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WO2000047993A1 - Method and device for determining the toc content of aqueous samples - Google Patents

Method and device for determining the toc content of aqueous samples Download PDF

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Publication number
WO2000047993A1
WO2000047993A1 PCT/EP2000/001066 EP0001066W WO0047993A1 WO 2000047993 A1 WO2000047993 A1 WO 2000047993A1 EP 0001066 W EP0001066 W EP 0001066W WO 0047993 A1 WO0047993 A1 WO 0047993A1
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measuring
ultrapure water
space
determining
conductivity
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German (de)
French (fr)
Inventor
Jörg BETTMER
Rainer Feldhaus
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Institut fuer Chemo und Biosensorik Muenster eV ICB
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Institut fuer Chemo und Biosensorik Muenster eV ICB
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    • 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
    • G01N33/18—Water
    • G01N33/1826—Organic contamination in water
    • G01N33/1846—Total carbon analysis
    • 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
    • G01N31/005—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods investigating the presence of an element by oxidation

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  • the invention relates to a method and a device for determining the total organically bound carbon in aqueous samples according to the preamble of the main claim and the subordinate device claim.
  • the generated CO is removed from the solution by acidifying and passing a gas-permeable membrane (gas-liquid separator).
  • the C0 2 is passed into a gas cuvette and measured spectroscopically using infrared radiation.
  • the measurement solution is passed into a reaction cell.
  • the conductivity is measured and the solution is irradiated with UV light until all organic compounds have been destroyed.
  • the conductivity is measured continuously, which enables reaction control.
  • the TOC content of the solution can be inferred from the conductivity difference determined at the beginning and towards the end of the reaction. Disadvantages here are the impossibility of on-line measurements and the fact that the volume of the reaction solution cannot be varied, which therefore limits the working range of this device to samples with a very low TOC content.
  • the disadvantages of the known methods are thus in summary that the use of chemicals can usually not be dispensed with, which results in a relatively high level of maintenance.
  • none of the known, commercially available devices enables true on-line monitoring of the TOC content. All known devices for TOC trace analysis also have an extremely limited working range, which severely limits their usability for water samples with higher loads.
  • the invention is therefore based on the object of providing a method and a device for determining the TOC content in aqueous samples, in which the use of chemicals can largely be dispensed with and which involves both on-line measurement and measurements allow after the stopped-flow method, whereby water samples with a higher TOC content should be measurable.
  • the method according to the invention and the device according to the invention have advantages in particular in that the addition of chemicals and gases can be dispensed with entirely.
  • the resulting C0 2 does not have to be separated off and the setting of the C0 2 / HC0 3 " balance in favor of the HC0 3 ⁇ ion is favored by the electrolytic formation of OH " ions.
  • the work area can be varied by working in the flow method, which enables true online monitoring or working in the stopped-flow method.
  • the analyte is enriched in the stopped-flow method, so that extremely low detection limits are given.
  • water samples with a higher TOC content can be measured in online operation.
  • the outlay on used chemicals can be reduced to a minimum.
  • the modular structure of the device according to the invention also enables a particularly broad spectrum of analytical problems to be dealt with.
  • FIG. 1 shows a schematic representation of the device according to the invention with its components
  • Figure 2 is a schematic representation of the electrodialysis unit.
  • the overall system has an ion exchanger unit 1, for example a mixed bed ion exchanger for removing the inorganic carbon and possibly other inorganic substances, a downstream UV reactor 2, an electrodialysis unit 3, a control and evaluation unit 4 and an ion exchanger 5.
  • An option for measuring the conductivity from and after the ion exchanger unit 1 enables the salinity of the sample to be determined.
  • the electrodialysis unit 3 shown in FIG. 2 has a cathode space 6 with a cathode 7, in which an anion exchange resin is accommodated. Furthermore, an anode space 8 with anode 9 is provided and a measurement space 10 is arranged between anode space 8 and cathode space 6, an anion exchange membrane 11 being provided at the boundary between measurement space 10 and cathode space 6 and a cation exchange membrane 12 being provided between anode space 8 and measurement space 10.
  • the aqueous solution to be measured is fed to the cathode chamber 6 from the UV reactor 2 in accordance with the arrow 13, and the escaping liquid is conducted in accordance with the arrow representation 14 into the anode chamber 8, which it leaves in accordance with the arrow 15.
  • Ultrapure water as the measuring medium which, for example, emerges from the ion exchanger 5, is, as indicated by the arrows 16, passed through the measuring chamber in countercurrent to the flow in the cathode chamber 6.
  • one conductivity measuring cell 17 is indicated in front of and behind the measuring space 10 by the circuits.
  • the aqueous solution to be measured can first be passed through the anode compartment and then through the cathode compartment.
  • the aqueous sample is introduced into the unit 1, which is designed in a known manner and in which inorganic carbon compounds are removed or converted.
  • the treated aqueous solution is the UV reactor 2 supplied, in which the aqueous solution is irradiated with UV radiation, all organic compounds being oxidized to carbon dioxide.
  • the UV oxidation should take place catalytically.
  • the sample reaches the cathode space 6 of the electrodialysis unit 3 according to the arrow 13, a variable voltage being applied between the anode 9 and the cathode 7.
  • Hybrid formed are OH * at the cathode 7 droxylionen that Genat balance pushes the carbonic acid hydro on the side of HC0 3 ⁇ ions.
  • the hydrogen carbonate ions formed are actively transported to the anion exchange membrane 11, since the membrane is positively polarized by the applied voltage. This membrane is permeable to the HC0 3 " ions, so that they reach the measuring chamber in which there is ultrapure water in which an enrichment takes place.
  • the connection 14 leads the sample further into the anode chamber 8, the H + -Ions through the cation exchange membrane 12, which due to the applied
  • the conductivity of the ultrapure water is measured with the measuring device 17 as the basic value, wherein the temperature can be measured at the same time.
  • a second measurement of the ultrapure water enriched with HC0 3 ⁇ is carried out, and the temperature can also be recorded.
  • the specific resistance of the solution can be used to determine the TOC, but this is also included in the conductivity measurement.
  • the measured values are fed to the control and evaluation unit 4, using the differences the temperature-corrected conductivity measurement of the measuring medium pure water in front of and behind the measuring room the original TOC content of the sample solution is determined.
  • the measured values are compared with previously determined values.
  • the conductivity measurement is a relative method in which the method or the device is calibrated beforehand with known standard solutions.
  • the ultrapure water can be passed continuously through the measuring space 10 to implement on-line monitoring, the difference in the conductivity of the ultrapure water before and after the measuring space being measured continuously. If the quality of the ultrapure water supplied is constant, the continuous measurement of the base value, i.e. the conductivity of the ultrapure water supplied to the measuring space 10 is eliminated and would only have to be checked at certain intervals in a random manner.
  • the ultrapure water can, however, also be introduced into the measuring space 10 at intervals (stopped-flow method), it remaining in the measuring space 10 for a predetermined period of time and being drained after this period. Then water is added again.
  • the ultrapure water leaving the measuring room, i.e. the water enriched with hydrogen carbonate ions is fed to the mixed bed ion exchanger 5 after the conductivity measurement, in which it is regenerated and used again for the process.

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Abstract

The invention relates to a method and to a device for determining the TOC content of aqueous samples. According to the inventive method, inorganic carbon compounds in the samples are removed by acidification and the organic compounds are irradiated with UV light and oxidized to carbon dioxide. The carbon dioxide containing sample is run through a electrodialysis unit in which HCO3<-> ions and H<+> ions are produced which pass through corresponding exchanger membranes and enter a pure-water-rinsed measuring chamber. The conductivity of the pure water before entering the measuring chamber and after leaving the measuring chamber is measured and the TOC content is determined on the basis of the respective conductivity values.

Description

Verfahren und Vorrichtung zum Bestimmen des TOC- Gehaltes in wässrigen ProbenMethod and device for determining the TOC content in aqueous samples

Die Erfindung betrifft ein Verfahren und eine Vor- richtung zum Bestimmen des gesamten organisch gebundenen Kohlenstoffs in wässrigen Proben nach dem Oberbegriff des Hauptanspruchs und des nebengeordneten Vorrichtungsanspruchs .The invention relates to a method and a device for determining the total organically bound carbon in aqueous samples according to the preamble of the main claim and the subordinate device claim.

Bei den zur Zeit bekannten Analysensysteme zurIn the currently known analysis systems for

Erfassung des TOC-Gehaltes in wässrigen Proben im unteren Spurenbereich haben sich in den letzten Jahren vor allem zwei Verfahren durchgesetzt. Beiden Verfahren ist die oxidative Zerstörung der organi- sehen Wasserinhaltsstoffe durch Bestrahlung mit UV- Licht gemeinsam. Bei diesem Prozeß werden sämtliche organische Verbindungen bis zum Kohlendioxid oxi- diert. Anorganische KohlenstoffVerbindungen werden bei den meisten Verfahren vor der Photooxidation durch Ansäuern entfernt. Verwendung findet hier zum einen ein einfacher Säurezusatz und zum anderen ein sogenannter solid-phase-acidifier (US 5,672,516). Die Unterscheidung der genannten Verfahren erfolgt hauptsächlich bei der Detektion.Acquisition of the TOC content in aqueous samples in the lower trace range has become the main method in recent years. Both processes have in common the oxidative destruction of the organic water constituents by irradiation with UV light. In this process, all organic compounds are oxidized down to carbon dioxide. Inorganic carbon compounds are removed by acidification in most processes before photo-oxidation. Used here for a simple acid addition and a so-called solid-phase acidifier (US 5,672,516). The differentiation of the above-mentioned methods mainly occurs in the detection.

Bei dem einen Verfahren wird das generierte C0 durch Ansäuern und Vorbeileiten an einer gasmipermeablen Membran (gas-flüssig-Separator) aus der Lösung entfernt. Das C02 wird in eine Gasküvette geleitet und mittels Infrarotstrahlung spektroskopisch gemessen.In one method, the generated CO is removed from the solution by acidifying and passing a gas-permeable membrane (gas-liquid separator). The C0 2 is passed into a gas cuvette and measured spectroscopically using infrared radiation.

Es erfolgt eine Anreicherung in der Gasküvette, deren Dauer sich nach der erwarteten TOC-Konzentration richtet. Die wesentlichen Nachteile dieses Verfahrens sind die Unmöglichkeit einer on-line-Messung bzw. kontinuierlichen Messung (die typische Meßzeit beträgt hier ca. 10 bis 30 min.) und die Tatsache, daß zur Messung Hilfsgase sowie Chemikalien benötigt werden, wodurch die Betriebskosten steigen und eine regelmäßige Wartung erforderlich wird.There is an enrichment in the gas cuvette, the duration of which depends on the expected TOC concentration. The main disadvantages of this method are the impossibility of an on-line measurement or continuous measurement (the typical measurement time here is approximately 10 to 30 minutes) and the fact that auxiliary gases and chemicals are required for the measurement, which increases the operating costs and regular maintenance is required.

Beim zweiten Verfahren wird die Meßlösung in eine Reaktionszelle geleitet. Die Leitfähigkeit wird gemessen und die Lösung mit UV-Licht bestrahlt bis alle organischen Verbindungen zerstört worden sind. Die Leitfähigkeit wird dabei kontinuierlich gemessen, wodurch eine Reaktionskontrolle ermöglicht wird. Aus der ermittelten Leitfähigkeitsdifferenz zu Beginn und gegen Ende der Reaktion läßt sich auf den TOC-Gehalt der Lösung schließen. Nachteile sind hier wiederum die Unmöglichkeit von on-line-Messungen und die Tatsache, daß das Volumen der Reaktionslösung nicht variiert werden kann, was den Arbeitsbereich dieses Gerätes deshalb auf Proben mit sehr geringem TOC-Gehalt begrenzt . Die Nachteile der bekannten Verfahren sind somit in Zusammenfassung, daß auf den Einsatz von Chemikalien meist nicht verzichtet werden kann, was einen relativ hohen Wartungsaufwand zur Folge hat. Außerdem ermög- licht keines der bekannten, kommerziell erhältliche Geräte eine echte on-line-Überwachung des TOC-Gehal- tes. Alle bekannten Geräte zur TOC-Spurenanalytik haben zudem einen äußerst begrenzten Arbeitsbereich, was ihre Einsatzfähigkeit bei stärker belasteten Was- serproben stark einschränkt.In the second method, the measurement solution is passed into a reaction cell. The conductivity is measured and the solution is irradiated with UV light until all organic compounds have been destroyed. The conductivity is measured continuously, which enables reaction control. The TOC content of the solution can be inferred from the conductivity difference determined at the beginning and towards the end of the reaction. Disadvantages here are the impossibility of on-line measurements and the fact that the volume of the reaction solution cannot be varied, which therefore limits the working range of this device to samples with a very low TOC content. The disadvantages of the known methods are thus in summary that the use of chemicals can usually not be dispensed with, which results in a relatively high level of maintenance. In addition, none of the known, commercially available devices enables true on-line monitoring of the TOC content. All known devices for TOC trace analysis also have an extremely limited working range, which severely limits their usability for water samples with higher loads.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung zur Bestimmung des TOC-Gehaltes in wässrigen Proben zu schaffen, bei denen weitgehend auf den Einsatz von Chemikalien verzichtet werden kann und die sowohl eine on-line-Mes- sung als auch Messungen nach dem stopped-flow-Verfah- ren gestatten, wobei Wasserproben mit höherem Gehalt am TOC meßbar sein sollen.The invention is therefore based on the object of providing a method and a device for determining the TOC content in aqueous samples, in which the use of chemicals can largely be dispensed with and which involves both on-line measurement and measurements allow after the stopped-flow method, whereby water samples with a higher TOC content should be measurable.

Diese Aufgabe wird erfindungsgemäß durch die Merkmale des Hauptanspruchs und des Nebenanspruchs gelöst.This object is achieved by the features of the main claim and the subclaim.

Das erfindungsgemäße Verfahren und die erfindungsge- mäße Vorrichtung weisen Vorteile insbesondere dahingehend auf, daß vollständig auf den Zusatz von Chemikalien und Gasen verzichtet werden kann. Es muß entstehendes C02 nicht abgetrennt werden und die Einstellung des C02/HC03 "-Gleichgewichtes zugunsten des HC03 ~-Ions wird durch die elektrolytische Bildung von OH"-Ionen begünstigt. Der Arbeitsbereich kann durch Arbeiten im Durchflußverfahren, wodurch eine echte on-line-Überwachung möglich ist oder Arbeiten im stopped-flow-Verfahren sehr weit variiert werden. Im stopped-flow-Verfahren wird der Analyt angereichert, so daß äußerst geringe Nachweisgrenzen gegeben sind. Auf der anderen Seite können im on-line-Betrieb Wasserproben mit einem höheren Gehalt an TOC gemessen werden.The method according to the invention and the device according to the invention have advantages in particular in that the addition of chemicals and gases can be dispensed with entirely. The resulting C0 2 does not have to be separated off and the setting of the C0 2 / HC0 3 " balance in favor of the HC0 3 ~ ion is favored by the electrolytic formation of OH " ions. The work area can be varied by working in the flow method, which enables true online monitoring or working in the stopped-flow method. The analyte is enriched in the stopped-flow method, so that extremely low detection limits are given. On the other hand, water samples with a higher TOC content can be measured in online operation.

Durch die in den Unteransprüchen angegebenen Maßnahmen sind weitere vorteilhafte Weiterbildungen und Verbesserungen möglich.The measures specified in the subclaims make further advantageous developments and improvements possible.

Durch Regeneration des im Prozeß verbrauchten Reinst- wasser mit Hilfe eines Ionenaustauschers läßt sich der Aufwand an Gebrauchschemikalien auf ein Minimum reduzieren.By regenerating the ultrapure water used in the process with the help of an ion exchanger, the outlay on used chemicals can be reduced to a minimum.

Der modulare Aufbau der erfindungsgemäßen Vorrichtung ermöglicht zudem ein besonders breites Spektrum an analytischen Problemstellungen zu bearbeiten.The modular structure of the device according to the invention also enables a particularly broad spectrum of analytical problems to be dealt with.

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und wird in der nachfolgenden Beschreibung näher erläutert.An embodiment of the invention is shown in the drawing and is explained in more detail in the following description.

Es zeigenShow it

Figur 1 eine schematische Darstellung der erfindungs- gemäßen Vorrichtung mit ihren Bestandteilen,FIG. 1 shows a schematic representation of the device according to the invention with its components,

Figur 2 eine schematische Darstellung der Elektrodialyseeinheit .Figure 2 is a schematic representation of the electrodialysis unit.

In Figur 1 ist das Gesamtsystem zur Analyse von wässrigen Proben bzw. zur Bestimmung des gesamten organisch gebundenen Kohlenstoffs, genannt TOC, in wässrigen Proben. Dabei weist das Gesamtsystem eine Ionentauschereinheit 1 z.B. einen Mischbettionenaus- tauscher zum Entfernen des anorganischen Kohlenstoffs und gegebenenfalls anderer anorganischer Substanzen, einen nachgeschalteten UV-Reaktor 2, eine Elektrodialyseeinheit 3, eine Steuer- und Auswerteeinheit 4 sowie einen Ionenaustauscher 5 auf. Eine Option zur Leitfähigkeitsmessung von und nach der Ionenaustauschereinheit 1 ermöglicht die Bestimmung der Salinität der Probe.1 shows the overall system for the analysis of aqueous samples or for the determination of the total organically bound carbon, called TOC, in aqueous samples. The overall system has an ion exchanger unit 1, for example a mixed bed ion exchanger for removing the inorganic carbon and possibly other inorganic substances, a downstream UV reactor 2, an electrodialysis unit 3, a control and evaluation unit 4 and an ion exchanger 5. An option for measuring the conductivity from and after the ion exchanger unit 1 enables the salinity of the sample to be determined.

Die in Figur 2 dargestellte Elektrodialyseeinheit 3 weist einen Kathodenraum 6 mit Kathode 7 auf, in dem ein Anionenaustauscherharz aufgenommen ist. Weiterhin ist ein Anodenraum 8 mit Anode 9 vorgesehen und zwischen Anodenraum 8 und Kathodenraum 6 ist ein Meßraum 10 angeordnet, wobei an der Grenze zwischen Meßraum 10 und Kathodenraum 6 eine Anionenaustau- schermembran 11 und zwischen Anodenraum 8 und Meßraum 10 eine Kationenaustauschermembran 12 vorgesehen sind. Die zu messende wässrige Lösung wird dem Kathodenraum 6 aus dem UV-Reaktor 2 entsprechend dem Pfeil 13 zugeführt, die austretende Flüssigkeit wird ent- sprechend der Pfeildarstellung 14 in den Anodenraum 8 geleitet, den sie entsprechend dem Pfeil 15 verläßt. Reinstwasser als Meßmedium, das beispielsweise aus dem Ionenaustauscher 5 austritt, wird, wie die Pfeile 16 andeuten, im Gegenstrom zur Strömung im Kathoden- räum 6 durch den Meßraum geleitet. Jeweils eine Leitfähigkeitmeßzelle 17 ist vor und hinter dem Meßraum 10 durch die Schaltkreise angedeutet. In einem anderen Ausführungsbeispiel kann die zu messende wässrige Lösung zuerst durch den Anodenraum und dann durch den Kathodenraum geleitet werden.The electrodialysis unit 3 shown in FIG. 2 has a cathode space 6 with a cathode 7, in which an anion exchange resin is accommodated. Furthermore, an anode space 8 with anode 9 is provided and a measurement space 10 is arranged between anode space 8 and cathode space 6, an anion exchange membrane 11 being provided at the boundary between measurement space 10 and cathode space 6 and a cation exchange membrane 12 being provided between anode space 8 and measurement space 10. The aqueous solution to be measured is fed to the cathode chamber 6 from the UV reactor 2 in accordance with the arrow 13, and the escaping liquid is conducted in accordance with the arrow representation 14 into the anode chamber 8, which it leaves in accordance with the arrow 15. Ultrapure water as the measuring medium, which, for example, emerges from the ion exchanger 5, is, as indicated by the arrows 16, passed through the measuring chamber in countercurrent to the flow in the cathode chamber 6. In each case one conductivity measuring cell 17 is indicated in front of and behind the measuring space 10 by the circuits. In another embodiment, the aqueous solution to be measured can first be passed through the anode compartment and then through the cathode compartment.

Die wässrige Probe, deren TOC-Gehalt bestimmt werden soll, wird in die Einheit 1 eingeleitet, die in bekannter Weise ausgeführt ist und in der anorganische Kohlenstoff erbindungen entfernt bzw. umgewandelt werden. Die so behandelte wässrige Lösung wird dem UV-Reaktor 2 zugeführt, in dem die wässrige Lösung mit UV-Strahlung bestrahlt wird, wobei sämtliche organische Verbindungen bis zum Kohlendioxid oxidiert werden. Dabei sollte die UV-Oxidation katalytisch ab- laufen. Die Probe gelangt entsprechend dem Pfeil 13 in den Kathodenraum 6 der Elektrodialyseeinheit 3, wobei eine variable Spannung zwischen Anode 9 und Kathode 7 angelegt ist. An der Kathode 7 werden Hy- droxylionen OH* gebildet, die das Kohlensäure-Hydro- genat-Gleichgewicht auf die Seite der HC03 ~ Ionen schiebt. Die entstandenen Hydrogencarbonationen werden aktiv zur Anionenaustauschermembran 11 transportiert, da die Membran durch die anliegende Spannung positiv polarisiert ist. Diese Membran ist für die HC03 "-Ionen durchlässig, so daß sie in den Meßraum gelangen, in dem sich Reinstwasser befindet, in dem eine Anreicherung stattfindet. Über die Verbindung 14 wird die Probe weiter in den Anodenraum 8 geleitet, wobei die H+-Ionen durch die Kationenaus- tauschermembran 12, die aufgrund der angelegtenThe aqueous sample, the TOC content of which is to be determined, is introduced into the unit 1, which is designed in a known manner and in which inorganic carbon compounds are removed or converted. The treated aqueous solution is the UV reactor 2 supplied, in which the aqueous solution is irradiated with UV radiation, all organic compounds being oxidized to carbon dioxide. The UV oxidation should take place catalytically. The sample reaches the cathode space 6 of the electrodialysis unit 3 according to the arrow 13, a variable voltage being applied between the anode 9 and the cathode 7. Hybrid formed are OH * at the cathode 7 droxylionen that Genat balance pushes the carbonic acid hydro on the side of HC0 3 ~ ions. The hydrogen carbonate ions formed are actively transported to the anion exchange membrane 11, since the membrane is positively polarized by the applied voltage. This membrane is permeable to the HC0 3 " ions, so that they reach the measuring chamber in which there is ultrapure water in which an enrichment takes place. The connection 14 leads the sample further into the anode chamber 8, the H + -Ions through the cation exchange membrane 12, which due to the applied

Spannung negativ polarisiert ist, gleichfalls in das im Meßraum 10 vorhandene Reinstwasser gelangen.Voltage is polarized negatively, also get into the ultrapure water present in the measuring room 10.

Vor dem Erreichen des Meßraums 10 wird die Leitfähig- keit des Reinstwassers mit der Meßvorrichtung 17 als Grundwert gemessen, wobei gleichzeitig die Temperatur gemessen werden kann. Nach dem Verlassen des Meßraums 10 wird eine zweite Messung des mit HC03 ~ angereicherten Reinstwassers durchgeführt, wobei ebenfalls die Temperatur mit erfaßt werden kann. Alternativ läßt sich der spezifische Widerstand der Lösung zur TOC-Bestimmung heranziehen, der jedoch auch in der Leitfähigkeitsmessung enthalten ist.Before the measuring space 10 is reached, the conductivity of the ultrapure water is measured with the measuring device 17 as the basic value, wherein the temperature can be measured at the same time. After leaving the measuring room 10, a second measurement of the ultrapure water enriched with HC0 3 ~ is carried out, and the temperature can also be recorded. Alternatively, the specific resistance of the solution can be used to determine the TOC, but this is also included in the conductivity measurement.

Die Meßwerte werden der Steuer- und Auswerteeinheit 4 zugeführt, in der unter Verwendung der Unterschiede der temperaturkorrigierten Leitfähigkeitsmessung des Meßmediums Reinsrwasser vor und hinter dem Meßraum der ursprüngliche TOC-Gehalt der Probenlösung bestimmt wird. Dabei werden die Meßwerte mit vorher bestimmten Werten verglichen. Es handelt sich bei der Leitfähigkeitsmessung in diesem Zusammenhang um ein Relativverfahren, bei dem das Verfahren bzw. die Vorrichtung vorher mit bekannten Standardlösungen kalibriert werden.The measured values are fed to the control and evaluation unit 4, using the differences the temperature-corrected conductivity measurement of the measuring medium pure water in front of and behind the measuring room the original TOC content of the sample solution is determined. The measured values are compared with previously determined values. In this context, the conductivity measurement is a relative method in which the method or the device is calibrated beforehand with known standard solutions.

Das Reinstwasser kann zur Realisierung einer on-line- Überwachung kontinuierlich durch den Meßraum 10 geleitet werden, wobei kontinuierlich die Differenz der Leitfähigkeit des Reinstwassers vor und nach dem Meß- räum gemessen wird. Bei Konstanz der Qualität des zugeführten Reinstwassers könnte die kontinuierliche Messung des Basiswertes, d.h. die Leitfähigkeit des dem Meßraum 10 zugeführten Reinstwassers entfallen und müßte nur stichprobenartig in bestimmten Inter- vallen überprüft werden.The ultrapure water can be passed continuously through the measuring space 10 to implement on-line monitoring, the difference in the conductivity of the ultrapure water before and after the measuring space being measured continuously. If the quality of the ultrapure water supplied is constant, the continuous measurement of the base value, i.e. the conductivity of the ultrapure water supplied to the measuring space 10 is eliminated and would only have to be checked at certain intervals in a random manner.

Das Reinstwasser kann aber auch intervallartig in den Meßraum 10 eingeleitet werden (stopped-flow-Verfahren) , wobei es einen vorgegebenen Zeitraum im Meßraum 10 verbleibt und nach diesem Zeitraum abgelassen wird. Danach wird erneut Wasser zugeführt. Das den Meßraum verlassende Reinstwasser, d.h. das mit Hydrogenkarbonationen angereicherte Wasser wird nach der Leitfähigkeitsmessung dem Mischbettionenaustauscher 5 zugeführt, in dem es regeneriert wird und erneut für den Prozeß verwendet wird.The ultrapure water can, however, also be introduced into the measuring space 10 at intervals (stopped-flow method), it remaining in the measuring space 10 for a predetermined period of time and being drained after this period. Then water is added again. The ultrapure water leaving the measuring room, i.e. the water enriched with hydrogen carbonate ions is fed to the mixed bed ion exchanger 5 after the conductivity measurement, in which it is regenerated and used again for the process.

Zur Untersuchung von Reinstwasserproben bei denen eine sehr präzise Bestimmung des TOC-Gehaltes not- wendig ist und mit anorganischen Verbindungen nicht gerechnet werden muß, kann ein Entfernen von anorga- nischen Verbindungen komplett entfallen. Bei stärker verunreinigten Probenlösungen, in denen mit anorganischen Substanzen gerechnet werden muß, ist eine Entfernung dieser durch einen Mischbettionenaustauscher 1 vorgesehen. For the analysis of ultrapure water samples where a very precise determination of the TOC content is necessary and inorganic compounds do not have to be expected, the removal of inorganic African connections are completely eliminated. In the case of more contaminated sample solutions in which inorganic substances have to be expected, removal of these by a mixed bed ion exchanger 1 is provided.

Claims

Patentansprüche claims 1. Verfahren zur Bestimmung des gesamten organisch gebundenen Kohlenstoffs (TOC) in wässrigen Proben, bei dem organische Verbindungen bis zum Kohlendioxid oxidiert werden, d a d u r c h g e k e n n z e i c h n e t , daß die Kohlendioxid enthaltenden Proben durch eine Elektrodialyseeinheit geleitet werden, in der HC03 "-Ionen und H+-Ionen erzeugt werden, die durch entsprechende Austauschermembrane in einen mit Reinstwasser gespülten Meßraum gelangen und daß die Leitfähigkeit des Reinstwassers vor dem1. A method for determining the total organically bound carbon (TOC) in aqueous samples, in which organic compounds are oxidized to carbon dioxide, characterized in that the carbon dioxide-containing samples are passed through an electrodialysis unit in which HC0 3 " ions and H + -Ions are generated, which pass through appropriate exchange membrane into a measuring chamber rinsed with ultrapure water and that the conductivity of the ultrapure water before Erreichen in dem Meßraum und nach dem Verlassen des Meßraums gemessen wird und aus den gemessenen Leitfähigkeitswerten der TOC-Gehalt bestimmt wird.Reached in the measuring room and after leaving the measuring room is measured and the TOC content is determined from the measured conductivity values. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Reinstwasser kontinuierlich durch den Meßraum geleitet wird.2. The method according to claim 1, characterized in that the ultrapure water is passed continuously through the measuring room. 3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Reinstwasser im stopped-flow- Verfahren durch den Meßraum geleitet wird.3. The method according to claim 1, characterized in that the ultrapure water is passed in the stopped-flow method through the measuring room. 4. Verfahren nach einem der Ansprüche 1 bis 3, da- durch gekennzeichnet, daß die Temperatur des4. The method according to any one of claims 1 to 3, characterized in that the temperature of the Meßmedium-Reinstwassers vor dem Eintritt in den und nach dem Verlassen aus dem Meßraum gemessen wird und bei der Bestimmung des TOC-Gehaltes berücksichtigt wird. Measuring medium ultrapure water is measured before entering and after leaving the measuring room and is taken into account when determining the TOC content. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die organischen Verbindungen durch UV-Strahlung oxidiert werden.5. The method according to any one of claims 1 to 4, characterized in that the organic compounds are oxidized by UV radiation. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß die Oxidation katalytisch durchgeführt wird.6. The method according to claim 5, characterized in that the oxidation is carried out catalytically. 7. Verfahren nach einem der Ansprüche 1 bis 6, da- durch gekennzeichnet, daß das verbrauchte Meßmedium-Reinstwasser mit Hilfe eines Ionenaustauschers regeneriert wird.7. The method according to any one of claims 1 to 6, characterized in that the used measuring medium ultrapure water is regenerated with the aid of an ion exchanger. 8. Verfahren nach einem der Ansprüche 1 bis 7, da- durch gekennzeichnet, daß vor dem Oxidieren der organischen Verbindungen anorganische Kohlenstoffe und gegebenenfalls andere organische Verbindungen vorzugsweise durch Ionenaustausch entfernt werden.8. The method according to any one of claims 1 to 7, characterized in that before the oxidation of the organic compounds, inorganic carbons and optionally other organic compounds are preferably removed by ion exchange. 9. Vorrichtung zum Bestimmen des gesamten organisch gebundenen Kohlenstoffs (TOC) in wässrigen Proben mit einem UV-Reaktor (2) zum Bestrahlen und Oxidieren der Proben, d a d u r c h g e k e n n z e i c h n e t , daß dem UV-Reaktor (2) eine Elektrodialyseeinheit (3) nachgeschaltet ist, die einen Kathodenraum (6) mit einem Anionenaustauschermedium, einen Anodenraum (8) mit einem Kationenaustau- schermedium und einen Meßraum (10) aufweist, wobei zwischen Kathodenraum (6) und Meßraum (10) eine Anionenaustauschermembran (11) und zwischen Anodenraum (8) und Meßraum (10) eine Kationenaustauschermembran (12) vorgesehen sind und durch den Meßraum (10) Reinstwasser geführt wird und daß eine Meßvorrichtung (17) zum Messen der Leitfähigkeit des Reinstwassers vor und nach dem Meßraum (10) sowie eine Auswerteeinheit (4) zur Bestimmung des TOC-Gehaltes unter Verwendung der von der Meßvorrichtung (17) gelieferten Meßwerte vorgesehen sind.9. Device for determining the total organically bound carbon (TOC) in aqueous samples with a UV reactor (2) for irradiating and oxidizing the samples, characterized in that the UV reactor (2) is followed by an electrodialysis unit (3) which has a cathode space (6) with an anion exchange medium, an anode space (8) with a cation exchange medium and a measuring space (10), an anion exchange membrane (11) between cathode space (6) and measuring space (10) and between anode space (8) and Measuring space (10) a cation exchange membrane (12) are provided and is guided through the measuring space (10) ultrapure water and that a measuring device (17) for measuring the Conductivity of the ultrapure water before and after the measuring space (10) and an evaluation unit (4) for determining the TOC content using the measured values supplied by the measuring device (17) are provided. 10. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß eine Steuervorrichtung zur Steuerung der Zu- und Abfuhr des Reinstwassers in den und aus dem Meßraum (10) in kontinuierlicher oder diskontinuierlicher Weise vorgesehen ist.10. The device according to claim 9, characterized in that a control device for controlling the supply and discharge of the ultrapure water into and out of the measuring space (10) is provided in a continuous or discontinuous manner. 11. Vorrichtung nach Anspruch 9 oder Anspruch 10, dadurch gekennzeichnet, daß eine Temperaturmeß- Vorrichtung zur Messung der Temperatur des11. The device according to claim 9 or claim 10, characterized in that a temperature measuring device for measuring the temperature of the Reinstwassers am jeweiligen Ort der Leitfähigkeitsmessung vorgesehen ist.Ultrapure water is provided at the respective location of the conductivity measurement. 12. Vorrichtung nach einem der Ansprüche 9 bis 11, dadurch gekennzeichnet, daß ein Ionenaustauscher12. The device according to one of claims 9 to 11, characterized in that an ion exchanger (5) zur Regeneration des verbrauchten Reinstwassers vorgesehen ist.(5) is provided for the regeneration of the ultrapure water used. 13. Vorrichtung nach einem der Ansprüche 9 bis 12, dadurch gekennzeichnet, daß eine Ionenaus- tauscheinheit (1) zum Entfernen von in den wässrigen Proben enthaltenem anorganischen Kohlenstoff und gegebenenfalls anderen anorganischen Verbindungen dem UV-Reaktor (2) vorgeschaltet ist. 13. Device according to one of claims 9 to 12, characterized in that an ion exchange unit (1) for removing inorganic carbon contained in the aqueous samples and optionally other inorganic compounds is connected upstream of the UV reactor (2).
PCT/EP2000/001066 1999-02-10 2000-02-09 Method and device for determining the toc content of aqueous samples Ceased WO2000047993A1 (en)

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