is an elemental analysis technique
- Used to identify and quantify the elements present in a sample
Atomic Absorption (AA)
What are three reasons why atomic absorption is good?
how meany element measures
what samples its good with
sensitivity
- used for more than 70 elements even multiple at once
- good with samples that have complex matrix
- Great sensitivity - measure low as ppm or parts per trillion
Atomic absorption is very similar to UV-Vis except that
needs to be vaporized first
The Basics:
Samples are _____ and _______ into atoms
Concentrations of atoms in the vapor are measured by _______ or _______
Three main types:
vaporized, decomposed
emission, absorption
- atomic emission
- atomic absorption
- atomic fluorescence
Atomic Emission:
Sample is sucked into a _______
The flame _______ atoms to _____ ______ states
Then _____ photons to _________ to lower energy states
Emission intensity is ______ to the concentration
Most widely used and _____ lamp needed
flame
excites, excites electron
emit, return
proportional
no lamp needed
Atomic Absorption:
Sample sucked into _____
A lamp _____ lights through the _____
The detector determines ……….
_______ is measured
flame
emits, flame
how much light is transmitted
absorption
Atomic Fluorescence:
Sample sucked into _____
A laser ______ the sample through the flame
Atoms are _____ and then _____
The detector measures the
flame
irradiates
excites, fluoresce
fluooresence
Molecular vs Atomic:
______ transitions take into account the vibrational energy
- the transition between S0 and S1 includes a bunch of vibrational states
- gives a broad peak because of the slightly different energies
- poor resolution
________ transition are only electronic states.
- A single atom has no bonds and so no vibrational states.
- Very narrow peak with high specificity.
- Overlapping from non-analytes is extremely rare.
Molecular
Atomic
Atomization:
What are the three ways to achieve atomization
flame
furnace
plasma
Atomization - Flame: FLAME AA (FAAS)
- what type of burner is used?
- ______ everything ______ introduction to the flame
a. f___
b. o____
c. s_____ - flame is typically around ______ - _______ K
premix burner
mixes, before
a. fuel (acetylene)
b. oxidant
c. sample
2,000 -3,000K
Atomization - Flame:
Sample is drawn into the _______ by the oxidant
Liquid breaks down into fine mist (aerosol)
The spray is directed against a glass bead where droplets break down into smaller particles
Only ___ % of the initial sample becomes aerosol that reaches the flame
nebulizer
nebulization
5
Atomization - Flame:
Size of the ___ also plays a role
- its the ___ ____ of the measurement
- typically they are ___ ____
Light is ______ and the light from the flame is ______
burner
path length
- 10
measured, subtratcted
Atomization - Furnances
______ furnances are more _____ (1000x) than a flame
Requires _____ samples
Can be used for ______ samples
Light from a ________ e lamp travels through windows at each end of the ______ tube
graphite, sensitive
less
solid
hollow-cathode, graphite
Atomization - Furnace: Occur in four steps
- An electrical current is passed through the tube raising the temperature to around 800ºC.
- The electrical current is increased, rapidly raise the temperature to between 1200-1400ºC.
- The electrical current in increased again to increase the temperature to above 2000ºC.
Results in a plume of gaseous atoms. - After absorbance is read the current is increased again raising the temperature to over 3000ºC.
The residual sample matrix is “cleaned” from the furnace.
- Drying
- Ashing
- Atomization
- Conditioning
Atomization - Plasma:
consists of matter in a highly energized state
plasma reaches a _____ temperature than flame or furnace
_____ to ____ K
plasma
higher
- 6,000 to 10,000
Atomization - Plasma:
______-gas flows through concentric quartz tubes.
The top portion of the tubes are wrapped with a ______ ________.
A high-voltage is used to _______ some of the flowing argon atoms.
The ions are ________.
This creates a self-sustaining ______ _______argon plasma.
Argon
metal oil
ionize
accelerated
high temperature
Atomization - Plasma:
An aerosol mist of the analyte sample is carried into the _____ by the argon flow through the ___ _____.
The outermost sleeve is also flushed with gas.
Help with ______.
A typical torch consumes about __ _____ of high-purity argon gas per minute.
That’s a lot.
torch, center tube
cooling
12 liters
