Emission Spectroscopy Based upon Plasma Arc and Spark

Emission Spectroscopy Based upon Plasma, Arc, and Spark Atomization n Arc n 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 n n n Flame n Simpler, less expensive instrumentation Lower operating costs Greater reproducibility n n

Emission Spectroscopies Cont. n Plasma (def. ) Electrically conducting gaseous mixture containing significant concentrations of cations and electrons n ICP and DCP

Inductively Coupled Plasma n n Inductively coupled means that the plasma is generated due to differences in the magnetic field and currents Temp. very hot (40008000 K) u Good & bad

Direct Current Plasma (DCP) n n Plasma forms by bringing graphite and W electrodes in contact with one another Temp @ core 10, 000 K in viewing region 5000 K

ICP DCP Comparison n DCP is an order of magnitude less sensitive than ICP Similar reproducibilities DCP requires less Ar n n Auxillary power less expensive in DCP Graphite electrode must be replaced every couple of hours

Comparison of Plasma to Flame Emission Sources n 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 DCP ICP 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 DCP ICP Dynamic range limited wide Wide Qualitative analysis poor excellent Elemental range Trace analysis

Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Dynamic range limited wide Wide Qualitative analysis poor excellent Elemental range excellent Trace analysis excellent

Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Dynamic range limited wide Wide Qualitative analysis poor excellent Elemental range excellent excellent Trace analysis excellent excellent

Comparison of Metal Spectroscopic Techniques Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Dynamic range limited wide Wide Qualitative analysis poor excellent Elemental range excellent excellent Trace analysis excellent excellent

Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Matrix interfernces high low Spectral Interferences Precision & Accuracy Costs high

Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Matrix interfernces high low Spectral low Interferences low moderate high Precision & Accuracy Costs

Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP ICP Matrix interfernces high low Spectral low Interferences 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 DCP ICP Matrix interfernces high low Spectral low Interferences 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 DCP ICP 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 DCP Instrumentat low ion low moderate high Maintenance low low moderate high Costs Sample Preparation Operator skill

Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP Instrumentat low ion low moderate high Maintenance low low moderate high low moderate Costs Sample Preparation Operator skill moderate

Comparison of Metal Spectroscopic Techniques continued Performance Flame Criteria AA Electrothermal Flame Sampling AES DCP Instrumentat low ion low moderate high Maintenance low low moderate high Costs Sample Preparation moderate low moderate Operator skill lower higher