WO2004005893A2

WO2004005893A2 - Apparatus for metering analytes contained in a liquid sample and related process

Info

Publication number: WO2004005893A2
Application number: PCT/IB2003/002610
Authority: WO
Inventors: Pompeo Moscetta
Original assignee: Pompeo Moscetta
Priority date: 2002-07-03
Filing date: 2003-07-03
Publication date: 2004-01-15
Also published as: AU2003281296A1; ITRM20020356A0; WO2004005893A3; CN100408994C; CN1666098A; ITRM20020356A1

Abstract

Apparatus (1) for metering analytes in liquid samples apt to be used in underwater environment, comprising: a sampling unit (2) to allow the addition inside the apparatus itself of the liquid sample (C) to be analyzed; a unit (22) for the addition to the sample of reagents (R1, ..., Rn); a unit (28) for detecting the concentration of the analytes contained in the sample; a closed circuit (10) which connects the above mentioned units to allow the continuous and repeated circulation of the sample among them; and a peristaltic pump (29) arranged along the closed circuit, the arrangement being so that the reagent-inletting valves of the addition units are arranged along the closed circuit, implementing tracts with tortuous development of the latter and so that the mixing between sample and reagents takes place thanks to the turbulent motion which begins during the circulation of the sample inside the circuit.

Description

APPARATUS FOR METERING ANALYTES CONTAINED IN A LIQUID SAMPLE

AND RELATED PROCESS DESCRIPTION The present invention relates to an apparatus for metering analytes contained in a liquid sample apt for use in an underwater environment and to a related process. In particular, the invention relates to an apparatus of the type comprising: a sampling unit, to allow adding inside the apparatus the liquid sample to be analyzed; an addition unit to add to the sample at least one reagent; a unit for detecting the concentration of the analytes contained in the sample; and pump means for the circulation of the sample among the different units.

In manual practice, to carry out a chemical analysis the reaction chemistry and the conditions for the development thereof are firstly defined and then one proceeds to add to the sample to be analyzed the necessary reagents. At last, a mixing of such components is performed to minimize the times of molecular diffusion and to allow then a rapid development of the reaction itself. Once the latter has taken place, one proceeds to detect the analytes, for example with methodologies of a colorimetric type. In case of this last type of analysis methodologies, the reaction development involves a variation in the transmittance of the spectrum of the reaction products with transparency and/or absorption bands on specific wavelengths which can be correlated, by previous calibration, with the concentration of the parameter object of the measurement.

During the last fifty years several systems have been set up to automate chemical analyses ever more. In particular, many methodologies enabling such automation utilize instrumentation based upon the so-called analytical principles of "Continous Flow Analysis" (C.F.A.), "Flow Injection Analysis" (F.I.A.) and "Discrete Analysis"

(D.A.).

Such automated systems belonging to the state of art have been devised, for the most part, for the clinical field and have detectability limits insufficient to the analytical requirements of many fields. Furthermore, the analysis apparatuses of the known art have huge mechanical sizes which do not allow either an easy transportation or a comfortable use for in situ analyses. Due to this, said apparatuses are not suitable for applications of environmental monitoring, for examples seas, rivers, lakes, air and industrial release since such applications require a higher miniaturization of the used systems. Another drawback of the apparatuses of known art is that of the high consumption in reagents and electric energy, which in turn involve logistical problems. The drawbacks of the systems of the known art just mentioned have been partially overcome by the teachings of the Italian patent 1 249 433 in the name of the same applicant of the present application, which describes an apparatus comprising a closed hydraulic circuit for the repeated circulation of the sample to be analyzed inside the apparatus itself. Nevertheless, the apparatus of said patent is not suitable for applications in underwater environment at medium and high depths. In fact, such apparatus provides a mixing of sample and reagents based upon the use of a mixing chamber inside of which a depression is cyclically created, according to modes which are not suitable for applications in environments pressurized at high pressure. Furthermore, the need for additional miniaturization of the components and for the additional decrease in the used quantities of reagents still remains. The technical problem underlying the present invention is to provide an apparatus and a related process enabling to obviate to the drawbacks mentioned above with reference to the known art. Such problem is solved by an apparatus according to claim 1. The invention further provides a plant according to claim 18.

According to the same inventive concept, the invention also relates to a process according to claim 20. The term "valve" here is to be intended in its most general meaning, that is as referred to any means apt to allow/interdict the introduction of the reagent inside the circuit.

The present invention provides some important advantages. The main advantage lies in the fact that the apparatus of the invention does not require mixing chambers, since, owing to the arrangement and to the shape of the reagent-inletting valves, each reagent mixes effectively with the sample to be analyzed directly into the mixing circuit by means of a continuous circulation and in a turbulent state. This allows decreasing the necessary quantity of reagents and obtaining an additional miniaturization with respect to the systems of the known art. Furthermore, this allows wholly eliminating the air from the circuit of the apparatus, so that the latter results to be usable also in environments pressurized at several hundreds of bar and thus it can be efficiently used to perform chemical analyses in underwater environment at abyssal depths.

Other advantages, features and application modes of the present invention will be evident by the following detailed description of some embodiments, shown by way of example and not for limitative purposes. The figures of the enclosed drawings will be referred to, wherein: figure 1 shows an operating scheme of an embodiment of the apparatus according to the present invention; and figure 2 shows an operating scheme of a plant according to the present invention incorporating the apparatus of figure 1.

By firstly referring to figure 1, an apparatus for metering analytes in liquid samples is designated as a whole with 1.

The apparatus 1 comprises a plurality of units hydraulically connected one to the other to form a mixing hydraulic circuit 10.

In particular, the apparatus 1 comprises a sampling unit 2 apt to allow the introduction inside the apparatus itself of a liquid sample C to be analyzed. Such sampling unit 2, in turn, first of all comprises a first three-way valve 3, and in particular a deflector valve. The mobile end of the deflector, designated with 4, can assume a first position 5, wherein the valve 3 allows the adduction of the liquid sample C inside the apparatus 1, and in particular inside the hydraulic circuit 10 thereof, and a second position 6, wherein the valve 3 itself establishes a flow continuity with a second three-way valve 7. The latter too is a valve having a deflector 8, the end of which is mobile between a first position 9 and a second position 11. In the first position 9 the second valve 7 puts in communication, through the first valve 3, the circuit 10 with a tank 13 containing a calibrant. On the contrary, in the second position 11 the second valve 7 allows, still through the first valve 3, the adduction inside the circuit 10 of a washing fluid, for example water, contained in a tank 12.

The sampling unit 2 then comprises a third 2x3-way valve with double deflector, designated as a whole with 14 and inserted along the circuit 10 to open/close the circuit 10 itself. Such valve 14 is inserted into the circuit 10 so as to define a tract with a tortuous path thereof. The valve 14 has a first three-way section 141 comprising a first deflector 15, and a second section 142, with three ways too, comprising a second deflector 19.

The first deflector 15 has an end movable between a first position 16, wherein it establishes a fluid communication between the circuit 10 and the first valve 3, and a second position 17, wherein it establishes a fluid communication with the second section 142 by means of a channel 18, interdicting the sample inflow, washing fluid or calibrant in the circuit itself.

The second deflector 19 has instead an end movable between a first position 20, wherein it establishes a communication with the first section 141 by means of the channel 18, and a second discharge position 21, wherein it allows the discharge of the circuit 10 outside the apparatus 1. The apparatus 1 then comprises an addition unit, designated as a whole with 22, apt to add to the sample selectively, that is in a controlled way, a plurality of reagents R_l5 R₂, ..., R_n. For each reagent, the unit 22 comprises a tank 23 and a relative reagent- inletting valve 24 inserted along the circuit 10 and defining a tract of tortuous course thereof. Each reagent-inletting valve 24 is apt to selectively put in communication the relative tank 23 with the circuit 10 itself for the direct adduction of the reagent inside the latter. In particular, in the present embodiment the valves 24 are of a three-way and deflector type. Each deflector 25 has an end movable between a first position 26, wherein it allows the flow of the relative reagent in the circuit 10, and a second position 27, wherein it interdicts said flow. In such second position 27, the valves 24 implement a hydraulic connection between the valve 14 and the further units of the apparatus 1 inserted along the circuit 10.

The apparatus 1 then comprises a unit 28 for detecting the concentration of the analytes contained in the sample, for example a photometric detector, in particular of a colometric kind, a fluorometric detector, a ionoselective detector, a potentiometric detector or any other kind of detector known to a person skilled in the art.

Along the circuit 10 pump means are then arranged, and in particular a peristaltic volumetric pump 29 of a bidirectional type, apt to allow the circulation of the sample inside the latter. At last, the apparatus comprises control means (not shown) of all the valves 24, 14, 3 and 7, which can be for example of an electrically controlled kind, as well as of the several units of the apparatus 1 and of the pump 29.

According to embodiment variants, the apparatus of the invention can also comprise one or more additional units apt to cooperate with the detection unit 28 and selected in a group comprising: reduction columns, thermo-regulated serpentines, dialysis blocks, fractionating columns and ion exchange resins.

The operating modes of the apparatus 1 will be now illustrated. To carry out the sampling and thus filling up all the volume of the mixing circuit 10 with the sample to be analyzed, the deflector 15 of the first section 141 of the valve 14 is brought in the position 16 and the deflector 19 of the second section 142 of the valve 14 is brought in the discharge position 21. The deflectors 25 of the valves 24 are instead in their position 27. In this configuration, the apparatus 1 allows the adduction of the liquid sample to be analyzed in the circuit 10 by activating the pump 29. The action of the latter allows indeed the introduction of the sample in the circuit 10 and the circulation of the sample itself from the sampling unit 2 as far as the discharge W, according to a counter-clockwise direction in figure 1. After an adequate sampling time, necessary so that the sample wholly fills up the circuit, the pump 29 is blocked and the valve 14 is commanded so that the first deflector 15 be in the second position 17 and the second deflector 19 in the first position 20. In this way, the circuit 10 is closed with respect to the outside, and in particular with respect to the source of the sample to be analyzed and with respect to the discharge W. The sample added into the circuit in the preceding step is found also inside the detection unit 28, wherein the features thereof can be evaluated before the injection of the reagents.

In order to carry out this latter procedure, the second deflector 19 of the valve 14 is brought in the discharge position 21, and one of the valves 24 is driven to bring in the configuration corresponding to the position 26 of the deflector 25, so that the relative reagent can be called inside the circuit 10 by the action of the pump 29. The latter is thus driven for a pre-established time so as to call proportional quantities of reagent (on the average between about 50 to 400 microlitres). Owing to the configuration of the second section 142 of the valve 14, whenever some reagent is called into the circuit 10 an equivalent sample quantity is expelled towards the discharge W. At the end of the reagent injection, the pump 29 is deactivated and the valves 24 and

14 are brought in the configuration corresponding to the closure of the circuit 10, that is deflector 25 in position 27 and deflector 19 in position 21. To allow the mixing between the reagent and the sample contained in the circuit 10, the pump 29 is then placed in rotation so as to vortically recirculate the sample doped with the reagents. Upon passing through the valves 24 and the valve 14 a very strong turbulence is created by virtue of the particular geometry and arrangement of the valves themselves, which turbulence allows obtaining a perfect mixing between sample and reagent. The mixing between the sample and the reagent, thus, takes place substantially in each point of the closed circuit thanks to the continuous and repeated circulation of the sample moved by the pump 29.

The addition and mixing procedure just described is of course repeated for each reagent.

Once the injection of reagents and the mixing thereof with the sample has ended, the consequent reaction product can be dosed through the detection unit 28. For the washing of the apparatus 1, to be carried out at the end of each dosing and/or at the beginning thereof, the first deflector 15 of the first section 141 of the valve 14 is brought in the first position 15, the deflector 4 of the valve 3 in the position 6 and the deflector 8 of the valve 7 in position 11. On the contrary, the second deflector 19 of the valve 14 will be in discharge position 21. Then the pump 29 is driven, so as to adduct the washing fluid into the circuit 10 and up to the discharge W for a time sufficient to remove the reaction product. Operating simulations have shown that, with the apparatus of the present embodiment, the volumes of used samples and reagents are about four times lower that those used in the apparatus described in the Italian patent 1 249 433. This involves, among other things, a reduction in a factor four of the volume of the produced discharges and an increase in the operating autonomy of the system with respect to the ones of the known art.

It will be better appreciated at this point that the apparatus of the invention represents an evolution of the one described in the Italian patent 1 249 433 mentioned above, of which it preserves exclusively the principle of closed-circuit operation. However, the invention differs from the latter apparatus mainly in the injection modes of reagents which are not injected into the circuit by producing vacuum downwards the injection valves, but "sucked" in circle by the action of the pump.

It will be noted that the apparatus of the present invention is wholly without one or more mixing chambers under depression, as the apparatuses of the prior art, which makes it apt to be used in environments subjected to high pressure.

It will be appreciated that the number of devices needed for implementing the basic structure of the apparatus of the invention is surprisingly low. Furthermore, in the embodiment described above the apparatus is suitable for a low-cost implementation. Moreover, it is important noting that the sequence in the arrangement of the components along the mixing circuit 10 of the embodiment described sofar can be modified without compromising in any way the operation of the apparatus 1. For example, the sequence addition unit 22 - pump 29 - detection unit 28 can be replaced by the opposite sequence, that is detection unit 28 - pump 29 - addition unit 22, without altering in substance the operating modes of the apparatus 1 described above. Therefore, the apparatus of the invention is suitable for an extreme functional and structural simplicity, by allowing obtaining several configurations all showing equivalent operating modes, each configuration corresponding to a different combination and/or arrangement of the several components. In other words, the invention provides a dynamic-configuration apparatus. This latter feature thus represents an additional differentiation of the present invention with respect to the content of the Italian patent 1 249 433 mentioned above.

An additional difference is then represented by the fact that, contrary to the system of said preceding patent, the apparatus of the invention is not bound to a vertical orientation. In fact, the circuit of the latter can assume any orientation in the space, to the advantage of the application versatility and variety of the apparatus itself.

As already mentioned previously, thanks to the substantial absence of air from its own mixing circuit, the apparatus of the invention is suitable for applications in an underwater environment.

Figure 2 shows indeed a plant 100 for dosing analytes in liquid samples in an underwater environment comprising an apparatus according to the invention, and in particular the apparatus 1 of the embodiment described above. In this application, the sampling unit 2 is apt to take the liquid sample C from the underwater environment by means of a seal hydraulic system implementable with conventional means. The plant 100 then comprises means for compensating the outer pressure, that is the pressure of the underwater environment. In the present embodiment, the compensating means is of an hydraulic kind. In particular, this means, in turn, comprises a compensator 31 with deformable walls, exposed on the outside to the pressure of the underwater environment, and a housing 32 inside which the apparatus 1 is received, which housing 32 is in hydraulic communication with the compensator 31. Both the latter and the housing 32 are filled-up with inert oil, for example vaseline. Thanks to the arrangement just described, the apparatus 1 is subjected to a substantially constant pressure substantially equal to the one of the outer underwater environment and, therefore, to the same pressure of the sample to be analyzed. In other words, the plant 100 allows keeping all liquids in equi-pressure and utilizing the apparatus 1 also at abyssal depths, even equal to 6000 m, corresponding to about 600 bar.

It will be understood that the present invention is suitable to several embodiments alternative to the one sofar described.

The present invention has been sofar described by referring to preferred embodiments. It is to be meant that other embodiments belonging to the same inventive core may exist, all however comprised within the protective scope of the herebelow reported claims.

Claims

CLAIMS 1. An apparatus (1) for metering analytes in liquid samples, comprising:

- a sampling unit (2), apt to adduct in the apparatus a liquid sample (C) to be analyzed; - an addition unit (22), apt to selectively add to the sample at least a reagent (Ri, ...,

R_n), which unit, in turn, comprises at least a reagent-stocking tank (23) and at least an associated valve (24) for inletting the latter within the sample;

- a unit (28) for detecting the concentration of the analytes contained in the sample;

- means for hydraulically connecting said units, apt to implement a closed hydraulic mixing circuit (10) for the continuous and repeated circulation of the sample among said units; and

- pump means (29), arranged along said mixing circuit and apt to determine said sample circulation, the arrangement being such that at least one reagent-inletting valve of said addition unit is inserted into said mixing circuit by belonging thereto and allows the reagent recall directly inside said circuit by the action of said pump means, and such that said at least one reagent-inletting valve implements a tract with a tortuous development of said mixing circuit, so that the mixing between said sample and said at least one reagent takes place by virtue of the turbulent motion establishing inside said circuit.

2. The apparatus (1) according to claim 1, wherein said at least one reagent- inletting valve (24) is a three-way valve (25, 26, 27).

3. The apparatus (1) according to claim 1 or 2, wherein said at least one reagent- inletting valve (24) is a deflector valve (25).

4. The apparatus (1) according to any of the preceding claims, wherein said addition unit (22) comprises a plurality of tanks (23), each apt to the stocking of a different reagent (R_l5 ..., R_n), and a respective plurality of reagent-inletting valves (24) which are inserted in series along said mixing circuit (10) and which implement each a tract with tortuous development of said circuit.

5. The apparatus (1) according to any of the preceding claims, wherein said one sampling unit (2) comprises at least one sample-inletting valve (14) which is inserted in said mixing circuit (10) and which implements a tract with tortuous development of the latter.

6. The apparatus (1) according to the preceding claim, wherein said at least one sample-inletting valve (14) is a three-way valve (15, 16, 17).

7. The apparatus (1) according to claim 5 or 6, wherein said at least one sample- inletting valve (14) is a deflector valve (15).

8. The apparatus (1) according to any of the preceding claims, wherein said detection unit (28) comprises a detector selected in a group comprising photometric, fluorometric, iono-selective and potentiometric detectors.

9. The apparatus (1) according to the preceding claim, wherein said detection unit (28) comprises a colorimetric detector.

10. The apparatus according to any of the preceding claims, wherein said pump means (29) are of a bidirectional type.

11. The apparatus (1) according to any of the preceding claims, wherein said pump means comprises a volumetric pump (29).

12. The apparatus (1) according to any of the preceding claims, wherein said pump means comprises a peristaltic pump (29).

13. The apparatus (1) according to any of the preceding claims, comprising means (14, 19, 21) for discharging the analyzed sample, comprising in turn a respective valve (14) apt to open/close said mixing circuit (10) and hydraulically connected to a discharge (W).

14. The apparatus (1) according to the preceding claim, wherein said valve (14) of said discharge means (14, 19, 21) is inserted in said mixing circuit (10) and implements a tract with tortuous development of the latter.

15. The apparatus (1) according to claim 13 or 14, wherein said discharge valve

(14) is a three-way valve (19, 20, 21).

16. The apparatus (1) according to any of the claims 13 to 15, wherein said discharge valve (14) is a deflector valve (19).

17. The apparatus (1) according to any of the preceding claims, comprising one or more additional units apt to cooperate with said detection unit (28) and selected in a group comprising: reduction columns, thermo-regulated serpentines, dialysis blocks, fractionating columns and ion exchange resins.

18. A plant (100) for metering analytes in liquid samples in an underwater environment, comprising:

- an apparatus (1) according to any of the preceding claims, wherein said sampling unit (2) is apt to take the liquid sample (C) from the underwater environment; and - means for pressure compensation (31, 32), housing inside them said apparatus and apt to subject the latter to a substantially constant pressure substantially equal to the one of the outer underwater environment.

19. The plant (100) according to the preceding claim, wherein said pressure- compensating means is of an hydraulic type, comprising a compensator (31) with deformable walls exposed on the outside to the pressure of the underwater environment and a housing (32) inside which said apparatus (1) in hydraulic communication with said compensator is received, said compensator and housing being filled-up with inert oil.

20. A process for metering analytes in liquid samples, comprising the steps of:

- introducing a liquid sample (C) to be analyzed in a mixing circuit (10) ;

- selectively adding to the sample at least one reagent (R_ls ..., R_n), by directly inletting the latter from a respective tank (23) inside said circuit;

- establishing a state of turbulent motion inside said circuit in order to obtain the mixing of said sample with said at least one reagent; and

- detecting the concentration of the analytes contained in the doped sample along said mixing circuit.

21. The process according to the preceding claim, wherein said steps are carried out in an underwater environment.

22. The process according to claim 20 or 21, wherein said steps are carried out by means of an apparatus according to any of the claims 1 to 17.