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Cold vapour atomic fluorescence spectroscopy (CVAFS) is a subset of the analytical technique known asatomic fluorescence spectroscopy (AFS).

Used in the measurement of trace amounts of volatile heavy metals such asmercury, cold vapour AFS makes use of the unique characteristic of mercury that allows vapour measurement at room temperature.^{[citation needed]} Free mercuryatoms in a carrier gas are excited by acollimatedultraviolet light source at awavelength of 253.7nanometres. The excited atoms re-radiate their absorbed energy (fluoresce) at this same wavelength. Unlike the directional excitation source, the fluorescence is omnidirectional and may thus be detected using aphotomultiplier tube or UVphotodiode.

Gold coated traps may be used to collect mercury in ambient air or other media. The traps are then heated, releasing the mercury from the gold while passing argon through the cartridge. This preconcentrates the mercury, increasing sensitivity, and also transfers the mercury into aninert gas.^[1]

A number of companies have commercialized mercury detection via CVAFS and produced transportable analysers capable of measuring mercury in ambient air.^{[citation needed]} These devices can measure levels in the low parts perquadrillion range (10⁻¹⁵).

Various analytical methods approved by theUnited States Environmental Protection Agency (EPA) for measuring mercury in wastewater are in common use. EPA Methods 245.7 and 1631 are commonly used for measurement ofindustrial wastewater using CVAFS.^[2][3]

Other analytical techniques suitable for analyzing heavy metals in air or water:

• Inductively coupled plasma mass spectrometry
• Atomic absorption spectroscopy

• Spectroscopy
• Fluorescence techniques

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