MASS SPECTROMETRY Flashcards
What are the 4 key stages for mass spec?
Electrospray Ionisation
Acceleration
Drift Region
Detection.
What are the methods of ionisation?
Electron Impact Ionisation
Electrospray Ionisation
What is the main difference between electrospray ionisation and electron impact?
Electrospray a proton is added
Electron impact an electron removed by impact of another electron
What is needed at the end of the tip in electrospray ionisation?
High voltage
Why is a volatile solvent used in electrospray ionisation?
To ensure that the solvent evaporates to leave positive ions
How does electron impact influence the mass of the ion?
The mass of the ion equals the mass of the initial substance
How does electrospray influence the mass of the ion?
The mass of the ion equals the mass of the initial substance plus 1
What is the purpose of acceleration?
To get all ions to the same kinetic energy
What is the equation for voltage?
v=/[(2KE)/m]
Why is the mass spec kept under vacuum?
To prevent collisions between ions and any other molecules.
What happens at the detection stage?
Positive charged ions gain an electron which generates a charge.
What governs the current size?
The abundance of ions
What is the relative atomic mass equation?
For each isotope calculate the [(m/z)x(% abundance)]/Total % Abundance
Relative Atomic Mass
Weighted average mass of all the isotopes/ 1/12th mass of one atom of C-12
Relative Molecular Mass
The ratio of the average mass of one molecule of an element or compound to one twelfth of the mass of an atom of carbon-12
