1.3

Question 1

Mass spectrometry?

Answer 1

1) take a sample of the element
2)place it in the sample chamber
3)atoms then go through ionization
4) converts all the atoms into positive ions
5) positive atoms are now attracted to a negatively charged plate
6)negative charge causes ions to accelerate
7)increase the kinetic energy of the ions
8)all ions w the same charge have the same kinetic energy
9)when ions pass through the negative plate they stop accelerating
10) and they drift down the chamber towards the detector
11) ions drift down at different velocities
12)lighter ions move faster than heavier ions
13)once they reach the detector each positive ion gains electrons from the detector
14)trasnfer of electrons causes a current to flow

Question 2

How to determine the mass of the isotope?

Answer 2

By recording the time taken to move down the drift chamber

Question 3

How to determine the abundance of the isotope?

Answer 3

By recording the size of the current produced when each isotope hits the detector

Question 4

Explain electron impact

Answer 4

1)sample is vaporised
2)injected at low pressure.
3)Electron gun fires high energy electrons at the sample
4)the outer electron is removed forming positive ions.

Question 5

Explain electrospray ionisation

Answer 5

1)the sample is dissolved in volatile polar solvent
2)and is injected through a needle.
3)Due to the presence of high voltage at the needle, the molecule (M) gains a proton (H+) from the solvent.
4)The solvent evaporates and the positively charged (MH+) ions are then attracted towards the negative plate.

Question 6

What is electro spray ionsiation for

Answer 6

Electrospray injection is used for ionising larger organic molecules as the electron impact process may result in its fragmentation.

Question 7

What is electron impact process for

Answer 7

This method is used to ionise elements and substances with low formula
mass

Question 8

Why is the spectrometer under high vacuum conditions

Answer 8

To prevent the ions that are produced colliding with molecules from the air

Question 9

How to calculate RAM from mass spectrometer

Answer 9

1. Multiply the m/z value by the relative abundance % for each peak
2. Add results for each peak together
3. Divide by total relative abundance