Exam 3 Study Guide

In J.J. Thompson’s parabolic mass spectrometer, which two forces are necessary to separate ions based on mass to charge?

Define the following terms

• Atomic Mass Unit:

• Nominal Mass:

• Monoisotopic Mass:

• Average Atomic Mass:

• Average Molecular Weight:

How is resolution defined in mass spectrometry and how does that affect the ability to resolve compounds across the mass range?

Why must the MS be kept under high vacuum? How does choice of mass analyzer affect vacuum requirements?

What are the 3 fundamental steps in mass spectrometry. Given an example of each.

What are the issues with quantitation in MS? What is the “gold standard” for quantitation?

What is the role of the reagent gas in chemical ionization?

Why is electron ionization able to provide compound identification?

How do the salts/buffers affect electrospray ionization?

What is supercharging in electrospray ionization and what are the advantages?

What is the purpose of the matrix in MALDI-MS?

Describe the ionization process in MALDI-MS.

What are the advantages of MALDI-MS?

Describe the ionization process in ESI-MS.

What is adduct formation?

Why do ion traps lose linearity at high concentrations?

For the following scenarios, suggest mass analyzers that would be effective at performing the analysis.

• Measuring isotopic abundances of elements:

• Monitoring pollutants following LC/GC separations:

• Measuring all small to medium size proteins in a sample:

• Measuring small differences in very large molecules such as monoclonal antibodies:

• Measuring entire mass spectrum using intermittent ionization sources:

What are the advantages to high resolution mass spectrometry?

Why is the electron multiplier the most widely used detector in mass spectrometry?

What are the advantages of using “image current” detectors in FT-ICR-MS?

How does tandem mass spectrometry improve selectivity in quantitation?

For a triple quadrupole mass spectrometer, describe what Q1 and Q3 are doing (scanning or monitoring) for each of these types of tandem mass spectrometry techniques:

• Product Ion Spectrum:

• Precursor Ion Spectrum:

• Neutral Loss Spectrum:

• Single Reaction Monitoring:

What is the most commonly used fragmentation method in tandem mass spectrometry and how does it work?