FR3003948A1 - METHOD FOR DETECTING DISPERSED ELEMENTS CIRCULATING THROUGH A CAPILLARY TUBE, AND ASSOCIATED APPARATUS - Google Patents

Abstract

This method comprises the following steps: placing a light source (32) on one side of a measuring passage (38) with respect to a central axis (A-A '); - provision of a detector (70) on the other side of the measuring passage (38) with respect to the central axis (A-A '); the light source (32) generates an incident light beam (50). The detector (70) detects, for each dispersed element passing through the measurement passage (38), a variation in light intensity resulting from an output light beam. (54) exiting the measurement passage (38), the output light beam (54) being from the incident light beam (50), and forming a non-zero angle with the incident light beam (50).

Description

The present invention relates to a method for detecting dispersed elements circulating through a capillary tube, the capillary tube defining a central axis measurement passage through a capillary tube, the capillary tube defining a central axis measurement passage through a capillary tube. which circulates each dispersed element, the method comprising the following steps: placing a light source on one side of the measurement passage with respect to the central axis; - provision of a detector on the other side of the measuring passage relative to the central axis; the light source generating an incident light beam. Such a method is particularly applicable to the detection of dispersed elements formed by drops or bubbles, for their counting, referencing, or determination of their speed in a microfluidic device in which the drops or bubbles. This method is particularly applicable to devices comprising capillary tubes on a millimetric scale, that is to say having an internal diameter of the order of one tenth of a millimeter to the millimeter, preferably of between 0.5 mm and 1 mm. mm. The tube has an inner cross section of rounded contour, such as cicular or elliptical, or polygonal such as rectangular. The use of these devices is currently developing in multiple applications. Thus, it is possible to create drop trains of a dispersed phase, the drops being arranged in a carrier phase separating the different drops of the drop train.

The drops can then constitute microreservoirs for chemical or biological reactions, in order to perform, for example, particular syntheses, screening of products, monitoring of reaction kinetics, or various diagnoses, by subjecting a test product contained individually in each drop to a given reagent specific to each drop.

To do this, it is necessary to precisely reference each drop of the train of drops, in order to document its contents. This makes it possible to retrieve a given drop later, once this drop has circulated in a capillary tube to be subjected to given reaction conditions. For this purpose, it is known to individually fill each drop of the drop train with a number of products, and to successively count the drops passing through a drop detector.

Thus, the n-th drop of the drop train can be associated with its content during filling, and can be found later in the train of drops by successively counting the successive drops of drop train. This method makes it possible to carry out multiple tests in completely different and individualized conditions for each drop, in a simple manner and at a lower cost. However, the reliability of the method depends largely on the proper referencing of the drops and therefore, on their counting. It is therefore necessary to detect very precisely and individually each drop of the train of drops passing through the detection device, to prevent the omission of a drop of the drop train in the counting causes a shift SEO. To do this, known methods for detecting drops involve loading each drop with an optically active product, for example by fluorescence or absorbance, and then detecting the passage of the optically active product through the drop detector. No. 5,074,658 describes an example of drop detection involving the use of an organic cobalt complex in each drop. The apparatus described in this document is able to measure the size of each drop, as well as its speed, on the basis of a measured property of absorption of the medium as a function of the wavelength. Such a detection method is effective, but does not give complete satisfaction. Indeed, the presence of the optically active product is likely to disturb or modify the phenomena occurring in each drop. An object of the invention is therefore to obtain a detection method, which allows a very reliable detection of a number of dispersed elements passing in a measuring passage, and possibly the individual speed of each dispersed element, the process not disturbing the physical, chemical or biological phenomena occurring in each dispersed element. To this end, the subject of the invention is a method of the aforementioned type, characterized in that the detector detects, for each dispersed element passing through the measurement passage, a variation in light intensity resulting from an outgoing light beam. of the measuring passage, the output light beam coming from the incident light beam, and forming a non-zero angle with the incident light beam. The method according to the invention may comprise one or more of the following characteristics, taken alone or in any technically possible combination: the light source is a coherent light source when the passage of each element dispersed in the passage of light measurement, the output light beam moves along at least one axis of displacement between an initial position that it occupies in the absence of dispersed element, and a detection position that it occupies in the presence of a dispersed element, the detector detecting the output light beam in one and / or the other of the initial position and the detection position; the axis of displacement extends substantially in a plane transverse to the central axis, the transverse plane containing the incident light beam; the axis of displacement extends substantially in a plane parallel to the central axis or passing through the central axis; the detector comprises a first detection zone at a first axial position along the axis of displacement and a second detection zone axially offset with respect to the first detection zone along the axis of displacement, the method comprising, for each element dispersed in the measuring passage, a first detection of the passage of the output light beam in the first detection zone, a second detection of the output light beam in the second detection zone, and a measurement of the time separating the first detection of the the second detection, the method comprising a step of calculating the speed of each dispersed element on the basis of the measured time; it comprises, before the step of calculating the speed, a calibration step to establish, under given physico-chemical conditions, a relation between the measured time and the circulation velocity of a dispersed element, the calculation of the velocity of each element dispersed in the measuring step being performed on the basis of said relationship; it comprises a step of counting the number of elements dispersed as a function of the number of displacements of the output light beam between the initial position and the detection position; each dispersed element completely fills at least one cross section of the measuring passage as it passes opposite the incident light beam; the incident light beam has a non-zero incidence with respect to the normal to the external contour of the measuring passage, taken at the point of entry of the incident light beam into the measuring passage. The invention also relates to a dispersed element detection apparatus, comprising: - a capillary tube, the capillary tube defining a central axis measuring passage through which each dispersed element circulates, - a light source placed d one side of the measuring passage with respect to the central axis; a detector placed on the other side of the measuring passage with respect to the central axis; the light source being configured to generate an incident light beam, characterized in that the detector is adapted to detect, for each dispersed element passing through the measurement passage, a variation in light intensity resulting from an output light beam emerging from the measuring passage, the output light beam coming from the incident light beam and forming a non-zero angle with the incident light beam. The apparatus according to the invention may comprise one or more of the following characteristics, taken separately or in any technically possible combination: the output light beam is movable along at least one axis of displacement between an initial position which is it occupies in the absence of dispersed element, and a detection position that it occupies in the presence of a dispersed element, the detector being able to detect the output light beam in one and / or in the other of the initial position and the detection position; the axis of displacement extends substantially in a plane transverse to the central axis, the transverse plane containing the incident light beam; the axis of displacement extends substantially in a plane parallel to the central axis or passing through the central axis; the detector comprises a first detection zone at a first axial position along the axis of displacement and a second detection zone axially offset with respect to the first detection zone along the axis of displacement, the apparatus comprising a set of timing of the time separating a first detection of the passage of the output light beam in the first detection zone and a second detection of the output light beam in the second detection zone, and a unit for calculating the speed of each element dispersed on the time base measured by the timing set; it comprises a unit for counting the number of elements dispersed as a function of the number of displacements of the output light beam between the initial position and the detection position; the light source is configured to generate an incident light beam of non-zero incidence with respect to the normal to the external contour of the measuring passage, taken at the point of entry of the incident light beam. The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which: FIG. 1 is a view of a capillary tube containing a drop train intended to be detected by a first detection device according to the invention; FIG. 2 is a view from above of a first detection apparatus intended for implementing the method according to the invention; - Figure 3 is a view taken in section along the transverse plane III of Figure 1, in the absence of drop in the measuring passage; - Figure 4 is a view similar to Figure 3, in the presence of a drop in the measuring passage; FIG. 5 is a view of a graph illustrating the deflection distance observed for different angles of incidence of an incident light beam introduced into a measuring passage of the apparatus according to the invention, for two media presenting indices. different optics; FIG. 6 is a view of a variant of the apparatus of FIG. 1, for the detection of the speed of each drop, when a droplet enters the measurement passage. A first apparatus 10 for detecting dispersed elements according to the invention is illustrated in FIGS. 1 to 4. In the following, an example of a dispersed element is a drop of liquid present in a continuous phase of transport. Alternatively, the dispersed element is a gas bubble, a solid or a gel present in a continuous phase. The apparatus 10 is intended to be implemented in a microfluidic device 12 shown diagrammatically in FIG. 1. The microfluidic device 12 comprises at least one capillary tube 14, and a set 16 for loading and putting into circulation a train 18 of dispersed elements 20 formed by drops 20 in the capillary tube 14. In all that follows, the capillary tube 14 is generally a fluid tube on a millimetric scale, that is to say having a smaller inner diameter or equal to the millimeter, for example of the order of one-tenth of a millimeter to the millimeter, in particular between 0.5 mm and 1 mm.

The tube 14 has an inner cross section of rounded contour, such as circular or elliptical, or polygonal such as rectangular.

The microfluidic device 12 is for example a device for implementing a plurality of individual chemical or biological reactions in each of the drops 20 of the drop train 18. The charging assembly 16 is capable of filling individually and in a controlled manner each at least one reagent, before its introduction into the capillary tube 14. The loading assembly 16 is also able to successively circulate each drop 20 of the drop train 18 in a continuous transport phase 21, advantageously immiscible with each drop 20.

The continuous phase 21 is also able to separate two successive drops 20 from the drop train 18 to prevent their contact. To allow the detection of each drop 20 by the apparatus 10 according to the invention, each drop 20 has an optical index or refraction n1 distinct from the optical index nO of the continuous phase 21. The optical index difference between each drop 20 and the continuous phase 21 is for example greater than 0.05, preferably greater than 0.1. The optical index is for example measured by a refractometer. With reference to FIG. 1, the microfluidic device 12 comprises, downstream of the loading assembly 16, a set 22 for analyzing the contents of each drop 20 of the drop train 18. An example of a microfluidic device 12 is described in FIG. the application WO 2012/120384 of the Applicant. In a variant, the microfluidic device 12 is a millifluidic system for dispensing the drops in a multiwell plate or a conventional microfluidic chip for example in PDMS with rectangular channel sections. In other variants, the device 12 is a millifuidic system for delivering the drops in a well multipoint plate, or is a conventional microfluidic chip, for example in PDMS with rectangular channel sections The microfluidic device 12 comprises at least one drop detection apparatus 10 according to the invention. The apparatus 10 according to the invention is for example placed downstream of the assembly 16, just at the outlet of the assembly 16, on the capillary tube 14, or just upstream of the analysis unit 22. In the example shown in FIG. 1, the apparatus 10 is placed in series on the capillary tube 14.

The apparatus 10 is adapted to detect the passage of each drop 20 of the drop train 18, and optionally to measure the speed of each drop 20 passing through the apparatus 10. As illustrated by FIGS. 1 to 4, the apparatus 10 has a measurement capillary section 30 defining a central axis A-A ', a coherent light emission source 32 placed transversely on one side of the central axis A-A' and a detection assembly 34, placed opposite the emission source 32, on the other side of the central axis A-A '. The measuring capillary section 30 is advantageously arranged in series on the capillary tube 14. In one embodiment, the measuring capillary section 30 is connected between an upstream portion and a downstream portion of the capillary tube 14. As a variant, the capillary section 30 is formed directly in the capillary tube 14, being integral with the capillary tube 14.

The measuring capillary section 30 comprises a tubular wall 36 which internally defines an inner measuring passage 38 of central axis A-A '. The tubular wall 36 is at least partially transparent to the light radiation emitted by the emission source 32. It is for example made of plastic, such as fluoropolymer, such as polytetrafluoroethylene copolymer FEP or PFA glass. The thickness of the tubular wall 36 is less than 0.5 mm and is for example between 0.25 mm and 0.1 mm. The internal measuring passage 38 is delimited externally sealingly by the tubular wall 36. It has a constant cross section along its length.

The internal measuring passage 38 has a maximum transverse dimension of less than 1 mm, especially between one tenth of a millimeter and 1 mm, advantageously between 0.5 mm and 1 mm. Preferably, as illustrated in Figure 3, the outer contour of the inner passage 38 is circular. Thus, the inner passage 38 has a disc-shaped cross section. The cross section of the internal passage 38 is advantageously less than the maximum cross section of each drop 20, taken to rest in the continuous phase of separation 21. Thus, when each drop 20 passes into the internal passage 38, the drop 20 deforms and has a rounded upstream section 40 of decreasing cross section upstream, an intermediate section 42, of shape conjugated to the internal passage 38, the intermediate section 42 being completely applied to the tubular wall 36, and a rounded downstream section 44 of cross section descending downstream. With reference to FIG. 2 and FIG. 4, when the tubular wall 36 of the measurement section 30 is cylindrical, the intermediate section 42 of each droplet 20 passing through the internal passageway 38 has a cylindrical shape conjugate to that of the internal passageway. 38. The emission source of a coherent light 32 preferably comprises a laser 46. It is advantageously arranged transversely with respect to the central axis A-A '. The source 32 is thus able to emit a coherent incident beam 50, propagating linearly. The beam 50 is directed towards the measuring capillary section 30 to penetrate the internal measuring passage 38. According to the invention and with reference to FIG. 3, the source 32 is able to emit the incident light beam 50 with an impact. non-zero relative to the normal Ni to the outer contour of the measurement passage 38, taken at the point of entry 51 of the light beam 50 into the measuring passage 38. The incident light beam 50 is thus able to form an intermediate reflected light beam 52, flowing in the measuring passage 38, which in turn forms an outgoing light beam 54 directed towards the detector 34 out of the measuring passage 38.

Advantageously, the incident light beam 50 is a laser beam of wavelength between 200 nm and 1000 nm, in particular between 400 nm and 800 nm. It has a geometric width smaller than the inner diameter of the measuring section 30, for example half the inside diameter, and a spectral width advantageously less than 20 nm, taken between 10 and 15 nm. These values are indicative and depend on the nature of the detector used. Advantageously, the incident light beam 50 is emitted in a transverse plane T perpendicular to the central axis A-A '. In the plane T, the angle of incidence 11 of the incident light beam 50 with respect to the normal Ni is, for example, between 30 ° and 60 °.

When the intermediate beam 52 resulting from the beam 50 passes through a medium completely filling the cross section of the passage 38 in the transverse plane T, especially when the intermediate section 42 of a drop 20 or the continuous phase 21 separating two drops 20 extends into the plane T, the intermediate beam 52 also extends in the plane T.

It has an upstream exit angle ir (m) with the normal Ni, this angle ir (m) dependent on the medium present in the measuring passage 38 at the plane T.

Furthermore, the intermediate beam 52 has a downstream angle of incidence i2 (m) with the normal N2 to the outer contour of the measuring passage 38, taken at the exit point 56 of the intermediate beam 52 out of the passage 38. The output beam 54 has an exit angle i2 '(m) with the normal N2. It also extends in the plane T when the intermediate beam 52 resulting from the beam 50 passes through a medium completely filling the cross section of the passage 38 in the transverse plane T. The following relations apply between the angles 11, ir (m) , i2 (m), i2 '(m) to define a deflection angle θ (m) of the output beam 54 with respect to the incident beam 50. I sin (i1) n (m) sin (i; (m) The sensor assembly 34 is adapted to detect, for each drop 20 passing through the measurement passage 38, a variation in luminous intensity (see FIG. resulting from the output light beam 54 generated from the incident beam 50.

The variation in luminous intensity advantageously results from a displacement along at least one axis of displacement BB 'of the output light beam 54, between an initial position which it occupies in the absence of a drop 20 opposite the incident beam 50 in the measurement passage 38, and a detection position that it occupies in the presence of a drop 20.

The detection assembly 34 thus comprises at least one detector 70 able to detect the output beam 54 in one and / or the other of the initial position and the detection position. Detection assembly 34 further includes a counting unit 71 of the number of drops 20 detected by detector 70, based on the number of passes of the output beam between the initial position and the detection position. In the example illustrated in FIGS. 3 and 4, the detector 70 has at least one detection zone embodied by a sensor 72 extending along an axis BB 'perpendicular to the central axis A-A', in the transverse plane T. Advantageously, the detector 70 has a plurality of sensors 72 distributed along the axis B-B '. The detector 70 is for example formed by a sensor bar 72, such as a CCD sensor bar.

With reference to FIG. 3 and FIG. 4, the detector 70 is thus able to receive and detect the output beam 54 at a point P1 in the initial position of the output beam 54, in the absence of a drop. , and at a point P2 axially spaced from the point Pi, in the detection position of the output beam 54, in the presence of a drop 20.

A first drop detection method 20 according to the invention in the apparatus 10 will now be described. Initially, an apparatus 10 according to the invention is provided, with the source 32 placed on one side of the measuring passage 38 with respect to the central axis A-A ', the detector 34 being disposed on the other side of the passage measurement 38 with respect to the central axis A-A '.

The source 32 is then activated to continuously generate an incident light beam 50 of non-zero incidence with respect to the normal Ni to the external contour of the measuring passage 38, at the point of entry of the incident light beam 50 into the passage 38. When the continuous phase 21 completely fills the cross section located in the transverse plane T, the incident beam 50 enters the internal passage 38 with an angle of incidence 11 and is deflected by the continuous phase 21 to form the intermediate beam 52 having a output angle il '(m1) corresponding to the optical index nO of the continuous phase 21. Then, the intermediate beam 52 leaves the internal passage 38 with an angle of incidence i2 (m2) with respect to the normal N2 equal to the exit angle il '(ml). An output beam 54 is then formed with an exit angle i2 '(m1) with respect to the normal N2. The output beam 54 propagates to the detector 70 of the detection assembly 34 and hits this detector 70 at the point P1. The sensor 72 present at the point P1 detects the output beam 54 in its initial position, which is characteristic of the no drop 20 facing the incident beam 50. When the intermediate portion 42 of a drop 20 passes next to the incident beam 50, and completely fills the cross section in the transverse plane T, the incident beam 50 enters the passage internal 38 with an angle of incidence il and is deflected by the drop 20 to form the intermediate beam 52 having an exit angle il '(m2) corresponding to the optical index n1 of the drop 20. The exit angle il '(m2) in the presence of the drop 20 is then different from the exit angle il' (m1) in the presence of the continuous phase 21. Then, the intermediate beam 52 emerges from the internal passage 38 with an angle of incidence i2 (m2) compared to the nor male N2 equal to the exit angle il '(m2).

An output beam 54 is then formed with an exit angle i2 '(m2) with respect to the normal N2. The exit angle i2 '(m2), in the presence of a drop 20, is then different from the exit angle i2' (m1) in the absence of drop 20. The exit beam 54 propagates to the detector 70 of the detection assembly 34 and hits the detector 70 at the point P2 axially offset along the axis BB 'with respect to the point P1. The sensor 72 present at the point P2 detects the output beam 54 in its detection position, characteristic of the presence of a drop 20 facing the incident beam 50.

Depending on the position of the output beam 54 detected by the detector 70, it is therefore possible to identify the passage of each drop 20 in the measuring apparatus 10 accurately, simply and reliably. The presence of a drop 20 is determined by each movement of the output beam 54 along the axis B-B 'between the initial position at the point P1 and the detection position at the point P2. As illustrated in FIG. 5, the difference in deflection distance between the deflection observed in a first optical index medium n0 and a second optical index medium n1 increases with the angle of incidence. By choosing an adequate incidence, associated with a detector 70 provided with sufficiently close sensors 72, the accuracy of the measurement can be important, even if the optical index difference is relatively small. The apparatus 10 according to the invention, and the method implemented using this apparatus 10 therefore do not require to charge the drops 20 with an optically active compound. As a result, the content of each drop 20 is not disturbed by the detection measure of the drop 20. This ensures the integrity of the conditions within the drop 20, especially when a chemical or biological reaction is performed in the In a variant (not shown), the detector 24 comprises a sensor 72 able to detect one of the initial position and the detection position of the output beam 54, but does not include a sensor 72 able to detect the other the initial position and the detection position of the output beam 54. In a variant of the apparatus 10, shown in Figure 6, the detection assembly 34 comprises at least one detector 80 extending axially relative to the central axis A-A '. In this example, the detector 80 extends along an axis C-C 'parallel to the axis A-A'. The detector 80 comprises at least two sensors 82, 83 spaced axially along the axis C-C ', and a timing element 84, able to measure the time T between the illumination of a first sensor 82 of the illumination of a second sensor 83. The detection assembly 34 further comprises a unit 86 for calculating a speed of movement of a drop 20, as a function of the time T measured by the timing element 84, and a predetermined calibration. Thus, the detection assembly 34 is able to detect the speed of displacement of the output beam 54 along the axis CC 'when the incident beam 50 enters a drop 20 level of its upstream section 40. As illustrated by the FIG. 6, as a function of the shape of the interface between the drop 20 and the continuous phase 21 in the upstream section 40, the angle y of axial deflection of the output beam 54 with respect to the incident beam 50, projected into an axial plane passing through the axes AA 'and CC' varies during the passage of the upstream section 40 facing the incident beam 50. The output beam 54 thus hits the first sensor 82 first, then the second sensor 83. The time T separating the illumination of the first sensor 82, then the second sensor 83 is measured by the timing assembly 84. The calculation assembly 86 then determines the speed of displacement of the drop 20 on the basis of the time T measured by the assembly Timing 84 for each drop 20 and on the basis of a predetermined calibration relationship.

The calibration relationship is, for example, a calibration curve determined under given physico-chemical conditions, at the temperature and at the pressure corresponding to the temperature and the measurement pressure, by passing form and composition calibration drops. known in front of the incident light beam 50 and changing the speed of movement of the train of calibration drops.

The calibration drops are chosen with a composition that is as close as possible to the drops to be measured. In a variant of the apparatus shown in FIG. 6, the source 32 emits the incident light beam 50 with a zero incidence with respect to the normal Ni to the outer contour of the measuring passage 38, taken at the point of entry 51 of the light beam 50 into the measuring passage 38. As previously indicated, depending on the shape of the interface between the drop 20 and the phase continuous 21 in the upstream section 40, the axial deflection angle y of the output beam 54 relative to the incident beam 50, projected in an axial plane passing through the axes AA 'and CC' varies during the passage of the section upstream 40 facing the incident beam 50.

Claims (16)

CLAIMS 1. A method for detecting dispersed elements (20) flowing through a capillary tube (30), the capillary tube (30) defining a central axis measuring passage (38) (A-A ') through which circulates each dispersed element (20), the method comprising the steps of: - placing a light source (32) on one side of the measurement passage (38) with respect to the central axis (A-A '); - arranging a detector (70; 80) on the other side of the measuring passage (38) with respect to the central axis (A-A '); the light source (32) generating an incident light beam (50), characterized in that the detector (70; 80) detects, for each dispersed element (20) passing through the measuring passage (38), a variation of intensity light resulting from an output light beam (54) issuing from the measuring passage (38), the output light beam (54) coming from the incident light beam (50) and forming a non-zero angle with the incident light beam (50). 2. Method according to claim 1, characterized in that, during the passage of each dispersed element (20) in the measuring passage (38), the output light beam (54) moves along at least one axis of displacement (BB '; C-C') between an initial position which it occupies in the absence of dispersed element (20), and a detection position which it occupies in the presence of a dispersed element (20), the detector (70; 80) detecting the output light beam (54) in one and / or the other of the initial position and the detection position. 3. A process according to claim 2, characterized in that the axis of displacement (B-B ') extends substantially in a transverse plane (T) with respect to the central axis (A-A'), the transverse plane (T) containing the incident light beam (50). 4.- Method according to claim 2, characterized in that the axis of displacement (C-C ') extends substantially in a plane parallel to the central axis (A-A') or passing through the central axis (A-A '). 5.- Method according to any one of claims 2 to 4, characterized in that the detector (80) comprises a first detection zone (82) at a first axial position along the axis of displacement (C-C ') and a second detection zone (83) axially offset from the first detection zone (82) along the displacement axis (C-C '), the method comprising, for each dispersed element (20) passing through the passage measuring device (38), a first detection of the passage of the output light beam (54) in the first detection area (82), a second detection of the output light beam (54) in the second detection area (83), and a measurement of the time (T) separating the first detection from the second detection, the method comprising a step of calculating the speed of each dispersed element (20) on the basis of the measured time (T). 6. A method according to claim 5, characterized in that it comprises, before the step of calculating the speed, a calibration step for establishing, under given physico-chemical conditions, a relationship between the time (T) measured and the flow velocity of a dispersed element (20), the calculation of the velocity of each dispersed element (20) in the measuring step being performed on the basis of said relationship. 7. A method according to any one of the preceding claims, characterized in that it comprises a step of counting the number of dispersed elements (20) as a function of the number of displacements of the output light beam (54) between the position initial position and the detection position. 8. A process according to any one of the preceding claims, characterized in that each dispersed element (20) completely fills at least one cross section of the measuring passage (38) as it passes opposite the incident light beam (50). . 9. A method according to any one of the preceding claims, characterized in that the incident light beam (50) has an incidence (il)) non-zero relative to the normal to the outer contour of the measuring passage (38), taken at the point of entry (51) of the incident light beam (50) into the measuring passage (38). 10. Apparatus (10) for dispersed element detection (20), comprising: - a capillary tube (30), the capillary tube (30) defining a central axis measuring passage (38) (A-A ') ) through which each dispersed element (20) circulates; - a light source (32) placed on one side of the measuring passage (38) with respect to the central axis (A-A '); a detector (70, 80) placed on the other side of the measuring passage (38) with respect to the central axis (A-A '); the light source (32) being configured to generate an incident light beam (50), characterized in that the detector (70, 80) is capable of detecting, for each dispersed element (20) passing through the measuring passage (38) a variation in luminous intensity resulting from an output light beam (54) emerging from the measurement passage (38), the output light beam (54) originating from the incident light beam (50) and forming a non-zero angle with the incident light beam (50). 11. Apparatus (10) according to claim 10, characterized in that the output light beam (54) is movable along at least one axis of displacement (B-B ', C-C') between an initial position that it occupies in the absence of dispersed element (20), and a detection position that it occupies in the presence of a dispersed element (20), the detector (70, 80) being able to detect the output light beam (54) in one and / or the other of the initial position and the detection position. 12. Apparatus (10) according to claim 11, characterized in that the axis of displacement (B-B ') extends substantially in a plane transverse to the central axis (A-A'), the transverse plane containing the incident light beam (50). 13. Apparatus (10) according to claim 11, characterized in that the axis of displacement (C-C ') extends substantially in a plane parallel to the central axis (A-A') or passing through the central axis (A-A '). 14. Apparatus (10) according to any one of claims 11 to 13, characterized in that the detector (80) comprises a first detection zone (82) at a first axial position along the axis of displacement (C- C ') and a second detection zone (83) axially offset with respect to the first detection zone (82) along the displacement axis (C-C'), the apparatus (10) comprising an assembly (84) time-keeping method (T) separating a first detection of the passage of the output light beam (54) in the first detection zone (82) and a second detection of the output light beam (54) in the second detection zone (83) ), and a unit (86) for calculating the speed of each dispersed element (20) based on the time (T) measured by the timing assembly (84). 15. Apparatus (10) according to any one of claims 11 to 14, characterized in that it comprises a unit (71) counting the number of dispersed elements (20) according to the number of displacements of the light beam output (54) between the initial position and the detection position. 16. Apparatus (10) according to any one of claims 10 to 15, characterized in that the light source (32) is configured to generate an incident light beam (50) incidence (il)) non-zero relative normal to the outer contour of the measuring passage (38), taken at the point of entry (51) of the incident light beam (50).