Chapter 10 - Chapter 10 ATOMIC EMISSION SPECTROMETRY...

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Unformatted text preview: Chapter 10 ATOMIC EMISSION SPECTROMETRY Advantages emission Spectrometer over absorption methods: 1. Lower interelement interference because of higher temperature. 2. Emission spectra are obtained under a single set of excitation conditions and several elements can be recorded simultaneously. 3. Multielement can be analyzed from very small sample. 4. Low concentration refractory compounds can be determined 5. Nonmetals can also be determined by plasma sources. 6. Very high concentration range (linear range) for plasma sources. Disadvantages of emission spectrometry: 1. More expensive equipments needed. 2. Procedures are somewhat complicated than absorption method. 3. More operating cost than absorption technique. Atomic emission and absorption methods are complementary to each other. EMISSION SPECTROSCOPY BASED ON PLASMA SOURCES A plasma is an electrical conducting gaseous mixture containing a significant concentration of cations and electrons. (The concentrations of the two are such that the net charge approaches zero). In the argon plasma frequently employed for emission analyses, argon ions and electrons are the principle conducting species, although cations from the sample will also be present in lesser amounts. …Emission spectroscopy based on plasma sources continued… Argon ions, once formed in a plasma, are capable of absorbing sufficient power from an external source to maintain the temperature at a level at which further ionization sustains the plasma indefinitely; temperatures as great as 10,000 K are encountered. Three types of high- temperature plasmas are encountered: (1) the inductively coupled plasma (ICP), (2) the direct current plasma (DCP), and (3) the microwave induced plasma (MIP). The Inductively Coupled Plasma Source Fig. 10-1 is a schematic of a typical inductively coupled plasma source called a torch . It consists of three concentric quartz tubes through which streams of argon gas flow. The diameter of the largest tube is often about 2.5 cm. Surrounding the top of this tube is a water-cooled induction coil that is powered by a radio-frequency generator....
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This note was uploaded on 05/06/2010 for the course CHEM 4414 at Arkansas Tech.

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Chapter 10 - Chapter 10 ATOMIC EMISSION SPECTROMETRY...

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