WO2001029540A1 - Device for analysing and dosing light elements and apparatus for carrying out said analysis and dosing - Google Patents

Device for analysing and dosing light elements and apparatus for carrying out said analysis and dosing Download PDF

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Publication number
WO2001029540A1
WO2001029540A1 PCT/FR2000/002867 FR0002867W WO0129540A1 WO 2001029540 A1 WO2001029540 A1 WO 2001029540A1 FR 0002867 W FR0002867 W FR 0002867W WO 0129540 A1 WO0129540 A1 WO 0129540A1
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sample
plasma
plasma torch
inert gas
dosing
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PCT/FR2000/002867
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French (fr)
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Jean-Claude Rouchaud
Michel Fedoroff
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Centre National De La Recherche Scientifique
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/73—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited using plasma burners or torches

Definitions

  • the present invention relates to a method for analyzing and dosing elements by plasma emission spectrometry, and more particularly to a method for precisely dosing elements, including light elements, in samples of various materials, as well as 'an apparatus for its implementation.
  • ICPAES Inductively Coupled Plasma Atomic Emission Spectrometry
  • ICPAES Inductively Coupled Plasma Atomic Emission Spectrometry
  • the assay is generally carried out after dissolving the sample in an appropriate bath, then putting it in the form of an aerosol by nebulization, and introduction into a plasma of inert gas, for example argon, that is to say a gas.
  • inert gas for example argon
  • ionized and electrically neutral brought to very high temperature, where the atoms and ions emit characteristic radiations; using a monochromator, the intensity of the emission lines is measured, then the concentration in the sample by comparison with a known reference.
  • plasma emission spectrometers currently available on the market are not suitable for assaying light elements such as carbon, oxygen and nitrogen, which are nevertheless important elements because of their influence on the material properties.
  • plasma emission spectrometry is done using a solution of a sample, which is transformed into an aerosol in a nebulizer to inject it into the plasma, for example in a flow of argon or helium.
  • a disadvantage of this method is that the dissolution and the passage in aerosol involve losses all the more important as the elements are more volatile, with then consequence of important dosing errors in the case of light elements like carbon and nitrogen.
  • the risk of contamination by the elements present in the ambient air can disturb the dosages and distort the results.
  • Some methods have been proposed to improve the selectivity and the accuracy of the elementary analysis and the assay of elements by plasma emission spectrometry, generally by means of reagents injected into the stream of argon or helium, and by example US-A-4,776,690 describes a method consisting in injecting a mixture of oxygen and hydrogen into the gas flow coming from the sample to be analyzed in order to improve the selectivity of nitrogen detection .
  • Such a method may be suitable in special cases such as the analysis or the determination of nitrogen in a sample, at the outlet of a gas chromatography apparatus.
  • GB-A-2,043,945 describes an apparatus useful for the determination of sulfur comprising a nebulizer for introducing the sample into the plasma in the form of an aerosol.
  • the present invention therefore relates to an improved method of analysis and metering of elements contained in a sample of material, usable in particular for the metering of light elements such as carbon and nitrogen.
  • the invention more particularly relates to a method for dosing elements contained in a sample, limiting contamination by ambient air.
  • the invention also relates to an apparatus for implementing such a method.
  • the method of analysis and metering of elements, by emission spectrometry plasma consists of dissolving the sample to be assayed in a bath containing an appropriate attack reagent, heating, if necessary, the solution to cause gas evolution and injecting the gas directly into the plasma to measure the intensity emission lines.
  • the sample to be assayed is dissolved in an etching reagent preferably chosen from nitric, sulfuric, hydrofluoric, perchloric or orthophosphoric acids, alone or as a mixture.
  • an oxidant such as potassium tetra-oxoiodate or potassium persulfate.
  • the gas used to generate the plasma is generally an inert gas chosen from helium, argon or neon, or mixtures of gases, and argon is preferably used, which offers a good compromise between cost, implementation and ionization energy, optionally mixed with nitrogen or hydrogen.
  • the device according to the present invention consists of a plasma emission spectrometry apparatus of conventional type supplemented by an appropriate device comprising a container, for example a balloon, equipped with an inlet connected to a source of inert gas and d '' a sample introduction system, etching reagent and / or reference solution, and an output connected to the plasma torch.
  • the plasma emission spectrometry apparatus itself, conventionally consists of a source of inert gas, a plasma torch and a spectrometer connected to a measurement system, but it does not include a nebulizer for the formation of an aerosol.
  • a conventional plasma emission spectrometry apparatus includes a source of inert gas (argon) feeding a plasma torch (TP) comprising a quartz tube (T) placed in a strong magnetic field created by a coil powered by a high frequency generator (HF).
  • argon inert gas
  • TP plasma torch
  • HF high frequency generator
  • the solution of the sample (E) to be analyzed is driven by a peristaltic pump (PP) to a nebulizer (N) and then projected into the plasma.
  • PP peristaltic pump
  • N nebulizer
  • the radiation emitted is collected by a spectrometer (S) connected to a computer (0) by an interface (I).
  • the apparatus according to the invention essentially consists in replacing the nebulizer (N) of the conventional apparatus by the device shown in Figure 2 comprising a balloon (B) comprising an argon inlet, a device for introducing the sample (E) and a device for introducing a standard solution (SE).
  • the outlet of the flask (B) is preferably equipped with a cooling column (R) and is connected to the plasma torch identical to that of FIG. 1.
  • a conventional device for washing gases can be provided between the column of cooling (R) and the plasma torch.
  • the flask (B) contains the attack reagent, for example a solution of concentrated nitric acid, sulfuric acid or orthophosphoric acid.
  • the attack reagent is chosen according to the sample and the elements to be assayed. For example, it is advantageous to use nitric acid 1 to 3 N for carbonates in solution, nitric acid 2 to 6 N for carbonate minerals and apatites, sulfuric acid and orthophosphoric acid (added oxidant) for iron, steels and magnesium, sulfuric acid (with an oxidant) for silver and silver-based alloys, sulfuric acid, sodium fluoride and potassium tetraoxoiodate for zirconium, sulfuric acid, nitric acid and perchloric acid for organic compounds.
  • acidification is generally sufficient, otherwise the addition of the oxidant in the etching bath is preferable in order to oxidize the carbon.
  • the calibration of the apparatus is carried out by introducing increasing determined doses of the standard solution. Knowing the carbon or nitrogen content, for example, of the reference solution, and the measured intensity of the emission line, we can draw the calibration curve giving the carbon or nitrogen content as a function of l intensity measured.
  • the attacking reagent is first introduced into the flask, it is heated to an appropriate temperature, determined by the boiling temperature of the mixture of acids, and we wait until the emission intensity has stabilized. - read.
  • the sample, solid or liquid, is then introduced into the etching bath by appropriate means. Its progressive dissolution is accompanied by an increase, then a decrease in the intensity of the signal measured on the plasma emission spectrometry apparatus.
  • the total quantity of the sought-after element present in the sample is proportional to the integral of the signal measured during the entire period when it is greater than the background noise.
  • the calibration for calculating the quantity of the element considered is carried out using a reference sample containing known quantities of element, in the same apparatus and with the same attack reagent.
  • the method according to the present invention has the advantage of allowing the precise analysis and metering of a large number of elements contained in various materials, for example the metering of carbon in a metal sample, with excellent precision, even in the case of light elements such as carbon and nitrogen. More particularly, according to the method of the invention, the element to be assayed is introduced entirely into the plasma, while the conventional method using a nebulizer, a small percentage only reaches the plasma. In addition, the technique of the invention makes it possible to considerably limit contamination by ambient air, and consequently, the precision and reliability of the assay are improved.
  • Another advantage of the present invention is to extend the field of application of analysis and metering equipment by plasma emission spectrometry, in particular in certain industrial and medical sectors where it is important to be able to perform precisely and reliable detection and dosing of light elements such as nitrogen.
  • fields of application of the invention mention may be made of the metering of iron, steels, or of various metals or alloys in metallurgy, the analysis of materials with very diverse carbon contents, in the chemistry of solid, the determination in carbonate minerals or containing traces of carbon, in mineralogy and geology, as well as the determination in blood or physiological fluids, in biology.
  • an advantage of the present invention is to provide these results without it being necessary to substantially modify the conventional apparatuses of the plasma emission spectrometry technique.
  • an assay of a sample of calcite (calcium carbonate) in the form of powder is carried out.
  • the attack bath used is a 6N nitric acid solution.
  • the calibration is carried out by successively introducing known increasing amounts of sodium carbonate into the bath and by measuring the intensity obtained.
  • Quantities carbonate used correspond to 0 to 10 mg of carbon. 198.1 mg of Na 2 CO (22.45 mg of carbon) are used, which is dissolved in 100 ml of boiled water, and the volumes indicated in the table below are introduced.
  • the carbon is then measured in a calcite powder (calcium carbonate) of which the theoretical amounts of carbon are known, in order to control the accuracy of the dosage.
  • Example 2 The procedure is as in Example 1, by carrying out the determination of an iron sample of known content (CRM088 iron with carbon content equal to 25 ⁇ g / g) used in powder form.
  • the attack bath used is a solution based on sulfuric acid (20 ml), playing the role of oxidant, and orthophosphoric acid (20 ml) playing the role of complexing agent, added with potassium tetraoxoiodate (KI0 2 g).
  • the reaction kinetics are first determined. For this, the sample of iron powder is introduced into the flask containing the hot attack bath, and the evolution of the emission intensities is observed over time.
  • the integration time is 30 seconds.
  • the calibration is carried out as in Example 1, using a sodium carbonate powder with a known carbon content. 255 mg of powder are placed in 100 ml of water, i.e. a carbon content of 0.2886 mg / ml, and introducing increasing volumes (from 0 to 7 ml) and measuring the intensity of the carbon line C_193 per ⁇ g. Then draw the calibration curve, as in Example 1.

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Abstract

The invention relates to a method for analysing and dosing elements by means of plasma emission spectroscopie. The method for analysing and dosing elements contained in a sample of solid or liquid matter consists in dissolving the sample which is to be dosed in a bath containing an etching reagent; in heating the solution if necessary so that gassing can occur and injecting said gas into the plasma in order to measure the intensity of the emission lines. The apparatus comprises an inert gas source, a plasma torch (TP) and a spectrometer (S) which is connected to a measuring system (O), in addition to a container (B) which is equipped with an inlet connected to the inert gas source (Ar) and a system for introducing a sample (E), an etching agent and/or reference solution (SE), together with an outlet connected to the plasma torch. The invention can be used in metallurgy, solid chemistry, mineralogy and biology in order to dose light elements such as carbon and nitrogen.

Description

Procédé d'analyse et de dosage d'éléments légers et appareillage pour sa mise en œuvre. La présente invention concerne un procédé d'analyse et de dosage d'éléments par spectrométrie d'émission au plasma, et plus particulièrement un procédé permettant de doser précisément des éléments, y compris des éléments légers, dans des échantillons de divers matériaux, ainsi qu'un appareillage pour sa mise en oeuvre. Method of analysis and metering of light elements and apparatus for its implementation. The present invention relates to a method for analyzing and dosing elements by plasma emission spectrometry, and more particularly to a method for precisely dosing elements, including light elements, in samples of various materials, as well as 'an apparatus for its implementation.
La spectrométrie d'émission au plasma (Inductively Coupled Plasma Atomic Emission Spectrometry ou ICPAES) est une technique couramment utilisée de nos jours pour doser divers éléments contenus dans des échantillons, dans des gammes de concentrations pouvant aller de quelques traces jusqu'à des teneurs importantes. Le dosage est généralement effectué après dissolution de l'échantillon dans un bain approprié, puis mise sous forme d'aérosol par nébulisation, et introduction dans un plasma de gaz inerte, par exemple l'argon, c'est-à-dire un gaz ionisé et électriquement neutre porté à très haute température, où les atomes et ions émettent des radiations caractéristiques ; à l'aide d'un monochromateur, on mesure l'intensité des raies d'émission, puis la concentration dans l'échan- tillon par comparaison avec une référence connue.Inductively Coupled Plasma Atomic Emission Spectrometry (ICPAES) is a technique commonly used nowadays to measure various elements contained in samples, in concentration ranges which can go from a few traces to significant contents . The assay is generally carried out after dissolving the sample in an appropriate bath, then putting it in the form of an aerosol by nebulization, and introduction into a plasma of inert gas, for example argon, that is to say a gas. ionized and electrically neutral brought to very high temperature, where the atoms and ions emit characteristic radiations; using a monochromator, the intensity of the emission lines is measured, then the concentration in the sample by comparison with a known reference.
Cependant, les spectromètres d'émission au plasma actuellement disponibles sur le marché ne sont pas adaptés au dosage d'éléments légers tels que le carbone, l'oxygène et l'azote, qui sont pourtant des éléments importants en raison de leur influence sur les propriétés des matériaux. En effet, la spectrométrie d'émission au plasma se fait en utilisant une solution d'un échantillon, que l'on transforme en aérosol dans un nébuliseur pour l'injecter dans la plasma, par exemple dans un flux d'argon ou d'hélium. Un inconvénient de cette méthode est que la dissolution et le passage en aérosol entraînent des pertes d'autant plus importantes que les éléments sont plus volatils, avec alors pour conséquence des erreurs de dosage importantes dans le cas d'éléments légers comme le carbone et l'azote. De plus, les risques de contamination par les éléments présents dans l'air ambiant peuvent perturber les dosages et fausser les résultats.However, the plasma emission spectrometers currently available on the market are not suitable for assaying light elements such as carbon, oxygen and nitrogen, which are nevertheless important elements because of their influence on the material properties. Indeed, plasma emission spectrometry is done using a solution of a sample, which is transformed into an aerosol in a nebulizer to inject it into the plasma, for example in a flow of argon or helium. A disadvantage of this method is that the dissolution and the passage in aerosol involve losses all the more important as the elements are more volatile, with then consequence of important dosing errors in the case of light elements like carbon and nitrogen. In addition, the risk of contamination by the elements present in the ambient air can disturb the dosages and distort the results.
Quelques méthodes ont été proposées pour améliorer la sélectivité et la précision de l'analyse élémentaire et du dosage d'éléments par spectrométrie d'émission au plasma, généralement au moyen de réactifs injectés dans le courant d'argon ou d'hélium, et par exemple le brevet US-A-4.776.690 décrit une méthode consistant à injecter un mélange d'oxygène et d'hydrogène dans le flux de gaz provenant de l'échantillon à analyser afin d'améliorer la sélectivité de la détection de l'azote. Une telle méthode peut convenir dans des cas particuliers tels que l'analyse ou le dosage de l'azote dans un échantillon, en sortie d'un appareillage de chromatographie en phase gazeuse. Le brevet GB-A-2.043.945 décrit un appareil utile pour le dosage du soufre comportant un nébulliseur pour introduire l'échantillon dans le plasma sous forme d'aérosol.Some methods have been proposed to improve the selectivity and the accuracy of the elementary analysis and the assay of elements by plasma emission spectrometry, generally by means of reagents injected into the stream of argon or helium, and by example US-A-4,776,690 describes a method consisting in injecting a mixture of oxygen and hydrogen into the gas flow coming from the sample to be analyzed in order to improve the selectivity of nitrogen detection . Such a method may be suitable in special cases such as the analysis or the determination of nitrogen in a sample, at the outlet of a gas chromatography apparatus. GB-A-2,043,945 describes an apparatus useful for the determination of sulfur comprising a nebulizer for introducing the sample into the plasma in the form of an aerosol.
Les études et essais effectués par la demanderesse ont montré qu'il est possible d'éviter de devoir former un aérosol à partir d'une solution de l'échantillon à analyser, ce qui permet de s'affranchir des inconvénients inhérents à la méthode classique. Cet avantage peut être obtenu au moyen d'un perfectionnement apporté à la méthode classique de dosage par spectrométrie d'émission au plasma, en travaillant directement sur les formes gazeuses des éléments dans le plasma.The studies and tests carried out by the applicant have shown that it is possible to avoid having to form an aerosol from a solution of the sample to be analyzed, which makes it possible to overcome the drawbacks inherent in the conventional method . This advantage can be obtained by means of an improvement made to the conventional method of determination by plasma emission spectrometry, by working directly on the gaseous forms of the elements in the plasma.
La présente invention a donc pour objet un procédé perfectionné d'analyse et de dosage d'éléments contenus dans un échantillon de matériau, utilisable en particulier pour le dosage d'éléments légers tels que le carbone et l'azote. L'invention a plus particulièrement pour objet un procédé de dosage d'éléments contenus dans un échantillon, limitant la contamination par l'air ambiant. L'invention a également pour objet un appareillage pour la mise en oeuvre d'un tel procédé.The present invention therefore relates to an improved method of analysis and metering of elements contained in a sample of material, usable in particular for the metering of light elements such as carbon and nitrogen. The invention more particularly relates to a method for dosing elements contained in a sample, limiting contamination by ambient air. The invention also relates to an apparatus for implementing such a method.
Conformément à la présente invention, le procédé d'analyse et de dosage d'éléments, par spectrométrie d'émis- sion au plasma, consiste à dissoudre l'échantillon à doser dans un bain contenant un réactif d'attaque approprié, à chauffer, si nécessaire, la solution pour provoquer un dégagement gazeux et à injecter le gaz directement dans le plasma pour mesurer l'intensité des raies d'émission.According to the present invention, the method of analysis and metering of elements, by emission spectrometry plasma, consists of dissolving the sample to be assayed in a bath containing an appropriate attack reagent, heating, if necessary, the solution to cause gas evolution and injecting the gas directly into the plasma to measure the intensity emission lines.
L'échantillon à doser est dissous dans un réactif d'attaque choisi de préférence parmi les acides nitrique, sulfurique, fluorhydrique, perchlorique ou orthophosphorique, isolément ou en mélange. Suivant une forme préférentielle de réalisation, le bain d'attaque contenant la solution de l'échantillon est additionné d'un oxydant tel que le tétra- oxoiodate de potassium ou le persulfate de potassium.The sample to be assayed is dissolved in an etching reagent preferably chosen from nitric, sulfuric, hydrofluoric, perchloric or orthophosphoric acids, alone or as a mixture. According to a preferred embodiment, the attack bath containing the sample solution is supplemented with an oxidant such as potassium tetra-oxoiodate or potassium persulfate.
Le gaz utilisé pour générer le plasma est généralement un gaz inerte choisi parmi l'hélium, l'argon ou le néon, ou des mélanges de gaz, et on utilise de préférence l'argon, qui offre un bon compromis entre le coût, la mise en oeuvre et l'énergie d'ionisation, éventuellement en mélange avec de l'azote ou de l'hydrogène.The gas used to generate the plasma is generally an inert gas chosen from helium, argon or neon, or mixtures of gases, and argon is preferably used, which offers a good compromise between cost, implementation and ionization energy, optionally mixed with nitrogen or hydrogen.
Le dispositif conforme à la présente invention est constitué par un appareillage de spectrométrie d'émission au plasma de type classique complété par un dispositif approprié comprenant un conteneur, par exemple un ballon, équipé d'une arrivée raccordée à une source de gaz inerte et d'un système d'introduction d'échantillon, de réactif d'attaque et/ou de solution de référence, et d'une sortie connectée à la torche à plasma. L'appareillage de spectrométrie d'émission au plasma, lui-même, est constitué classiquement par une source de gaz inerte, d'une torche à plasma et d'un spectromètre connecté à un système de mesure, mais il ne comporte pas de nébuliseur pour la formation d'un aérosol.The device according to the present invention consists of a plasma emission spectrometry apparatus of conventional type supplemented by an appropriate device comprising a container, for example a balloon, equipped with an inlet connected to a source of inert gas and d '' a sample introduction system, etching reagent and / or reference solution, and an output connected to the plasma torch. The plasma emission spectrometry apparatus, itself, conventionally consists of a source of inert gas, a plasma torch and a spectrometer connected to a measurement system, but it does not include a nebulizer for the formation of an aerosol.
Un appareillage usuel de spectrométrie d'émission au plasma est représenté schématiquement sur la Figure 1 ci- après, et un appareillage utilisable pour la mise en œuvre du procédé conforme à la présente invention est représenté sur la Figure 2. Comme le montre la Figure 1, un appareillage de spectrométrie d'émission au plasma de type usuel comprend une source de gaz inerte (argon) alimentant une torche à plasma (TP) comportant un tube de quartz (T) placé dans un fort champ magnétique créé par une bobine alimentée par un générateur de hautes fréquences (HF) . La solution de l'échantillon (E) à analyser est entraînée par une pompe péristaltique (PP) jusqu'à un nébuliseur (N) puis projetée dans le plasma. Les radiations émises sont collectées par un spectromètre (S) raccordé à un ordinateur (0) par un interface (I) .A conventional apparatus for plasma emission spectrometry is shown diagrammatically in FIG. 1 below, and an apparatus which can be used for implementing the method according to the present invention is represented in FIG. 2. As shown in Figure 1, a conventional plasma emission spectrometry apparatus includes a source of inert gas (argon) feeding a plasma torch (TP) comprising a quartz tube (T) placed in a strong magnetic field created by a coil powered by a high frequency generator (HF). The solution of the sample (E) to be analyzed is driven by a peristaltic pump (PP) to a nebulizer (N) and then projected into the plasma. The radiation emitted is collected by a spectrometer (S) connected to a computer (0) by an interface (I).
L'appareillage conforme à l'invention consiste essentiellement à remplacer le nébuliseur (N) de l'appareillage classique par le dispositif représenté sur la Figure 2 comprenant un ballon (B) comportant une arrivée d'argon, un dispositif d'introduction de l'échantillon (E) et un dispositif d'introduction d'une solution étalon (SE) . La sortie du ballon (B) est de préférence équipée d'une colonne de refroidissement (R) et est raccordée à la torche à plasma identique à celle de la Figure 1. Un dispositif usuel de lavage des gaz peut être prévu entre la colonne de refroidissement (R) et la torche à plasma.The apparatus according to the invention essentially consists in replacing the nebulizer (N) of the conventional apparatus by the device shown in Figure 2 comprising a balloon (B) comprising an argon inlet, a device for introducing the sample (E) and a device for introducing a standard solution (SE). The outlet of the flask (B) is preferably equipped with a cooling column (R) and is connected to the plasma torch identical to that of FIG. 1. A conventional device for washing gases can be provided between the column of cooling (R) and the plasma torch.
Le ballon (B) contient le réactif d'attaque, par exemple une solution d'acide nitrique concentré, d'acide sulfurique ou d'acide orthophosphorique . Le réactif d'attaque est choisi en fonction de l'échantillon et des éléments à doser. Par exemple, on peut avantageusement utiliser de l'acide nitrique 1 à 3 N pour des carbonates en solution, de l'acide nitrique 2 à 6 N pour des minéraux carbonates et des apatites, l'acide sulfurique et l'acide orthophosphorique (additionné d'un oxydant) pour le fer, les aciers et le magnésium, l'acide sulfurique (additionné d'un oxydant) pour l'argent et les alliages à base d'argent, l'acide sulfurique, le fluorure de sodium et le tétraoxoiodate de potassium pour le zirconium, l'acide sulfurique, l'acide nitrique et l'acide perchlorique pour les composés organiques . Lorsque le carbone à doser est sous forme carbonate, l'acidification est généralement suffisante, sinon l'addition de l'oxydant dans le bain d'attaque est préférable afin d'oxyder le carbone.The flask (B) contains the attack reagent, for example a solution of concentrated nitric acid, sulfuric acid or orthophosphoric acid. The attack reagent is chosen according to the sample and the elements to be assayed. For example, it is advantageous to use nitric acid 1 to 3 N for carbonates in solution, nitric acid 2 to 6 N for carbonate minerals and apatites, sulfuric acid and orthophosphoric acid (added oxidant) for iron, steels and magnesium, sulfuric acid (with an oxidant) for silver and silver-based alloys, sulfuric acid, sodium fluoride and potassium tetraoxoiodate for zirconium, sulfuric acid, nitric acid and perchloric acid for organic compounds. When the carbon to be dosed is in carbonate form, acidification is generally sufficient, otherwise the addition of the oxidant in the etching bath is preferable in order to oxidize the carbon.
L'étalonnage de l'appareillage est effectué en intro- duisant des doses déterminées croissantes de la solution étalon. Connaissant la teneur en carbone ou en azote, par exemple, de la solution de référence, et l'intensité mesurée de la raie d'émission, on peut tracer la courbe d'étalonnage donnant la teneur en carbone ou en azote en fonction de l'intensité mesurée.The calibration of the apparatus is carried out by introducing increasing determined doses of the standard solution. Knowing the carbon or nitrogen content, for example, of the reference solution, and the measured intensity of the emission line, we can draw the calibration curve giving the carbon or nitrogen content as a function of l intensity measured.
En pratique, on introduit d'abord le réactif d'attaque dans le ballon, on le chauffe à une température appropriée, déterminée par la température d'ébullition du mélange d'acides, et on attend que l'intensité d'émission soit stabi- lisée. L'échantillon, solide ou liquide, est ensuite introduit dans le bain d'attaque par des moyens appropriés. Sa dissolution progressive s'accompagne d'une augmentation, puis d'une diminution de l'intensité du signal mesuré sur l'appareillage de spectrométrie d'émission au plasma. La quantité totale de l'élément recherché présent dans l'échantillon est proportionnelle à l'intégrale du signal mesuré pendant toute la période où il est supérieur au bruit de fond. L'étalonnage permettant de calculer la quantité de l'élément considéré est effectué en utilisant un échantillon de référence contenant des quantités connues d'élément, dans le même appareillage et avec le même réactif d'attaque.In practice, the attacking reagent is first introduced into the flask, it is heated to an appropriate temperature, determined by the boiling temperature of the mixture of acids, and we wait until the emission intensity has stabilized. - read. The sample, solid or liquid, is then introduced into the etching bath by appropriate means. Its progressive dissolution is accompanied by an increase, then a decrease in the intensity of the signal measured on the plasma emission spectrometry apparatus. The total quantity of the sought-after element present in the sample is proportional to the integral of the signal measured during the entire period when it is greater than the background noise. The calibration for calculating the quantity of the element considered is carried out using a reference sample containing known quantities of element, in the same apparatus and with the same attack reagent.
Le procédé suivant la présente invention présente l'avantage de permettre l'analyse et le dosage précis d'un grand nombre d'éléments contenus dans divers matériaux, par exemple le dosage du carbone dans un échantillon de métal, avec une excellente précision, même dans le cas d'éléments légers tels que le carbone et l'azote. Plus particulièrement, suivant le procédé de l'invention, l'élément à doser est introduit en totalité dans le plasma, tandis que le procédé classique utilisant un nébuliseur, un faible pourcentage seulement parvient jusqu'au plasma. De plus, la technique de l'invention permet de limiter considérablement la contamination par l'air ambiant, et en conséquence, la précision et la fiabilité du dosage sont améliorées. Un autre avantage de la présente invention est d'étendre le domaine d'application des appareillages d'analyse et de dosage par spectrométrie d'émission au plasma, en particulier dans certains secteurs industriels et médicaux où il est important de pouvoir effectuer de manière précise et fiable la détection et le dosage d'éléments légers tels que l'azote. A titre d'exemple de domaines d'application de l'invention, on peut citer le dosage du fer, des aciers, ou de divers métaux ou alliage en métallurgie, l'analyse de matériaux à teneurs très diverses en carbone, en chimie du solide, le dosage dans les minéraux carbonates ou contenant des traces de carbone, en minéralogie et géologie, ainsi que le dosage dans le sang ou les liquides physiologiques, en biologie. Enfin, un avantage de la présente invention est de procurer ces résultats sans qu'il soit nécessaire de modifier substantiellement les appareillages classiques de la technique de spectrométrie d'émission au plasma.The method according to the present invention has the advantage of allowing the precise analysis and metering of a large number of elements contained in various materials, for example the metering of carbon in a metal sample, with excellent precision, even in the case of light elements such as carbon and nitrogen. More particularly, according to the method of the invention, the element to be assayed is introduced entirely into the plasma, while the conventional method using a nebulizer, a small percentage only reaches the plasma. In addition, the technique of the invention makes it possible to considerably limit contamination by ambient air, and consequently, the precision and reliability of the assay are improved. Another advantage of the present invention is to extend the field of application of analysis and metering equipment by plasma emission spectrometry, in particular in certain industrial and medical sectors where it is important to be able to perform precisely and reliable detection and dosing of light elements such as nitrogen. By way of example of fields of application of the invention, mention may be made of the metering of iron, steels, or of various metals or alloys in metallurgy, the analysis of materials with very diverse carbon contents, in the chemistry of solid, the determination in carbonate minerals or containing traces of carbon, in mineralogy and geology, as well as the determination in blood or physiological fluids, in biology. Finally, an advantage of the present invention is to provide these results without it being necessary to substantially modify the conventional apparatuses of the plasma emission spectrometry technique.
Les divers avantages et caractéristiques de la présente invention apparaîtront plus en détail dans les exemples suivants, donnés pour illustrer l'invention sans en limiter la portée.The various advantages and characteristics of the present invention will appear in more detail in the following examples, given to illustrate the invention without limiting its scope.
Exemple 1Example 1
Au moyen de l'appareillage représenté sur la Figure 2, on effectue un dosage d'un échantillon de calcite (carbonate de calcium) se présentant sous forme de poudre. Le bain d'attaque utilisé est une solution d'acide nitrique 6N .Using the apparatus shown in Figure 2, an assay of a sample of calcite (calcium carbonate) in the form of powder is carried out. The attack bath used is a 6N nitric acid solution.
L'étalonnage est effectué en introduisant successivement des quantités croissantes connues de carbonate de sodium dans le bain et en mesurant l'intensité obtenue. Les quantités utilisées de carbonate correspondent à 0 à 10 mg de carbone. On utilise 198,1 mg de Na2C0 (soit 22,45 mg en carbone) que l'on dissout dans 100 ml d'eau bouillie, et on introduit les volumes indiqués au tableau ci-dessous.The calibration is carried out by successively introducing known increasing amounts of sodium carbonate into the bath and by measuring the intensity obtained. Quantities carbonate used correspond to 0 to 10 mg of carbon. 198.1 mg of Na 2 CO (22.45 mg of carbon) are used, which is dissolved in 100 ml of boiled water, and the volumes indicated in the table below are introduced.
Tableau 1Table 1
Figure imgf000009_0001
Figure imgf000009_0001
On effectue ensuite le dosage du carbone dans une poudre de calcite (carbonate de calcium) dont on connaît les quantités théorique de carbone, afin de contrôler la précision du dosage.The carbon is then measured in a calcite powder (calcium carbonate) of which the theoretical amounts of carbon are known, in order to control the accuracy of the dosage.
Les résultats obtenus sont regroupés au tableau 2 ci- après .The results obtained are collated in Table 2 below.
Tableau 2Table 2
Figure imgf000009_0002
Ces expériences confirment la précision du dosage.
Figure imgf000009_0002
These experiments confirm the accuracy of the assay.
L'expérience est répétée avec des poudres d'apatite, et les résultats sont regroupés au tableau 3 ci-après. Tableau 3The experiment is repeated with apatite powders, and the results are collated in Table 3 below. Table 3
Figure imgf000010_0001
Figure imgf000010_0001
Ces résultats mettent en évidence les différences entre une apatite pure (BR2.6) et une apatite carbonatée (FF21T)These results highlight the differences between a pure apatite (BR2.6) and a carbonated apatite (FF21T)
Exemple 2Example 2
On procède comme dans l'Exemple 1, en effectuant le dosage d'un échantillon de fer de teneur connue (fer CRM088 de teneur en carbone égale à 25 μg/g) utilisé sous forme de poudre . Le bain d'attaque utilisé est une solution à base d'acide sulfurique (20 ml), jouant le rôle d'oxydant, et d'acide orthophosphorique (20 ml) jouant le rôle de complexant, additionnée de tétraoxoiodate de potassium (KI0 2 g) .The procedure is as in Example 1, by carrying out the determination of an iron sample of known content (CRM088 iron with carbon content equal to 25 μg / g) used in powder form. The attack bath used is a solution based on sulfuric acid (20 ml), playing the role of oxidant, and orthophosphoric acid (20 ml) playing the role of complexing agent, added with potassium tetraoxoiodate (KI0 2 g).
On détermine tout d'abord la cinétique de réaction. Pour cela, l'échantillon de poudre de fer est introduit dans le ballon contenant le bain d'attaque, à chaud, et on observe l'évolution des intensités d'émission au cours du temps. Le temps d'intégration est de 30 secondes.The reaction kinetics are first determined. For this, the sample of iron powder is introduced into the flask containing the hot attack bath, and the evolution of the emission intensities is observed over time. The integration time is 30 seconds.
L'étalonnage est effectué comme dans l'Exemple 1, en utilisant une poudre de carbonate de sodium à teneur connue en carbone. 255 mg de poudre sont placés dans 100 ml d'eau, soit une teneur en carbone de 0,2886 mg/ml, et en introduisant des volumes croissants (de 0 à 7 ml) et en mesurant l'intensité de la raie du carbone C_193 par μg . On trace ensuite la courbe d'étalonnage, comme dans l'Exemple 1.The calibration is carried out as in Example 1, using a sodium carbonate powder with a known carbon content. 255 mg of powder are placed in 100 ml of water, i.e. a carbon content of 0.2886 mg / ml, and introducing increasing volumes (from 0 to 7 ml) and measuring the intensity of the carbon line C_193 per μg. Then draw the calibration curve, as in Example 1.
La mesure effectuée ensuite sur l'échantillon de fer certifié procure un résultat mesuré de teneur en carbone de 26,4 ± 1,5 μg/g très proche de la valeur théorique. Ces résultats confirment la grande précision du procédé de l'invention, même dans le cas du dosage d'éléments légers tels que le carbone. The measurement then carried out on the certified iron sample provides a measured carbon content of 26.4 ± 1.5 μg / g very close to the theoretical value. These results confirm the great precision of the process of the invention, even in the case of the metering of light elements such as carbon.

Claims

REVENDICATIONS
1. Procédé d'analyse et de dosage, par spectrométrie d'émission au plasma, d'éléments contenus dans un échantillon de matériau solide ou liquide, caractérisé en ce qu'il comprend les étapes consistant à dissoudre l'échantillon à doser dans un bain contenant un réactif d'attaque approprié, à chauffer, si nécessaire, la solution pour provoquer un dégagement gazeux et à injecter le gaz directement dans le plasma pour mesurer l'intensité des raies d'émission.1. A method of analysis and metering, by plasma emission spectrometry, of elements contained in a sample of solid or liquid material, characterized in that it comprises the steps consisting in dissolving the sample to be assayed in a bath containing an appropriate attack reagent, to heat, if necessary, the solution to cause gas evolution and to inject the gas directly into the plasma to measure the intensity of the emission lines.
2. Procédé selon la revendication 1, caractérisé en ce que l'échantillon à doser est dissout dans un réactif d'attaque choisi de préférence parmi les acides nitrique, sulfurique, fluorhydrique, perchlorique ou orthophosphorique, isolément ou en mélange.2. Method according to claim 1, characterized in that the sample to be assayed is dissolved in an attack reagent preferably chosen from nitric, sulfuric, hydrofluoric, perchloric or orthophosphoric acids, alone or as a mixture.
3. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le bain d'attaque contenant la solution de l'échantillon est additionné d'un oxydant.3. Method according to any one of the preceding claims, characterized in that the attack bath containing the sample solution is added with an oxidant.
4. Procédé selon la revendication 3, caractérisé en ce que l'oxydant est le tétraoxoiodate de potassium ou le persulfate de potassium. 4. Method according to claim 3, characterized in that the oxidant is potassium tetraoxoiodate or potassium persulfate.
5. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le gaz utilisé pour le plasma est un gaz inerte choisi parmi l'hélium, l'argon ou le néon .5. Method according to any one of the preceding claims, characterized in that the gas used for the plasma is an inert gas chosen from helium, argon or neon.
6. Appareillage pour la mise en oeuvre du procédé selon l'une quelconque des revendications précédentes, comportant un appareillage de spectrométrie d'émission au plasma de type classique comprenant une source de gaz inerte, une torche à plasma (TP) et un spectromètre (S) connecté à un système de mesure (O) , caractérisé en ce qu'il comprend un conteneur (B) , équipé d'une arrivée raccordée à la source de gaz inerte (Ar) et d'un système d'introduction d'échantillon (E) , de réactif d'attaque et/ou de solution de référence (SE), et d'une sortie connectée à la torche à plasma. 6. Apparatus for implementing the method according to any one of the preceding claims, comprising a plasma emission spectrometry apparatus of conventional type comprising a source of inert gas, a plasma torch (TP) and a spectrometer ( S) connected to a measurement system (O), characterized in that it comprises a container (B), equipped with an inlet connected to the source of inert gas (Ar) and with a system for introducing sample (E), attack reagent and / or reference solution (SE), and an output connected to the plasma torch.
7. Appareillage selon la revendication 6, caractérisé en ce que la sortie du conteneur est équipée d'une colonne de refroidissement raccordée à la torche à plasma.7. Apparatus according to claim 6, characterized in that the outlet of the container is equipped with a cooling column connected to the plasma torch.
8. Appareillage selon la revendication 7, caractérisé en ce qu'un dispositif de lavage des gaz est prévu entre la colonne de refroidissement et la torche à plasma. 8. Apparatus according to claim 7, characterized in that a gas washing device is provided between the cooling column and the plasma torch.
PCT/FR2000/002867 1999-10-18 2000-10-13 Device for analysing and dosing light elements and apparatus for carrying out said analysis and dosing WO2001029540A1 (en)

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WO1991005241A1 (en) * 1989-09-29 1991-04-18 Research Corporation Technologies, Inc. Infrared emission detection
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JPH0868735A (en) * 1994-08-31 1996-03-12 Kyocera Corp Method of acid decomposition of undecomposable sample using microwave heating

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Publication number Priority date Publication date Assignee Title
US4230665A (en) * 1977-07-01 1980-10-28 Bodenseewerk Perkin-Elmer & Co., Gmbh Apparatus for automatically generating and measuring gaseous measuring samples from a series of liquid samples
GB2043945A (en) * 1979-02-23 1980-10-08 Dow Chemical Co VUV Plasma Atomic Spectroscopic Apparatus and Method
US5055409A (en) * 1981-05-26 1991-10-08 Bifok Ab Method for reducing interferences in the analysis of substances which form volatile hydrides
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JPH0868735A (en) * 1994-08-31 1996-03-12 Kyocera Corp Method of acid decomposition of undecomposable sample using microwave heating

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