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Metals Analysis of Water Samples by Flame Atomic Absorption Spectrophotometry

Last revised July 22, 1997
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Page contents (click to skip down):

* [Available analytes]
* [Overview of technique]
* [Water sample requirements and handling]

(IMAGE: AA spec, aad03.gif)

Available analytes

- water Calcium:
* [dissolved/total partitioning]
* [Flame-AA assay for Ca]
- water Magnesium:
* [dissolved/total partitioning]
* [Flame-AA assay for Mg]
- water Potassium:
* [dissolved/total partitioning]
* [Flame-AA assay for K]

Overview of technique

In flame atomic absorption spectroscopy a liquid sample is aspirated and mixed as an aerosol with combustible gasses (acetylene and air or acetylene and nitrous oxide.) The mixture is ignited in a flame of temperature ranging from 2100 to 2800 degrees C (depending on the fuel gas used.) During combustion, atoms of the element of interest in the sample are reduced to the atomic state. A light beam from a lamp whose cathode is made of the element being determined is passed through the flame into a monochronometer and detector. Free, unexcited ground state atoms of the element absorb light at characteristic wavelengths; this reduction of the light energy at the analytical wavelength is a measure of the amount of the element in the sample.

Water sample requirements and handling

To allow for repeat measurements of dissolved element, the investigator should collect 20 ml of sample for each desired analyte. If a digest for total element is desired, considerably more sample must be collected. See the U.S. E.P.A. discussion of [Total element digests] of water samples.

The investigator should also refer to the E.P.A.'s table of recommended [Sample collection/preservation] procedures for specific details concerning these.

References
Allen, S. E., et al. 1974.
Chemical Analysis of Ecological Materials. John Wiley and Sons, New York.

U. S. Environmental Protection Agency. 1983.
Metals (atomic absorption methods). pp. 55-72. In Methods for Chemical Analysis of Water and Wastes, EPA-600/4-79-020. U.S.E.P.A., Cincinnati, Ohio, USA.

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