1. Atomic Emission - AES M* → M + hn Thermal excitation M → M*
Radiative decay to lower energy level
M* → M + hn
Emission signal directly proportional to concentration

2. Holy Grail of Atomic Spectroscopy
For one sample:
The ability to measure all elements at all ranges of concentration at one time.

3. Excitation Source
The atoms are excited by energy provided by the source.
The energy created by a flame can excite only a few atoms, e.g. alkali metals
Other atoms (especially non-metals) need much higher energy - plasma
If you only have a flame instrument, you can use AES for alkali metals (and a few others), otherwise you should use AAS to achieve good detection limits.

4. Types of high energy analytical plasmas
DC Arc K
HV Spark
40,000
Direct Current Plasma
,000
Inductively Coupled Plasma (ICP)
Microwave Induced Plasma (MIP) electrodeless
Capacitively Coupled Microwave Plasma (CMP) electrode

5. Plasmas Ionized gas that is electrically neutral
Very high temperature and energy
Contains ions, electrons, neutral atoms & molecules

6. Inductively Coupled Plasmas
Ionized Ar flow, sustained in a torch by the RF field generated by induction coils.
Up to 20 mL/min Ar flow
Annual cost of several thousand dollars
The sample is nebulized and entrained in the flow of plasma support gas, which is typically Ar. The plasma torch consists of concentric quartz tubes, with the inner tube containing the sample aerosol and Ar support gas and the outer tube containing an Ar gas flow to cool the tubes (see schematic). A radiofrequency (RF) generator (typically MHz or 41 MHz) produces an oscillating current in an induction coil that wraps around the tubes. The induction coil creates an oscillating magnetic field, which produces an oscillating magnetic field. The magnetic field in turn sets up an oscillating current in the ions and electrons of the support gas. These ions and electrons transfer energy to other atoms in the support gas by collisions to create a very high temperature plasma.

7. Characteristics of Plasma AES
Sufficient energy to excite all elements
Capable of doing solids, liquids, or gases
-sample introduction via nebulizer, ETV, laser ablation, others
Tolerant to variety of solvents and solutions
Simultaneous multielement analysis
Large Linear Dynamic Range (LDR)
Low LOD

8. ICP-AES spectrum

9. ICP AES Calibration Curve
If you can interpret your spectrum, you can get great quantitative results.
Calibration curve is plotted as log/log, because the LDR spans several orders of magnitude.

10. Internal Standard
An internal standard is used to compensate for various random (and even systematic) errors.
A big random error in plasma emission spectroscopy is power/intensity fluctuations of the plasma.
Reasoning: fluctuations effect on analyte will be the same as the effect on the internal standard.

11. Quantitative Analysis - Calibration with Internal Standard
Internal standard must be something not present in your standards or sample
(in this example, Y)
The signal plotted is the ratio:
Intensity ratio = Analyte signal
Yttrium signal

12. Homework problem log-log plot linear-linear plot
When your LDR spans more than 2 orders of magnitude, it can be helpful to do a log-log plot so you can see your data points better.

13. ICP Disadvantages ionization leads to complex spectra
need high resolution monochromator
Expensive
Plasma source leads to messy background - fluctuations
Advantages
Analysis of solutions or dissolved solids
LDR spans several orders of magnitude
Detection limits in the parts per billion range
Multielement analysis: Determine up to 70 elements in two minutes per sample