Why Do Tof Mass Spectrometers Have Unlimited m/z Range?

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In summary: I would say that ion trap has a better range as it can measure up to 6000 m/z values. However, ion trap is more sensitive to atmospheric contamination and is more expensive.
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gravenewworld
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Why is it that time of flight mass spectrometers have basically an unlimited range of m/z values that they can analyze? I have looked, but can not find a definitive answer.
 
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  • #2
Maybe this can be moved to a physics or engineering forum since it seems we don't have any analytical chemists?
 
  • #3
This looks suspiciously like homework. Maybe it is, and maybe it isn't. If it is, we do want to see you take a stab at it. If it isn't, I, at least, still want you to take a stab at it.

What are the relationships between mass and instrument output signals for TOF and other types of mass spectrometry?
 
  • #4
Homework no, curiosity yes. If this were homework it probably would have been overdue by now. What I do know about mass spec

-m/z range <2000 for quadrapole mass detector
-m/z range for quad. ion-trap is <6000

I know m/z for TOF can be calculated by t^2/(d^2/2Ve)
 
  • #5
Mass is proportional to "time of flight" squared. Compared to "mass is proportional to the inverse of the accelerating potential" for a Dempster type mass spec, do you see any advantages when you consider the resolutions and uncertainties in measurements of time and electric potential?
 
  • #6
Ah why didn't this hit me over the head before? You only have to measure the time it takes for a substance to travel a fixed distance with fixed potential. Then you can simply find m.

Dempster type mass spec

I am not familiar with this type of mass spec.

BTW, the reason I asked this question is because we have TOF mass specs at the pharm company where I work (I do medicinal chem). I just always wondered how they worked. I assume they use them to measure proteins etc. since they usually have large mws.
 
  • #7
"Dempster" is the beast that bends flight paths through a magnetic field.
 
  • #8
Why is it that time of flight mass spectrometers have basically an unlimited range of m/z values that they can analyze? I have looked, but can not find a definitive answer.
certainly not the best of the mass spectrometers in relevance to precision and accuracy;currently on a lab session based of TOF, it's not the most convenient instrument to use of the mass spectrometers.
 

1. Why do TOF mass spectrometers have unlimited m/z range?

TOF (time-of-flight) mass spectrometers have unlimited m/z (mass-to-charge) range because they use a pulsed ionization method. This means that the ions are accelerated by an electric field and then allowed to travel a certain distance before being detected. The time it takes for the ions to reach the detector is directly proportional to their m/z ratio. This allows for a wider range of m/z values to be detected compared to other mass spectrometry methods.

2. What is the advantage of having an unlimited m/z range in TOF mass spectrometry?

The advantage of having an unlimited m/z range in TOF mass spectrometry is that it allows for the detection of both low and high mass ions in the same experiment. This means that a wider range of molecules can be analyzed, making it a versatile tool for various research applications.

3. Are there any limitations to the unlimited m/z range of TOF mass spectrometers?

While TOF mass spectrometers have a wider range compared to other mass spectrometry methods, they still have limitations. For example, they may have lower sensitivity and resolution for higher m/z values compared to other methods such as quadrupole mass spectrometry. Additionally, the accuracy of the m/z values may decrease at higher ranges.

4. How is the unlimited m/z range of TOF mass spectrometers achieved?

The unlimited m/z range of TOF mass spectrometers is achieved by using a reflectron, which is a curved electric field that reflects the ions back towards the detector. This allows for longer flight times and thus, a wider range of m/z values to be detected.

5. Can the m/z range of TOF mass spectrometers be adjusted?

Yes, the m/z range of TOF mass spectrometers can be adjusted by changing the strength of the electric field used to accelerate the ions. This can be useful for targeting specific m/z ranges in an experiment or for optimizing the instrument's performance for different types of samples.

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