What is time-of-flight mass spectrometer?
Time-of-flight mass spectrometer (TOFMS)
is a very common mass spectrometer. TOF mass spectrometer is a type of organic mass spectrometer. This mass spectrometer's mass analyzer is an ion drift tube. The ions generated by the ion source are accelerated into the field-free drift tube and fly at a constant velocity toward the ion receiver. The larger the ion mass, the longer the time taken to reach the receiver, and the smaller the ion mass, the shorter the time taken to reach the receiver. According to this principle, ions of different masses can be separated according to their m/z values.
Application of time-of-flight mass spectrometer
Time-of-flight mass spectrometry
is mainly used for qualitative analysis as a high-resolution mass spectrometer, which has high separation and accurate mass numbers. It can be applied to drug research, metabolite identification, proteomics and metabolomics research, food safety, forensic identification, toxicology, and environmental screening.
The following are specific applications of time-of-flight mass spectrometry:
1. TOFMS can be used for aerosol analysis studies.
2. TOFMS can be used for atmospheric particle characterization, emission source identification, and semiconductor processing processes.
3. TOFMS is suitable for indoor air quality monitoring, and aerosol-drug release studies.
4. TOFMS can also be used for inhalation toxicology studies, drug-enhanced sample analysis, and chemical and biological aerosol detection.
5. TOFMS is also suitable for engine emission measurements, powder production quality, and process control.
Time-of-flight mass spectrometer working principle
The working principle of time-of-flight mass spectrometer is to measure the time it takes for ions to travel from the ion source to the detector. The process involves generating ion beams in the ion source, then accelerating them and measuring their time from the ion source to the detector. In between, there is a drift tube, usually about 2 m long, as shown in the equation below. All ions receive the same kinetic energy in the acceleration region, but they have different masses and thus different velocities and the time to a detector (TOF) through the drift tube is different. Thus there are:
It can be seen that lighter ions have higher velocities, while heavier ions have slower velocities. If the distance from the ion source to the detector is away from L:
The m/z value of the ion gram is determined by its arrival time at the detector.
TOF mass spectrometers have a fast scanning speed, and the time required to record a mass spectrum is measured in microseconds. This instrument has a wide mass range and can determine ions above m/z 10000.
Advantages of using time-of-flight mass spectrometer
a. Time-of-flight mass spectrometer is a very commonly used mass spectrometer. The mass analyzer of this TOF mass spectrometer is an ion shift pipe. The ions generated by the ion source are accelerated into the field-free drift tube and fly at a constant speed to the ion receiver.
b. The larger the ion mass of TOFMS, the longer the time taken to reach the receiver, and the smaller the ion mass, the shorter the time taken to reach the receiver. According to this principle, ions of different masses can be separated according to the size of their m/z values.
c. The time mass spectrometer can detect a large range of molecular weight, fast scanning speed, and simple instrument structure. The main drawback of this time mass spectrometer is the low resolution because the ions have different initial energies when they leave in the ion source.
d. Time-of-flight mass spectrometers make a certain distribution of the time for ions with the same mass-to-charge ratio to reach the detector, causing a decrease in resolution. One of the ways to improve is to add a set of electrostatic field reflectors in front of the linear detector.
e. The time-of-flight mass spectrometer can push back the ions in free flight, the initial energy of the ions due to the initial speed, the distance into the electrostatic field mirrors is long, the return distance is also long, the initial energy of the ions returned to the short distance. This focuses the ions at a certain location on the return journey, thus improving the resolving power of the mass spectrometer instrument. This type of time-of-flight mass spectrometer with an electrostatic field reflector is known as a reflectance time-of-flight mass spectrometer.
Types of time-of-flight mass spectrometer
There are various types of time-of-flight mass spectrometers.
|TOFMS classification method||TOFMS Name
|Purpose of analysis||* Laboratory time-of-flight mass spectrometer
* Industrial time-of-flight mass spectrometer
|Analyzing the state of an object||* Time-of-flight atomic mass spectrometer
* Time-of-flight molecular mass spectrometer
|Analyzing the properties of an object||* Time-of-flight organic mass spectrometer
* Time-of-flight inorganic mass spectrometer
* Time-of-flight isotope mass spectrometer
|Usage||* Time-of-flight biological mass spectrometer
* Time-of-flight pharmaceutical mass spectrometer
* Time-of-flight chemical mass spectrometer
* Time-of-flight food mass spectrometer
* Time-of-flight medical mass spectrometer
* Time-of-flight alcohol mass spectrometer
* Time-of-flight catalyst mass spectrometer
* Time-of-flight reagent mass spectrometer
* Time-of-flight nuclear industry mass spectrometer
Time-of-flight mass spectrometer specifications and features
Quadrupole time-of-flight mass spectrometry
|Mass number range||1~1200amu
|Ion source|| large electron emission current 300uA
|Detection sensitivity||1pg/μ OFN, S/N﹥500RMS
1. Quadrupole time-of-flight mass spectrometry
uses a four-jet modulator, which can alternate between cold focusing and hot desorption with variable modulation periods.
2. Optional consumption-free modulators or high-performance liquid nitrogen modulators are available.
3. The two columns are independently temperature-controlled, eliminating the interference of temperature during the analysis of two-dimensional columns. The modulator is located in the second-dimensional column chamber, which eliminates the interference of the modulation temperature switching on the peak retention time and makes the column easy to install.
4. The integrated software system allows the time-of-flight mass spectrometer to be designed for operation control, data acquisition, and data processing in a unified manner, and the instrument can be automatically tuned for vacuum protection.
Time-of-flight mass spectrometer sample pre-treatment method
Specimen type, component and sample volumeTime-of-flight mass spectrometer
is good at determining peptides and proteins, but also other biological macromolecules such as polysaccharides, nucleic acids and polymers, synthetic oligomers, and some organic substances with small relative molecular masses, e.g., C60 or C60 graft, etc. The measured sample can be single or multi-component, but the more components of the sample, the more complex the spectrum, and the more difficult the spectrum analysis; if there is mutual inhibition between the components during ionization, it is not always possible to guarantee that every component has a peak, and the sample volume for routine determination is about 1-10 picomoles/μL.Measuring the solubility of the sample
Before measuring a sample using a TOF mass spectrometer, the sample to be measured must be soluble in a suitable solvent, preferably an undissolved solid or a pure liquid. If the sample is a solution, information on the solvent, concentration, or content of the sample should be provided.Measuring sample purity
To obtain high-quality mass spectra, peptide and protein samples should be measured using time-of-flight mass spectrometry avoiding sodium chloride, calcium chloride, potassium hydrogen phosphate, trinitrotoluene, dimethyl sulfoxide, urea, glycerol, tween, sodium dodecyl sulfate, etc. If the sample under test cannot avoid the above reagents during pretreatment, the sample must be purified by dialysis and high-performance liquid chromatography Water, ammonium bicarbonate, ammonium acetate, ammonium formate, acetonitrile, and trifluoroacetic acid are suitable reagents used to purify the sample. After purification, protein samples should be lyophilized whenever possible. The salt in the specimen can be eliminated by ion exchanging.
How to maintain time-of-flight mass spectrometer?
Replace TOFMS mechanical pump pump oil
Time of flight mass spectrometer requires regular replacement of the mechanical pump pump oil, some models of time of flight mass spectrometer system prompts the replacement time will be 3000 hours, the replacement pump oil need to stop the instrument vacuum down, in order to avoid burns, need to wait for the mechanical pump down to room temperature before the replacement pump oil work.
When replacing the pump oil, place the container for collecting the pump oil under the oil release port of the mechanical pump, open the oil release port nut to discharge the pump oil cleanly, and then tighten the oil release port nut. Add the special oil for mechanical pump to the mechanical pump through the oiling port, fill the pump oil to about 80% of the pump's scale line, and tighten the oiling port.
Cleaning the TOFMS filter
The role of the filter in the TOFMS is to filter the air entering or exiting the instrument, and play the function of heat dissipation inside the instrument. If the filter is too dirty, it will make the air inside the instrument not flow smoothly, causing high temperature or bringing dust into the instrument, causing the vacuum system or circuit system to malfunction and causing harm to the high voltage power supply inside the instrument.
First, unscrew the four screws on the right side cover of the time-of-flight mass spectrometer, and then remove the right side cover. After removing the cover plate, you can see two pieces of filters, each of which is fixed by 6 fixing screws.
Cleaning the TOFMS ion source
To have good performance of TOFMS it is recommended to carry out routine cleaning of the ion source. Before carrying out ion source cleaning, it is necessary to turn off the ion source high voltage power supply, heating, and gas. Wait for the ion source temperature down to room temperature before maintenance, daily ion source maintenance using dust-free paper or dust-free cloth, and use methanol-water cleaning. (Note: Please wear gloves throughout the cleaning process)
First, loosen the two ion source fixing nuts by hand, take out the ion source from the ion source cavity, then use dust-free paper with a methanol-water solution to wipe the ion source, for safety take care not to touch the tip of the spray needle.
Continue to loosen the ion source cavity by fixing screws by hand, open the ion source cavity, use methanol-water moistened dust-free paper or dust-free cloth to wipe the ion source cavity, wipe take care not to wipe the CDL.
After cleaning the ion source and ion cavity, the ion source will be installed back into the ion source cavity, and ion source maintenance work is complete.
How to order time-of-flight mass spectrometer?
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