DE2824340A1 - METHOD AND DEVICE FOR DETERMINING THE PRESENCE OF A SUBSTANCE IN A FLUID MEDIUM - Google Patents

Description

PATENT ADVOCATE h ,

DR. RICHARD KNEISSL ^Ί 3 ^] · Ψ _ο Ψη _o . _η

Widenmayerstr. 46 £ O Z H J 4 U

D-8000 MUNICH 22
Tel. 089/295125

Folder 24 479

ICI Case Kr. Dd. 29598/29960

IMPERIAL CHEtIICAL INDUSTRIES LIMITED London / Great Britain

Method and device for determining the presence of a substance in a fluid medium

809884/0647

description

The invention relates to an analytical method.

The invention relates to a method for determining presence a substance in a fluid medium which additionally contains a suspended particulate substance, which thereby is characterized in that at least a portion of the fluid medium is passed to a first permeable sheet material which the fluid medium can be separated from the particulate material by diffusion, and that one can use a detector instrument investigated the presence of the substance in the fluid medium within a detector area in which the fluid medium from the particulate Substance is diffused away, wherein the detector area is on the first permeable sheet material or a second permeable sheet material is located, which during the application of the fluid medium in such a way with the first sheet material in Contact is that the particulate matter in the fluid medium does not pass from the first sheet material to the second sheet material can.

Although the method is suitable for separating a particulate Substance from a gas phase that contains a certain gas which is to be determined, but the method is special suitable for the determination of a substance dissolved in a liquid medium which also contains an undissolved suspended substance. The following description refers to this particular situation in which the fluid is a liquid, the particulate Substance is a solid and the substance to be determined is dissolved in the liquid medium.

It is true that any substance which is soluble in a liquid medium and which is subsequently used as a "Soluble matter" can be determined if a suitable detector instrument (hereinafter referred to as detector device is designated) for the examination of the detector area

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is used, but the method is particularly suitable when the readable material is determined by a non-contact technique can be, for example, by photometry. The method is also suitable when the soluble substance is not directly through a non-contact Technology can be grounded in a certain way, but through implementation a developer applied to either or both of the sheet materials before, along with, or after the liquid Kediun is applied to form a soluble product which is determined by a non-contact technique such as photometry v / can earth.

It may be that the solute itself is not the primary substance is that is to be observed by the process, but it may be the product of the reaction of the primary substance that is in the liquid Medium is present with a developer that is added to the liquid medium before it is applied to the first sheet material will.

According to the invention there is also a method for determining a soluble substance which is dissolved in a liquid which additionally contains a suspended insoluble solid, proposed which is characterized in that at least applies a portion of the liquid to one side of a first permeable sheet material, while the opposite Side of the first sheet material is in contact with a second permeable sheet material in such a way that the insoluble Substance is completely retained by the first sheet material and the liquid can diffuse into the second sheet material, that the two sheet materials are then separated and that the presence of the soluble Investigated the substance.

If the detector device is able to generate a signal, which is related to the amount of the soluble substance present in the detector area, then the method is suitable after a calibration for the determination of the concentration of the

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soluble substance in the liquid medium. The procedure is thus capable To be used in monitoring the progress of certain chemical reactions and especially those in which a insoluble product formed from a first soluble reactant and the presence of the insoluble product is the direct determination the state of the reaction prevented. By the present method, a soluble reactant or a more easily determinable one can be obtained Product thereof, which is formed by reaction with an added developer, easily from the insoluble product for determination the ercteren are separated.

An example of such a reaction is the azo coupling reaction between a diazonium compound and a coupling component may be mentioned, one of which and / or the other in the reaction medium may be soluble to an insoluble colored product such as a pigment or a dispersed dye. The state of the reaction can be determined by determining the amount of the diazonium compound or the coupling component either directly or after a reaction with a developer, whereby an easier determinable substance is formed, must be monitored. examples for Suitable developers for this purpose are (a) coupling components or diazonium compounds that interact with the diazonium compound or the coupling component can react in the azo coupling reaction play a role so that a soluble dye is formed, and (b) ferrous chloride in the event that one the reaction participant contains a group of the structure: = CH-C-OH, since it is known that iron (III) chloride reacts with compounds containing this group, producing a colored substance.

The permeable 31attmaterials preferably consist of an absorbent material, such as filter or blotting paper, by v. ^r which a liquid can diffuse and which in certain cases can also contain other materials. If a single sheet of material is used, then depending on the size of the sheet of material in relation to the amount of liquid medium applied, the detector area may be on the same side of the

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Material to which the liquid medium is applied, or on the other side, or even if the sheet material is sufficient thick, be on one edge. Other possible sheet materials are, for example, an ultrafiltration membrane or a woven textile material.

The first sheet material should preferably allow a large proportion of the liquid containing the solute to can diffuse through and into the second sheet material, so that there is an ample supply for the second sheet material is when the two are in contact. The second sheet of material preferably allows the liquid to spread evenly, preferably also a neutral one Should provide background against which the soluble substance is determined. Preferred porous sheet materials are filter paper and others gloss-free absorbent papers. They are preferably white.

The method is suitable for determining a soluble substance in a given hatred or in a flowing stream of the liquid Medium. Ss is preferred, in particular in the case of a flowing liquid medium, the liquid medium being continuous peel off and apply it to a continuously running first sheet of material so that a continuous detector area arises. If this area has been properly calibrated by a Detector device is examined, then can be a continuous indication of the dc-n state of the liquid medium in with respect to the solute which is just passing the draw-off point. Examples of suitable flowing liquid media are continuous reaction media that contain insoluble reaction parts or products containing waste liquids in sewers and rivers or other watercourses that are often a mixture of dissolved and suspended solids.

If the substance to be determined is not easily through a non-contact Technique, such as photometry, can be determined, then it is expediently, the sample stream derived from the liquid medium

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is to mix continuously with a stream of a suitable developer, so that a more easily identifiable substance is produced, the is soluble in the medium. As an alternative, the developer can or else in the detector area on the corresponding sheet material be abandoned after the application of the liquid medium.

According to the invention there is also a first device for determining the presence of a soluble substance in a liquid medium, which also contains an undissolved suspended substance, suggested, which is characterized in that it comprises the following parts: a holder for a sheet material which the Can separate liquid from the undissolved substance by diffusion, means for directing at least a portion of the liquid the surface of the sheet material and a detector instrument which examines a detector area on the sheet material, in which the liquid diffuses away from the undissolved substance by diffusion and determines the soluble substance or a product formed therefrom on the surface of the sheet material.

Although the first device is suitable for intermittent operation, however, it is particularly suitable for continuous operation with either a given mass or a flowing one Flow of the liquid medium.

In an embodiment of the first device that is suitable for continuous operation, the holder for the Sheet material preferably a drive device with which the sheet material is moved at a constant speed can. For use in such a device, the sheet material conveniently consists of a strip, which is preferably consists of an absorbent paper and which is driven in a direction parallel to its longitudinal axis. Alternatively For example, the sheet material can be circular and rotated about its center point by the drive means.

The device with which the liquid medium is brought to the sheet material preferably has a pipe system that extends from the pipe

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or container which contains the liquid medium, leads to sheet material. The pipe system preferably ends in a distribution device, with which the amount and the direction the liquid supplied to the sheet material can be determined. The pipe system in which the liquid medium is absorbed Sheet material flowing may include a pump, if desired, and such a pump facilitates mixing of the liquid medium with a developer that converts the soluble substance into a substance that can be determined by instruments. When the sheet material moves, the liquid medium can fall onto this material in the form of a strip along the direction of movement can be applied to one or both sides of the strip, the liquid medium then diffusing.

Any suitable instrument can be used to determine the solubility in detector sreioli, but that of the present invention is effective Vorrichtimg preferably a photometer and in particular a calibrated photometer that delivers a signal which related to the amount of solute in the detector area.

In the embodiment of the first device, which is for a continuous determination is suitable, the detector device is sufficiently far downstream of the point at which the liquid Medium is applied to the sheet material, arranged to allow the liquid medium from the undissolved solids into the detector area can diffuse and that, if necessary, the soluble substance can also react with a developer in order to make an instrument part to form determinable product.

A preferred embodiment of a detector device has a photometer which, preferably quantitatively, the presence of the soluble substance in the detector area in the presence of other substances that are in this area, such as the liquid medium or any developer that has been added to the liquid medium or is already present in the detector area.

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Vi

According to the invention there is also a second device for determining the presence of a soluble substance in a liquid that also contains a suspended undissolved solid, proposed, which is characterized in that it comprises the following parts: a holder for a first and a second permeable sheet material, which initially holds them together along two opposing surfaces and then separates them, one Applicator which directs at least a portion of the liquid onto the free surface of the first sheet material during it is in contact with the second sheet material, and a Detectorinstrurner.t, which has a detector area on the second Sheet material examined after the two sheet materials have been separated from each other and the soluble matter or a determined product formed therefrom on the surface of the sheet material.

Although the second device is suitable for intermittent operation, however, it is particularly suitable for continuous operation with either a given mass or a flowing one Flow of the liquid medium.

In one embodiment, the second device, which is suitable for continuous operation, the holder in an appropriate ^T, ieisG has a driving means for the sheet materials, and suitably arranged rollers or guide surfaces with which the two sheet materials can be kept in contact while at the Applying device run past, whereupon they are then separated and the second sheet material is guided past the detector device. For use in such a device, each sheet material preferably consists of a strip of absorbent paper, such as filter paper.

The means for directing the liquid medium onto the first sheet material preferably has a system of pipes extending from the pipe or container which contains the liquid medium leads to sheet material. The pipe system preferably ends in

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a distribution device with which the amount and the direction of the liquid supplied to the first sheet material can be determined. The pipe system in which the liquid medium flows to the first sheet material can comprise a pump, if this is desired, and such a pump facilitates the mixing of the liquid medium with a developer which converts the soluble substance into an instrumentally determinable substance. As the sheet materials move, the liquid medium can hit the first sheet material in the form of a strip along the direction of movement
be applied.

Any suitable instrument can be used to determine the solubility in the detector area on the second sheet of material are, however, the device according to the invention preferably has a. Photometer and in particular a calibrated photometer, which gives a signal which is related to the amount of the soluble substance is related in the detector area.

In the embodiment of the second device, which is for a continuous determination is suitable, the detector device is sufficient placed far downstream of the point at which the liquid medium is applied to the first sheet material, so that the liquid medium can diffuse from the undissolved solids into the detector area on the second sheet material and that, if necessary, the soluble substance can also react with a developer in order to form a product which can be determined by an instrument.

The invention will now be explained in more detail with reference to the accompanying drawings.

In the drawings show:

Fig. 1 is a side view of a preferred embodiment of the device according to the invention, which is ruled out on a pipe that carries a liquid medium;

"T the dividing point of the sheet material" ψιθ 809884/0647

FIG. 2 shows a plan view of the device from FIG. 1;

Fig. 3 is a plan view of a paper tape while it is through the in the device shown in Figures 1 and 2 is performed;

Fig. 4 shows a vertical section through a preferred embodiment of the inventive device of the second type on the Line IV-IV of Figure 5; and

FIG. 5 is a horizontal section on the line V-V of FIG.

In the ir. D_n Figures 1, 2 and 3 shown u device is used Pair of Qucit rolls 111, 112 attached to axles 111a, 112a and are driven by motors 111b, 112b (not shown), in addition, an absorbent paper strip 113 from a supply roll 114, which is fixed on an axle 114a, around a guide roller 115 which is fixed on an axle 115a, and horizontally on a liquid medium application device 116 vjid a photometric detector device 117 to pull. The axes 111a, 112a, 1i4a, 115a are rotatable between rack parts 127, 123 attached.

The application device 116 for liquid medium comprises a pipe system 113, from an extension point 119 in a pipe 120, which carries the liquid medium, via a pump 121 and a Käscher 122 up to a point just before the underside of the papisr strip 113 leads. An Ileben pipe system 123 leads from a supply 129 for developer via a pump 124 into the mixer 122.

The detector device 117 has a light source 125, a Detector 126 and an analyzer 130 from a mirror-free reflection photometer. The pipe systems 118, 123, the light source 125 and the detector 126 are made of cross braces 113a, 123a, 125a and 126a of frame parts 127, 128, which are fastened on the tube 120, carried.

In operation, the paper strip 113 is removed from the supply roll 114 pulled off and guided around the guide roller 115 and between the driven squeezing rollers 111, 112 .. A part of the liquid

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Medium flowing through the Holir 120 is drawn by the pump 121 through aas Rohrsysteu 11-3 and fed into the mixer 122, where it is mixed with developer. The developer is withdrawn from the supply 129 for developer by the Pusp = 124 and guided through the Ilebenrohrsysten 123. The mixture of liquid medium and developer goes up through the pipe system 1i3, from the end of which it is guided to the underside of the paper strip 113, namely to an application point A (see FIG. 3), which is laterally on the edge of the paper strip 113 is located. The liquid kediun initially spreads on the surface of the paper strip 113, carrying the undissolved solid with it. After a short distance, however, the liquid medium is completely absorbed, with the undissolved solid remaining in a band B, which lies in the vicinity of an edge on the underside of the paper strip. The liquid medium continues to ciiffuncli3r-3: i through the paper strip, taking with it all the dissolved material until it reaches the edges of the paper strip C,

C reached, so that a wide and a narrow band of more fluid Medium D, D on either side of belt B of undissolved solid is produced.

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The speed of the paper strip 113, which is bsstinr.t by the nip rollers 111, 112, is adjusted so that the bands D, D are formed before the paper strip 113 passes under the detection device 117. The light source 125 and the detector 126 of the spectrophotometer 130 are directed in a detector area E, which lies on an intermediate band F in the line of the band D and on the upper side of the paper strip 113.

It is true that the position of the application point A according to FIG opposite, but this is not essential. However, it is preferred to apply the liquid iledium to the underside of the paper strip apply to reduce the possibility of undissolved solid overflowing onto the liquid band D and the analysis by the detector device 117 interference>.

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According to an alternative to mixing the developer with the liquid The paper strip can be used in advance with the medium in the Ilischer 122 impregnated with the developer or on the paper strip With the aid of a second application system for the liquid medium, which is provided upstream or downstream of the location of the application point A. may be abandoned provided there is sufficient time for the developer to react with the solute remains before the paper strip 113 the detector device happened.

n the solute itself directly through the detector device 117 can be determined, then it is not necessary to provide the mixer 122 and the developer supply system, the liquid liedium directly at the application point A on the paper strip 113 is applied.

The various parts of the device of the second type shown in FIGS. 4 and 5 are fixed between a pair of rigid plates 11, 13 which are spaced apart by a rib 15 and holder 17. The guide device for the absorbent sheet material consists of a series of rollers 19 to 27, which are mounted on shafts 29, and a guide device 31. The application device has a V-shaped distributor 33, and a drain device 35- The detector device has a mirror 37 and a photoelectric detector 39.

The three ^rolls 19, 21, 23 are aligned so that the absorbent sheet materials, in the present case paper strips, are passed together between the distributor 33 and the discharge device 35 before they are separated as they pass around the roll 21. The rollers 25 and 27 are held in contact by a spring 41 which presses against lever arms 43 on which the roller 27 is fastened. The spring 41 is attached to an adjustable cap 45. The cap 45, which is adjustable by a plurality of screws (not shown), and the levers 43 are both mounted on a bracket 47 which is carried by the rib 15.

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The roller 25 is driven by a drive gear (not shown) a motor (not shown) arranged between the holders 17 is driven.

The guide system 31 has two plates 49, 51 made of plastic, one of which is fastened on the rib 15 and the other on a metal plate 53 which is carried by the holder 17 via Bsine 55 is. The plates 49, 51 define a detector slot 5δ, the nit the gap 57 between the rollers 25, 27 and the edge of the Roll 21 is aligned. A circular detector aperture 59 is formed in the rib 15 and in the plate 51.

The manifold 33 has a slot nozzle 61 which extends over the central region of the space between the plate 11, 13 extends. The drainage device 35 has a depression 63 an inclined floor 65, at the lower end of which a drain pipe 67 is provided which leads through the rear plate 11.

The mirror 37 is adjustable with the aid of a threaded pin 71 and a nut 73 fixed to a holder 69 so that it is with a light transmitting aperture in the rear plate 11 and is aligned with the detector aperture 59. The photoelectric detector 39 is also attached to the holder 69 at an angle such that that it only picks up diffuse reflected light coming from the detector aperture 59. The detector 39 is through a cable 77 is connected to an analyzer (not shown).

When operating the device of the second type, two absorbent Paper strips 79,31, which are fed from supply rolls (not shown), over the roll 19 and over the top of the Drain device 35 led to roller 21, v / o they are separated. The upper strip 79 continues its way to the roller 23, from where from it is led into a collecting container (not shown). The lower paper strip 81 passes through the detector slot 56 and between the rollers 25, 27 through and also arrives at one Receptacle (not shown).

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Sine slurry containing the soluble matter to be detected is fed into the distributor 33 and via the slot nozzle 61 onto the central area of the upper belt 79. The solid in the slurry is on the top surface of the top belt 79 held, and the liquid goes through both paper strips 79, 31 and wets them carefully, excess Liquid drips into the depression o3 and is through the drain pipe 67 removed. The moistened tapes 79 »81 stick together, until they are separated at the roller 21. A single drive on the roller 25 is usually sufficient, both paper tapes 79, 81 guide through the device.

When the lower band 81, which has carefully been saturated with the liquid from the slurry, but which is free of solids, passes the detector aperture 59, it is exposed to a light beam 83 from a light source (not shown) which enters the device through the transparent aperture 75 and through the adjustable mirror 37 through the detector aperture 59 is judged. Part of the diffuse reflected light of the exposed strip is picked up by the detector 39, and that The resulting electrical signal is fed to the analyzer via the cable 77.

The light source and the detector 39 are matched to one another in such a way that that a response to "the substance to be detected in the liquid the slurry takes place while the anarysator does so it is calibrated to give a signal which is representative of the concentration of the substance detected in the slurry is.

Any tendency for relative movement between the two ligaments To avoid this, a pressure arm can be provided which rests against the first roller 19. This makes the ligaments tight together kept in contact while they run over this roller 19, so that they are together by the single driven roller 25, which acts on the lower paper strip 81 are moved.

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The invention will now be explained in more detail with reference to the following examples, where I describe how the process according to the invention can be used, the progress of the coupling reaction in the production of azo dyes !! to monitor. It is natural clear that the method according to the invention is also used in others Similar cases can be used to determine the presence of critical substances in a chemical reaction and in other fluid systems to monitor, especially when these are flowing.

In the examples, all tsiles and percentages are by weight unless otherwise stated.

example 1

Three aqueous dye slurries (A, B and C) are prepared by coupling diazotized 2-brono-4,6-dinitroaniline with 5-acetylanino-II- (β-methoxyethoxycarbonylethyl) -2-methoxyaliiline, Seäe slurry 3% by weight. -X of the dye, 5 wt .- ^ j sodium sulfate and 3 wt .- / j of an ITodium acetate / acetic acid mixture (expressed as ilodium acetate) to buffer the pH to 4.5. The Aufschlämsiungen contain different excess amounts of the coupling component (A contains 5% excess, B contains Υ, λ excess and C contains no excess) compared to the amount required, the amount of diazotized 2-brono-4,6-diniti'oanilins to implement.

In separate experiments, each slurry becomes continuous at a rate of 10 ml / min with an O, 1m solution of diazotized aniline-2,5-disulfonic acid (developer), which flows at 2 ml / min, mixed. The Sntwiekler reacts with the excess Coupling component in the slurry, producing a water-soluble dye that causes an absorption peak 435 nm and an extinction coefficient of 3 x 10.

Part of the mixture is continuously fed to the distributor 33. of the shown in Figures 4 and 5 of the accompanying drawings

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Device fed at a rate of 2 ml / min. That The mixture flows through the slot nozzle 61 onto the paper surface cTes ob-sr-sn paper strips 79 of the two absorbent paper strips 79, S1 passing through the device at a steady rate of 1 nm / sec with the aid of the squeegee rollers 25, 27 are passed through.

The solids in the slurry are captured on the top surface of the upper belt 79 while the solute-containing liquid diffuses into both belts.

The lower band 31 is exposed by a light beam from the light source, vxid with two wavelengths 485 × 20 nm and 730-2G nm, which are filtered out by suitable filters in the light path, while the light beam passes through the detector aperture 59. A part of the diffuse reflected light of each wavelength is picked up by the detector 39, which feeds a signal to the analyzer. The analyzer compares the intensities of the reflected light of the two wavelengths and generates a signal which is representative of the logarithm of the ratio of the intensities of the two wavelengths. With every attempt the analyzer registers a steady signal if the steady flow inputs are set.

The results of the three runs using the slurries A, D and C are given in the table below:

Ver Aufschläm- Uol-yt excess of · analysis signal search for coupling component

1 ■ A 5 1.23

2 3 1 1.00

3 C 0 o.74

These results are used to create a graphic representation of the analyzer signal made against excess coupling component. This graph is a calibration curve of the device

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for their use "in" monitoring the extent of the coupling in the preparation of the aforementioned dye using the aforementioned descender.

Example 2

Two aqueous dyes on ε clilammungen (A and B) are produced by diazotized / i-Cß-HethosryätlioxyJ-ethyl ^ -aminobenzoate with 3-cyano-1-ethyl-6-hydro: x: y-4-methylpyrid -2-one is coupled, each slurry containing 14.6% dye and approximately 5% dispersant. Each slurry contains a different amount of excess coupling component (A contains 3.2 excess and B contains 4 excess) over that amount which is required to react with the diazotized ß- (ß-methoxyethoxy) -ethyl-4 -aminobenzoate to enter.

In separate experiments, each slurry is continuously used at a rate of 2 ml / min with a 1Obigen solution of Iron (III) chloride mixed in colorless industrial methyl alcohol (developer) flowing at 2 ml / min. The developer reacts with the excess coupling component in the slurry, being a water soluble colored substance with an absorption tip at 530 nm and an extinction coefficient of 80.

The mixture is fed to the manifold at a rate of 2 ml / min 33 of the device shown in Figures 4 and 5 of the accompanying drawings at a rate of 2 ml / min fed. The mixture flows through the slot nozzle 61 onto the upper surface of the upper paper strip 79 of the two absorbent Paper strips 79, 81, which with a constant speed of 1 mm / see with the help of the nip rollers 25, 27 through the device can be pulled through.

The solid in the slurry will be on the top surface of the upper belt 79 held in place, the soluble solids containing liquid diffuses into both bands.

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The lower belt 31 is formed by a light beam from the light source having two wave lengths of 530 - mn and 20,730 ί 20 nm exposed, which are filtered by suitable filters in the light path, while the light beam passes through the detector aperture 59th Part of the diffuse reflected light of each wavelength is picked up by the detector 39, which sends a signal for analysis. sator leads. The analyzer compares the intensities of the reflected light of the two wavelengths and generates a signal which is representative of the logarithm of the ratio of the intensities of the two wavelengths. With each attempt, the analyzer registers a steady signal if the steady flow conditions are set.

The results of the two runs using the slurries A and B are given in the following table:

Ver slurry mol% excess of analytical signal search for clutch components

1 A 3.2 1.25

2 B 4.0 1.75

A graphic representation of the analyte or signal against excess coupling component is produced from these results. This graph is a calibration curve of the device for its use in monitoring the extent of the reaction in the preparation of the aforementioned dye using the aforementioned developer.

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Claims (12)

Claims .) Method for determining the presence of a substance in a fluid medium, which is also a suspended particulate Contains substance, characterized that at least a portion of the fluid medium leads to 'a first permeable sheet material, which through Diffusion can separate the fluid medium from the particulate matter, and that one can use a detector instrument investigated the presence of the substance in the fluid ileum within a detector area in which the fluid medium from particulate matter is diffused away, wherein the detector area is on the first permeable sheet material or a second permeable sheet material, which during the application of the fluid medium in such a manner with the first Sheet material is in contact that the particulate matter in the fluid medium does not move from the first sheet material to the second Sheet material can get. 2. The method according to claim 1, characterized in that that the fluid medium is a liquid in which the substance is soluble. 3. Procedure for the determination of a soluble substance which is present in a Liquid is dissolved, which additionally contains a suspended insoluble solid, characterized in that applying at least a portion of the liquid to one side of a first permeable sheet material during the opposite side of the first sheet material with a second permeable sheet material in such a manner Touch is that the insoluble matter is completely retained by the first sheet material and the liquid into the second sheet material can diffuse, that one then separates the two sheet materials and that one using a detector instrument examines the presence of "the soluble substance." ■ 8098 84/0647 4. The method according to claim 2 or 3, characterized in that the detector instrument gives a signal, which is related to the amount of solute in the detector area. 5. The method according to any one of claims 2 to 4, characterized g e characterizing η st that the sheet material on which the liquid is applied, moves. 6. The method according to any one of claims 2 to 5, characterized in that the soluble substance by reaction a substance dissolved in the liquid with a developer is generated, dor is added, bsvor the liquid on the first sheet material is applied. 7. The method according to any one of claims 2 to 6, characterized in that the liquid is a reaction medium in the production of an insoluble Figments or The dye is composed of at least one soluble reactant. 8. Device for determining the presence of a soluble substance in a liquid that atxh a suspended undissolved Contains solid, characterized in that it comprises the following parts: a holder for a sheet material, which can separate the liquid from the undissolved material by diffusion, means for directing at least a part of the liquid on the surface of the sheet material and a detector instrument which has a detector area on the sheet material investigates in which the liquid can diffuse away from the undissolved substance by diffusion, and the soluble Substance or a product formed from it determined on the surface of the sheet material. 9. Device for determining the presence of a soluble substance in a liquid that is also a suspended undissolved 809884/0647 Contains solid, characterized in that it comprises the following parts: a holder for a first and a second permeable sheet material, which this at the beginning holding together and then separating along two opposite surfaces, an application device which at least eir.cn part of the liquid is directed onto the free surface of the first sheet material while it is with the second Sheet material is in contact, and a detector instrument, vaiches a detector area on the second sheet material examined after the two sheet materials separated from each other have become, and the soluble substance or one formed from it Product determined on the surface of the sheet material. 10. Performing according to claim 8, characterized in that that the holder has a drive device with which the sheet material at a constant speed can be moved. 11. The device according to claim 9, characterized in that that the holder has a drive means which the sheet materials at a constant speed moves, and also has suitably arranged rollers or guide surfaces, plural the two sheet materials in hold ilontalrt while they pass the application device, but then separate them and attach the second sheet of material to the detector instrument pass by. 12. Device according to one of claims 8 to 11, characterized in that the detector device is a. includes calibrated photometer. 809884/0647