Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Patent
1995-10-10
1997-09-30
Pyon, Harold
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
422 8203, 422 8205, 436 52, 436 63, 204409, 204415, B01D 6128, C02F 144, G01N 3508
Patent
active
056723199
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for analyzing a fluid medium, in particular a liquid.
Fluid analyzers may be used for controlling chemical and biological processes such as the treatment of sewage water. It is desirable, for example, to lower the concentrations of nutritive salts, such as nitrogen salts, in the effluent from waste water treatment plants. Proper control of the biological processes in the plant is required. It is therefore advantageous to be able to measure the concentrations of the different kinds of ions in the waste water as they, amongst other variables, influence on or inform about the biological processes.
Numerous patents deal with the object of analyzing fluids, especially liquids, for the presence of various analytes. The measurement methods can in principle be divided into three groups: analyzed; the bulk process fluid, filtered and then at regular intervals automatically analyzed; entirely or partly immersed in the medium to be analyzed, or sampling is direct and analysis is carried out so close to the process, that the time between a sampling and the development of the analysis result is short enough to allow reliable, real-time control of the process.
An analyzing system for use in process control applications should enable the user to take immediate precautions; for example in waste water treatment, precautions against a suddenly increasing content of nitrate in the fluid medium. The methods in group (1) however are predominantly carried out in the laboratory which inevitably entails a delay in time from sample collection to actual analysis.
Moreover, as water samples are often analyzed spectrophotometrically, long transfer distances may present a further problem because the continuing biological activity in the samples tends to render them less representative. Even if the samples are transported quickly from the sampling site to the laboratory, the analysis results are somewhat uncertain because of problems relating to background turbidity in the samples.
Group (2) above includes UV measurements as well as ion selective electrodes and segmented flow analysis (SFA). The so-called flow injection analysis (FIA), belongs to group (2) as well as to group (1).
The use of ultraviolet (UV) spectrophotometry for water quality analyzing has not been very successful because of interferences from suspended solids and organic matters in the samples. Thomas et al., Fresenius J. Anal. Chem. 338, 234-237 and 238-240 (1990), have attempted to improve the applicability of the UV method by means of the so-called UV multiwavelength absorptiometry (UVMA) method, the purpose of which is to cancel the background signal and simultaneously compute the concentrations of specific absorbing components which significantly disturb the typical shape of the spectrum. The UVMA method, which is intended for use in connection with nitrate determination in natural water and waste water, does however have the drawback, that it requires ultrafiltration of the samples. A similar principle is exploited and marketed by the firm Dr. Lange GmbH, Germany.
The segmented flow analysis (SFA) method was first described in U.S. Pat. Nos. 2,797,149 and 2,879,141, the basic principle being that the samples to be analyzed are separated from one another by air. A refinement of this technique comprising a fluid handling system is described in U.S. Pat. No. 4,853,336. This system is particularly useful for mixing liquid samples with previously separated processing liquids, such as reagents or diluents, in continuous flow analyzers. The system permits the delayed on-line mixing of different components of an analysis mixture, such as samples with reagents or diluents, as well as mixing and interaction of such components in a single conduit.
The basic FIA principle is outlined in U.S. Pat. Nos. 4,022,575 and 4,224,033. A metered amount of the sample is introduced in a moving liquid carrier flow, constituting a well-defined zone, the volume and geometry of which should be strictly reproducible. The sample zone within the carr
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Danfoss A/S
Pyon Harold
Tecator AB
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