Chapter 10 – Atomic Emission Spectroscopy

Thermal excitation Radiative decay to lower energy level Emission signal ______________________________ to concentration. Holy Grail of Atomic Spectroscopy: Excitation Source The atoms are excited by energy provided by the source. A _____________ can excite only a few atoms, e.g. alkali metals Other atoms (especially non-metals) need much higher energy - ________________ If you only have a flame instrument, you can use _________ for __________________________ - otherwise you should use _______________ to achieve good detection limits. Plasma: ________________________ that is electrically neutral Very high ________________________________ Contains ions, electrons, neutral atoms & molecules

DC Arc

4000-5000 K

HV Spark

40,000

Direct Current Plasma

6000-10,000

Inductively Coupled Plasma (ICP)

6000-8000

Microwave Induced Plasma (MIP) electrodeless

5000-7000

Capacitively Coupled Microwave Plasma (CMP) electrode

5000-7000

ICP Torch Characteristics of ICP AES Sufficient energy to excite __________________ Capable of doing solids, liquids, or gases -sample introduction via ____________________________________ Tolerant to variety of ___________________________________ Simultaneous ___________________________________ Large ________________________________ Low ________________________

Advantages Analysis of solutions or dissolved solids Detection limits in the _________________________ range Multielement analysis: Determine up to _______ elements in ________minutes per sample Disadvantages ionization leads to _____________________ need _______________________ monochromator expensive

An internal standard is used to compensate for various __________________ (and even ____________________) errors.

A big random error in plasma emission spectroscopy is power/intensity ___________________ of the plasma.

Internal standard must be something _______________ in your standards or sample (in this example, Y) The signal plotted is the ratio: Homework (6th ed.): 1, 2, 6, 9, 10, 11, plus problem on the next page.

Concentration Emission signal

Cu (ppm) Pb Cu 0.500 8.3 40.67 1.00 7.7 161.7 5.00 10.1 303 10.0 8.1 388.8 30.0 7.6 1026 50.0 9.2 2051.6 75.0 8.5 2609.5 100.0 7.2 3240

unknown 7.4 774

A series of copper standards were made up, each containing 1.00 ppm Pb as an internal standard (IS). An unknown copper solution was also spiked to contain 1.00 ppm Pb. The standards and unknowns were analyzed using ICP-AES. The data is in the table above.

1. Construct a calculation curve for the data of y = ratio of analyte signal/ IS signal, x = analyte concentration. Use Excel to get the line equation.

2. Use the line equation to calculate the amount of copper in the unknown sample.