[Homer Jay]

Hello,

is there any interaction between the plasma and the analyt?

If one could reach the same temperatures with another technique, would the same spectra result?

The use of the term ICP-AES is depreciated, because the spectra result from ionization and not atomization. Is the explanation that electrons are in an excited state and fall back to ground state and that's why energy is emitted correct for atoms AND ions?

Thanks in advance,

Homer Jay

[ARGOS++]

Dear Homer Jay;

There should not be any other interaction as I know, because the Degree of Ionisation of the Analyte is handled nearly by everyone with the “Equation of Boltzman”, and that means, that the Temperature is the most important Parameter.


Good Luck!
                    ARGOS⁺⁺

[Alpha-Omega]

ICP is used in conjunction with other analytical instruments, such as the Atomic Emission Spectroscopy (AES) and the Mass Spectroscopy (MS).

This is an advantageous practice, as both the AES and MS require that sample to be in an aerosol or gaseous form prior to injection into the instrument. Thus, using an ICP in conjunction with either of these instruments eliminates any sample preparation time which would be required in the absence of an ICP.

ICP-AES is an emission spectrophotometric technique, exploiting the fact that excited electrons emit energy at a given wavelength as they return to ground state.

The fundamental characteristic of this process is that each element emits energy at specific wavelengths peculiar to its chemical character.

Although each element emits energy at multiple wavelengths, in the ICP-AES technique it is most common to select a single wavelength (or a very few) for a given element.

The intensity of the energy emitted at the chosen wavelength is proportional to the amount (concentration) of that element in the analyzed sample. Thus, by determining which wavelengths are emitted by a sample and by determining their intensities, the analyst can quantify the elemental composition of the given sample relative to a reference standard.

All ICP-AES systems consist of several components. The three main aspects: the sample introduction system, the torch assembly, and the spectrometer. The sample introduction system on the ICP-AES consists of a peristaltic pump, Teflon tubing, a nebulizer, and a spray chamber. The fluid sample is pumped into the nebulizer via the peristaltic pump. The nebulizer generates an aerosol mist and injects humidified Ar gas into the chamber along with the sample.

This mist accumulates in the spray chamber, where the largest mist particles settle out as waste and the finest particles are subsequently swept into the torch assembly. Approximately 1% of the total solution eventually enters the torch as a mist, whereas the remainder is pumped away as waste.

Humidification of the Ar gas injected into the nebulizer is important when analyzing samples with high dissolved solids, as is often the case with analysis of ODP rocks, sediments, and interstitial waters. Humidification takes place in the Ar humidifier, where Ar is bubbled through deionized water prior to its expulsion in the nebulizer.

The fine aerosol mist containing Ar gas and sample is injected vertically up the length of the torch assembly into the plasma. There are several recommended Ar flow rates used in the torch, as described in detail in the owner's manual and in the various publications provided. The radio frequency-generated and maintained Ar plasma, portions of which are as hot as 10,000 K, excites the electrons. When the electrons return to ground state at a certain spatial position in the plasma, they emit energy at the specific wavelengths peculiar to the sample's elemental composition.

The plasma is viewed horizontally by an optical channel. Light emitted from the plasma is focused through a lens and passed through an entrance slit into the spectrometer. There are two types of spectrometers used in ICP-AES analysis: sequential (monochromator) and simultaneous (polychromator).

In a sequential spectrometer the diffraction grating in the spectrometer is analogous to a prism that refracts visible light into its component colors. The detector (photomultiplier tube) is fixed in space at the far end of the spectrometer. Rotation of the diffraction grating sequentially moves each wavelength into the detector. The computer control ensures that the detector is synchronized with the grating so that the intensity at the detector at any given time is correlated with the wavelength being diffracted by the grating.

The analyst enters the wavelengths they wish to detect into the computer, the grating sequentially moves to the specified wavelengths, and the energy intensity at each wavelength is measured to provide a quantitative result that can be compared to a reference standard. Using standard spectroscopic techniques (e.g., background corrections), sequential ICP-AES can provide extremely flexible and rapid analysis of a number of chemical elements.

The spectrometer is flushed with N₂ gas to improve the detection limits of elements with emission wavelengths that are severely compromised by interference with air. This N₂ flush, which is constantly maintained in the instrument regardless of whether such elements are being analyzed, also protects the optics from the corrosive aspects of the atmosphere.

ABOUT PLASMA:  http://www.harrickplasma.com/plasma.php

ICP-AES TUTORIAL: http://www.colby.edu/chemistry/CH332/ICP/index.html

Useful Refereneces Discussing ICP-AES Techniques:

Jarvis, I., and Jarvis, K.E., 1992a. Inductively coupled plasma-atomic emission spectrometry in exploration geochemistry. J. Geochem. Expl., 44:139-200.
————, 1992b. Plasma spectrometry in the earth sciences: techniques, applications and future trends. Chem. Geol., 95:1-33.
 
Montaser, A., and Golightly, D.W., 1992. Inductively Coupled Plasmas in Analytical Atomic Spectrometry: New York (VCH Publ.).
 
Potts, P.J., 1987. Inductively coupled plasma-emission spectrometry. In Potts., P.J. (Ed.), A Handbook of Silicate Rock Analysis: London (Blackie Academic and Professional), 153-197.
 
Totland, M., Jarvis, I., and Jarvis, K.E., 1992. An assessment of dissolution techniques for the analysis of geological samples by plasma spectrometry. Chem. Geol., 95:35-62.
 
Walsh, J.N., and Howie, R.A., 1986. Recent developments in analytical methods: uses of inductively coupled plasma source spectrometry in applied geology and geochemistry. Appl. Geochem., 1:161-171.

Varian has an excellent paper that addresses/compares the pros and cons of ICP-AES vs. ICP-AAS.

LINK:  http://www.varianinc.com.cn/products/spectr/icpms/atworks/icpms01.pdf

Additionally, their website has a huge array of application notes.

Their home:  http://www.varianinc.com/cgi-bin/nav?/

Links for Minerolagists-ICP:  http://www.mineralogie.uni-wuerzburg.de/links/tools/icp-ms.html