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What Is Online Mass Spectrometer

Posted on September 29, 2022 by Zeng YingLab Equipment

What is online mass spectrometer?

Online mass spectrometer is made according to Faraday's law of electromagnetic induction and is used to measure the volume flow of conductive liquids. Due to its advantages, the mass spectrometer has been widely used in the flow measurement of various conductive liquids in industrial processes, such as various acids, alkalis, salts, and other corrosive media.

Application of online mass spectrometer

Online-spectrometer
Online-spectrometer

Online mass spectrometry analyzer is a new generation of gas analysis system with modular design, intelligent software, and a wide range of applications. Mass spectrometry is a widely used analytical method in the identification of chemical elements and compounds. In particular, it has an excellent performance in the connection of chemical processes, in the semiconductor industry, metallurgy, fermentation, catalysis, laser technology, and environmental analysis.

The following are the main application areas of online mass spectrometry analyzers.
* Fermentation reaction
* Fuel cell research
* Catalytic reactions 4. Semiconductor exhaust monitoring
* Gas monitoring
* Mixed gas monitoring
* Vacuum equipment monitoring
* Detection of dosing solvents after drying
* Gas scrubber outgassing rate
* Reaction process monitoring
* Program temperature desorption experiment
* Pharmaceutical packaging testing

Online mass spectrometer working principle

Gas-spectrometer
Gas-spectrometer

The working principle of online spectrometer is as follows
When a conductor moves in a magnetic field cutting magnetic lines of force, an induced potential is generated in the conductor, and the magnitude of the induced potential is proportional to the neutral length of the conductor in the magnetic field and the speed of the conductor moving in the magnetic field in a direction perpendicular to the magnetic field. Similarly, when a conductive fluid flows in a magnetic field in a perpendicular direction and cuts the magnetic lines of induction, it also generates an induced potential at the electrodes on both sides of the pipe. The direction of the induced potential is determined by the right-hand rule, and the magnitude of the induced potential is determined by the following equation.
The ionization of the measured substance by electron bombardment or other means forms ions of various mass-to-charge ratios (m/e), and then electromagnetism is used to separate the ions by different mass-to-charge ratios and measure the intensity of the various ions to determine the molecular weight and structure of the measured substance.
The conductive liquid flows in a non-magnetic measuring tube perpendicular to the magnetic field, generating an induced potential in the direction perpendicular to the flow direction proportional to the flow rate, E=KBdvE-is the signal voltage between the electrodes (v) B-magnetic flux density (T) d-measurement tube inner diameter (m) v -average flow rate (m/s) in the formula k, d is a constant because the excitation current is constant, so B is also a constant, then from E=KBdv can be seen that the volume flow Q is proportional to the signal voltage E-, that is, the signal voltage E of flow induction is linearly related to the volume Q. Therefore, the flow rate Q can be determined by measuring E.

Features of online mass spectrometer

The online mass spectrometer injection system has a single channel real-time split injection (1.6 seconds a set of data) and 16-channel injection options; ion source using the classical electron bombardment ion source (EI), and equipped with dual filament, one working, one backup, can automatically switch and calibration, reducing downtime maintenance; mass analyzer equipped with mature and stable, fast scanning speed four-stage rod mass analyzer, to meet the separation of complex components requirements.

In addition, the online mass spectrometer has the following performance features
a. Analysis speed: fast 1.6s analysis of a set of data; analysis of the components is not limited, analysis time can be set according to the requirements of the analysis process
b. Sensitivity: Faraday detector: 100%~10ppm; electron multiplier detector: 100%~10ppb
c. Stability: instrument 30 days continuous operation RSD ≤ 0.5%, based on 1% Ar in air
d. Analytical accuracy: RSD≤0.25%, based on 1% Ar in air
e. Each channel has an independent air inlet and exhaust, eliminating interference between channels.
f. Continuous flow sampling to ensure real-time gas update.
g. Temperature-controlled inlet piping prevents process gas from condensing during sampling.
h. Software set online cleaning program to ensure analysis accuracy.

Online mass spectrometer composition

Gas-mass-spectrometer
Gas-mass-spectrometer

Online mass spectrometer mainly consists of an injection system, ion source, and ion detector.

Injection system
The sample capillary can be directly connected to the reactor by ferrules, and the change in sample gas type and content can be detected online in real-time by continuous injection and rapid detection. The injection pressure (100 bar-2 bar) and the response time can be as short as 300 ms. There are two main types of injection capillaries: quartz and stainless steel. Quartz does not react with acidic gases and the gases are not easily adsorbed on its surface.

Ion source
Generally, choose an electron bombardment ion source (EI). The current better filament material is iridium, which has a life of up to 5 years, while the life of tungsten filament is only 1 year. Mass analyzers - Most commercially available online gas mass spectrometers use quadrupole mass analyzers. A quadrupole mass analyzer is also known as a quadrupole filter mass analyzer. It consists of four metal rods placed parallel to each other and evenly, and the cross-section of the full genus rod is hyperbolic in shape. After the ion beam enters the electric field, it oscillates under the effect of the alternating electric field. Under a certain electric field strength and frequency, only a certain mass of ions can pass through the electric field to the detector, while other ions are "filtered" due to the increase in amplitude and finally hit the poles and are pumped away by the vacuum pump.

Ion detector
Faraday cup (direct electrometry) ion flow is received directly by the metal electrode, and the size of the ion flow is recorded electrically. Secondary electron multiplier (secondary effect electrical measurement method) certain energy of positive ions striking the surface of the cathode, producing several secondary electrons, and then multi-stage tile-like secondary electrode (or called hitting the pole) so that the secondary electrons continue to multiply, and finally detected by the anode. The detection limit of the secondary electron multiplier is much lower. A good mass spectrometer will be equipped with both types of detectors.

How to use online mass spectrometer?

Online mass spectrometer power on

Turn on the power switch at the lower left corner of the front of the online mass spectrometer, and then you can hear the sound of the solvent switching valve switching inside the mass spectrometer, while the mechanical pump starts to work and the instrument starts to self-test. After waiting for about two minutes and hearing the second sound of solvent valve switching (indicating the completion of the self-test of the mass spectrometer), it means that the self-test of the instrument is completed and the instrument can be connected.

As soon as the online mass spectrometry equipment is powered on, the pre-stage vacuum gauge starts to work to monitor the pre-stage vacuum value, but only after the speed of both Turbo1 and Turbo2 turbopumps is greater than 95%, the high vacuum gauge of the four-stage rod will start to work and read the vacuum value normally.

The different colors of the Online spectrometer module represent the different states of the instrument

Green: Ready, indicating that the online spectrometer is ready for sample analysis.
Blue: indicates that the online spectrometer is running a sample.
Pink: indicates that the online mass spectrometer is waiting for an operation.
Yellow: Not Ready, indicating that the online mass spectrometer is not ready or the instrument conditions have not yet reached the set value.
Gray: indicates that the online mass spectrometer is in Standby or Shut Down state.
Red: indicates that the online mass spectrometer has an error.

Online mass spectrometer shutdown

Click the MS QQQ icon, select vent, a prompt will appear to confirm the venting, and observe the decrease of turbopump speed in the diagnostics interface. Wait for about 10 min to finish the venting (loosen the vent valve on the instrument to speed up the vacuum drainage), and close the software. Then turn off the power to the mass spectrometer and LC modules and shut down the computer. If using liquid nitrogen tank, close the booster valve at the same time, and if using nitrogen generator, close the nitrogen generator.
Note: It is recommended not to close the pressure reducing valve of high purity nitrogen for collision gas. After the mass spectrometer is turned off, it does not consume high purity nitrogen, however, this can keep the whole pipeline at positive pressure and effectively protect the trap of high purity nitrogen from being contaminated by ambient air.

Common faults and solutions of online mass spectrometer

1. Failure of chromatographic peaks after injection: first check whether the online mass spectrometer syringe is blocked, if there is no problem then check whether the graphite gasket of the inlet and detector is tight and does not leak then check whether the column is broken and leaking, and finally observe whether the detector outlet is clear.

2. Baseline problems: When encountering baseline problems should first check whether the instrument conditions have changed and whether the recent replacement of gas cylinders and equipment accessories, when the above may cause the causes of baseline problems are ruled out, then you should check whether the inlet pad aging. Detector contamination may also cause baseline problems, which can be solved by cleaning or thermal cleaning methods.

3. Peak loss of failure: can be solved by repeated empty runs and cleaning the gas path (inlet, detector, etc.), the second case of peak loss is not separated from the peak, in addition to the above reasons, it may also be caused by system contamination caused by the decline in column efficiency, or due to the aging of the column, but the peak loss caused by the aging of the column is gradual and slow.

4. Incomplete separation of peaks, several peaks overlap, can not be separated, treatment: reduce the carrier gas flow rate, reduce the injection volume, and reduce the column temperature. For the original can be completely separated, the use of a period will not be able to complete the separation, indicating that the loss of stationary fluid, the life of the column has ended, and the need to replace the stationary fluid. Separation time is too long so that the late distillation of the peak flat, treatment: can be solved by increasing the column temperature, detector sensitivity is too low so that the content of small components can not be detected. Treatment: can be solved by increasing the injection volume, and improving the sensitivity of the detector.

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