Chemistry Reference
In-Depth Information
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1.1.2.3
Fluorescence spectroscopy
Spectrofluorimetric methods have been described for the determination of the following
18 anions.
Non saline
waters:
borate, bromide, free cyanide, fluoride, iodide, nitrate, nitrite, phosphate,
selenite, silicate, sulphide, sulphite and vanadate. Also ascorbate, citrate,
oxalate and tartrate.
Estuary water:
selenate and selenite.
Aqueous
precipitation:
bromide and iodide.
Potable waters:
selenate and selenite.
Trade effluents:
free cyanide, selenate, selenite and sulphide.
High purity
waters:
chloride.
Chemilumtnescence analysis has been applied to the determination of the following
seven anions.
Non saline waters:
free cyanide, iodide, nitrate, nitrite, silicate, sulphite and vanadate.
Seawater:
nitrate.
Generally speaking, concentrations down to the microgram per litre level can be
determined by this technique with recovery efficiencies near 100%.
Potentially, fluorometry is valuable in every laboratory, including water laboratories,
for the performance of chemical analysis where the prime requirements are selectivity
and sensitivity. While only 5-10% of all molecules possess a native fluorescence, many
can be induced to fluoresce by chemical modification or tagged with a fluorescent
module.
Luminescence is the generic name used to cover all forms of light emission other than
that arising from elevated temperature (thermo-luminescence). The emission of light
through the absorption of ultraviolet or visible energy is called photoluminescence, and
that caused by chemical reactions is called chemiluminescence. Light emission through
the use of enzymes in living systems is called bioluminescence, the only known
application of which to water analysis is the determination of adenosine triphosphate.
Photoluminescence may be further subdivided into fluorescence, which is the immediate
release (10
−8
s) of absorbed light energy, as opposed to phosphorescence, which is
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