mass spec

Sample is vaporised (g)

1. Carried out under a vacuum

Electron bombardment / electrospray ionisation

1. An electron gun fires high energy electrons at the sample, knocks an electron off leaving an X + (g)

   1. X(g) --> X+ (g) + e-

2. Sample is dissolved in a volatile solvent ( vaporises easily). Injected through a hypodermic needle to give a fine mist ( aerosol)

   1. Tip of needle is attached to a high voltage power supply - as it sprayed, sample gains H+

   2. X(g) + H+ --> XH+(g)

Acceleration area

1. +ve ions accelerates towards the negatively charged plate

   1. They accelerate until they reach the same Ke

   2. Ke = 1/2mv2  v = d/t

ION drift

1. Ions pass through the flight tube and are separated based on mass

Ion detector

1. When ions reach the detector plate they gain an e-

2. This causes a current to flow

   1. current is directionally proportional to abundance

Spectrum

1. Computer generated graph

what are the two methods of ionisation that could be used in a mass spectrometer

a. give the equation to show the formation of an ion of metal X for each method

b. describe each process

compare the speed and kinetic energy of a lithium and potassium ion in TOF mass spectrometry.

how are ions detected in a mass spectrometer

how can you determine the number of ions hitting the detector at m/z value

which of these ions will reach the detector first? 63CU+ or 65Cu+

give the equation to show the relationship between distance, time and velocity. state all units

how many peaks would you expect in the spectra of a diatomic molecule that exists as two different isotopes. Explain you answer

calculate the mass in Kg of a Ni+ ion ( Mr = 58) using avagadro’s number (6.022×10²³)

a sample of copper contains two isotopes, 63-copper and 65-copper. all the ions were accelerated to have 1.130×10^-15 J of kinetic energy and travelled through a flight tube that was 0.700m long. 63Cu+ ions took 1.749 ×10^-5s. how long would 65Cu+ ions of mass 1.079×10-25 kg take to travel along the same flight tube.

how will the mass of a species ionised by electron bombardment differ to the mass of a species ionised by electrospray \