Chemistry: analytical and immunological testing – Composition for standardization – calibration – simulation,...
Patent
1997-01-08
1998-08-04
Wallenhorst, Maureen M.
Chemistry: analytical and immunological testing
Composition for standardization, calibration, simulation,...
436 52, 436177, 436178, 422 681, 422 81, 73 102, G01N 3100
Patent
active
057892490
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for calibrating an analysis system having a membrane, the outside of which is in contact with a medium to be analyzed, in order to detect a concentration of a species there, and to an analysis system having a membrane, the outside of which is in contact with a medium to be analyzed, a flow path being arranged on the inside of the membrane, which flow path is connected on its input side to a reservoir for a carrier liquid and on its output side to a detector.
In analysis systems of that kind, the species to be detected, for example, ions or other particles, for example, low-molecular particles, pass from the fluid to be analyzed, which is present at or flows past the outside of the membrane, into a carrier fluid which flows past the inside of the membrane. Mostly, the fluids are liquids. The following description is therefore made with reference to liquids.
It is known that such analysis systems have to be calibrated from time to time. Such a calibration is necessary at least whenever a new membrane is used. The membranes normally have only a limited service life. Although in principle they are of identical construction, variations do occur from membrane to membrane, which can be taken into account by means of a calibration.
For example, U.S. Pat. No. 5,293,770 discloses a calibration device in which a calibration liquid is contained in a vessel. To effect calibration, a sensor provided with the membrane is immersed in this vessel.
U.S. Pat. No. 4,587,219 discloses a different analysis system, in which a liquid to be examined is conveyed past the outside of the membrane. Alternatively, a calibration liquid can be used in place of the liquid to be investigated.
Such calibrations are easy to perform in a laboratory because the corresponding measurements can be effected in a controlled environment. Problems arise, however, when the analysis apparatus is not readily accessible, for example, when it is being used in a sewage treatment plant and is floating in the settling basin or in the main outfall. Corresponding difficulties also occur when the analysis apparatus is being used to test the water quality of a flowing body of water or a lake or the sea. In all these cases the analysis apparatus would have to be recovered, the calibration performed and the analysis apparatus then re-located again. The effort involved in this is in many cases too great. An aggravating factor is that it is precisely in the said application purposes that a repeated calibration is required, and in fact also during the service life of membrane, because the properties of the membrane may change, for example, because of algal or other live growths or because of mechanical stresses, such as waves, for example, or because of ageing phenomena which are accelerated by changing temperatures.
SUMMARY OF THE INVENTION
The invention is based on the problem of allowing a calibration to take place in situ, that is, on site. This problem is solved in a method of the kind mentioned in the introduction in that a first fluid of a predetermined first concentration of the species is conveyed along the inside of the membrane, that at least a second fluid of a predetermined second concentration which differs from the first concentration is conveyed past the inside of the membrane, that the concentrations of the fluids after passing the inside of the membrane are recorded and from these concentrations parameters for a correlation between the concentration of the species on the outside of the membrane and a measurement signal are ascertained.
During the actual measuring process, a carrier liquid is conveyed past the membrane. From the concentration of the species in the carrier liquid, which is created as the carrier liquid flows past the membrane, one can now deduce the concentration of the species in the liquid to be analyzed. The following law applies: membrane, the membrane, P. M., Lonsdale, H. K., de Pinho, M. N., D. Reidel Publishing Company,, Dordrecht/Boston/Lancaster/Tokyo, page 629
REFERENCES:
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patent: 5124042 (1992-06-01), Bredeweg et al.
patent: 5238853 (1993-08-01), Calzi et al.
patent: 5293770 (1994-03-01), Hansen et al.
patent: 5672319 (1997-09-01), Eisum
Danfoss A/S
Wallenhorst Maureen M.
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