Multi-ion sensor, flow measuring cell and system for measuring ions in aqueous systems

Abstract

The present invention relates to a multi-ion sensor (1) for measuring ions in aqueous systems comprising a flexible or semi-flexible substrate (11), a reference electrode (13) applied to the substrate (11), at least three working electrodes (15a, 15b, 15c) applied to the substrate (11), wherein the substrate (11), the reference electrode (13) and the working electrodes (15a, 15b, 15c) form an ion-selective sensor unit (101), a connection device (17) for the ion-selective sensor unit (101) and a sensor housing (19) which accommodates an assembly of ion-selective sensor unit (101) and connection device (17), wherein the reference electrode (13) has dimensions of max. 4 mm×4 mm×4 mm.

The present invention is furthermore directed to a flow measuring cell (3) for measuring ions in aqueous systems as well as to a respective method for measuring ions in aqueous systems and a system for measuring ions in aqueous systems and for adjusting the ion contents in the aqueous systems.

Claims

1. A multi-ion sensor (1) for measuring ions in aqueous systems comprising a flexible or semi-flexible substrate (11), a reference electrode (13) applied to the substrate (11), at least three working electrodes (15a, 15b, 15c) applied to the substrate (11), wherein the substrate (11), the reference electrode (13) and the working electrodes (15a, 15b, 15c) form an ion-selective sensor unit (101), a connection device (17) for the ion-selective sensor unit (101) and a sensor housing (19) which accommodates an assembly of ion-selective sensor unit (101) and connection device (17), wherein the reference electrode (13) has dimensions of max. 4 mm×4 mm×4 mm.

2. The multi-ion sensor (1) according to claim 1, wherein the material of the reference electrode (13) is selected from polymer-coated fibres and Ag/AgCl.

3. The multi-ion sensor (1) according to claim 1, wherein the sensor housing (19) accommodates the assembly of ion-selective sensor unit (101) and connection device (17) such that the rear side of the substrate (11) rests on a supporting part (191) of the sensor housing (19), and wherein the sensor housing (19) encloses the assembly of ion-selective sensor unit (101) and connection device (17) to such an extent that the ends of the reference electrode (13) and the working electrodes (15a, 15b, 15c) are exposed with respect to the outside and thus form the measuring head (103) of the multi-ion sensor (1).

4. The multi-ion sensor (1) according to claim 3, wherein the sensor housing (19) has a recessed partial surface (193) which corresponds geometrically with the supporting part (191) with an ion-selective sensor unit (101) resting thereon, so that a measuring gap (S) is formed between the ion-selective sensor unit (101) on the supporting part (191) and the recessed partial surface (193).

5. The multi-ion sensor (1) according to claim 4, wherein the height (H) of the measuring gap (S) and the width (B) of the measuring gap (S) are in a geometric ratio H:B of 1:1 to 4:1.

6. A flow measuring cell (3) for measuring ions in aqueous systems, comprising a receiving opening (31) for mounting a multi-ion sensor (1) according to of claim 1, wherein the measuring head (103) of the multi-ion sensor (1) can be mounted in a form-fitting manner in the receiving opening (31) and together with the rear wall of the receiving opening (31) can form a flow-through measuring chamber, at least one calibration supply line (33), at least one sample supply line (35), a manifold (37) receiving the at least one calibration supply line (33) and the at least one sample supply line (35) and extending towards the receiving opening (31) a drain line (39) which connects upstream of the receiving opening (31).

7. The flow measuring cell (3) according to claim 6, wherein the diameters of the calibration supply line (33) and/or the sample supply line (35) and/or the collecting line (37) are 2 mm to 4 mm.

8. The flow-through measuring cell (3) according to claim 6, wherein the cumulative volume of the calibration supply line (33), the sample supply line (35), the collecting line (37) and the flow-through measuring chamber is 2 ml to 5 ml.

9. A method for measuring ions in aqueous systems comprising the steps of a) providing a flow-through measuring cell (3) according to claim 6 with an assembled multi-ion sensor (1) according to claim 1, b) introducing a first aqueous calibration solution into the flow measurement cell (3) with flushing of the ion-selective sensor unit (101) of the multi-ion sensor (1), thereby performing a first calibration and recording a first reference measurement value, c) introducing an aqueous sample into the flow measuring cell (3) with flushing of the ion-selective sensor unit (101) of the multi-ion sensor (1), thereby recording a measurement value bundle, d) introducing a second aqueous calibration solution into the flow measuring cell (3) with flushing of the ion-selective sensor unit (101) of the multi-ion sensor (1), thereby carrying out a second calibration and recording a second reference measured value, wherein steps a), b) c) and d) are carried out quasi-continuously without draining the flow measuring cell (3), e) calculating the measurement values from first and second reference measurement values and measurement value bundles, f) processing the measurement values in a computing unit.

10. The method according to claim 9, wherein the volume of the first aqueous calibration solution, the aqueous sample and the second aqueous calibration solution required for the measurement is 3 ml to 10 ml.

11. The method according to claim 9, wherein before step b) the volume of liquid present in the feed lines to the flow-through measuring cell (3) is completely replaced by fresh volume of liquid of the aqueous system, the replaced volume of liquid present being returned to the aqueous system.

12. A system for measuring ions in aqueous systems and for adjusting the ion contents in the aqueous systems, comprising a flow-through measuring cell (3) according to claim 6, a multi-ion sensor (1) mounted in the flow measuring cell (3) according to claim 1, a pump unit which is fluid-dynamically connected on the input side to the aqueous system and to storage containers for the first and second aqueous calibration solution for taking the sample and which is fluid-dynamically connected on the output side to the at least one calibration supply line (33) and to the at least one sample supply line (35), a control unit which is electronically connected on the input side to the multi-ion sensor (1), the control unit having evaluation electronics for processing the first and second reference measured values and measured value bundles.

13. The system according to claim 12, wherein the control unit is designed to regulate the ion concentration in the aqueous system as a function of the control difference.

Description

[0082] Further objectives, features, advantages and possible applications result from the following description of embodiments not limiting the invention on the basis of the figures. In this context, all the features described and/or illustrated constitute the subject-matter of the invention, either individually or in any combination, even irrespective of their summary in the claims or their relation back. The figures show:

[0083] FIG. 1 a schematic drawing of the ion-selective sensor unit 101 according to one embodiment of the invention,

[0084] FIG. 2 a schematic drawing of the multi-ion sensor 1 according to an embodiment of the invention in an opened state,

[0085] FIG. 3 a schematic drawing of the multi-ion sensor 1 according to one embodiment of the invention in the closed state, and

[0086] FIG. 4 a schematic sectional view of the flow measuring cell 3 according to an embodiment of the invention.

[0087] FIG. 1 schematically shows the ion-selective sensor unit 101 in a preferred embodiment of the invention. The electrodes are mechanically printed on the substrate 11, in this case a flexible printed circuit board, for example as graphite tracks. In the present embodiment, four of the printed electrodes are designed as working electrodes 15a, 15b, 15c, 15d, whereby the majority of the conductive tracks are covered with a lacquer for protection and essentially the end shown round in the figure forms the measuring point. Depending on the ions to be measured, the measuring points are formed accordingly with an ion-sensitive material.

[0088] The fifth electrode in this illustration represents the real reference electrode 13, which also initially consists of a printed conductive path (e.g. graphite) with regard to its lead. However, the actual, miniaturised electrode is applied or contacted at the round measuring point, whereby the material consists particularly preferably of polymer-coated fibres to which Ag/AgCl (silver/silver chloride) has been added.

[0089] The arrangement or sequence of the reference electrode 13 and the working electrodes 15a, 15b, 15c, 15d in FIG. 1 is merely exemplary and does not define the invention in any specific way.

[0090] The ion-selective sensor unit 101 is contacted at the end of the substrate 11 opposite the measuring points by a connection device 17. In a preferred embodiment, the printed conductive tracks have a contact surface at the end with which they can be inserted into the connection device 17. The connection device 17 also has a data cable with a corresponding plug for connection to a computer unit.

[0091] FIG. 2 shows how the ion-selective sensor unit 101 with attached connection device 17 is accommodated in the sensor housing 19, whereby the sensor housing 19 is shown open here. The sensor housing 19 may be of one-piece construction, but in a preferred embodiment, which is also shown here, the sensor housing 19 is of two-piece construction, which makes assembly somewhat easier.

[0092] The supporting part 191 of the sensor housing 19 is shown with a dashed line, on which the front part of the ion-selective sensor unit 101 rests with its rear side, the measuring points are exposed towards the front. This part of the housing or of the ion-selective sensor unit 101 is washed around or washed over by the liquid to be measured, while the part shown here to the left of the dashed line is firmly and tightly sealed.

[0093] FIG. 3 schematically shows the multi-ion sensor 1 of the preferred embodiment of the invention in a closed state. Here the ion-selective sensor unit 101 is shown dashed, which rests on the supporting part 191 of the sensor housing 19. Opposite it, the measuring head 103 is formed by a recessed partial surface 193, so that the measuring gap S can be formed between them. The width B and the height H are shown.

[0094] In FIG. 4, the flow measuring cell 3 according to the invention is schematically shown in section according to an embodiment of the invention. In principle, one calibration supply line 33, through which two calibration liquids can be introduced, is sufficient.

[0095] However, in practice it has been found to be advantageous to provide a separate calibration supply lines 33a, 33b for each of the two calibration liquids. In the present embodiment, the sample supply line 35 is located between the two calibration supply lines 33a, 33b, but this does not necessarily have to be the case. Depending on the requirements, a further sample supply line 35 could also be provided. The supply lines 33a, 33b, 35 are brought together in the collecting line 37 and led to the receiving opening 31.

[0096] This receiving opening 31 is designed to positively receive the measuring head 103 of the multi-ion sensor 1 so that no liquid escapes from the flow measuring cell 3 at this point. The measuring gap S, together with the rear wall of the receiving opening 31, forms a flow measuring space in which a laminar flow can be formed. This is supported by the fact that the collecting line 37 leads into the receiving opening 31 at the bottom, while the drain line 39 is arranged above it.

[0097] The present invention is for measuring ions in aqueous systems, in particular, but not limited thereto, for monitoring ion concentrations in aquariums, in this case especially seawater aquariums.

[0098] The system for measuring ions in aqueous systems and for adjusting the ion contents in the aqueous systems comprises the flow measuring cell 3 according to the invention with a multi-ion sensor 1 according to the invention installed therein. A pump unit is connected on the input side to the aqueous system for taking the sample, here specifically for example to an aquarium. Dosing pumps are used which can deliver small volumes very precisely.

[0099] The hoses from the aquarium to the measuring system in the measuring cell usually contain several millilitres of sample, i.e. in this case aquarium water. Before a measurement, fresh sample water should be added to obtain a current value. In order not to waste the water present in the hoses by discharging it as waste water, it is provided that first a predetermined amount of sample water is pumped through the hoses, whereby the water previously standing in the hoses is returned to the aquarium. Subsequently, the flow of the sample water can be directed into the measuring system, specifically into the flow measuring cell 3, via a change-over valve.

[0100] Since each ion-selective electrode drifts over time, calibration is performed before each measurement to ensure reliable measurement. For this purpose, a first calibration liquid is passed through the flow measuring cell 3, the concentration of which is below the expected concentration of the sample water to be measured. Next, the sample water is then passed through the flow measuring cell 3 and the corresponding measured values are recorded as a measurement bundle. Finally, a second calibration liquid is passed through the flow measuring cell 3, the concentration of which is above the expected and to be measured concentration of the sample water.

[0101] The liquid volumes of the two calibration liquids and the measured sample water are discarded and added to the waste water. After the measurement is completed, the flow is stopped without the need to empty the flow measuring cell 3 and without the multi-ion sensor 1 falling dry. Herein lies another great advantage of the present invention.

REFERENCE SIGNS

[0102] 1 Multi-ion sensor [0103] 11 substrate [0104] 101 ion-selective sensor unit [0105] 103 measuring head [0106] 13 reference electrode [0107] 15 working electrodes [0108] 17 connection device [0109] 19 sensor housing [0110] 191 supporting part [0111] 193 recessed partial surface [0112] 3 flow measuring cell [0113] 31 receiving opening [0114] 33 calibration supply line [0115] 35 sample supply line [0116] 37 collector line [0117] 39 drain line [0118] B width [0119] H height [0120] S measuring gap