Atomic Spectrsocopy

Question 1

Methods of atomic spectroscopy

Answer 1

• flame photometry - AES
• Atomic absorption - AAS
• Atomic fluorescence
• inductively couple plasma

Question 2

principle in atomic spectroscopy

Answer 2

• these method deal specifically with atoms and not molecules
• used for determination of the concentration of particular metal elements within a sample
• capable of analysing up to 72 different elements in solution

Question 3

the transition of atoms between their electronic fundamental and excited states, occur either by the effect of…

Answer 3

the heat of the flame–> atomic emission spectroscopy -AES

an excitation light –> atomic absorption spectroscopy - AAS

laser excitation –> atomic fluorescent spectroscopy - AFS

argon torch –> inductively coupled plasma - ICP

Question 4

principle of the techniques

Answer 4

atom in flame- atomic emission signal- monochromator- detector

hollow cathode lamp- atomic absorption signal- monochromator- detector

laser- atomic fluorescence signal- monochromator- detector

Question 5

principle- the electronic transitions

Answer 5

look at diagram on powerpoint

Question 6

energy levels

Answer 6

• energy level diagram for magnesium (see powerpoint)
• wavelengths are given by the figures (2000-3000)
• atomic orbitals are labelled by 3s, 3d…
• electronic transition are represented by the lines between orbitals
• 1 Ǻ = 10-10 m = 0.1 nm

Question 7

sample preparation and analysis- turning the liquid sample into an atomic gas

Answer 7

The flame- the sample is aspired into the flame (T= 1500 -300 C)

Desolvation- the liquid solvent is evaporated, and the dry sample remains in the flame

Vaporisation- The solid sample vaporises to a gas

Atomisation- the compounds making up the sample are broken into free atoms

Question 8

sample prep and analysis- detection and quantification

Answer 8

Analysis- the flame is the sample holder (as the cuvette is for UV) allowing the analysis to take place. The signal received from the ions allows the quantification.

Question 9

the burner

Answer 9

• Nebulizer : liquid breaks into fine mist
• Glass bead : spray is directed at high speed against glass beads, upon which the droplets break into even smaller particles, ie, nebulization.
• Aerosol : a fine suspension of liquid (or solid) particles in a gas
• Fuel : usually acetylene (2400-2700 K)
• Oxidant : usually air

The mist, fuel and oxidant flow past
baffles that promote further mixing
and block large droplets of liquid.
Excess liquid flows out to a drain

(look on ppt for diagram of the burner)