Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Patent
1995-01-24
1997-05-20
Snay, Jeffrey
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
422 8209, 436 53, 436178, G01N 2159
Patent
active
056309872
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an apparatus and a method used to measure concentration of chemical pollutants such as ammonia, nitrate ions, organic matter and suspended matter in fluids such as water.
BACKGROUND AND SUMMARY OF THE INVENTION
An instrument has been developed to use absorption of radiation for the on-line determination of the concentration of contaminants such as nitrate ions, ammonia and organic matter which are indicative of the extent of pollution occurring in a wide range of natural and processed waters.
UV spectroscopy can be utilized for the determination of most organic and certain non-organic compounds (e.g. chlorine) using simple techniques. This method relies on the absorption of light in a more restricted band than the visible i.e. from 180 to 400 nm. Many elements absorb ultra-violet light selectively in the band from 200 to 300 nm, each at a specific wavelength. The absorption peak profile is wide since it results from absorption from different origins, mainly due to electronic transitions on to which vibrations, rotations and translation are superimposed. As a consequence, characterization of the sensing wavelength is not very specific. It is not always possible to provide light of adequate intensity at the wavelength of peak absorption. Hence an adjacent wavelength must be used, even though it reduces the sensitivity somewhat. Another alternative which is more complex and costly would be the use of a grating system to provide any particular wavelength and deconvoluting the spectra obtained. However, in the simple system chosen, deviations from the peak absorption wavelength do not give rise to major difficulties.
According to the present invention there is provided an apparatus for measuring the level of a contaminant in a fluid comprising a measuring chamber, a first source of optical radiation of a predetermined wavelength adapted to direct the radiation through the chamber, detector means to detect the radiation after passage through the measuring chamber, pump means to urge a test fluid test from a fluid source to the measuring chamber, fluid processing means positioned between the fluid source and the measuring chamber to process the fluid to change an optical effect of the contaminant, bypass means to bypass the fluid processing means and valve means alternately to direct the fluid to the processing means and the bypass means.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be particularly described with reference to the accompanying drawings in which:
FIGS. 1 to 19 illustrate various optical effects,
FIG. 20 shows a liquid handling unit,
FIG. 21 shows an ion exchange column used in the apparatus of FIG. 1,
FIGS. 22a and b show emission spectra of UV lamps used in association with the apparatus of FIG. 1
FIG. 23 shows an automatic fiber positioner,
FIG. 24 is a side view of a sample cell,
FIG. 25 shows an alternative sample cell,
FIG. 26 shows the spectral response of a detector device,
FIGS. 27 to 29 show the arrangement of various signal processing circuits,
FIGS. 30 and 31 show the response of specific circuits,
FIG. 32 shows the timing sequences from the different parts of a timer circuit, and
FIG. 33 is a block diagram of a timer and control unit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The optical properties of nitrate ions, ammonia, suspended and organic matter were investigated in detail. As a result it was decided to use 253.7 nm as the wavelength for absorption of ammonia (measured as monochloramine), suspended and organic matter. Although monochloramine absorbs at 244 nm, the sensitivity of the measurement carried out at 253.7 nm was found to be acceptable since the peak of absorption is very broad for elements absorbing in the ultra-violet region.
The use of two different types of resins was found to be suitable for provision of background measurement on the samples. Hence it is practical to use the 253.7 nm wavelength as the measuring wavelength for ammonia, organic and suspended matter, making it possible to use a single
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Briggs Ronald
Grattan Kenneth T. V.
Movaziz Zoheir
British Technology Group Limited
Snay Jeffrey
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