Essentials (AS)

Question 1

Process of measurement AAS

Answer 1

(1) liquid sample drawn up capillary tube into nebulizer
(2) droplets form as liquid leaves nebulizer (nebulization)
(3) cloud of droplets leave nebulizer, hit obstruction forming smaller droplets
(4) small droplets go to burner head, hit baffle where larger droplets removed to waste
(5) fine droplets travel to burner head, mix with fuel/oxidant then enter flame
(6) solvent evaporated (desolvation), salt particles liquefied (liquefaction), then vaporized (vaporization)
(7) gas phase particles atomized (atomization) to form gaseous metal atoms
(8) ground state metal atoms absorb light, absorbance measured

Question 2

How to account for fluctuations in light source intensity (AAS)?

Answer 2

Double beam instrument (light beam split prior to flame, corrects for short-term changes in light intensity)

Question 3

How to account for strong background absorptions from polyatomic species in atomizer (AAS)?

Answer 3

Continuum-source correction
Zeeman background correction

Question 4

How does a hollow cathode lamp operate (AAS)?

Answer 4

Contains argon gas (ionized as a result of high voltage of anode/cathode)
(1) ionized Ar atoms hit surface of cathode causing sputtering of metal atoms into gas phase
(2) gaseous metal atoms collide with Ar+ or e-, exciting metal
(3) excited metal returning to ground state, releases energy as light

Question 5

When is an electrodeless discharge lamp used in (AAS)?

Answer 5

Used for volatile elements like Hg, As, Cd

Question 6

How does an electrodeless discharge lamp used operate (AAS)?

Answer 6

(1) small amount of metal or iodide salt is sealed in quartz bulb of low pressure of Ar
(2) bulb is centered inside radiofrequency coils
(3) RF field couples with metal/salt in bulb, and coupling energy causes vaporization and excitation of the metal
(4) excited metal returning to ground state, releases energy as light

Question 7

What is the process of obtaining metal atoms in GFAAS?

Answer 7

(1) drying - remove solvent
(2) pyrolyze - remove sample matrix (organics) without volatilizing sample
(3) cool
(4) atomize - produce gas phase free analyte atoms (fast)
(5) clean out - burn out residue prior to next sample
(6) cool down (before next sample)

Question 8

Advantages of GFAAS compared to FAAS

Answer 8

GFAAS has lower detection limits
GFAAS requires much smaller sample size
GFAAS can handle liquid samples as well as slurry samples and high dissolved solids

Question 9

Process of measurement AAS

Answer 9

(1) liquid sample drawn up capillary tube into nebulizer
(2) droplets form as liquid leaves nebulizer (nebulization)
(3) cloud of droplets leave nebulizer, hit obstruction forming smaller droplets
(4) small droplets go to burner head, hit baffle where larger droplets removed to waste
(5) fine droplets travel to burner head, mix with fuel/oxidant then enter flame
(6) solvent evaporated (desolvation), salt particles liquefied (liquefaction), then vaporized (vaporization)
(7) gas phase particles atomized (atomization) to form gaseous metal atoms
(8) Flame has enough energy to excite metal atoms (excitation)
(9) excited metal returning to ground state, releases energy as light