Chemistry Reference
In-Depth Information
Orion supply both electrodes and measuring equipment. Ingold, on the other hand,
supply only electrodes. EDT Analytical (UK) also manufacture ion selective electrodes.
1.1.8
X-ray methods
1.1.8.1
X-ray spectrometry
The application of this technique is limited to the determination of traces of bromide in
seawater.
1.1.8.2
X-ray fluorescence spectroscopy
This technique has been applied to the determination of seven anions as indicated below.
Non saline waters:
selenate, selenite and phosphate.
Seawater:
bromide.
Aqueous precipitation:
chloride, bromide and iodide.
Waste waters:
phosphate.
Trade effluents:
selenate and selenite.
1.1.8.3
Energy-dispersive X-ray fluorescence spectrometry
Energy-dispersive X-ray fluorescence (EDXRF) spectrometry is an instrumental
analytical technique for non-destructive multi-elemental analysis. The use of modern-day
technologies coupled with the intrinsic simplicity of X-ray fluorescence spectra (as
compared for instance with optical emission (OE) spectra) means that the powerful
EDXRF technique can be used routinely. The EDXRF spectrum for iron is a clearly
resolved doublet, while the optical emission spectrum contains more than 4000 lines.
This simplicity is a direct consequence of the fact that XRF spectra are a result of inner
shell electron transitions which are possible only between a limited number of energy
levels for the relatively few electrons. Optical emission spectra, on the other hand, arise
from electron transitions in the outer, valence shells which are closer together in energy,
more populated than the inner shells and from which it is easier to promote electron
transitions.
In order to generate X-ray spectra, we may excite the elements in the specimen with
any one of the following:
• X-ray photons
• High-energy electrons
• High-energy charged particles
• Gamma rays
• Synchrotron radiation.
The term XRF is generally applied when X-ray photons are used to generate
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