EP1495314A1 - Method and device for amperometric measurement of the iodine absorption rate of a substance - Google Patents

Method and device for amperometric measurement of the iodine absorption rate of a substance

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Publication number
EP1495314A1
EP1495314A1 EP03746319A EP03746319A EP1495314A1 EP 1495314 A1 EP1495314 A1 EP 1495314A1 EP 03746319 A EP03746319 A EP 03746319A EP 03746319 A EP03746319 A EP 03746319A EP 1495314 A1 EP1495314 A1 EP 1495314A1
Authority
EP
European Patent Office
Prior art keywords
iodine
substance
solution
electrodes
electrolysis current
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03746319A
Other languages
German (de)
French (fr)
Inventor
Jacques Deruelle
Arnaud Dubat
Emmanuel Lecomte
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CHOPIN
Original Assignee
CHOPIN
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CHOPIN filed Critical CHOPIN
Publication of EP1495314A1 publication Critical patent/EP1495314A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/02—Food
    • G01N33/10—Starch-containing substances, e.g. dough
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/283—Means for supporting or introducing electrochemical probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
    • G01N31/162—Determining the equivalent point by means of a discontinuity
    • G01N31/164—Determining the equivalent point by means of a discontinuity by electrical or electrochemical means

Definitions

  • the invention relates to a method and an apparatus for amperometric measurement of the iodine absorption rate of a substance.
  • the starch absorbs iodine while the concentration of iodine in a solution can be evaluated by measuring an electrolysis current, the quantity of iodine absorbed being inversely proportional to the intensity of said current. electrolysis.
  • the known devices for such a measurement include a container in which the electrolysis current between two electrodes of a mixture of flour and an iodine solution is measured.
  • the invention proposes a method and an apparatus which are original for measuring by amperometry the rate of absorption of iodine of a substance and in particular of a flour to determine its level of damaged starch.
  • the method according to the invention is notably remarkable in that it consists in preparing a solution capable of supplying iodine by electrochemical reaction, in generating iodine by electrochemical reaction, in measuring an electrolysis current of the solution , introduce the substance to be analyzed into the solution, measure an electrolysis current of the mixture and determine the rate of iodine absorption by the substance as a function of the measured currents which are themselves a function of the concentration of iodine.
  • the method according to the invention recommends, contrary to known art and what could have been imagined, to introduce, or here to generate iodine before introducing the substance rather than introducing iodine into a suspension already containing the substance.
  • the method according to the invention which therefore notably consists in introducing the substance after the generation of iodine offers, in addition to the advantages linked to the electrochemical manufacture of iodine, the advantage of easier internal calibration.
  • the solution comprises distilled water, iodide and a weak acid and in particular boric acid.
  • the solution also comprises a small amount of thiosulfate to neutralize the iodine which may have become attached to the electrodes for measuring and / or generating the iodine.
  • the solution is previously heated and mixed by stirring before the introduction of the substance to be measured, the heating and stirring being maintained throughout the duration of the measurement cycle.
  • the solution is heated to a temperature of about 30 to 40 degrees, the possible first measurement of the current of the solution is carried out for a few seconds, the generation of iodine is carried out for a time proportional to the mass of the substance to be introduced on the basis of approximately one hundred seconds for one gram of substance, the measurement of the electrolysis current of the solution is carried out after obtaining a concentration plateau obtained after a few tens of seconds, the introduction of the substance is carried out gradually for a few seconds and the measurement of the residual electrolysis current of the mixture is carried out after several tens of seconds from the end of the introduction of the substance.
  • the method according to the invention makes it possible to measure the rate of iodine absorption of a substance, it is more particularly recommended to make such a measurement with wheat flour in order to measure its level of damaged starch which is a function of the rate of absorption of iodine.
  • the invention also relates to an apparatus for amperometric measurement of the iodine absorption rate of a substance comprising a container intended to receive a suspension of the substance to be measured and an agitator, an apparatus which is particularly remarkable in that it further comprises at least one pair of electrodes for measuring the electrolysis current and at least one pair of electrodes for generating iodine.
  • the apparatus also includes a feed vibrator for dispersing the substance in a solution previously introduced into the container.
  • the pair of electrodes for measuring the electrolysis current and the pair of iodine generation electrodes are in the form of pairs of rings arranged on the same conductivity probe. and preferably in this case, a temperature sensor is also fitted on the conductivity probe.
  • the apparatus comprises a heating means in the form of a heating resistance immersed in the container.
  • the apparatus comprises a fixed part forming a base arranged to receive the container and a movable part mounted in a pivoting manner and which comprises the agitator, the pairs of electrodes, the temperature sensor and any resistance electric, these elements being arranged on said movable part in order to be able to come into the container or to come out of it during the pivoting which brings angularly closer or respectively deviates said respectively mobile and fixed parts.
  • FIG. 1 shows a front view of an apparatus according to the invention
  • FIG. 2 is a side view of the apparatus of FIG. 1,
  • FIG. 3 shows an advantageous embodiment of electrodes for an apparatus according to the invention.
  • an apparatus comprising two parts, respectively a fixed part forming a V base and a mobile part forming a 1 "measuring head pivotally mounted on said base V, being able to rotate around a axis 2.
  • the base 1 ' is designed to receive a container 3 and the measuring head 1 "comprises in particular, as shown more particularly in FIG. 1, an agitator 4, a conductivity probe 5 and a heating resistor 6, which is said plunging as will be explained below.
  • the measuring head 1 "comprises a guide 7 equipped with a vibrator 8 intended to receive an instrument for loading the substance in the form of a small shovel shown diagrammatically at 9 in FIG. 2.
  • the elements 4, 5 and 6 mentioned above are grouped and positioned so as to be able to come and plunge into the container 3 as shown in FIGS. 1 and 2, when the head 1 "is brought closer by pivoting of the base 1 ', position in which said elements are substantially vertical.
  • the conductivity probe 5 comprises two pairs of electrodes 10 and 11 respectively and a temperature regulating sensor 12.
  • the pairs of electrodes 10 and 11 are in the form of pairs of rings, the pair of electrodes 10 being intended to generate iodine and the pair of electrodes 11 to be measured. iodine consumed as will be explained below.
  • a solution is prepared in the container 3 based on distilled water, iodide and a weak acid such as boric acid.
  • thiosulfate is added thereto to neutralize the iodine which may have become attached to the measurement electrodes and / or the iodine generation electrodes.
  • iodine which may have become attached to the measurement electrodes and / or the iodine generation electrodes.
  • thiosulfate is added thereto to neutralize the iodine which may have become attached to the measurement electrodes and / or the iodine generation electrodes.
  • iodide 3 grams of boric acid and a drop of thiosulfate are introduced.
  • the solution is then mixed by stirring by means of the stirrer 4 and it is heated using the heating resistor 6.
  • the solution is thus heated to a temperature of about 35 degrees, which is controlled by the temperature regulating sensor 12 fitted on the probe 5.
  • the controlled heating and mixing by stirring are maintained throughout the duration of the cycle.
  • the pair of measurement electrodes 11 makes it possible to make a first current measurement, for example for ten seconds in order to determine if need be. current of zero, this being generally zero due to the presence of the thiosulfate which neutralizes the iodine possibly attached to the electrodes.
  • iodine is generated by electrochemical reaction by means of the pair of electrodes 10 for a time proportional to the mass of the substance to be measured on the basis for example of one hundred seconds for a mass of one gram, therefore a iodine generation time in seconds equal to a hundred times the mass of substance.
  • the electrolysis current is measured, which gives a value denoted “Im”.
  • the substance to be measured is introduced, for example wheat flour for which the level of damaged starch is to be known.
  • the amount of flour is predetermined, as already said, by the time of generation of iodine (or vice versa), for example one gram.
  • the shovel 9 is used which contains the substance and which is introduced into the guide 7, the said substance then being poured out and gradually dispersed in the container 3 by means of the vibrator 8 which shakes the shovel 9, for example during a few seconds with stronger vibrations towards the end.
  • the residual electrolysis current ie “Ir”, is measured after several tens of seconds.
  • This measurement of the ratio makes it possible in particular to obtain a self-calibration knowing that the current can vary as a function of the position of the electrodes and the agitation in the solution.
  • the weighing of the substance which is going to be introduced can be precise while it is difficult to introduce a precise precise quantity. Consequently, it is possible, for example, to correct the current Im as a function of the real mass of flour in order to reduce its value to that which corresponds to one gram.

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  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Pathology (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Food Science & Technology (AREA)
  • Immunology (AREA)
  • Medicinal Chemistry (AREA)
  • Molecular Biology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Abstract

The invention relates to a method for amperometric measurement of the iodine absorption rate of a substance, wheat flour in particular. The inventive method is characterized in that it consists in preparing a solution which can provide the iodine by electrochemical reaction, generate iodine by electrochemical reaction, measure the electrolysis current of the solution, introduce the substance to be analyzed into the solution, measure an electrolysis current of the mixture and determine the rate of iodine absorption by the substance as a function of the measured currents which are themselves a function of the iodine concentration. The invention also relates to a device for carrying out said method, comprising a receptacle (3) for receiving a suspension of the substance to be measured and an agitator (4), also comprising at least one pair of electrodes (11) for measuring the electrolysis current and at least one pair of electrodes (10) for the generation of iodine.

Description

Procédé et appareil de mesure par ampérométrie du taux d'absorption d'iode d'une substance. Method and apparatus for amperometric measurement of the rate of iodine absorption of a substance.
L'invention concerne un procédé et un appareil de mesure par ampérométrie du taux d'absorption d'iode d'une substance.The invention relates to a method and an apparatus for amperometric measurement of the iodine absorption rate of a substance.
En vue d'analyses qualitatives, il est. connu de mesurer le taux d'amidon endommagé d'une farine de blé. A cet effet, pour pallier les inconvénients des méthodes enzymatiques, il a été imaginé d'évaluer ce taux d'endommagement en mesurant par ampérométrie la quantité absorbée d'iode d'une suspension très diluée de farine.For qualitative analysis, it is. known to measure the level of damaged starch in wheat flour. To this end, to overcome the drawbacks of enzymatic methods, it has been imagined to evaluate this rate of damage by measuring by amperometry the amount of iodine absorbed from a very dilute suspension of flour.
En effet, l'amidon absorbe l'iode tandis que la concentration d'iode d'une solution peut être évaluée par la mesure d'un courant d'électrolyse, la quantité d'iode absorbée étant inversement proportionnelle à l'intensité dudit courant d'électrolyse.In fact, the starch absorbs iodine while the concentration of iodine in a solution can be evaluated by measuring an electrolysis current, the quantity of iodine absorbed being inversely proportional to the intensity of said current. electrolysis.
Les appareils connus pour une telle mesure comportent un récipient dans lequel on mesure le courant d'électrolyse entre deux électrodes d'un mélange de farine et d'une solution iodée.The known devices for such a measurement include a container in which the electrolysis current between two electrodes of a mixture of flour and an iodine solution is measured.
Toutefois, les solutions chimiques utilisables sont peu stables, les électrodes sont fragiles et l'étalonnage de tels appareils est particulièrement difficile.However, the usable chemical solutions are not very stable, the electrodes are fragile and the calibration of such devices is particularly difficult.
C'est pourquoi l'invention propose un procédé et un appareil qui sont orignaux pour mesurer par ampérométrie le taux d'absorption d'iode d'une substance et en particulier d'une farine pour déterminer son taux d'amidon endommagé.This is why the invention proposes a method and an apparatus which are original for measuring by amperometry the rate of absorption of iodine of a substance and in particular of a flour to determine its level of damaged starch.
Le procédé selon l'invention est notamment remarquable en ce qu'il consiste à préparer une solution susceptible de fournir de l'iode par réaction électrochimique, à générer de l'iode par réaction électrochimique, à mesurer un courant d'électrolyse de la solution, à introduire la substance à analyser dans la solution, à mesurer un courant d'électrolyse du mélange et à déterminer le taux d'absorption d'iode par la substance en fonction des courants mesurés qui sont eux-mêmes fonction de la concentration d'iode.The method according to the invention is notably remarkable in that it consists in preparing a solution capable of supplying iodine by electrochemical reaction, in generating iodine by electrochemical reaction, in measuring an electrolysis current of the solution , introduce the substance to be analyzed into the solution, measure an electrolysis current of the mixture and determine the rate of iodine absorption by the substance as a function of the measured currents which are themselves a function of the concentration of iodine.
En plus de la nouveauté d'une fabrication électrochimique de l'iode, le procédé selon l'invention préconise, contrairement à l'art connu et ce qui aurait pu être imaginé, d'introduire, ou ici de générer de l'iode avant l'introduction de la substance plutôt que d'introduire l'iode dans une suspension contenant déjà la substance. Le procédé selon l'invention qui consiste donc notamment à introduire la substance après la génération de l'iode offre, outre les avantages liés à la fabrication électrochimique de l'iode, l'avantage d'un étalonnage interne plus facile.In addition to the novelty of an electrochemical manufacture of iodine, the method according to the invention recommends, contrary to known art and what could have been imagined, to introduce, or here to generate iodine before introducing the substance rather than introducing iodine into a suspension already containing the substance. The method according to the invention which therefore notably consists in introducing the substance after the generation of iodine offers, in addition to the advantages linked to the electrochemical manufacture of iodine, the advantage of easier internal calibration.
Pour éviter d'éventuelles dérives dans les mesures, on peut mesurer le courant dans la solution avant la génération de l'iode pour établir un courant de zéro. De préférence, la solution comporte de l'eau distillée, de l'iodure et un acide faible et en particulier de l'acide borique.To avoid possible drifts in the measurements, one can measure the current in the solution before the generation of iodine to establish a current of zero. Preferably, the solution comprises distilled water, iodide and a weak acid and in particular boric acid.
Avantageusement, la solution comporte en outre en faible quantité du thiosulfate pour neutraliser l'iode qui se serait éventuellement fixée sur les électrodes de mesure et/ou de génération de l'iode.Advantageously, the solution also comprises a small amount of thiosulfate to neutralize the iodine which may have become attached to the electrodes for measuring and / or generating the iodine.
Selon un mode de réalisation, la solution est préalablement chauffée et mélangée par brassage avant l'introduction de la substance à mesurer, le chauffage et le brassage étant maintenus pendant toute la durée du cycle de mesure.According to one embodiment, the solution is previously heated and mixed by stirring before the introduction of the substance to be measured, the heating and stirring being maintained throughout the duration of the measurement cycle.
Par exemple, la solution est chauffée jusqu'à une température d'environ 30 à 40 degrés, l'éventuelle première mesure du courant de la solution est effectuée pendant quelques secondes, la génération d'iode est réalisée pendant un temps proportionnel à la masse de la substance à introduire sur la base d'environ cent secondes pour un gramme de substance, la mesure du courant d'électrolyse de la solution est effectuée après l'obtention d'un palier de concentration obtenu au bout de quelques dizaines de secondes, l'introduction de la substance est réalisée progressivement pendant quelques secondes et la mesure du courant d'électrolyse résiduel du mélange est effectuée après plusieurs dizaines de secondes à compter de la fin de l'introduction de la substance.For example, the solution is heated to a temperature of about 30 to 40 degrees, the possible first measurement of the current of the solution is carried out for a few seconds, the generation of iodine is carried out for a time proportional to the mass of the substance to be introduced on the basis of approximately one hundred seconds for one gram of substance, the measurement of the electrolysis current of the solution is carried out after obtaining a concentration plateau obtained after a few tens of seconds, the introduction of the substance is carried out gradually for a few seconds and the measurement of the residual electrolysis current of the mixture is carried out after several tens of seconds from the end of the introduction of the substance.
Si le procédé selon l'invention permet de mesurer le taux d'absorption d'iode d'une substance, il est plus particulièrement préconisé pour faire une telle mesure avec de la farine de blé en vue de mesurer son taux d'amidon endommagé qui est fonction du taux d'absorption de l'iode.If the method according to the invention makes it possible to measure the rate of iodine absorption of a substance, it is more particularly recommended to make such a measurement with wheat flour in order to measure its level of damaged starch which is a function of the rate of absorption of iodine.
L'invention concerne aussi un appareil de mesure par ampérométrie du taux d'absorption d'iode d'une substance comportant un récipient destiné à recevoir une suspension de la substance à mesurer et un agitateur, appareil qui est notamment remarquable en ce qu'il comporte en outre au moins une paire d'électrodes de mesure du courant d'électrolyse et au moins une paire d'électrodes de génération d'iode.The invention also relates to an apparatus for amperometric measurement of the iodine absorption rate of a substance comprising a container intended to receive a suspension of the substance to be measured and an agitator, an apparatus which is particularly remarkable in that it further comprises at least one pair of electrodes for measuring the electrolysis current and at least one pair of electrodes for generating iodine.
De préférence, il comporte aussi un vibreur d'alimentation pour disperser la substance dans une solution préalablement introduite dans le récipient. Selon un mode de réalisation tout à fait avantageux, la paire d'électrodes de mesure du courant d'électrolyse et la paire d'électrodes de génération d'iode se présentent sous la forme de paires d'anneaux aménagés sur une même sonde de conductivité et de préférence dans ce cas, un capteur de température est également aménagé sur la sonde de conductivité. Par exemple, l'appareil comporte un moyen de chauffage sous forme d'une résistance chauffante plongeante dans le récipient.Preferably, it also includes a feed vibrator for dispersing the substance in a solution previously introduced into the container. According to an entirely advantageous embodiment, the pair of electrodes for measuring the electrolysis current and the pair of iodine generation electrodes are in the form of pairs of rings arranged on the same conductivity probe. and preferably in this case, a temperature sensor is also fitted on the conductivity probe. For example, the apparatus comprises a heating means in the form of a heating resistance immersed in the container.
Selon un mode de réalisation, l'appareil comporte une partie fixe formant socle aménagée pour recevoir le récipient et une partie mobile montée de manière pivotante et qui comporte l'agitateur, les paires d'électrodes, le capteur de température et l'éventuelle résistance électrique, ces éléments étant disposés sur ladite partie mobile pour pouvoir venir dans le récipient ou en ressortir au cours du pivotement qui rapproche ou respectivement écarte angulairement lesdites parties respectivement mobile et fixe. L'invention sera bien comprise et d'autres particularités apparaîtront à la lecture de la description qui va suivre et qui se réfère aux dessins annexés dans lesquels :According to one embodiment, the apparatus comprises a fixed part forming a base arranged to receive the container and a movable part mounted in a pivoting manner and which comprises the agitator, the pairs of electrodes, the temperature sensor and any resistance electric, these elements being arranged on said movable part in order to be able to come into the container or to come out of it during the pivoting which brings angularly closer or respectively deviates said respectively mobile and fixed parts. The invention will be clearly understood and other particularities will appear on reading the description which follows and which refers to the appended drawings in which:
- la figure 1 montre vu de face un appareil selon l'invention,FIG. 1 shows a front view of an apparatus according to the invention,
- la figure 2 est une vue de côté de l'appareil de la figure 1 ,FIG. 2 is a side view of the apparatus of FIG. 1,
- la figure 3 montre un mode de réalisation avantageux d'électrodes pour un appareil selon l'invention.- Figure 3 shows an advantageous embodiment of electrodes for an apparatus according to the invention.
Sur les figures 1 et 2, on peut voir un appareil selon l'invention comportant deux parties, respectivement une partie fixe formant socle V et une partie mobile formant tête de mesure 1" montée pivotante sur ledit socle V en pouvant tourner autour d'un axe 2. Le socle 1 ' est prévu pour recevoir un récipient 3 et la tête de mesure 1" comporte notamment, comme le montre plus particulièrement la figure 1 , un agitateur 4, une sonde de conductivité 5 et une résistance chauffante 6, laquelle est dite plongeante comme il sera expliqué ci-après.In FIGS. 1 and 2, an apparatus according to the invention can be seen comprising two parts, respectively a fixed part forming a V base and a mobile part forming a 1 "measuring head pivotally mounted on said base V, being able to rotate around a axis 2. The base 1 'is designed to receive a container 3 and the measuring head 1 "comprises in particular, as shown more particularly in FIG. 1, an agitator 4, a conductivity probe 5 and a heating resistor 6, which is said plunging as will be explained below.
En outre, la tête de mesure 1" comporte un guide 7 équipé d'un vibreur 8 destiné à recevoir un instrument de chargement de la substance sous forme d'une petite pelle schématisée en 9 sur la figure 2.In addition, the measuring head 1 "comprises a guide 7 equipped with a vibrator 8 intended to receive an instrument for loading the substance in the form of a small shovel shown diagrammatically at 9 in FIG. 2.
Les éléments 4, 5 et 6 mentionnés ci-avant sont regroupés et positionnés de manière à pouvoir venir plonger dans le récipient 3 comme le montrent les figures 1 et 2, lorsque la tête 1" est rapprochée par pivotement du socle l', position dans laquelle lesdits éléments sont sensiblement verticaux.The elements 4, 5 and 6 mentioned above are grouped and positioned so as to be able to come and plunge into the container 3 as shown in FIGS. 1 and 2, when the head 1 "is brought closer by pivoting of the base 1 ', position in which said elements are substantially vertical.
On comprend bien entendu qu'un pivotement inverse dans le sens d'un écartement angulaire des parties V et 1" permet de retirer les éléments 4, 5 et 6 du récipient 3.It is of course understood that a reverse pivoting in the direction of an angular spacing of the parts V and 1 "makes it possible to remove the elements 4, 5 and 6 from the container 3.
En outre, comme le montrent les figures et en particulier la figure 3, la sonde de conductivité 5 comporte deux paires d'électrodes respectivement 10 et 11 et un capteur régulateur de température 12.In addition, as shown in the figures and in particular in FIG. 3, the conductivity probe 5 comprises two pairs of electrodes 10 and 11 respectively and a temperature regulating sensor 12.
Avantageusement dans le mode de réalisation représenté, les paires d'électrodes 10 et 11 se présentent sous la forme de paires d'anneaux, la paire d'électrodes 10 étant destinée à générer de l'iode et la paire d'électrodes 11 à mesurer l'iode consommée comme il sera expliqué ci-après.Advantageously in the embodiment shown, the pairs of electrodes 10 and 11 are in the form of pairs of rings, the pair of electrodes 10 being intended to generate iodine and the pair of electrodes 11 to be measured. iodine consumed as will be explained below.
Suite à la description qui précède d'un appareil selon l'invention, l'utilisation de celui-ci et le procédé selon l'invention sont simples à comprendre. On prépare une solution dans le récipient 3 à base d'eau distillée, d'iodure et d'un acide faible tel que de l'acide borique.Following the foregoing description of an apparatus according to the invention, the use thereof and the method according to the invention are simple to understand. A solution is prepared in the container 3 based on distilled water, iodide and a weak acid such as boric acid.
Eventuellement, on y ajoute du thiosulfate pour neutraliser l'iode qui se serait éventuellement fixée sur les électrodes de mesure et/ou les électrodes de génération de l'iode. Par exemple, pour 120 ml d'eau distillée, on introduit 3 grammes d'iodure, 3 grammes d'acide borique et une goutte de thiosulfate.Optionally, thiosulfate is added thereto to neutralize the iodine which may have become attached to the measurement electrodes and / or the iodine generation electrodes. For example, for 120 ml of distilled water, 3 grams of iodide, 3 grams of boric acid and a drop of thiosulfate are introduced.
Cette solution étant prête, on dispose le récipient 3 sur le socle l', la tête 1 " étant relevée et on fait pivoter cette dernière vers le socle l' de telle sorte que l'appareil prend la position représentée sur les figures 1 et 2, position dans laquelle la sonde 5, l'agitateur 4 et la résistance 6 plongent dans la solution contenue dans ledit récipient.This solution being ready, the container 3 is placed on the base l ', the head 1 "being raised and the latter is pivoted towards the base l' so that the device takes the position shown in Figures 1 and 2 , position in which the probe 5, the agitator 4 and the resistor 6 immerse in the solution contained in said container.
On mélange alors par brassage la solution au moyen de l'agitateur 4 et on la chauffe à l'aide de la résistance chauffante 6.The solution is then mixed by stirring by means of the stirrer 4 and it is heated using the heating resistor 6.
La solution est ainsi chauffée jusqu'à une température d'environ 35 degrés, ce qui est contrôlé par le capteur régulateur de température 12 aménagé sur la sonde 5. Le chauffage contrôlé et le mélange par brassage sont maintenus durant toute la durée du cycle.The solution is thus heated to a temperature of about 35 degrees, which is controlled by the temperature regulating sensor 12 fitted on the probe 5. The controlled heating and mixing by stirring are maintained throughout the duration of the cycle.
La paire d'électrodes de mesure 11 permet de faire une première mesure de courant, par exemple pendant dix secondes afin de déterminer si besoin est un courant de zéro, celui-ci étant généralement nul du fait de la présence du thiosulfate qui neutralise l'iode éventuellement fixée sur les électrodes.The pair of measurement electrodes 11 makes it possible to make a first current measurement, for example for ten seconds in order to determine if need be. current of zero, this being generally zero due to the presence of the thiosulfate which neutralizes the iodine possibly attached to the electrodes.
Ensuite, on génère de l'iode par réaction électrochimique au moyen de la paire d'électrodes 10 pendant un temps proportionnel à la masse de la substance à mesurer sur la base par exemple de cent secondes pour une masse de un gramme, soit donc un temps de génération d'iode en secondes égal à cent fois la masse de substance.Then, iodine is generated by electrochemical reaction by means of the pair of electrodes 10 for a time proportional to the mass of the substance to be measured on the basis for example of one hundred seconds for a mass of one gram, therefore a iodine generation time in seconds equal to a hundred times the mass of substance.
Après stabilisation du courant d'électrolyse pendant un certain palier de concentration, par exemple de quelques dizaines de secondes, on mesure le courant d'électrolyse ce qui donne une valeur notée « Im ».After stabilization of the electrolysis current for a certain concentration level, for example of a few tens of seconds, the electrolysis current is measured, which gives a value denoted “Im”.
Suite à cette mesure, on introduit la substance à mesurer, par exemple de la farine de blé dont on veut connaître le taux d'amidon endommagé.Following this measurement, the substance to be measured is introduced, for example wheat flour for which the level of damaged starch is to be known.
La quantité de farine est prédéterminée, comme déjà dit, par le temps de génération d'iode (ou inversement), soit par exemple un gramme. Pour cette introduction, on utilise la pelle 9 qui contient la substance et que l'on introduit dans le guide 7, ladite substance étant ensuite déversée et dispersée progressivement dans le récipient 3 au moyen du vibreur 8 qui secoue la pelle 9, par exemple pendant quelques secondes avec des vibrations plus fortes vers la fin.The amount of flour is predetermined, as already said, by the time of generation of iodine (or vice versa), for example one gram. For this introduction, the shovel 9 is used which contains the substance and which is introduced into the guide 7, the said substance then being poured out and gradually dispersed in the container 3 by means of the vibrator 8 which shakes the shovel 9, for example during a few seconds with stronger vibrations towards the end.
Dès l'introduction de la substance, celle-ci absorbe plus ou moins l'iode et le courant d'électrolyse chute brutalement. On mesure après plusieurs dizaines de secondes le courant d'électrolyse résiduel, soit « Ir ».As soon as the substance is introduced, it more or less absorbs iodine and the electrolysis current drops suddenly. The residual electrolysis current, ie “Ir”, is measured after several tens of seconds.
Il est alors facile de déterminer le taux d'absorption d'iode et donc par exemple le taux d'amidon endommagé, notamment en mesurant le rapport « Ir/lm ».It is then easy to determine the rate of absorption of iodine and therefore, for example, the rate of damaged starch, in particular by measuring the ratio "Ir / lm".
Cette mesure du rapport permet notamment d'obtenir un auto-étalonnage sachant que le courant peut varier en fonction de la position des électrodes et l'agitation dans la solution.This measurement of the ratio makes it possible in particular to obtain a self-calibration knowing that the current can vary as a function of the position of the electrodes and the agitation in the solution.
De nombreuses variantes peuvent évidemment être imaginées sans sortir du cadre de l'invention.Many variations can obviously be imagined without departing from the scope of the invention.
Par exemple, la pesée de la substance qui va être introduite peut être précise alors qu'il est difficile d'introduire une quantité précise déterminée. En conséquence, on peut par exemple corriger le courant Im en fonction de la masse réelle de farine pour ramener sa valeur à celle qui correspond à un gramme. En outre, on peut aussi avec un tel appareil faire d'autres mesures, comme par exemple mesurer la vitesse d'absorption qui permet d'évaluer la dureté de la farine, etc. For example, the weighing of the substance which is going to be introduced can be precise while it is difficult to introduce a precise precise quantity. Consequently, it is possible, for example, to correct the current Im as a function of the real mass of flour in order to reduce its value to that which corresponds to one gram. In addition, it is also possible with such a device to make other measurements, such as for example measuring the absorption rate which makes it possible to evaluate the hardness of the flour, etc.

Claims

REVENDICATIONS
1) Procédé de mesure par ampérométrie du taux d'absorption d'iode d'une substance, caractérisé en ce qu'il consiste à préparer une solution susceptible de fournir de l'iode par réaction électrochimique, à générer de l'iode par réaction électrochimique, à mesurer un courant d'électrolyse de la solution, à introduire la substance à analyser dans la solution, à mesurer un courant d'électrolyse du mélange et à déterminer le taux d'absorption d'iode par la substance en fonction des courants mesurés qui sont eux-mêmes fonction de la concentration d'iode. 2) Procédé selon la revendication 1 , caractérisé en ce qu'il consiste à mesurer le courant dans la solution avant la génération de l'iode pour établir un courant de zéro.1) Amperometric method for measuring the rate of iodine absorption of a substance, characterized in that it consists in preparing a solution capable of supplying iodine by electrochemical reaction, in generating iodine by reaction electrochemical, to measure an electrolysis current of the solution, to introduce the substance to be analyzed into the solution, to measure an electrolysis current of the mixture and to determine the rate of iodine absorption by the substance as a function of the currents measured which are themselves a function of the concentration of iodine. 2) Method according to claim 1, characterized in that it consists in measuring the current in the solution before the generation of iodine to establish a current of zero.
3) Procédé selon l'une des revendications 1 et 2, caractérisé en ce que la solution comporte de l'eau distillée, de l'iodure et un acide faible. 4) Procédé selon la revendication 3, caractérisé en ce que l'acide faible est de l'acide borique.3) Method according to one of claims 1 and 2, characterized in that the solution comprises distilled water, iodide and a weak acid. 4) Method according to claim 3, characterized in that the weak acid is boric acid.
5) Procédé selon l'une des revendications 3 et 4, caractérisé en ce que la solution comporte en outre en faible quantité du thiosulfate pour neutraliser l'iode qui se serait éventuellement fixée sur les électrodes de mesure et/ou de génération de l'iode.5) Method according to one of claims 3 and 4, characterized in that the solution further comprises in small quantity of thiosulfate to neutralize the iodine which would have possibly fixed on the electrodes for measuring and / or generating the iodine.
6) Procédé selon l'une des revendications 1 à 5, caractérisé en ce que la solution est préalablement chauffée et mélangée par brassage avant l'introduction de la substance à mesurer, le chauffage et le brassage étant maintenus pendant toute la durée du cycle de mesure. 7) Procédé selon l'une des revendications 1 à 6, caractérisé en ce que la solution est chauffée jusqu'à une température d'environ 30 à 40 degrés, l'éventuelle première mesure du courant de la solution est effectuée pendant quelques secondes, la génération d'iode est réalisée pendant un temps proportionnel à la masse de la substance à introduire sur la base d'environ cent secondes pour un gramme de substance, la mesure du courant d'électrolyse de la solution est effectuée après l'obtention d'un palier de concentration obtenu au bout de quelques dizaines de secondes, l'introduction de la substance est réalisée progressivement pendant quelques secondes et la mesure du courant d'électrolyse résiduel du mélange est effectuée après plusieurs dizaines de secondes à compter de la fin de l'introduction de la substance.6) Method according to one of claims 1 to 5, characterized in that the solution is previously heated and mixed by stirring before the introduction of the substance to be measured, the heating and stirring being maintained throughout the duration of the cycle of measured. 7) Method according to one of claims 1 to 6, characterized in that the solution is heated to a temperature of about 30 to 40 degrees, the possible first measurement of the current of the solution is carried out for a few seconds, the generation of iodine is carried out for a time proportional to the mass of the substance to be introduced on the basis of approximately one hundred seconds for one gram of substance, the measurement of the electrolysis current of the solution is carried out after obtaining d '' a concentration plateau obtained after a few tens of seconds, the introduction of the substance is carried out gradually for a few seconds and the measurement of the residual electrolysis current of the mixture is performed after several tens of seconds from the end of the introduction of the substance.
8) Procédé selon l'une des revendications 1 à 7, caractérisé en ce que la substance utilisée est de la farine de blé en vue de mesurer son taux d'amidon endommagé qui est fonction du taux d'absorption d'iode.8) Method according to one of claims 1 to 7, characterized in that the substance used is wheat flour in order to measure its level of damaged starch which is a function of the rate of absorption of iodine.
9) Appareil de mesure par ampérométrie du taux d'absorption d'iode d'une substance comportant un récipient (3) destiné à recevoir une suspension de la substance à mesurer et un agitateur (4), caractérisé en ce qu'il comporte en outre au moins une paire d'électrodes (1 1 ) de mesure du courant d'électrolyse et au moins une paire d'électrodes (10) de génération d'iode.9) Apparatus for amperometric measurement of the iodine absorption rate of a substance comprising a container (3) intended to receive a suspension of the substance to be measured and an agitator (4), characterized in that it comprises in addition to at least one pair of electrodes (1 1) for measuring the electrolysis current and at least one pair of electrodes (10) for generating iodine.
10) Appareil selon la revendication 9, caractérisé en ce qu'il comporte en outre un vibreur d'alimentation (8) pour disperser la substance dans une solution préalablement introduite dans le récipient.10) Apparatus according to claim 9, characterized in that it further comprises a feed vibrator (8) for dispersing the substance in a solution previously introduced into the container.
11) Appareil selon l'une des revendications 9 et 10, caractérisé en ce que la paire d'électrodes (11) de mesure du courant d'électrolyse et la paire d'électrodes (10) de génération d'iode se présentent sous la forme de paires d'anneaux aménagés sur une même sonde (5) de conductivité.11) Apparatus according to one of claims 9 and 10, characterized in that the pair of electrodes (11) for measuring the electrolysis current and the pair of electrodes (10) for generating iodine are present under the form of pairs of rings arranged on the same conductivity probe (5).
12) Appareil selon la revendication 11 , caractérisé en ce qu'un capteur de température (12) est également aménagé sur la sonde de conductivité (5). 13) Appareil selon l'une des revendications 9 à 12, caractérisé en ce qu'il comporte en outre un moyen de chauffage sous forme d'une résistance chauffante (6) plongeante dans le récipient (3).12) Apparatus according to claim 11, characterized in that a temperature sensor (12) is also arranged on the conductivity probe (5). 13) Apparatus according to one of claims 9 to 12, characterized in that it further comprises a heating means in the form of a heating resistor (6) immersed in the container (3).
14) Appareil selon l'une des revendications 9 à 13, caractérisé en ce qu'il comporte une partie fixe formant socle (1') aménagée pour recevoir le récipient (3) et une partie mobile (1") montée de manière pivotante et qui comporte l'agitateur (4), les paires d'électrodes (10,11), le capteur de température (12) et l'éventuelle résistance électrique (6), ces éléments étant disposés sur ladite partie mobile (1") pour pouvoir venir dans le récipient (3) ou en ressortir au cours du pivotement qui rapproche ou respectivement écarte angulairement lesdites parties respectivement mobile (1") et fixe (1'). 14) Apparatus according to one of claims 9 to 13, characterized in that it comprises a fixed part forming a base (1 ') arranged to receive the container (3) and a mobile part (1 ") pivotally mounted and which comprises the agitator (4), the pairs of electrodes (10,11), the temperature sensor (12) and the possible electrical resistance (6), these elements being arranged on said movable part (1 ") for be able to come into the container (3) or come out during the pivoting which brings angularly closer or respectively apart said mobile (1 ") and fixed (1 ') parts respectively.
EP03746319A 2002-04-12 2003-04-04 Method and device for amperometric measurement of the iodine absorption rate of a substance Withdrawn EP1495314A1 (en)

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FR0204587A FR2838518B1 (en) 2002-04-12 2002-04-12 METHOD AND APPARATUS FOR AMPEROMETRY MEASUREMENT OF THE IODY ABSORPTION RATE OF A SUBSTANCE
FR0204587 2002-04-12
PCT/FR2003/001069 WO2003087799A1 (en) 2002-04-12 2003-04-04 Method and device for amperometric measurement of the iodine absorption rate of a substance

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