UV Analyzers Flashcards
What wavelength range is considered ultraviolet EMR?
100-400 nm
What are the 4 types of compounds that absorb UV radiation?
1) Oxidizing agents such as Chlorine, Chlorine Dioxide, and Ozone
2) Sulfur compounds such as H2S, and Sulfur Dioxide
3) Nitrogen compounds like NO2
4) Aromatic organic compounds like Benzene and Phenol
Why are UV analyzers so useful for measuring pollutants?
Interfering chemicals such as H2O and CO2 do not absorb UV therefore do not interfere
What common gas can be used to zero a UV gas analyzer?
Air
What common liquid can be used to zero a UV liquid analyzer?
Water
Describe the difference between a UV absorption spectrum and an IR absorption spectrum.
IR typically shows more absorption peaks while UV shows one or two
Describe how the two wavelengths are chosen for single component analysis with UV
photometers.
Measured wavelength: a wavelength that is strongly absorbed by the sample
Reference wavelength: a wavelength not absorbed by the sample
What are two examples of line emission sources for UV analyzers?
1) Metal vapour lamp
2) Hollow cathode lamp
What are two examples of continuous emission sources for UV analyzers?
1) Deuterium arc lamp
2) Hydrogen arc lamp
A photodiode responds to UV radiation because the photons ___________ electrical conductivity of
the reverse-bias junction, reducing the diode’s ___________ and
allowing a measurable current to flow through the device.
increase, resistance
Explain the advantage(s) of the photodiode array?
Can measure the intensities of all wavelengths in a dispersive UV analyzer
How is dispersion achieved in a UV analyzer with a photodiode array?
Diffraction grating
What category of UV analyzers are used for CEM SO2 analysis and why?
UV absorption as they are not as sensitive and measure in the ppm range
What category of UV analyzers are used for ambient air (environmental) SO2 analysis and why?
UV fluorescence as they can measure in the ppb range
What 2 types of detectors measure radiation intensity in non-dispersive UV analyzers?
1) PMT
2) Photodiode
What function does the rotating filter wheel have?
Pass a narrow band of wavelengths to choose between the measured and the reference wavelengths
What type of UV radiation causes the most damage to living tissue?
UV-C
What is the most common use for UV analyzers?
SO2 monitoring in ambient air
