Chapter 20 - Atomic Spectroscopy

Question 1

is an elemental analysis technique

- Used to identify and quantify the elements present in a sample

Answer 1

Atomic Absorption (AA)

Question 2

What are three reasons why atomic absorption is good?

how meany element measures
what samples its good with
sensitivity

Answer 2

1. used for more than 70 elements even multiple at once
2. good with samples that have complex matrix
3. Great sensitivity - measure low as ppm or parts per trillion

Question 3

Atomic absorption is very similar to UV-Vis except that

Answer 3

needs to be vaporized first

Question 4

The Basics:

Samples are _____ and _______ into atoms

Concentrations of atoms in the vapor are measured by _______ or _______

Three main types:

Answer 4

vaporized, decomposed

emission, absorption

1. atomic emission
2. atomic absorption
3. atomic fluorescence

Question 5

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

Answer 5

flame

excites, excites electron

emit, return

proportional

no lamp needed

Question 6

Atomic Absorption:

Sample sucked into _____

A lamp _____ lights through the _____

The detector determines ……….

_______ is measured

Answer 6

flame

emits, flame

how much light is transmitted

absorption

Question 7

Atomic Fluorescence:

Sample sucked into _____

A laser ______ the sample through the flame

Atoms are _____ and then _____

The detector measures the

Answer 7

flame

irradiates

excites, fluoresce

fluooresence

Question 8

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.

Answer 8

Molecular

Atomic

Question 9

Atomization:

What are the three ways to achieve atomization

Answer 9

flame
furnace
plasma

Question 10

Atomization - Flame: FLAME AA (FAAS)

1. what type of burner is used?
2. ______ everything ______ introduction to the flame
   a. f___
   b. o____
   c. s_____
3. flame is typically around ______ - _______ K

Answer 10

premix burner

mixes, before

a. fuel (acetylene)
b. oxidant
c. sample

2,000 -3,000K

Question 11

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

Answer 11

nebulizer

nebulization

5

Question 12

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 ______

Answer 12

burner

path length
- 10

measured, subtratcted

Question 13

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

Answer 13

graphite, sensitive

less

solid

hollow-cathode, graphite

Question 14

Atomization - Furnace: Occur in four steps

1. An electrical current is passed through the tube raising the temperature to around 800ºC.
2. The electrical current is increased, rapidly raise the temperature to between 1200-1400ºC.
3. The electrical current in increased again to increase the temperature to above 2000ºC.
   Results in a plume of gaseous atoms.
4. After absorbance is read the current is increased again raising the temperature to over 3000ºC.
   The residual sample matrix is “cleaned” from the furnace.

Answer 14

1. Drying
2. Ashing
3. Atomization
4. Conditioning

Question 15

Atomization - Plasma:

consists of matter in a highly energized state

plasma reaches a _____ temperature than flame or furnace
_____ to ____ K

Answer 15

plasma

higher
- 6,000 to 10,000

Question 16

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.

Answer 16

Argon

metal oil

ionize

accelerated

high temperature

Question 17

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.

Answer 17

torch, center tube

cooling

12 liters