Ion cyclotron resonance: An 16O2 + ion circulates at 500. MHz in an ICR cell.
science
Description
Due Friday March 13, in class. ,Please show details of all calculations and justify your answers.
1) Ion cyclotron resonance: An 16O2 + ion circulates at 500. MHz in an ICR cell.
i) What would the cyclotron frequency be for a 14N2 + ion in this same cell under the same conditions, in MHz? Please use integer atomic weights as indicated. (Hint: take ratios of expressions for the cyclotron frequency, cancel like terms and rearrange.)
ii) What would the m/z ratio be for a singly charged ion that is circulating at one half the frequency of 16O2 + ?
iii) What would the cyclotron frequency be for a doubly charged ion, O2 2+?
iv) Suppose you were collecting data over a 0.2 second sampling interval, and your resolution were 10,000. How long would your data sampling interval need to be to increase the resolution to 25,000?
2) The Orbitrap: Two ions of mass 200.0 and 200.1 u are injected into an orbitrap from a 1.5 kV source. The orbitrap spindle electrode’s final voltage is 2.5 kV with respect to the grounded barrel electrodes. (i) What are the axial frequencies in Hz for each ion? (ii) What is the percent relative difference between these two values? (Since there is no “true” value, use the average of the two values as the denominator)
3) TICs and RICs: Use the data in the spreadsheet provided to (i) construct a total ion
chromatogram from the GC-MS data therein, and (ii) construct RICs for the all ions. (iii)
Determine which of these m/z value ions are fragments from the same source ion, and
justify your answer. (Hint: Use the histogram plotting approach in Excel to make the
TICs and RICs.
This assignment is the intellectual property of Prof. J.M. Parnis of Trent University,
Peterborough, Canada. Any unauthorized reproduction for any use other than personal
study by students in CHEM 4400H at Trent University is strictly prohibited. © 2020
J.M.Parnis
