Emission Spectroscopy Based upon Plasma, Arc, and Spark Atomization
Arc
Flame
Higher Temperature Lower interelement interference Single set of excitation conditions can excite multiple elements Permit low detection limits for refractory complexes Larger linear range Can directly measure hard to measure samples
Simpler, less expensive instrumentation Lower operating costs Greater reproducibility
Emission Spectroscopies Cont.
Plasma (def.) Electrically conducting gaseous mixture containing significant concentrations of cations and electrons
I and D
Inductively Coupled Plasma
Inductively coupled means that the plasma is generated due to differences in the magnetic field and currents Temp. very hot (40008000K) Good & bad
Direct Current Plasma (D)
Plasma forms by bringing graphite and W electrodes in with one another Temp @ core 10,000K in viewing region 5000K
I D Comparison
D is an order of magnitude less sensitive than I Similar reproducibilities D requires less Ar
Auxillary power less expensive in D Graphite electrode must be replaced every couple of hours
Comparison of Plasma to Flame Emission Sources
Plasma sources offer significantly better quantitative data than do other flame emission sources - High stability - Low noise - Low background - Freedom from interferences
Comparison between Atomic Absorption & Emission Techniques Instruments
Operator Skill Bkgd.Correction Prec. & Accuracy
Interferences
Detection limit
AAS
AES
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Comparison between Atomic Absorption & Emission Techniques AAS
AES
Instruments
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Operator Skill
Lower skill
Higher skill
Bkgd.Correction Prec. & Accuracy
Interferences
Detection limit
Comparison between Atomic Absorption & Emission Techniques AAS
AES
Instruments
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Operator Skill
Lower skill
Higher skill
Bkgd.Correction Harder to do Prec. & Accuracy
Interferences
Detection limit
Easier to do
Comparison between Atomic Absorption & Emission Techniques AAS
AES
Instruments
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Operator Skill
Lower skill
Higher skill
Bkgd.Correction Harder to do
Easier to do
Prec. & Accuracy
Unskilled worse
Interferences Detection limit
Unskilled better Same for skilled
Comparison between Atomic Absorption & Emission Techniques AAS
AES
Instruments
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Operator Skill
Lower skill
Higher skill
Bkgd.Correction Harder to do
Easier to do
Prec. & Accuracy
Unskilled better Same for skilled
Unskilled worse
Interferences
Spectral interferences corrected Chemical interferences in AES on AE (flame) bad, plasma eliminated
Detection limit
Comparison between Atomic Absorption & Emission Techniques AAS
AES
Instruments
Requires HC lamp for each element No high quality MC required
Flame/ sample is source Requires high quality MC
Operator Skill
Lower skill
Higher skill
Bkgd.Correction Harder to do
Easier to do
Prec. & Accuracy
Unskilled better Same for skilled
Unskilled worse
Interferences
Spectral interferences corrected Chemical interferences in AES on AE (flame) bad, plasma eliminated
Detection limit Flame some metals better on AA than AES
Plasma comparable to flame for some metals, other metals plasma better
Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Dynamic range
limited
wide
Wide
Qualitative analysis Elemental range
Trace analysis
limited
wide
Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Dynamic range
limited
limited
wide
wide
Wide
Qualitative analysis
poor
poor
excellent excellent excellent
Elemental range
Trace analysis
Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Dynamic range
limited
limited
wide
wide
Wide
Qualitative analysis
poor
poor
excellent excellent excellent
Elemental range
excellent excellent
Trace analysis
excellent excellent excellent
Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Dynamic range
limited
limited
wide
wide
Wide
Qualitative analysis
poor
poor
excellent excellent excellent
Elemental range
excellent excellent
excellent excellent excellent
Trace analysis
excellent excellent
excellent excellent excellent
Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Dynamic range
limited
limited
wide
wide
Wide
Qualitative analysis
poor
poor
excellent excellent excellent
Elemental range
excellent excellent
excellent excellent excellent
Trace analysis
excellent excellent
excellent excellent excellent
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Matrix interfernces
high
low
low
Spectral Interferences Precision & Accuracy Costs
high
high
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Matrix interfernces
high
high
high
low
low
Spectral low Interferences
low
low
moderate high
Precision & Accuracy Costs
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Matrix interfernces
high
high
high
low
low
Spectral low Interferences
low
low
moderate high
Precision & Accuracy
Costs
Better for unskilled Same skilled
Worse for unskilled same skilled
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Matrix interfernces
high
high
high
low
low
Spectral low Interferences
low
low
moderate high
Precision & Accuracy
Better for unskilled Same skilled
Costs
$$
Worse for unskilled same skilled $$$
$
$$$
$$$$
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
low
moderate high
Costs Instrumentat low ion Maintenance Sample Preparation Operator skill
low
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Instrumentat low ion
low
low
moderate high
Maintenance low
low
low
moderate high
Costs
Sample Preparation Operator skill
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Instrumentat low ion
low
low
moderate high
Maintenance low
low
low
moderate high
low
moderate moderate
Costs
Sample Preparation Operator skill
moderate moderate
Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA
Electrothermal Flame Sampling AES
D
I
Instrumentat low ion
low
low
moderate high
Maintenance low
low
low
moderate high
Costs
Sample Preparation
moderate moderate
low
moderate moderate
Operator skill
lower
higher
higher
higher
higher