1.1.4, 1.1.5: Mass Spectrometry and analysis

Question 1

Methods of ionisation

2

Answer 1

electrospray

electron impact

Question 2

Electrospray ionisation

prevents

Answer 2

gentler technique

which prevents fragmentation

Question 3

Electrospray

uses

Answer 3

polymers and biological molecules

Question 4

Electrospray

method

Answer 4

sample dissolved in a solvent and a high voltage is applied

causes a proton from solvent to attach to the sample molecules = + ions

Question 5

Electron impact ionisation

method

Answer 5

sample vaporised then hit with electrons from an electron gun
knocks electrons off the molecule
= + ions

Question 6

Electron impact ionisation

disadvantage

Answer 6

often causes sample to fragment

Question 7

Kinetic energy equation

Answer 7

Ke = 1/2 m v2

Question 8

Acceleration

Answer 8

Gives all molecules the same Ke
so speed is dependent on their mass
(lighter particles move faster and detected before heavier particles)

Question 9

Ion drift

Answer 9

Time of flight

Question 10

Time of flight equation

Answer 10

distance/velocity

Question 11

Detection

Answer 11

Ions hit a - charged plate
electrons move to plate
which causes a current = measure of molecules hitting plate
= abundance

Question 12

Analysing the spectrum

Answer 12

x axis = mass/charge ratio

y axis = % abundance

Question 13

Main peak on the spectrum

Answer 13

molecular ion peak

peak of greatest mass/charge ratio which represents the mass/charge of the molecule being analysed

Question 14

Smaller peaks on the spectrum

Answer 14

isotopes from same molecule but have different masses

Question 15

Fragmentation

Answer 15

causes smaller and significantly lighter peaks

molecule fragmenting in the spectrometer