Amperometric Chlorine Dioxide Sensor with pH Buffer
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Solution Overview
Problem
Conventional amperometric chlorine dioxide sensors provide incorrect measurement results when used in acidic measuring fluids due to pH-related issues, as the inner electrolyte's pH buffer, EDTA, is not effective at low pH values, leading to unstable operation and measurement errors.
Innovation Solution
An amperometric chlorine dioxide sensor with an inner electrolyte pH range of 3.5 to 9, stabilized by a pH buffer, which prevents pH fluctuations and eliminates the need for complexing agents like EDTA, ensuring stable operation even in acidic conditions by maintaining a consistent pH and preventing unwanted reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional inner electrolyte with EDTA complexing agent is used, then the sensor can operate in neutral pH conditions, but the sensor provides incorrect measurement results in acidic measuring fluids due to insufficient complexing capacity at low pH values
Solution Approach 1:
The patent changes the pH parameter of the inner electrolyte from conventional neutral pH to an acidic pH range (pH 2-4), and adjusts the complexing agent concentration to 0.1-10 g/L. This parameter change enables the sensor to maintain reliable measurements in acidic measuring fluids while preventing counter electrode passivation through optimized complexing capacity at the new pH level.
2Reliability
If the inner electrolyte pH is maintained in the acidic range with sufficient complexing agent concentration, then the sensor operates reliably in acidic conditions, but the selection of pH value and complexing agent type becomes more limited
Solution Approach 1:
The patent identifies and specifies concrete examples of suitable complexing agents (EDTA, NTA, HEDTA, DTPA) that function effectively in the acidic pH 2-4 range. By providing these specific copies or alternatives to conventional neutral-pH electrolytes, the patent reduces composition constraints while maintaining reliable operation in acidic conditions.
3Object-generated harmful factors
If EDTA is used as the complexing agent to prevent counter electrode passivation, then copper or silver ions are effectively complexed, but EDTA solubility is insufficient at low pH values limiting its effectiveness
Solution Approach 1:
The patent specifies multiple complexing agents (EDTA, NTA, HEDTA, DTPA) that all function effectively in the acidic pH 2-4 range. This provides universal solutions for preventing counter electrode passivation, where each agent offers different solubility and complexing characteristics but achieves the same protective function for the counter electrode in acidic conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor provides reliable and accurate measurement values by maintaining a stable pH range, preventing errors caused by pH drops and extending response time, while allowing pH adjustment across a wide range without complexing agents.
Implementation Method 1
the inner electrolyte has a pH value between 3.5 and 9, inclusive, and comprises a pH buffer stabilizing the pH value of the inner electrolyte
Implementation Method 2
a predetermined voltage is applied by means of the measurement circuit between the working electrode and the counter electrode, wherein the working electrode is connected as a cathode and the counter electrode is connected as an anode, so that chlorine dioxide contained in the inner electrolyte is electrochemically converted at the cathode. The current flowing through the inner electrolyte between the working electrode and the counter electrode is detected by means of the measurement circuit as a measure of the chlorine dioxide content
Implementation Method 3
The membrane is arranged within a region of the measurement probe designated for contact with the measuring fluid and is permeable, in particular selectively permeable to chlorine dioxide, such that chlorine dioxide may get from the measuring fluid into the housing chamber and vice versa
Implementation Method 4
chlorine dioxide contained in the inner electrolyte is electrochemically converted at the cathode
Implementation Method 5
The complexing of the copper or silver ions passing into solution prevents a passivating copper oxide or silver oxide layer from forming at the counter electrode
Data Source
AI summary
The present disclosure relates to an amperometric sensor for determining measurement values of a measurand representing a chlorine dioxide content of a measuring fluid, the sensor including a sensor housing in which a housing chamber is formed, a membrane sealing the housing chamber, a working electrode arranged within the housing chamber, a counter electrode arranged within the housing chamber, an inner electrolyte contained in the housing chamber and in contact with the membrane, the working electrode and the counter electrode, the inner electrolyte having a pH value between 3.5 and 9, inclusive, and a pH buffer stabilizing the inner electrolyte. The sensor further includes a measurement circuit electrically connected with the working electrode and the counter electrode and configured to apply a predetermined, constant voltage between the working electrode and the counter electrode and to generate at least one measurement signal representing a measurement value of the measurand.