would force it it would burn in it they pump into energy, placing the burner into the induction coil. When atoms and molecules fall into the plasma of argon burner, they immediately are converted into the ions. So that it would introduce the atoms and the molecules of the material into their plasma interesting they usually dissolve in the water and pulverize into the plasma in the form by the smallest it weighed. Another method lies in the fact that would convert substance into the gas. For example, this they will make with the aid of the powerful laser beam, which burns out crater in the piece of material substituted under it, converting its small part to the gaseous state (laser ablation).

Another method - this the so-called thermoionization or surface ionization. The analyzing substance it is applied to the delay from the refractory metal, on which is passed the current, which heats it to the high temperature. The substituted substance it is evaporated and is ionized due to the high temperature. This method usually is used in изотопной масс-спектрометрии.

Other two methods can it adapted for the ionization of the materials conducting current. These are spark ionization and ionization in the glow discharge. Without stopping on the details of these methods, let us say only that in the first due to the difference of potentials between kosochkom of the investigated material and by another electrode breaks through the spark, which pulls out from the surface of target ions, but the secondly it is occurred also the very, but due to the so-called glow discharge, ignited between the piece of the conducting material and the electrode in an atmosphere of inert gas, find under the very low pressure (the same argon in the majority of the cases).

Must it noted for those, who yet not osoznal of this, that beginning from the ionic source and to the detector the mass spectrometer is vacuum device. Sufficiently high vacuum ensures the free motion of ions inside the mass spectrometer, and ions it is simply scattered with its absence and they recombine (tyuey prevratyatsya back into the uncharged particles).

Mass analyzers

Thus, we received ions. Since these are the charged particles, we can with the aid of the electric field it extended them from that region, where they were formed. Now, begins the second stage of the masses of spectrometric analysis - sorting of ions throughout the masses (more precise according to the mass ratio to the charge, or m/z), strictly that which giv name to this method. This it is occurred in that part of the mass spectrometer, which is called "mass analyzer".

All mass analyzers use physical laws of the motion of the charged particles. Historically by the first mass analyzer, which is remained unsurpassed according to its characteristics and today, byl magnet. The trajectory of the charged particles in the magnetic it fell it is bent according to physical laws, and radius of curvature is dependent on the mass of particles. Specifically, this is used for the mass analysis of ions. , so that it would increase разрешение, on the way of ions was installed even the electrostatic analyzer. Magnetic mass spectrometers have high resolution and can it was used with all forms of ionization.

In spite of the significant advantages of the contemporary magnetic mass analyzers over rest (record sensitivity, the uniqueness of identification, large working mass range), they possess two basic "deficiencies" - these instruments large both according to the sizes and on the cost. , where cannot it managed without them, by them there is no alternative (organic analysis with the high resolution, analysis изотопных соотношений, high-precision element analysis), but in the contemporary peace there are thousands of analytical applications of a mass spectrometry, for many of them godyatsya the instruments also of smaller caliber.

Scientists in the long period searched for alternative to magnet as the mass analyzer. First of the success of dobilsya the professor of the Stanford university Robert Finnigan, who built in 1967 the first commercial chromate-mass- spectrometer with the quadrupole analyzer. Quadrupole is four rods, to which in pairs in the opposite polarity is fed the specific combination constant and radio-frequency alternating voltage. The ions, which fly in parallel to the axis of these rods, fall into the hyperbolic it fell and it, depending on the relationship of their mass (as always, m/z) and frequency, they are passed by this I will fall or they are not passed further. The creation of quadrupole mass analyzers sufficed by revolution in the mass spectrometry. Magnetic mass spectrometers require the use of high voltages (thousand of volts), but quadrupole no, and this simplifies its construction, the smaller dimensions of vacuum part simplify the system of the creation of vacuum. Mass spectrometers decreased in the sizes, they became more simply in the operation and, that most important, is considerably cheaper, which opened the possibility used this analytical method to many thousands of users. (look also TRACE MS, Automass)

Further development of quadrupole analyzers led to the creation of the "ion trap". One pair of rods was twisted into the ring, and the second pair became ball-shaped cups. Now the combination of radio-frequency and constant stresses, applied to the electrodes of the ion trap, sufficed it allowed it retained ions inside it or it ejected from it. The first ion traps, released by firm Finnigan in 1983, lost even ionic source. The ionization of molecules sufficed it was carried out directly inside the trap. Subsequently, true, from this they refused, having again carry ouied the place, where are created ions, beyond the limits of the ion trap, which proved to be more winning (illustration). First, external with respect to the mass analyzer, ionic source is guaranteed the absence of the samokhimicheskoy ionization, which leads to the distortion of the mass-spectra of electron collision, and in the second place, will make instrument much more universal - possible it analyzed the negative ions, which are formed with dissociative capture of electrons, classical direct introduction possible was used and so forth mass spectrometers on the base of the ion trap with the internal source of ions at present continue he was let out by firm Varian, which acquired license for this mass-spectrometric detector in Finnigan in 1991.

Use of the ion traps giv pulse to the development of the systems of tandem mass spectrometry or MS/MS. MS/MS - this when mass analyzers erect consecutively after each other. Why this was required? Let us suppose we imeyem the matter concerning the complex organic molecule (for example, biochemists they almost always deal concerning similar) and after breaking it into the fragments, we nevertheless not imeyem are sufficient inofrmatsii about its structure. From the ions divided in the first mass analyzer possible it selected those, which are for us of interest, such as means forced they it was pulled down to the smaller fragments and it again sorted out that which was received, throughout the masses. This will be made in the second mass analyzer. In the case of using the magnetic and quadrupole mass analyzers this means that to us necessarily it erected their after each other into the line. But indeed those, who deal with the analysis of complex molecules, encountered with the fact that both two and three sequential mass analyzers sometimes it is not sufficient so that it would decipher their structure. Here here ion trap proved to be right on target. As we already spoke in the ion trap possible it retained the ions, which are of interest, and rest "rejected" from it. The ions left in the trap possible it subjected to disintegration (by manager of fragmentation), registered they, those, which are of interest, left in the trap, it rejected rest, subjected to fragmentation, registered and so forth in instrument LCQ DECA so possible entered 10 times and thus we imeyem system MSY0, in chromate-mass- spectrometer POLARISQ - 5 times (system MSSHCH). But here mass spectrometer MAT 900 XP- ladder or MAT 95 XP- ladder has a double focusing during the first stage (magnet and electrostatic sector) and a trap on the second and can rabotati' as MSYY. Another mass spectrometer TSQ Quantum is "classical" MS/MS by system - two quadrupole analyzers stand consecutively after each other (between them one more, but this is not mass analyzer, but the "camera of collisions").

In reality, today's progress v протеомике in many respects is obliged to the tandem systems LCQ, and from other side, the enormous need of this rapidly developing branch of science stimulates the rapid developments of new instruments and methods of the analysis of biomolecules. Today in this region by the most advanced and extended method of the analysis of stal 2dlc-esi-ms/ms, i.e., two-dimensional micro-column highly effective liquid chromatography- ionization into the the elektrospreye - tandem mass spectrometry, and by the most extended instrument - LCQ (Advantage or DECA XP).

Let us return, however, to other types of mass analyzers. Is one additional type of mass analyzer, as if combined of those two previously described - magnetic and ion trap. This the so-called mass analyzer of ion-cyclotron resonance with the Fourier transform. In this analyzer the ions fly into the strong magnetic it fell and they are revolved there along the cyclic orbits (as in the cyclotron, the particle accelerator). This mass analyzer possesses the definite advantages: has very high resolution, the range of the measured masses is very wide, can it analyzed the ions, obtained by all methods. However, for its work it requires strong magnetic field, and it is meant, the use of an enormous magnet with superconductive solenoydom, pm! - - systran dnt_.block open - >.dderzhivayemym at a very low temperature (liquid helium, approximately - 2"0oS). An example of this mass spectrometer is NewStar.

Recently ever greater popularity acquired "overflight time" (Time Of Flight, TOF) mass analyzers. We previously said that the ions are sorted throughout the masses due to laws governing the motion of the charged particles in it fell (magnetic or electrostatic). And this it is not entirely related to the overflight time analyzers, since in them, exactly, the ions are moved in bespolevom space. Ions from the source are accelerated with electrical I will fall, acquiring sufficiently high kinetic energy, and they depart into the bespolevoye space. At the entrance into this space all ions have identical kinetic energy, and if it recalled by all known formlulu, which expresses the value of the kinetic energy through the mass and speed (E=.mv2/2), then, obviously, depending on mass ions will be it moved with the different speeds and, sootvestvenno, they will reach the detector, located at the end of their pipe it flew in the different time. After registering them and after measuring time, possible it calculated their mass. All processes, about which we here speak tyuey proiskhodyat for the millionth it add by pouringed second. I.e., this mass analyzer very "rapid". On the basis of this mass analyzer possible built very rapid (and чувствительный) mass spectrometer, which can it proved to be very winning, especially with the analysis of the organic matter, which are the mixture of the enormous number of individual connections (for example, oil). An example of this instrument is GC/TOF MS TEMPUS. However, earlier analysts used another advantage of this method - with this analyzer was much more simply obtained very wide mass range, i.e., with its aid the masses of very large molecules easily were measured. This is important for many studies, concentrated on the enormous molecules (with masses of ten and hundreds of thousands of atomic units). But the most suitable method of ionization is that described above MALDI. (look MALDI TOF DYNAMO).

We described the processes of obtaining of ions, sorting to their masses (mass analysis), now to us it remained them anything to pomeryat'. Measuring a mass of ions (m/z) and their quantity on each mass (intensity), we will receive the mass-spectrum, which can, for example, it looked like this shown on the pictures.

Detector

Thus, the last element of the simplified mass spectrometer described by us, is the detector of the charged particles. The first mass spectrometers used as the detector photographic plate. Now are used the dynode secondary-electron multipliers, in which the ion, falling on the first dynode, knocks out from it electron beam, which in turn, falling on the following dynode, knock out of it an even larger quantity of electrons and so forth the different version - fotoumnozhiteliregistriruyushchiye the glow, which appears with the ion bombardment of phosphor. Furthermore, are used microchannel multipliers, systems of the type of diode matrices and collectors, which gather all ions, which fell into this point of space (Faraday's collectors). The interested reader can it turned to the details of the detection of ions into the specialized literature, we not budem stopped at this in more detail.

What there are the mass spectrometers

Thus, mass spectrometers are used for the analysis of organic compounds and inorganic.

Organic matter in the majority of the cases are multicomponent it compounded individual components. For example, it is shown that it smelled fried hen they compose 400 components (i.e., 400 individual organic compounds). Task analysts lies in the fact that it would determine how many components they compose organic matter, it learned what this of the component (it identified them) and it learned how much each connection it was contained in it compounded. Ideal the combination with the mass spectrometry is хроматографии for this. Gassing chromatography as is cannot better for combination with the ionic source of mass spectrometer with the ionization by electron collision or the chemical ionization, since in the column of the chromatograph of connection already tyuey nakhodyatsya in the gas phase. The instruments, in which mass-spectrometric detector is combined with the gas chromatograph, are called chromate-mass- spectrometers.

Many organic compounds impossibly it divided into the components with the aid of gas chromatography, but it is possible with the aid of the liquid chromatography. For the combination of liquid chromatography with the mass spectrometry today use the sources of ionization into the the elektrospreye (ESI) and chemical ionization with atmospheric pressure (APCI), and the combination of liquid chromatographs with the mass spectrometers is called ZHKH/MS or LC/MS on English. Camye the powerful systems for the organic analysis, claimed of contemporary proteomikoy, stroyatsya on the basis of superconducting coil electromagnet and work according to the principle of ion-cyclotron resonance. They also nosyat name FT/MS, since in them is used the Fourier transform of signal.

Most of all they are used for the analysis of element composition масс-спектрометры с индуктивно-связанной плазмой. With the aid of this instrument they determine of what atoms comprised substance. The same method of analysis can it showed isotopic composition. But best anything was measured isotopic composition with the aid of the specialized isotopic instruments.

However, before passing to instruments for measuring the isotopic composition, briefly let us pause at what are isotopes.

Natural and artificial isotopy

Atoms it is consisted of nucleus and electron shells. The properties of atoms are determined by the fact, how many protons (the positively charged elementnarnykh particles) it is contained nucleus. Nucleus besides the protons it is contained and neutrons. Nature was ordered so that with an equal quantity of protons the nucleus can it contained a different quantity of neutrons. Atoms with an identical quantity of protons in the nucleus, but with a different quantity of neutrons differ in the mass to one or several atomic mass units (amu.) and they are called isotopes. The majorities of elements have the specific collection of stable isotopes. Radioactive isotopes are not stable and are decomposed with the formation of stable isotopes. Natural isotope abundance for each element is known. Some elements in prirorde are mono-isotopic, i.e., 100 % for natural prevalence it is to one isotope (for example, Al, Sc, Y, Rh, Nb, etc.), and others have many stable isotopes (S, Ca, Ge, Ru, Pd, Cd, Sn, Xe, Nd, Sa, etc.). In the technological activity the people learned it changed the isotopic composition of elements for the purpose of obtaining any specific properties of materials (for example, U235 it has a capability for spontaneous chain reaction can it was used as the fuel for the atomic power plants or the A-bomb) or use of isotopic markers (for example, in medicine).

Since the masses of isotopes differ, and mass spectrometry it is measured mass, naturally, this method is become most convenient for determining the isotopic composition. At the same time information by the isotopic composition helps it identified organic compounds it allows it gave answers to many questions nachianaya from the determination it increased species for geology and ending with the determination of the falsification of many products and establishment of the place of the origin of goods and raw material.

Mass spectrometers for the isotopic analysis

Mass spectrometers for determining the isotopic composition must it was very precise. For the analysis of the isotopic composition of light elements (carbon, hydrogen, oxygen sulfur, nitrogen so forth.) ionization by electron collision is used. In this case godyatsya all methods of the introduction of gas phase as in the organic mass spectrometers (DELTAPlus, DELTAPlus XL and MAT2SHCHE).

For the analysis of the isotopes of more heavy elements is used the thermoionization (TRITON TI) or ionization in the inductively connected plasma (NEPTUN, ELEMENT2).

In practice magnetic mass analyzers are used in all types of isotopic mass spectrometers.

Characteristics of mass spectrometers and mass-spectrometric detectors

The most important technical characteristics of mass spectrometers are sensitivity, dynamic range, permission, speed.

Rate of scanning. Mass analyzer, as we showed above, passes ions with the specific relationship of mass and charge in the specific time. So that would analyze all ions it it must it would scan, i.e., the parameters of its field must for the zadanyy time interval it passed all values, necessary for the transmission to the detector of all ions interesting. This skrost' of unwinding field is called rate of scanning and must it was as much as possible (respectively, the time of scanning must it was as less as possible), since the mass spectrometer must it had time it measured signal in short time, for example in the time of the output of chromatographic peak, which can it was 1 second. Magnet is the slowest mass analyzer, the minimum time of its scanning without the special loss of sensitivity comprises it add by pouringed second (MAT 95XP). Quadrupole mass analyzer can it turned spectrum for the tenth it add by pouringed second (TSQ 7000, TRACE DSQ), and the ion trap is still more rapid (POLARIS, LCQADVANTAGE, LCQDECA). But the most rapid mass analyzer is overflight time (TEMPUS). It is capable were written mass-spectra with a velocity of 40,000 per second!

Razresheniye.Naglyadno permission (resolution) possible defined as the possibility of analyzer it divided ions with the adjacent masses or, in other words, was determined the precise mass of ion. For the magnetic mass analyzers, for which peak separation of mass-spectrum it is not dependent on the masses of ions, permission is value equal to M/DM. this value, as a rule, it is determined from 10 % heights of peak. So for example, permission 1000 means that peaks with masses of 100.0 amu. and 100.1 amu are separated from each other, i.e., they are not superimposed up to 10 % heights. For analyzers, whose peak separation changes in the working mass range (the greater the mass, the less the distance), such as quadrupole analyzers, the ion traps, overflight time analyzers, storogo speaking, permission makes another sense the permission, defined as M/DM in this case it kharayeterizuyet specific mass. Makes sense were characterized these mass analyzers in the width of peaks, the value, which is remained constant in entire mass range this width of peaks, usually, it was measured to their 50 % heights. The width of peak on the half-height equal to 1 is not bad index and means that for such instruments this mass analyzer is capable it distinguished the nominal masses, which are differed by one practically in entire its operating range. By nominal mass or mass number is called near to the precise mass of ion integer in the scale of the atomic units of mass. For example, the mass of ion of hydrogen N+ is equal to 1.00787 amu, and its mass number to equal 1. But such mass analyzers, which, in essence, measure the nominal masses, they call the analyzers of poor resolution. We wrote "in essence", because today there are such mass analyzers, which formally otnosyatsya to those being low-resolving, but in reality such no longer appear high technology, first of all quite progressive-minded developer Thermo Finnigan, it already today proposed for the market for analytical equipment the high-resolution quadrupole instruments. So for example, newest TSQQuantum easily works with the width of the peak of mass-spectrum on the half-height 0.1 amu. The knowing people can it objected: "but this width of peak possible was obtained on each quadrupole mass spectrometer!" And they will be right really each quadrupole possible built thus far it evened permissions. But which proizoydet in this case with the signal? Upon transfer from the width of peak on the half-height in 1 amu. to 0.1 amu the value of signal on all quadrupoles upadet practically to two orders in the value. But not on TSQQuantum, on it it is decreased in all to two and one-half of times. The ion traps in the narrow mass range can it worked as the mass spectrometers of high resolution, ensuring, as a minimum, the separation of the peaks, which be distant on 1/4 amu behind each other. Double-focusing mass spectrometers (magnetic and electrostatic), ion-cyclotron resonance - instruments of average or high resolution. Permissions into several thousand also possible attained with the use of overflight time mass analyzers.

Permission is tightly connected with another important characteristic - the accuracy of the measurement of mass. Illustrated the value of this characteristic possible on I will stand an example. The masses of the molecular ions of nitrogen and mono-oxide of carbon () are 28.00615 amu. and 27.99491 amu, respectively (both they are characterized by one mass number 28). These ions will be it was recorded by mass spectrometer separately with permission 2500, and the precise value of mass will give answer - which of the gases is recorded. The measurement of precise mass is accessible on the instruments with the double focusing and on the tandem quadrupole mass spectrometer TSQQuantum.

Dynamic range. If we analyze the mixture, which contains 99.99 % of one connection or any element and 0.01% any mixed, we must it was assured that we correctly determine both that and, etc. , so that it would be confident in the determination of components in this example, necessarily had the range of linearity into 4 orders. Contemporary mass spectrometers for the organic analysis are characterized by dynamic range into 5-6 orders, and mass spectrometers for the element analysis of 9-10 orders. Dynamic range into 10 orders means that the admixture in was opened it wakes visible even when it is 10 milligrams to 10 tons.

Sensitivity. This is one of the most important characteristics of mass spectrometers. Sensitivity this the value, which shows what quantity of substance necessarily it introduced into the mass spectrometer so that it possible it would be it would detect. For simplicity budem were examined the parameter connected with the sensitivity - the minimum determining quantity of substance, or the detection threshold. The typical value of the threshold of detection of a good chromate-mass- spectrometer, used for the analysis of organic compounds, is 1 picogram with the introduction of 1 microliters of liquid. Give let us present to itself that this similar. If we collect by special shpritsom 1 microliter of liquid (one millionth fraction of liter) and I will let out it to the leaf of clean white paper, then with its examination into the magnifier we will see speck, equal according to the sizes it followed from the prick by thin needle. Now let us visualize that we threw 1 gram of substance (for example, one tablet of aspirin) into 1000 tons of water (for example, into this nemalen'kiy pond with a length of 50 meters, with a width of 10 meters and with a depth of 2 meters). Thoroughly peremeshayem water in the pond, let us collect by shpritsom 1 microliter of this water and zakolem into the chromate-mass- spectrometer. As a result of analysis we will receive the mass-spectrum, which we smozhem compared with the library spectrum and the method it was fingerprint it was convinced of the fact that this is the actually acetylsalicylic acid, otherwise called aspirin.

The limit of the detection of inorganic substances, for example, by the method ICP/MS (ELEMENT2) is still below. Here pond already wakes malovat for the preparation of solution with the concentration, which corresponds to the limit of detection. The limit of detection for ELEMENT2 on the row of metals is 1 ppq (one portion to the quadrillion). This it is meant, that the sensitivity of instrument it is sufficient so that would detect 1 kilogram of metal (for example, it would mercurate, lead so forth.) dissolved in dissolved in lake Baykal for its mixing and complete dissolution)!

In the mass spectrometry of isotopes, for example, sufficient 1000 molecules of the dioxide of carbon (SO2, carbon dioxide) so that would be obtained the signal of carbon. So that it would demonstrate, with what accuracy and isotopic sensitivities isotopic mass spectrometry deals, let us resort to the following allegory. I will assume to one thousand completely identical apples, each of which are weighed 100 grams, are come 11 apples, which weigh to 8 % more, i.e., 108 grams. All these apples are assembled in one bag. This example sootvestvuyet to the relationship of the isotopes of carbon in nature - to 1000 atoms of y2S are fallen 11 atoms of yeS. Isotopic mass spectrometry it is measured relationship, i.e., it is capable it distinguished not simply these 11 apples, but it found among many bags those, in which of 1000 stogrammovykh apples not 11 by stovos'mi of gram, but 10 or 12. This example is very light for the isotopic mass spectrometry, in reality such instruments as DELTAPlus, DELTA Plus XL and MAT2SHCHE are capable was determined the difference into one isotope (one stovos'migrammovoye apple) among ten million atoms (ten million apples).

The most important characteristic with the analysis of organic compounds - this is sensitivity. In order to dostignut' largest possible sensitivity with an improvement in the signal-to-noise ratio they come running to the detection on the separate selected ions. Gain in the sensitivity and the selectivity in this case colossal, but with the use of instruments of poor resolution is come it brought in it sacrificed another important parameter - authenticity. Indeed if you recorded only one peak of entire characteristic mass-spectrum, by you was still much it worked, so that it would prove that this peak sootvestvuyet precisely to that component, which interests you. But how it did solve this problem? High resolution on the instruments with the double focusing, where possible it attained high it evened authenticities without sacrificing sensitivity, was used. Or was used the tandem mass spectrometry, when each peak, which corresponds to single ion possible confirmed by the mass-spectrum of daughterly ions. Thus, the organic chromate-mass- spectrometer of high resolution with the double focusing is absolute record holder on the sensitivity. Thus, for instance, the certified characteristic MAT 95 xp it is said, that 2,3,7,8-тетрахлоро-п-дибензодиоксин, introduced through the chromatographic column in a quantity of 10 femtograms will give the peak, which is characterized by signal-to-noise ratio = 40: 1. not dostizhimyy not on what other instrument result! According to the characteristic of the combination of sensitivity with the authenticity of the determination of components after the instruments of high resolution go the ion traps. The classical quadrupole instruments of new generation (TRACE DSQ) have the improved characteristics because of a number of the innovations, used in them, for example, to the use of the bent quadrupole preliminary filter, which prevents contact of neutral particles with detector and, therefore, to reduction in noise.

Why the mass spectrometry is necessary

Deep physical laws, foremost scientific and engineering developments, highly technological vacuum systems, high voltages, the best materials, the high quality of their of treatment, sovremenneyshaya moving rapidly numbering and analog electronics and computer technology, inventive software - here from what is complex contemporary mass spectrometer. And for which all this? For the answer to one of the most important questions of universe - from what is folded the material. But this is a question not of high science, but everyday life of man.

For example, the development of new medicines for the rescuing of man from earlier than incurable diseases and the control of the production of medicines, genetic engineering and biochemistry протеомика. Without the mass spectrometry are unthinkable the control over the illegal propagation of narcotic and psychotropic means, the criminological and clinical analysis of toxic preparations, the analysis of explosives.

The explanation of the source of origin is very important for solving the whole series of the questions: for example, the determination of the origin of explosives helps it found terrorists, narcotics - it fought with their propagation and the ways of their traffic overlapped. Economic national safety is more reliable, if customs services can not only it confirmed by analyses in the doubtful cases the country of the origin of goods, but also its sootvestviye to the declared form and to quality. But анализ нефтей и нефтепродуктов it is necessary not only for the optimization of the processes of petroleum refining or to geologists for looked new petroleum fall, but also so that it would determine guilty of the floods petroleum spots in the ocean or on the earth.

In the epoch the "chemicalization of agriculture" by the very important of stal a question about the presence of trace quantities of used chemical means (for example, pesticides) in the foodstuffs. In scanty quantities these substances can it did irreparable damage to human health.

A whole series of technogenic (i.e., not existing in nature, but appeared as a result of industrial human activity) substances they are supers-toxicant (having the toxic, cancerogenic or harmful for human health action in the lowest possible concentrations). An example is well known диоксин.

Existence of nuclear power engineering is unthinkable without the mass spectrometry. With its aid it is determined the degree of the enrichment of the split materials and their cleanliness.

Certainly and medicine it is not managed without mass spectrometry. The isotopic mass spectrometry of carbon atoms it is used for straight medical diagnostics of the infection of man Helicobacter Pylori and is most reliable of all methods of diagnostics.

With difficulty represented the region of the human activity, where the places for mass spectrometry would not be located. Let us be limited simply by the enumeration: biokhimiyaklinicheskaya chemistry, general chemistry and organic chemistry is pharmaceutics, cosmetic perfumery, food industry chemical synthesis, petroleum chemistry and nefteperarabotka environmental monitoring, the production of polymers and plastics medicine and toxicology, criminology dopingovyy control, the inspection of narcotic drugs the control of alcoholic beverages, geochemistry, geology, hydrology petrography, mineralogy geochrony, archaeology, the nuclear industry and power engineering semiconductor industry, metallurgy.

Applications of a mass spectrometry of system V3JX-mass- spectrometer, the Chromate-mass- spectrometers of column for VEZHKH, mass spectrometers for the element and isotopic analysis, liquid chromatography mass spectrometers for the isotopic analysis

--Jvraba 18:14, 21 Jul 2004 (UTC)