DEVICES AND METHOD FOR MIXING LIQUIDS BY RECIRCULATION BETWEEN PUMP AND MEASURING CELL AND PHYSICOCHEMICAL ANALYSIS OF LIQUIDS MIXED IN THIS WAY

Description

technical field

[0001] The invention relates to the field of devices and methods for collecting and mixing liquids.

[0002] The invention is of particular interest in the field of analytical chemistry, especially for the preparation of solutions to be analyzed.

[0003] The invention is not limited to this particular field of application. It can be implemented in all industrial and scientific research fields. Prior art

[0004] The physico-chemical analysis of a liquid generally requires that the liquid be mixed beforehand with reagents.

[0005] A conventional analytical technique, known as sequential injection, involves injecting a sample of the liquid and the reagents into a circuit filled with a carrier liquid. The injection is performed using a syringe pump, which forces the reagents through a helical mixing tube. The resulting mixed solution is then pumped to a through-flow spectrophotometer cell where a spectral analysis is performed continuously.

[0006] Compared to conventional benchtop analysis, this technique reduces the volume of samples analyzed (approximately 10 µL per sample versus approximately 5 mL on the benchtop), reduces the volume of effluents generated (approximately 1.5 mL per sample analyzed versus approximately 60 mL on the benchtop), and reduces the analysis time (approximately 2 min 30 sec per sample versus more than 20 min on the benchtop).

[0007] However, this technique has some drawbacks.

[0008] On the one hand, the mixing within the helical tube produces a non-homogeneous solution.

[0009] On the other hand, the configuration of the spectrophotometric cell allows only time-domain measurements to be performed.

[0010] Furthermore, the unused portion of the sample cannot be recovered for further analysis because the sample taken is completely mixed with the carrier liquid.

[0011] Document EP 3 023 782 A1 describes a liquid chromatography device, comprising two piston sampling pumps, a dosing pump and a drain pump, and in which the liquids sampled by the sampling pumps are mixed within a mixer. Description of the invention

[0012] One aim of the invention is to provide devices and methods capable of improving the homogeneity of the mixture, providing a mixture suitable for analysis in an independent, non-temporal analysis step, and further reducing the volume of effluents generated.

[0013] Another objective of the invention is to increase the automation of the analysis process. Automation makes it possible to reduce sources of error in measurements and to increase the rate of analyses.

[0014] Another purpose of the invention is to enable the collection of a small volume of a liquid sample from a significant distance.

[0015] For this purpose, the invention relates to a liquid mixing device according to claim 1.

[0016] According to the invention, at least in one configuration of use of this device, the cavity defines a low point and said second connecting conduit is connected to the container so as to be able to introduce said liquids into or extract from the cavity through this low point.

[0017] The concepts of "low point" and "high point" are understood in their common meaning in fluid mechanics. Thus, the low point of the cavity is the lowest point of the cavity when the device is in said operating configuration, that is to say in a configuration allowing a movement of liquids from the chamber to the cavity under the action of a movement of the piston in the second direction and from the cavity to the chamber under the action of a movement of the piston in said first direction, when the valve is in the transfer position.

[0018] Positioning the second connecting conduit at the lowest point of the cavity allows for the extraction of a majority, if not all, of the liquids contained in the cavity through this conduit.

[0019] It is therefore possible to perform a mixing step by recirculating the liquids within the device after their initial introduction into the cavity. More precisely, this mixing step includes at least one movement of the liquids from the cavity to the chamber and then from the chamber back to the cavity; that is, at least one back-and-forth movement of the liquids between the cavity and the chamber.

[0020] During such a mixing stage, the liquids are subjected to stresses resulting from changes in cross-section between the cavity, the conduits, and the chamber. The conduits have a cross-section smaller than the cavity and the chamber, for example, approximately ten times smaller.

[0021] In tests in which this device was used to mix aqueous solutions for spectrophotometric analysis, it was found to be surprising that one or two round trips of the liquids between the cavity and the chamber make it possible to obtain a homogeneous solution capable of providing measurement results with both a very low standard deviation and bias.

[0022] The invention makes it possible to improve and automate both the mixing of liquids and the rinsing of the device while simplifying the device.

[0023] Positioning the second connecting conduit at the lowest point of the cavity allows for the automation of rinsing the device, and in particular the container cavity, by introducing a rinsing liquid into the device via one of the inlet conduits.

[0024] The aforementioned tests also showed the effectiveness of such rinsing in terms of removing traces that could affect a new measurement.

[0025] The invention thus makes it possible to automate most of the steps including rinsing the device and to obtain a homogeneous mixture of liquids in a fast, reliable and simple way, in particular without resorting to a mechanical mixing device such as a magnetic stirrer, a vibrating plate or a pump mixing mechanism.

[0026] Preferably, the cavity can be opened at one end of the container opposite the lowest point.

[0027] The cavity can thus be exposed to surrounding pressure such as atmospheric pressure.

[0028] This helps to avoid depression or overpressure phenomena in the cavity and the fluidic circuit during the implementation of the device.

[0029] In one embodiment, the cavity may have a section narrowing towards the bottom point.

[0030] Such a narrowing of the cavity helps to prevent liquid retention in the cavity, improves the mixing of liquids when they are extracted from the cavity through the second connecting conduit and improves the efficiency of cavity flushing.

[0031] When the container is a spectrophotometric measuring cuvette, such a narrowing of the cavity also makes it possible to reduce the volume of this cuvette while defining a sufficient height to carry out a suitable spectrophotometric measurement.

[0032] Preferably, at least when the device is in said operating configuration, the chamber can define a low point and said first connecting conduit can be connected to the pump so as to be able to introduce said liquids into or extract from the chamber through this low point.

[0033] Thus, when both air and liquids are introduced into the chamber, the air can rise up into the chamber against the piston while the liquids can occupy a space located vertically between the volume of air and the lowest point of the chamber.

[0034] When the piston is moved in the second direction, the air in the chamber pushes the liquids out, allowing all of these liquids to be moved into the container cavity and potentially injecting air bubbles into the liquids within the cavity. To this end, the device can be sized so that, when all the liquids from the chamber have been introduced into the container cavity, a residual amount of air remains in the chamber, causing air bubbles to form in the liquids within the cavity at the end of the piston's stroke.

[0035] The container can be used solely for mixing liquids or for both mixing and analyzing them. In other words, the container can form a measuring cell.

[0036] In a preferred embodiment, the container can be a spectrophotometric measuring cuvette.

[0037] The mixing device is of course compatible with other detection techniques such as colorimetry, atomic absorption spectrometry, inductively coupled mass spectrometry, refractometry, chemiluminescence or electrochemistry.

[0038] Preferably, the mixing device defined above is a microfluidic device.

[0039] In one embodiment, the valve referred to above may be a main valve, and the mixing device may include a sampling device comprising a sampling valve and a sampling conduit connected to a sampling port of the sampling valve. Preferably, the sampling valve may selectively occupy: a liquid sampling position establishing a fluidic communication between the sampling conduit and a first of said inlet conduits so as to be able to move the liquid from the sampling conduit to the chamber under the action of a movement of the piston in the first direction when the main valve is in a first sampling position establishing a fluidic communication between said first inlet conduit and the chamber, an air sampling position establishing a fluidic communication between an open way of the sampling valve and said first inlet conduit, said open way being exposed to the surrounding air, so as to be able to move surrounding air to the chamber under the action of a movement of the piston in the first direction when the main valve is in said first sampling position.

[0040] Such a sampling device makes it possible to take a relatively small volume of liquid over a relatively large distance, by conveying this volume of liquid between two volumes of air taken through said open channel.

[0041] Outside the scope of the present invention, the sampling device may be associated with a device different from the mixing device described above.

[0042] The invention also relates to a device for the physico-chemical analysis of a liquid, this analysis device comprising a mixing device as defined above.

[0043] This analysis device may include a system implementing one or more of the aforementioned detection techniques.

[0044] Thus, the analysis device may, for example, include a spectrophotometric detector.

[0045] According to another aspect, the invention relates to a method for mixing liquids using a mixing device as defined above, this method comprising: a sampling step in which said liquids are respectively moved from said inlet conduits to the pump chamber, this step including a positioning of the valve in said respective sampling positions, a container filling step including a movement of at least a part of the liquids from the chamber to the cavity, this step including a positioning of the valve in said transfer position, a mixing step including a movement of at least a part of the liquids from the cavity to the chamber and then from the chamber to the cavity.

[0046] This mixing process provides the same advantages as those indicated above with reference to the mixing device.

[0047] The invention also relates to a method for the physico-chemical analysis of a liquid using an analytical device as defined above, this analytical method including a mixing method as defined above.

[0048] Other advantages and features of the invention will become apparent from the detailed, non-limiting description that follows. Brief description of the drawings

[0049] The detailed description that follows refers to the attached drawings on which: There figure 1 is a schematic view of a mixing device according to the invention, comprising a piston pump, the piston being in a first position; The figure 2 is a schematic view of the device of the figure 1 the pump piston being in a second position; The figure 3 is a schematic cross-sectional view of a spectrophotometric measuring cuvette according to the invention; The figure 4is a schematic view of a sampling device according to the invention. Detailed description of implementation methods

[0050] He is represented at Figures 1 And 2 , schematically and in a simplified manner, a device conforming to the invention.

[0051] This device includes a pump 1, a valve 2 and a container 3 connected together in such a way as to be able to move and mix liquids.

[0052] Pump 1 comprises a body 4 and a piston 5.

[0053] In this example, the body 4 forms a cylindrical housing extending along a longitudinal axis A1 along which the piston 5 can slide.

[0054] On the Figures 1 And 2 the device is in a so-called usage configuration.

[0055] In this usage configuration, the longitudinal axis A1 is substantially parallel to the vertical, that is to say to the direction along which the gravitational force F1 is exerted.

[0056] The body 4 of the pump 1 includes a vertically lower end 7, a vertically upper end 8 and a side wall 9 connecting the lower end 7 and the upper end 8 to each other.

[0057] The terms "lower" and "upper", or "vertically lower" and "vertically upper" are defined with respect to the orientation of the gravitational force F1. Thus, when an element comprises a lower part and an upper part, a liquid subjected to the gravitational force F1 tends to move under the action of this force in a direction from the upper part to the lower part.

[0058] With reference to the figure 2, the piston 5 and the lower end 7 of the body 4 vertically delimit between them a chamber 10. Radially, the chamber 10 is delimited by the lateral wall 9 of the body 4 of the pump 1.

[0059] On the figure 1 , piston 5 is in a first position in which chamber 10 has zero volume. Piston 5 is shown in the figure 2 in a second position in which chamber 10 has a positive volume.

[0060] The volume when piston 5 is in the second position defines a total filling capacity of chamber 10 and corresponds, in this example, to a volume of approximately 1000 µL.

[0061] Pump 1 is a piston pump also known as a "syringe pump".

[0062] With reference to the figure 1 , valve 2 in this example is a multi-way rotary valve.

[0063] This valve 2 includes a common distribution point V0 connected to the chamber 10 of the pump 1 by a first connecting conduit 15.

[0064] THE Figures 1 And 2 The diagrams show the pump 1, valve 2, and conduit 15 as separate components. However, the conduit 15 can be molded into the body of valve 2 and connected to chamber 10 of pump 1 via a threaded fitting (not shown). In this case, the common distribution point V0 is formed by one end of conduit 15. More generally, the pump 1, valve 2, and conduit 15 can form a single product, such as the product known as the "XCalibur Cavro pump" (registered trademark).

[0065] In all cases, the first connecting conduit 15 is configured to establish fluid communication between the common distribution point V0 and chamber 10.

[0066] In general, valve 2 should include at least one inlet for introducing liquids into the device and one connection to the container 3. In this minimalist embodiment, liquids can be discharged through this same inlet. However, it is preferable to introduce the different liquids into the device through their respective inlets and discharge them through a dedicated outlet. For this reason, it is preferable that valve 2 include at least four ports: at least two inlets, one outlet, and one connection to the container 3.

[0067] In the example of the figure 1 Valve 2 comprises twelve ports V1-V12.

[0068] Since tracks V8 to V12 are not used in this example, they are equipped with plugs represented by crosses.

[0069] Regardless of the number of ways and the position change mechanism of valve 2, it is configured to be able to be placed selectively in different positions in each of which the common distribution point V0 and one of said ways V1-V12 are put into fluidic communication with each other.

[0070] The first connecting conduit 15 is connected to the pump 1 so as to be able to introduce into or extract liquids from chamber 10 through a low point 16 of chamber 10.

[0071] The lowest point 16 of chamber 10 is in this example located vertically at the level of the lower end 7 of the body 4 of the pump 1.

[0072] The lower end 7 includes for this purpose an opening forming this low point 16 and allowing to establish a fluidic communication between the chamber 10 and the first conduit 15, and consequently between the chamber 10 and the common distribution point V0.

[0073] Thus, the first connecting conduit 15 is connected to the pump 1 so as to be able to introduce into the chamber 10 or extract liquids from it through the lowest point 16.

[0074] As can be deduced from the following description, when chamber 10 is filled with both a volume of air and a volume of liquids which are assumed to be immiscible, the connection of the first conduit 15 at the level of the lowest point 16 of the pump 1 results in the air occupying an upper part of chamber 10 and the liquids a lower part of chamber 10, so that the volume of liquids is evacuated through the first conduit 15 before the volume of air.

[0075] Regarding container 3, it includes a cavity 18 configured to receive liquids.

[0076] In the example of Figures 1 And 2 , cavity 18 is formed by an opening passing through the container 3 along a longitudinal axis A2.

[0077] In the device's usage configuration, this longitudinal axis A2 is in this example substantially parallel to the vertical and to the longitudinal axis A1.

[0078] The container 3 comprises a body 20 forming a vertically lower end 21 and a vertically upper end 22.

[0079] In this example, the opening forming cavity 18 has a variable cross-section along axis A2.

[0080] Moving along axis A2 from the upper end 22 to the lower end 21 of the body 20, the cavity 18 comprises a first substantially cylindrical section 23, a second substantially conical section 24, and a third substantially cylindrical section 25. The diameter of the first section 23 is greater than the diameter of the third section 25.

[0081] The first section 23 of the cavity 18 opens onto an external surface of the upper end 22 of the container 3 so that the cavity 18 is exposed to atmospheric pressure, or in any case to the pressure of the environment in which the container 3 is placed.

[0082] The third section 25 of the cavity 18 opens onto an external surface of the lower end 21 of the container 3, defining a low point 26 of the cavity 18, at least in said configuration of use.

[0083] On the Figures 1 And 2 The proportions of cavity 18 and of each of the other elements of the device are not realistic, these figures being intended solely to illustrate the principle of the invention.

[0084] As a non-limiting example, it is represented at the figure 3 a container 3 actually designed within the framework of this invention.

[0085] Container 3 of the figure 3is a spectrophotometric measuring cuvette.

[0086] Tank 3 of the figure 3 is described solely according to its differences from container 3 of the figure 1 .

[0087] The cavity 18 of the tank 3 includes a fourth substantially cylindrical section 28 opening onto the external surface of the lower end 21 of the container 3, defining said low point 26 of the cavity 18.

[0088] The fourth section 28 is configured to cooperate with a conduit, via a threaded fitting (not shown), in order to convey liquids into the cavity 18 through this conduit.

[0089] Preferably, the third section 25 has a cross-section with a diameter substantially identical to the internal diameter of such a conduit.

[0090] The first section 23 is made in the form of a partially cylindrical opening machined so as to form two surfaces 29 parallel to each other and parallel to the longitudinal axis A2.

[0091] The surfaces 29 are polished and separated from each other by a distance D1 defining an optical path. In this example, the optical path D1 is 10 mm.

[0092] The surfaces 29 are respectively arranged opposite housings 40 intended to receive collimation lenses (not shown) allowing optimization of the optical path.

[0093] Such a tank 3 allows spectrophotometric measurements to be carried out on a mixture of liquids received in the cavity 18 at least partly at the level of the first section 23.

[0094] In one embodiment, the container 3 of the device Figures 1 And 2 is a spectrophotometric measuring cuvette such as the one shown in the figure 3 .

[0095] With reference to the figure 1 , the device includes a second conduit 27 for connecting the cavity 18 of the container 3 to the V1 channel of the valve 2, also called the transfer channel.

[0096] When container 3 is the tank of the figure 3 , the aforementioned conduit mentioned above in the description relating to the figure 3 consists of this second connecting conduit 27.

[0097] More generally, the second connecting conduit 27 is configured to establish fluidic communication between the transfer path V1 of valve 2 and the cavity 18 of vessel 3.

[0098] The second connecting conduit 27 is connected to the container 3 so as to allow liquids to be introduced into or extracted from the cavity 18 through said low point 26 of this cavity 18.

[0099] In the configuration of the figure 1 Or 2, when cavity 18 contains liquids, these tend to move towards the second connecting conduit 27 under the action of the gravitational force F1.

[0100] This configuration allows in particular to extract a majority or even all of the liquids contained in cavity 18 through this second connecting conduit 27.

[0101] In the example of the figure 1 The device comprises five inlet conduits 31-35 and one outlet conduit 36.

[0102] The inlet conduits 31-35 are respectively connected to the V2-V6 channels, known as inlet channels, by one of their ends.

[0103] In this example, the other end of each of the inlet conduits 31 and 32 is intended to be connected to a sampling point (not shown) in order to establish fluidic communication between this sampling point and the inlet channel V2 or V3 respectively.

[0104] The device in this example comprises four bottles 41-44, of which three bottles 41-43 each contain a respective liquid and one bottle 44 intended to receive liquid effluents.

[0105] The inlet conduits 33 to 35 are immersed by their other end in the bottles 41 to 43, respectively, so as to be able to draw the liquids contained in these bottles.

[0106] The outlet conduit 36 ​​is connected to the channel V7, called the outlet channel, at one of its ends. Its other end is placed in the bottle 44 so that liquid effluents can be discharged into it.

[0107] As indicated above, valve 2 can be placed in different positions in each of which one of the ways V1 to V12 is put into fluidic communication with the common distribution point V0.

[0108] In particular, valve 2 can selectively occupy sampling positions, each establishing a fluidic communication between one of the respective inlet conduits 31-35 and chamber 10 of pump 1.

[0109] Taking the example of the inlet conduit 33, the valve 2 can occupy a sampling position establishing a fluidic communication between the channel V4 and the distribution point V0 and therefore between the inlet conduit 33 and the chamber 10 of the pump 1. Such a sampling position makes it possible to take a part of the liquid contained in the bottle 41 and to move this part of the liquid towards the chamber 10 under the action of a movement of the piston 5 in a first direction S1.

[0110] The first direction S1 corresponds to a movement of the piston 5 towards the second position illustrated in the figure 2 , starting from the first position illustrated in the figure 1 or an intermediate position (not shown).

[0111] The liquids contained in bottles 42 and 43 can be taken and introduced into chamber 10 of pump 1 according to the same principle, respectively via inlet conduits 34 and 35, by placing valve 2 in a corresponding taking position.

[0112] A liquid sample can also be made in a similar way using the inlet conduit 31 or 32, for example by immersing the free end of one of these inlet conduits, i.e. the end opposite to that connected to valve 2, in a tank (not shown) containing such a liquid, and placing valve 2 in a sampling position establishing a fluidic communication between the distribution point V0 and the channel V2 or V3.

[0113] Another position of the valve 2, called the transfer position, allows a fluidic communication to be established between the distribution point V0 and the transfer path V1, and therefore between the chamber 10 of the pump 1 and the cavity 18 of the container 3.

[0114] Such a transfer position allows liquids previously introduced into chamber 10 to be moved from this chamber 10 into the cavity 18 of the container 3, via the connecting conduits 15 and 27.

[0115] To do this, the piston 5 of the pump 1 is moved in a second direction S2.

[0116] The second direction S2 corresponds to a movement of the piston 5 towards the first position illustrated in the figure 1 , starting from the second position illustrated in the figure 2 or an intermediate position (not shown).

[0117] To prevent the liquids introduced into cavity 18 from overflowing, the latter forms a volume greater than the total filling capacity of chamber 10.

[0118] The transfer position also allows liquids contained in cavity 18, typically after being introduced into it according to the principle described above, to be moved from this cavity 18 to the chamber 10 of the pump 1, via the connecting conduits 27 and 15, by moving the piston 5 in the first direction S1.

[0119] When valve 2 is in the transfer position, it is possible to move liquids back and forth between chamber 10 of pump 1 and cavity 18 of container 3, in particular to mix these liquids and improve the homogeneity of this mixture.

[0120] In order to precisely control the movement of piston 5 and the volume of liquid displaced by piston 5, the pump 1 may include an encoder mounted on its motor (not shown).

[0121] This device usage configuration is so named because it allows its implementation, in particular, for mixing liquids. This configuration therefore permits the movement of liquids from chamber 10 to cavity 18 and from cavity 18 to chamber 10 when valve 2 is in the transfer position.

[0122] It is evident that in another configuration in which the container 3 would be vertically arranged in the other direction, that is to say with the point 26 constituting a high point and not a low point and with the end 22 constituting a lower end and not a higher end, the liquids arriving in the cavity 18 by the second conduit 27 would be driven out of it under the action of the force of gravity F1 due to the opening of the cavity 18 on the external surface of the end 22 of the container 3.

[0123] Valve 2 can also be placed in a drain position establishing, in this example, a fluidic communication between the distribution point V0 and the outlet path V7, and therefore between the chamber 10 of the pump 1 and the outlet conduit 36.

[0124] Such a draining position allows liquids present in chamber 10 and / or in the first connecting conduit 15 to be evacuated to the bottle 44, by moving the piston 5 in the second direction S2.

[0125] The device of the figure 1 thus forms a mixing device.

[0126] As a non-limiting indication, the various conduits 15, 27 and 31-36 may have an external diameter of approximately 16 mm and an internal diameter of approximately 500 µm.

[0127] In an embodiment where the inlet pipes 31 and / or 32 are intended to draw one or more liquids from a relatively large distance from the valve 2, for example several meters, the internal diameter of these inlet pipes should be increased to reduce pressure losses. For example, the internal diameter of the inlet pipes 31 and / or 32 could in this case be 800 µm.

[0128] There figure 4shows a device 50 allowing a relatively small volume of liquid to be collected from a relatively large distance.

[0129] This sampling device 50 can be connected to the mixing device of the figure 1 in the manner described below, or to any other device requiring such remote sampling while limiting the volume of liquid taken.

[0130] Device 50 of the figure 4 includes a multi-way rotary valve 51 and a sampling conduit 52.

[0131] Valve 51 in this example includes a common distribution point V21, a sampling route V22 and a route V23 exposed to ambient air, also called an open route.

[0132] Valve 51 is configured to be able to be placed selectively either in a liquid sampling position in which the distribution point V21 is put into fluidic communication with the sampling path V22, or in an air sampling position in which the distribution point V21 is put into fluidic communication with the open path V23.

[0133] In this example, the inlet conduit 31 of the device is connected to the distribution point V21. figure 1 , by its end opposite to that connected to the inlet channel V2 of valve 2.

[0134] The sampling conduit 52 is connected at one end to the sampling line V22. The other end of conduit 52, which is free, is immersed in the liquid to be sampled, at a sampling point located relatively close to valve 51 compared to the distance between valves 2 and 51. In other words, the length of the inlet conduit 31 is much greater than that of the sampling conduit 52.

[0135] In one embodiment, the device of the figure 1 includes one or more magnetic stirrers (not shown) configured to homogenize, before sampling, the liquid(s) respectively contained in one or more of the bottles 41 to 43. Each stirrer includes, for example, a magnetic bar placed in the bottom of the corresponding bottle.

[0136] The invention also relates to a physico-chemical analysis device comprising, on the one hand, a detector (not shown), for example of the spectrophotometric type, and on the other hand, a mixing device as described above, the mixing device comprising or not one or more sampling devices such as device 50 of the figure 4 .

[0137] In one embodiment, the various components forming the mixing device of the figure 1 and possibly such a detector allowing measurements to be taken on liquids present in cavity 18, are integrated into a housing (not shown).

[0138] In one embodiment, this housing is produced by additive manufacturing. Generic example of a mixing and analysis process

[0139] The following example aims to illustrate the general operating principle of the mixing and analysis device described above, and the implementation of a mixing and analysis process according to the invention.

[0140] For this example, it is assumed that the device initially contains no liquid in chamber 10 of pump 1, in valve 2, in cavity 18 of container 3, in connecting conduits 15 and 27, in inlet conduits 31 to 35, and in outlet conduit 36.

[0141] In this example, bottles 41 and 42 contain a first and a second liquid respectively.

[0142] The following steps are carried out in order.

[0143] Initially, piston 5 of pump 1 is in the first position illustrated in the figure 1 .

[0144] Valve 2 is first placed in a first sampling position establishing a fluidic communication between the inlet conduit 33 and the chamber 10 of the pump 1, via the path V4, the distribution point V0 and the first connecting conduit 15.

[0145] Piston 5 is moved in the first direction S1.

[0146] During a first phase of this movement, the air present in the inlet duct 33 and in the first connecting duct 15 gradually enters the chamber 10 and, simultaneously, a part of the first liquid present in the bottle 41 is taken up by moving in the inlet duct 33 towards the chamber 10 until it reaches the end of the duct 15 connected to the pump 1.

[0147] During a second phase of the movement of the piston 5 in the first direction S1, the first liquid gradually enters the chamber 10.

[0148] At the end of this second phase, a first volume of the first liquid is present in chamber 10 and a second volume of the first liquid fills the first connecting conduit 15.

[0149] The movement of the piston 5 is interrupted at least for the time it takes to place the valve 2 in a second sampling position establishing fluid communication between the inlet conduit 34 and the chamber 10, via the path V5, the distribution point V0 and the first connecting conduit 15.

[0150] The movement of piston 5 can then continue its stroke in the first direction S1 so that, during a third phase of this movement: said second volume of the first liquid present in the first connecting conduit 15 gradually enters the chamber 10, followed by the volume of air present in the inlet conduit 34 before aspiration of the second liquid, and simultaneously a part of the second liquid present in the bottle 42 is taken up by moving in the inlet conduit 34 towards the chamber 10 until reaching the end of the conduit 15 connected to the pump 1.

[0151] During a fourth phase of the movement of the piston 5 in the first direction S1, the second liquid gradually enters the chamber 10.

[0152] At the end of this fourth phase, chamber 10 comprises: an air volume in the upper part, including on the one hand the volume of air initially present in the inlet duct 33 and in the first connecting duct 15 and, on the other hand, the volume of air present in the inlet duct 34 before aspiration of the second liquid, said first and second volumes of the first liquid, a first volume of the second liquid.

[0153] A second volume of the second liquid fills the first connecting conduit 15.

[0154] In this example, piston 5 occupies, at the end of this fourth phase, the second position illustrated in the figure 2 .

[0155] Valve 2 is then placed in the transfer position establishing fluid communication between chamber 10 of pump 1 and cavity 18 of container 3.

[0156] The piston 5 is moved in the second direction S2 so as to convey at least part, preferably all, of the first and second liquids present in the chamber 10 and in the first connecting conduit 15 into the cavity 18 of the container 3.

[0157] In this example, the device is configured so that the volume of air present in chamber 10 before the initiation of this movement, that is, when piston 5 is in the second position ( figure 2 ), is greater than the capacity of the first connecting conduit 15 and the second connecting conduit 27. Thus, the displacement of the piston 5 from the second position ( figure 2 ) up to the first position ( figure 1 ) allows the introduction into cavity 18 of all the first and second liquids present in chamber 10 and in the first connecting conduit 15.

[0158] During this movement, which corresponds to a step in filling container 3, the first and second liquids are at least partially mixed. However, this mixing may prove insufficient to obtain satisfactory homogeneity for the purposes of a spectrophotometric measurement, for example.

[0159] A mixing step is then carried out by keeping the valve 2 in the transfer position, and moving the piston 5 according to at least one back-and-forth sequence consisting of a movement of the piston 5 in the first direction S1 then in the second direction S2.

[0160] Such a sequence of piston 5 movement results in a back-and-forth movement of liquids between cavity 18 and chamber 10.

[0161] It is therefore possible to improve the homogeneity of the solution formed by mixing the first and second liquids.

[0162] Of course, the amount of displacement of the piston 5 in the first direction S1 and in the second direction S2 during this mixing step, or the time between two respective displacements of the piston 5, can be adapted according to the nature of the liquids to be mixed and the desired level of homogeneity.

[0163] At the end of the mixing step, which therefore includes one or more sequences of back-and-forth movements of the piston 5, the cavity 18 of the container 3 contains a mixture of the first and second liquids forming a solution that can be measured.

[0164] In this example, container 3 is a spectrophotometric measuring cuvette, and the device is programmed to perform, using a spectrophotometric detector and after the mixing step, one or more measurements on this solution.

[0165] After such a measurement step, the valve 2 is held or repositioned in the transfer position, the piston 5 is moved in the first direction S1 so as to convey into chamber 10 at least a part of the liquids contained in the container 3.

[0166] Valve 2 is then placed in the drain position, then piston 5 is moved to the first position to drain the liquids into bottle 44.

[0167] Before carrying out a new measurement on a new combination of the same or other liquids, a rinsing step is preferably carried out using a rinsing liquid taken for example from bottle 43 through inlet conduit 35, and conveyed into the different parts of the device (chamber 10, cavity 18) and then evacuated to bottle 44 according to the same principles as those just described.

[0168] The invention makes it possible to carry out a cycle or a series of cycles comprising a sampling of liquids, their mixing, the taking of measurements on the solution constituted by the mixed liquids, as well as an analysis based on such measurements, all in an automated manner, which in particular makes it possible to limit the interventions of operators and to increase the safety of personnel.

[0169] The invention also makes it possible to reduce the volume of samples required for analyses as well as the volume of effluents generated by these analyses.

[0170] In an embodiment not shown, the container 3 is used solely for mixing, and the measurement is performed within a separate cell (not shown). To do this, after mixing the liquids by back-and-forth movement between chamber 10 and cavity 18, the homogenized solution is ejected to such a cell via a dedicated channel of valve 2, for example channel V8. Remote sampling method

[0171] In the preceding example, the liquids to be mixed are taken from bottles 41 and 42, these being located at a relatively short distance from valve 2, i.e. a distance allowing the use of conduits 33 and 34 whose short length limits the quantity of liquid that needs to be taken.

[0172] The following is described, within the framework of such a mixing process, the case of sampling at a sampling point located at a relatively large distance, that is to say at a distance requiring the use of a conduit of relatively large length, for example of several meters.

[0173] The sampling method of the invention makes it possible to transport a liquid over a relatively large distance while reducing the amount of liquid actually collected.

[0174] Unlike the mixing process described above, the first liquid to be drawn is not contained in the bottle 41 but is drawn from a remote sampling point, at which the free end of the conduit 52 of the device 50 is positioned. figure 4 The mixing process incorporating this remote sampling process is described solely by its differences with the mixing process already described above.

[0175] Starting from the initial state, in which piston 5 is in the first position, valve 2 is placed in a sampling position, establishing fluid communication between the inlet 31 and chamber 10, via port V2, distribution point V0, and the first connecting port 15. Valve 51 is placed in the liquid sampling position, establishing fluid communication between the inlet 31 and sampling port 52, via sampling port V22 and distribution point V21. Valves 2 and 51, thus positioned, establish fluid communication between sampling port 52 and chamber 10 of pump 1.

[0176] Piston 5 is moved in the first direction S1.

[0177] During a first phase of this movement, the air present in the first connecting conduit 15, in the inlet conduit 31 and in the sampling conduit 52 gradually enters the chamber 10 and, simultaneously, a part of the first liquid located at said sampling point is taken up by moving in the sampling conduit 52 and then in the inlet conduit 31 towards the chamber 10.

[0178] The movement of the piston 5 is interrupted at least long enough to place the valve 51 in the air sampling position establishing a fluidic communication between the open channel V23 and the inlet duct 31. The valve 2 is maintained in the sampling position described above.

[0179] During a second phase of the movement of the piston 5 in the first direction S1, air enters the inlet duct 31 via the open passage V23 while the first liquid continues to be moved in the inlet duct 31 and then in the first connecting duct 15 towards the chamber 10.

[0180] The principle of this sampling process therefore consists of taking a small quantity of liquid and conveying it through a conduit between two volumes of air.

[0181] In general, the arrival of the first liquid taken at valve 2, in this example at the level of channel V2, can be determined by calculation and / or detected by a sensor (not shown).

[0182] Depending on the length of the inlet conduit 31, intermediate air purges may be necessary to convey the first liquid thus drawn into the chamber 10 of the pump 1.

[0183] An intermediate air purge can be performed by placing valve 2 in the drain position or, optionally, in a purge position that connects the first connecting conduit 15 to a dedicated channel such as channel V12. After valve 2 is positioned in this way, piston 5 is moved in the second direction S2 to evacuate some of the air contained in the first connecting conduit 15 and chamber 10. Valve 2 is then returned to the sampling position described above, and piston 5 is moved in the first direction S1 to continue conveying the first liquid to chamber 10.

[0184] The introduction into chamber 10 of the first liquid and then of the second liquid, as well as their mixing, can then be carried out as described above.

[0185] The remote sampling process can also be implemented in other applications, for example to collect a liquid sample and analyze that sample without mixing it with other liquids. Example of implementation for a pH measurement

[0186] A specific example of the implementation of the mixing device is described below. figure 1 , to measure the pH of an acidic aqueous solution.

[0187] Bottles 41, 42 and 43 contain respectively a sodium oxalate solution, a pH-sensitive dye solution and a rinsing liquid such as an aqueous solution of a weak acid.

[0188] The initial conditions are as follows. Ducts 33, 34 and 35 are filled with the corresponding solutions and the other elements of the device are rinsed and exposed to ambient air.

[0189] The first step involves preparing a sample of the acidic aqueous solution for analysis.

[0190] To do this, an operator immerses the free end of the conduit 31 in a jug (not shown) containing the acidic aqueous solution. Valve 2 is positioned to connect the dispensing point V0 and the channel V2, and piston 5 is moved in the first direction S1 to draw a sample volume equivalent to the volume of the conduit 31, plus an additional 20 µL for rinsing. Valve 2 is then positioned to connect the dispensing point V0 and the channel V1, and piston 5 continues its stroke to the second position (maximum upper position) to draw in as much air as possible. Valve 2 is then positioned to connect the dispensing point V0 and the channel V7, and piston 5 is moved in the second direction S2 to the first position (maximum lower position) to push the remaining 20 µL of the sample into the effluent.

[0191] A second step involves rinsing the device with the sodium oxalate solution used as the main reagent medium.

[0192] To this end, valve 2 is positioned to connect the dispensing point V0 and the channel V4, and piston 5 is moved in the first direction S1 to draw a volume of 200 µL of the sodium oxalate solution. Valve 2 is then positioned to connect the dispensing point V0 and the channel V1, and piston 5 continues its stroke to its maximum upper position to draw in as much air as possible. Piston 5 is then moved to its maximum lower position to send the 200 µL of sodium oxalate solution into cavity 18 of container 3, and then back to its maximum upper position to return the 200 µL of sodium oxalate solution to chamber 10 of pump 1.Valve 2 is then positioned to connect the distribution point V0 and the channel V7 in fluidic communication, and piston 5 is moved to the lowest maximum position in order to push the 200 µL of sodium oxalate solution which has been used to pre-rinse the majority medium of the upcoming analysis.

[0193] A third sequence involves taking defined volumes of sodium oxalate solution, dye solution, and sample. Within this third sequence, one or more additional pre-rinses can be performed as described above, using different volumes of sodium oxalate solution; for example, a first additional pre-rinse with a volume of 1000 µL of sodium oxalate solution and a second additional pre-rinse with a volume of 200 µL of sodium oxalate solution.

[0194] To perform the sampling, valve 2 is positioned to connect dispensing point V0 and channel V4, and piston 5 is moved in the first direction S1 to withdraw a volume of 790 µL of the sodium oxalate solution. Valve 2 is then positioned to connect dispensing point V0 and channel V5, and piston 5 continues its movement in the first direction S1 to withdraw a volume of 100 µL of the dye solution. Valve 2 is then positioned to connect dispensing point V0 and channel V2, and piston 5 continues its movement in the first direction S1 to withdraw a volume of 10 µL of sample.

[0195] A fourth step involves mixing the liquids thus collected.

[0196] To achieve this, valve 2 is positioned to establish fluid communication between distribution point V0 and channel V1, and piston 5 continues its stroke in the first direction S1 until it reaches its maximum upper position to draw in as much air as possible. Piston 5 is then moved to its maximum lower position to send 900 µL of the mixture into cavity 18, then to its maximum upper position to return the 900 µL of the mixture to chamber 10, and finally back to its maximum lower position to return the 900 µL of the mixture to cavity 18.

[0197] A fifth step involves analyzing the mixture in cavity 18 of vessel 3. In this example, vessel 3 is a spectrophotometric measuring cuvette. A raw spectrum is acquired on the solution in cavity 18 of cuvette 3.

[0198] In a manner known in itself, a set of calculations taking into account this acquisition, as well as the standards previously made and the volumes involved, allows us to deduce the pH of the sample.

[0199] A sixth sequence consists of evacuating the mixture to the flask 44 intended to receive the effluent. To do this, the piston 5 is moved to its maximum upper position to introduce the 900 µL of the mixture into the chamber 10. The valve 2 is then positioned to establish fluid communication between the distribution point V0 and the channel V7, and the piston 5 is moved to its maximum lower position to push the 900 µL of solution towards the effluent.

[0200] A seventh sequence consists of rinsing the device with a weak acid. To do this, valve 2 is positioned to connect the distribution point V0 and the channel V6 in fluidic communication, and piston 5 is moved in the first direction S1 in order to withdraw a volume of 200 µL of the weak acid solution. Valve 2 is then positioned to connect the distribution point V0 and the channel V1 fluidically, and piston 5 is moved to the maximum upper position to draw in as much air as possible, then to the maximum lower position to send the 200 µL of weak acid into cavity 18, then back to the maximum upper position to return the 200 µL of weak acid to chamber 10. Valve 2 is then positioned to connect the distribution point V0 and the channel V7 fluidically, and piston 5 is moved to the maximum lower position to evacuate the 200 µL of weak acid which has been used for rinsing.

[0201] One or more additional rinses may be carried out in the manner described above, with different volumes of the weak acid solution, for example a first additional rinse with a volume of 1000 µL of the weak acid solution and a second additional rinse with a volume of 200 µL of the weak acid solution.

[0202] An eighth step involves returning the excess sample to the jug. To do this, valve 2 is positioned to connect dispensing point V0 and channel V1, and piston 5 is moved to its maximum upper position to draw in a volume of air corresponding to the volume of conduit 31 plus a 20 µL margin. Valve 2 is then positioned to connect dispensing point V0 and channel V2, and piston 5 is moved to its maximum lower position to push the air into conduit 31, thus returning the unused sample to the jug.

Claims

1. Mixing device for liquids, this device comprising a piston (5) pump (1), a multi-way valve (2), a recipient (3), a first duct (15) for connecting the valve (2) to a chamber (10) of the pump (1), a second duct (27) for connecting a cavity (18) of the recipient (3) to a transfer way (V1) of the valve (2), several inlet ducts (31-35) each connected to a respective inlet way (V2-V6) of the valve (2), the valve (2) being able to selectively occupy: - sampling positions each establishing a fluidic communication between a respective one of said inlet ducts (31-35) and the chamber (10) so as to be able to move a respective one of said liquids from this inlet duct towards the chamber (10) by the action of a movement of said piston (5) in a first direction (S1), - a transfer position establishing a fluidic communication between the chamber (10) and the cavity (18) so as to be able to move said liquids, via the first and the second connection duct (15, 27), from the chamber (10) to the cavity (18) by the action of a movement of the piston (5) in a second direction (S2) and from the cavity (18) to the chamber (10) by the action of a movement of the piston (5) in said first direction (S1), this device being characterised in that, at least in one use configuration of this device, the cavity (18) defines a low point (26) and said second connection duct (27) is connected to the recipient (3) so as to be able to introduce into the cavity (18) or extract therefrom said liquids through this low point (26).

2. Mixing device according to claim 1, wherein the cavity (18) is open at one end of the recipient (3) opposite to the low point (26).

3. Mixing device according to claim 2, wherein the cavity (18) has a section narrowing towards the low point (26).

4. Mixing device according to any one of claims 1 to 3, wherein, at least when the device is in said use configuration, the chamber (10) defines a low point (16) and said first connection duct (15) is connected to the pump (1) so as to be able to introduce into the chamber (10) or extract therefrom said liquids through this low point (16).

5. Mixing device according to any one of claims 1 to 4, wherein the recipient (3) is a spectrophotometric measuring cell.

6. Mixing device according to any one of claims 1 to 5, wherein said valve (2) is a main valve, this mixing device comprising a sampling device (50) comprising a sampling valve (51) and a sampling duct (52) connected to a sampling way (V22) of the sampling valve (51), the sampling valve (51) being able to selectively occupy: - a liquid sampling position establishing a fluidic communication between the sampling duct (52) and a first (31) one of said inlet ducts (31-35) so as to be able to move the liquid from the sampling duct (52) towards the chamber (10) by the action of a movement of the piston (5) in the first direction (S1) when the main valve (2) is in a first sampling position establishing a fluidic communication between said first inlet duct (31) and the chamber (10), - an air sampling position establishing a fluidic communication between an open way (V23) of the sampling valve (51) and said first inlet duct (31), said open way (V23) being exposed to the surrounding air, so as to be able to move surrounding air towards the chamber (10) by the action of a movement of said piston (5) in a first direction (S1) when the main valve (2) is in said first sampling position.

7. Analysis device for the physicochemical analysis of a liquid, this analysis device comprising a mixing device according to any one of claims 1 to 6.

8. Analysis device according to claim 7, this device comprising a spectrophotometric detector.

9. Method for mixing liquids using a mixing device according to any one of claims 1 to 6, this method comprising: - a sampling step in which said liquids are respectively moved from said inlet ducts (31-35) towards the chamber (10) of the pump (1), this step comprising positioning the valve (2) in said respective sampling positions, - a step of filling the recipient (3) comprising moving at least part of the liquids from the chamber (10) to the cavity (18), this step comprising positioning the valve (2) in said transfer position, - a mixing step comprising moving at least part of the liquids from the cavity (18) to the chamber (10) then from the chamber (10) to the cavity (18).

10. Analysis method for physicochemical analysis of a liquid using an analysis device according to claim 7 or 8, this analysis method including a mixing method according to claim 9.