What is organic mass spectrometry?
Organic mass spectrometry
is an instrument used for the structural identification of organic compounds, providing structural information such as molecular weight, elemental composition, and functional groups of compounds, organic mass spectrometers can be divided into quadrupole mass spectrometers, ion trap mass spectrometers, time-of-flight mass spectrometers, and magnetic mass spectrometers.
Application of organic mass spectrometry
Organic mass spectrometers are widely used in organic chemistry
, biology, geochemistry, nuclear industry, materials science, environmental science, medical health, food chemistry, petrochemical industry, and other fields, as well as space technology and public security work and other special analysis.
Organic mass spectrometer can obtain the molecular weight of organic compounds, the molecular formula of organic compounds, and the functional group attachment sites in organic compounds.
Organic mass spectrometer can also be used in conjunction with HPLC and a tandem mass analyzer to establish fingerprints of active ingredients of traditional Chinese medicine.
With the high sensitivity of organic mass spectrometry and standards, we can carry out pharmacokinetic studies, doping detection, and trace explosives detection.
Organic mass spectrometry working principle
The basic working principle of organic mass spectrometry
is to ionize the measured substance by electron bombardment or other means to form ions with various mass-to-charge ratios (m/e), and then use electromagnetism to separate the ions by different mass-to-charge ratios and measure the intensity of various ions to determine the molecular weight and structure of the measured substance.
Structure of organic mass spectrometry
Organic mass spectrometry instrument usually consists of six parts: ion source, mass analysis system, ion collection system, vacuum system, sample inlet system, and data system.
When using an organic mass spectrometer, molecules of organic compounds form charged ions, either positive or negative, in the ion source, which is, as the name implies, where the ions are generated. Currently, the ion sources commonly used as commercial ion sources are electron ionization sources, chemical ionization sources, field ionization sources, fast atom bombardment sources, laser desorption sources, and ion sources composed of those interfaces for high-performance liquid chromatography-mass spectrometry coupling, such as thermal spray interfaces, atmospheric pressure ionization interfaces including electrospray and atmospheric pressure chemical ionization sources.
Mass analysis system
The ion stream from the ion source contains ions with different mass-to-charge ratios. As an organic mass spectrometry analysis, the information on how many mass-to-charge ions the compound can produce and their respective intensities (earlier the name abundance was also used) is necessarily obtained using a mass analysis system. The various ions with different mass-to-charge ratios are separated spatially or temporally and arranged according to their mass-to-charge ratio for detection by the ion collection system.
There is a distinction between static and dynamic mass spectrometry systems. Static mass analyzers are those in which parameters such as electrical and magnetic fields and ion deflection orbits that play a role in mass-to-charge ratio separation are stable at different times. Changing some of these parameters over time, such as the magnetic field scan, is required to record the spectrum and not the mass separation. A dynamic mass analyzer has to use alternating or periodically varying electric and sometimes also static magnetic fields to achieve mass separation in space or time so that those of its parameters are time-varying.
Ion collection system
The ion collection system includes the detection of ions and signals acquisition and amplification, and here we focus on the detection of various ions. Sensitivity, accuracy, and response time are the main indicators for evaluating detector performance, and they vary depending on the operating requirements of various mass spectrometers. For example, isotope ratio determination requires high accuracy of ion intensity determination and allows slow scanning speed, while organic analysis by GC-MS requires fast scanning, such as up to 0.1s/decade multiplication and fairly high sensitivity. For the former, slow-response Faraday cups are used (determination accuracy better than 0.1%); for the latter, fast-response electron multipliers are used (sensitivity several hundred times higher than Faraday cups, but accuracy up to 0.5%). The commercially available ion detectors are Faraday rings, cascade electron multipliers, electron multipliers with continuous polarization, photomultipliers, and microchannel plates, all of which are detectors used in electrical measurements.
Types of organic mass spectrometry
There are three main types of organic mass spectrometers,
Gas chromatography-mass spectrometer (GC-MS)
Gas chromatography-mass spectrometer is an organic mass spectrometer. The mobile phase of gas chromatography is an inert gas, and adsorbent with a large surface area, and certain activity is used as a stationary phase in gas-solid chromatography.
Among GC-MS, there are GC-quadrupole mass spectrometers, GC-time-of-flight mass spectrometers, GC-ion trap mass spectrometers, etc. due to the different operating principles of mass spectrometers.
Liquid chromatography-mass spectrometry (LC-MS)
Online conductivity analyzer adopts a new design concept, which can realize online continuous monitoring of water conductivity, suitable for general industrial water, pure water conductivity monitoring, widely used in electric power, chemical, petroleum, environmental protection, pharmaceutical, and other industries in the measurement of a variety of water quality, is a high-precision, intelligent, high-performance field measurement instrument.
Other organic mass spectrometry
Matrix-assisted laser desorption time-of-flight mass spectrometer (MALDI-TOFMS)
can measure up to hundreds of samples per day, which is especially suitable for high-throughput screening of biological macromolecules such as proteins.
Fourier transform mass spectrometer (FT-MS)
Fourier transform mass spectrometer is the product of the combination of ion cyclotron resonance spectrometry and modern computer technology.
Organic mass spectrometry specifications
Benchtop organic mass spectrometry
|Temperature control range||400℃
|Measuring range||Room temperature+3℃～399℃
|Temperature control accuracy||0.5 %(±0.1℃)
Type: Gas chromatography-mass spectrometer
1. Benchtop organic mass spectrometry comes with an autonomous GC system with electronic flow and electronic pressure control.
2. Equipped with a single quadrupole mass analyzer with pre-quadrupole, effectively reducing the contamination of the quadrupole during the measurement process.
3. Equipped with full-range vacuum gauges for real-time monitoring of vacuum conditions.
Small organic mass spectrometry
|MRM rate||500 MRM transitions/s
|Size||47.5 cm x 77.3 cm x 84 cm
|Scanning speed||17000 Da/s
|Minimum MRM dwell time|| 0.5 ms
|Polarity switching speed||<25 ms
|Collision cell cleaning time||<0.5 ms
Type: Liquid chromatography-mass spectrometry
1. Small organic mass spectrometry performs screening, confirmation and quantification using triggered multiple reaction monitoring, which combines fast, sensitive MRM quantitative analysis with product ion spectrogram generation for library search, compound screening and confirmation.
2. A variety of versatile and easily configurable ion sources allow you to handle any type of LC-MS analysis.
Organic masss pectrometry and inorganic mass spectrometry
Inorganic mass spectrometry definition
Inorganic mass spectrometry
is used to ionize substances by inductively coupled high-frequency discharge (ICP) or other means.
Difference between organic massspectrometry and inorganic mass spectrometry
|Name ||Organic masss pectrometry||Inorganic mass spectrometry
|Working principle||Organic mass spectrometry uses an instrument with separation technology as the "feeder" of the mass spectrometer to separate the organic mix into pure components into the mass spectrometer, giving full play to the analytical strengths of the mass spectrometer and providing molecular weight and molecular structure information for each component.||Inorganic mass spectrometers work differently from organic mass spectrometers in that the ionization of the substance is not the same. Inorganic mass spectrometers use inductively coupled high-frequency discharges to ionize the measured substance.
|Application||Organic mass spectrometry is mainly used for structural identification of organic compounds, which can provide structural information such as molecular weight, elemental composition and functional groups of compounds. It is divided into quadrupole mass spectrometer, ion trap mass spectrometer, time-of-flight mass spectrometer and magnetic mass spectrometer, etc.||Inorganic mass spectrometer is mainly used for trace analysis of inorganic elements and isotope analysis, etc. It is characterized by fast testing speed and accurate results.
How to maintain organic mass spectrometry?
Leak detection of cylinders and gas pipelines
Check each pipeline connection of the organic mass spectrometer, paying special attention to the head of the cylinder. Every time you change the gas cylinder, you must check the cylinder and the inlet joints thoroughly to ensure that there is no gas leakage from the cylinder and the inlet line. Open the cylinder, adjust it to a certain pressure, close the pressure of the gas chromatograph inlet, close the main valve of the cylinder, and open the pressure divider, if there is a leak, the pressure of the pressure divider will drop significantly after a while. Regularly check the pressure gauge and pressure reduction, which can be used to find out whether the gas main line is leaking.
Inspection of the gas chromatography section
Air leaks in the gas chromatography section usually occur at the internal carrier gas fittings, spacer positioning nuts, column nuts, etc. An appropriate amount of acetone can be applied to the above locations, one at a time, in the order of proximity to the mass spectrometry section. After a suitable time, observe the peaks in the background pattern. If there is a steep and significant climb at m/z58 and m/z43, it indicates that there is an air leak at the location where the acetone has just been applied.
Precautions for using organic mass spectrometry
During the experiment, do not use soap bubbles to check the gas path of the organic mass spectrometer, including your gas path must also be disconnected from the mass spectrometer interface when checking (very important, many mass spectrometers are unable to continue to use because students use soap bubbles to check for leaks making the quaternary rod contaminated).
In general, the mass spectrometer should be kept in normal operation, unless the instrument is not used for more than 15 days before it is turned off. Because the mass spectrometer needs some time to stabilize (more than 24h), frequent switching on and off of the mass spectrometer will also accelerate the vacuum gauge contamination. In case of predicted power failure, please turn off the mass spectrometer in advance.
Pump oil replacement: Always observe the pump oil color and replace it immediately when it turns yellowish brown. If the instrument is used frequently and the gas is dirty, it is required to be replaced at least once every six months, and the amount of pump oil added should not exceed the uppermost liquid level.
The heat dissipation filter should be cleaned regularly, do it once every two months), and try to open the upper cover when using the room without air conditioning in summer, to prevent the instrument from affecting the heat dissipation.
Capillary tube when not connected to the external instrument, do not place directly on the dirty table, as far as possible suspended placed; capillary tube internal filter to be cleaned regularly, in the process of disassembly and assembly take care not to lose parts.
In the process of transporting organic mass spectrometry instruments, if there is an oil pump that needs to drain the pump oil, if the pump oil is clean can be collected later to continue to use), remove the RF head, and transported separately.
How to buy organic mass spectrometry?
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