What are the application areas of time of flight mass spectrometry

Time-of-flight mass spectrometer.

As a high-resolution mass spectrometry, it is mainly used for qualitative analysis, it has high resolution and accurate mass. It can be applied to drug research, metabolite identification, proteomics.

and metabolomics research, food safety.

Forensics, toxicology, and environmental screening.

Principle: After the charged ions are accelerated by the electric field, no electric field enters the time of flight. Due to the different mass-to-charge ratios, the magnitude of the received electric field force is different, and the flight time is also different.

Depending on the arrival time of the detector, different ions can be distinguished. The longer the flight distance, the better the resolution of the instrument. Now the mainstream is reflection time-of-flight mass spectrometry, which is to make ions fly at a certain distance under the action of a reflective field, and then turn around and fly back.

This can improve the performance of the instrument without increasing the volume of the instrument.

Principle: Charged ions enter a fieldless flight zone after the electric field accelerates. Due to the different mass-to-charge ratios, the magnitude of the received electric field force is different, and the flight time is also different.

Different ions can be distinguished based on the time they reach the detector. The longer the flight time distance, the better the resolution of the instrument. The mainstream is reflection time-of-flight mass spectrometry, which allows ions to fly a certain distance under the action of a reflective field, and then turn around and fly back.

This can improve instrument performance without increasing the volume of the instrument.

Principle: Charged ions enter a fieldless escape zone after the electric field accelerates. Due to the different mass-to-charge ratios, the magnitude of the received electric field force is different, and the flight time is also different.

Different ions can be distinguished based on the time they reach the detector. The longer the flight time distance, the better the resolution of the instrument. The most popular is reflected time-of-flight mass spectrometry, which causes ions to fly, flip, and fly back a certain distance under the action of a reflective field.

This can improve instrument performance without increasing the volume of the instrument.

Principle: After the charged ions enter the fieldless flight area after the action of accelerating the electric field, due to the different mass-to-charge ratios, the magnitude of the electric field force is different, the flight time is different, and different ions are resolved according to the time of reaching the detector. The longer the flight time distance, the better the resolution of the instrument, and now the mainstream is the reflection time-of-flight mass spectrometry, which is to let the ions fly a certain distance under the action of the reflected field, turn around and fly back, so that the performance of the instrument can be improved without increasing the volume of the instrument.

The time-of-flight mass spectrometer can detect a wide range of molecular weights, fast scanning speed, and simple instrument structure. The main disadvantage of this time-of-flight mass spectrometer is its low resolution, because the initial energy of the ions as they leave the ion source is different, so that the ions with the same mass-to-charge ratio reach the detector at a certain distribution in time, resulting in a decrease in resolution. One of the improved methods is to add a set of electrostatic field mirrors in front of the ** sex detector to push back the ions in free flight, the ions with large initial energy due to the fast initial speed, the distance to enter the electrostatic field mirror is long, and the distance when returning is long, and the distance of the ions with small initial energy is short, so that it will be focused at a certain position of the return distance, thereby improving the resolving ability of the instrument.

This time-of-flight mass spectrometer with an electrostatic field mirror is called a reflectron time-of-flight mass spectrometer.

Because ATOFMS can identify the specific compounds that make up particulate matter, it can provide new insights into the dynamic chemical processes between particles and surrounding gases and other particulate matter. Real-time chemical composition analysis can eliminate the problems inherent in traditional membrane or collider aerosol sampling methods, such as secondary chemical reactions or loss of semi-volatile compounds. Applications for the 3800-ATOFMS include:

Aerosol analysis studies.

Characterization of atmospheric particles, identification of emission sources.

Semiconductor processing processes.

Indoor air quality monitoring.

Aerosol drug release studies.

Inhalation toxicology studies.

Drug-fortified sample analysis.

Chemical and biological aerosol testing.

Engine emissions measurements.

powder production quality and process control, etc.

Time of Flight Mass Spectrometer (TOF) is a very commonly used mass spectrometer. The mass analyzer of this mass spectrometer is an ion drift tube. The ions produced by the ion source are collected first.

In the collector, the velocity of all ions becomes 0. It is accelerated using a pulsed electric field into a fieldless drift tube and flies towards the ion receiver at a constant speed.

The charged particles are accelerated by an electric field and then fed into an analyzer, which consists of a long, straight vacuum flight tube. (07 Chongqing) during flight, the homogeneous spectrometer can obtain the charge-to-mass ratio q m of ions by measuring the flight time of ions. As shown in Figure 1, the positively charged ions are accelerated by the electric field with voltage U and enter the vacuum tube AB with length L, and the time taken by ions to fly over AB L1 can be measured Improve the above method, as shown in Figure 2, let the ions fly through AB and enter the uniform electric field region BC with a field strength of E (direction as shown in the figure), and the ions return to the B terminal under the action of the electric field, at this time, the total time of the ions flying from A is measured T2, (excluding ion gravity).

1) ignore the initial velocity of the ions in the ion source and calculate the charge-to-mass ratio with t1; The charge-to-mass ratio is calculated using t2.

2) The initial velocities of ions with the same charge-to-mass ratio in the ion source are not the same, and if the velocities of two ions with a charge-to-mass ratio of q m are v and v (v≠v), respectively, the total time of their flight is usually different in the improved method, and there is a time difference δt. The magnitude of e can be found by adjusting the electric field e so that δt=0.

Solution: (1) Let the charge of the ion be q, the mass be m, and the velocity after acceleration by the electric field is v.

Ions fly over the vacuum tube AB to do a uniform linear motion, then.

The ion specific charge is obtained from (1) and (2).

The ions move back and forth in the region of a uniform electric field BC, and the acceleration is A, then.

l2= （5）

The ion-charge-mass ratio is obtained from equations (1), (4), and (5).

or (6)2) the initial velocities of the two ions are v and v respectively, then.

t=t-t′= （9）

To make δt=0, (10) is required

So e= (11) The time-of-flight mass spectrometer can analyze the gas molecules. As shown in the figure, in the vacuum state, the pulse valve P emits a trace amount of gas, which produces positive ions at different valences through laser irradiation, which enters the accelerated electric field between A and B from the small hole of plate A, and is shot out from the small hole of plate B, and enters the deflection control area between plate M and N along the midline direction to reach the detector. It is known that the charge of the element is E, the spacing between plates A and B is D, and the length and spacing of plates M and N are L.

Ion gravity and initial velocity when entering plate A are not taken into account.

1) When the voltage between A and B is U1, add the appropriate voltage U2 between M and N to make the ions reach the detector. Derive the relation between the total flight time of the ion and the specific charge k().

2) Remove the deflection voltage U2, add a uniform magnetic field perpendicular to the paper surface in the area between m and n, the magnetic induction intensity B, if the mass of all ions between A and B is m, to make all the ions fly out from the right side through the control area, what is the acceleration voltage U1 between A and B at least?

1) By the kinetic energy theorem:

Acceleration of n-valent cations between a and b:

2) Assuming that the n-valent positive ions are deflected towards the n-plate in the magnetic field, the Lorentz force acts as a centripetal force, and the radius of the trajectory is r, which is determined by Newton's second law.

When the ions just pass through the right edge of the n-plate, they are determined by the geometric relationship:

From all of the above:

When n=1, u1 takes the minimum value.

Clinical metabolomics studies, proteomics studies.