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Time-of-Flight Mass Spectrometry Calculator

Calculate ion flight times, flight distance, kinetic energy and atomic or isotopic mass. The calculator also compares the flight times of different isotopes under the same conditions.

What the calculator does

  • Uses the full time-of-flight equation.
  • Converts atomic or isotopic mass in g mol−1 into the mass of one ion in kg.
  • Accepts flight time and kinetic energy directly in standard form.
  • Calculates flight time, distance, mass or kinetic energy.
  • Compares the flight times of two isotopes.
  • Displays each stage of the calculation so the working can be checked.

The main equation

t2 / d2 = m / 2KE

Here, t is the flight time, d is the flight distance, m is the mass of one ion in kg and KE is its kinetic energy.

Open the calculator

Choose the full TOF equation or compare the flight times of two isotopes.

Launch TOF Mass Spectrometry Calculator

The calculator opens in a new browser tab.

Using the Time-of-Flight Calculator

Select the appropriate calculation route and enter the quantities supplied in the question.

1. Choose the calculation route

The calculator provides two routes:

  • Full TOF equation — calculate flight time, distance, atomic or isotopic mass, or kinetic energy.
  • Compare isotopes — calculate the flight time or mass number of a second isotope.

2. Using the full TOF equation

t2 / d2 = m / 2KE

Select the quantity you want to calculate and enter the other three quantities.

Enter the atomic or isotopic mass, M, in g mol−1. The calculator obtains the mass of one ion from:

m = M / 1000L

where L is the Avogadro constant. The factor of 1000 converts grams into kilograms.

3. Entering numbers in standard form

Flight time and kinetic energy are entered using three boxes:

  • the first part of the number;
  • the sign of the power;
  • the index or power of ten.

For example:

3.56   |   −   |   26  =  3.56 × 10−26

Flight-time answers are given in seconds in standard form.

4. Comparing isotope flight times

For two isotopes travelling under the same conditions:

ta / √a = tb / √b

To calculate the flight time of isotope b, the calculator uses:

tb = ta√(b / a)

Enter the known flight time in seconds using standard form. The calculated flight time is also displayed in seconds in standard form.

5. Check the displayed working

The calculator shows the rearranged equation, unit conversions, substituted values and final result. Use these stages to check the calculation and identify any incorrect entry.

Important: the isotope comparison assumes that the ions have the same charge, travel the same distance and have the same kinetic energy. The isotope mass numbers are used as close approximations to their isotopic masses.
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