Optical pH-Sensitive Acidity Measurement Resistant to Humidity

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Solution Overview

Problem

Existing analytical techniques for determining total and volatile acidity in liquids are inefficient and lack the sensitivity to humidity and, other volatile compounds such as alcohols, etc, which greatly affect the precision and accuracy of the measurements.

Innovation Solution

An optical method for the determination of total and volatile acidity in real samples are inefficient and lack the sensitivity to humidity and, other volatile compounds such as alcohols, etc, which greatly affect the precision and accuracy of the measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If gas sensors based on metal oxide semiconductor are used to measure volatile organic acids, then the response time is fast and reproducible, but the sensors are very sensitive to humidity and other volatile compounds which greatly affect the precision and accuracy of the measurements

Engineering Contradiction:
Improveresponse timeVSAvoidprecision and accuracy
Core Design Contradiction:
SpeedVSMeasurement precision

Solution Approach 1:

The patent introduces an ionic liquid as an intermediary layer between the metal oxide semiconductor sensor and the sample environment. This ionic liquid layer selectively interacts with volatile organic acids while being insensitive to humidity and other interfering volatile compounds, thereby mediating the sensor response to achieve both fast response and high precision measurements

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite sensing system combining metal oxide semiconductor with ionic liquid. This composite structure leverages the fast response characteristics of the metal oxide semiconductor while the ionic liquid component provides selectivity and resistance to interference from humidity and other volatile compounds, resolving the contradiction between speed and precision

Inventive Principle:
Principle #40Composite materials

2Measurement precision

If conventional instrumental methods such as capillary electrophoresis, ion exclusion chromatography, and liquid and gas chromatography are used to determine TA and VA, then the determination is accurate, but the methods are tedious, time-consuming, require expensive equipment and solvents, and do not offer quick analysis integrated into the production system

Engineering Contradiction:
Improvedetermination accuracyVSAvoidanalysis time and operational efficiency
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces complex mechanical and chemical separation systems (chromatography columns, electrophoresis apparatus) with a simplified sensor-based measurement system. The ionic liquid-coated metal oxide semiconductor sensor directly measures volatile organic acid content through vapor-phase interaction, eliminating the need for tedious sample preparation, separation, and detection procedures while maintaining accuracy and enabling rapid analysis

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and isolates the essential measurement function from complex instrumental systems. By using a sensor that directly detects volatile organic acids in the vapor phase above the sample, the method removes the need for complex separation and detection equipment, reducing analysis time and operational complexity while preserving measurement accuracy

Inventive Principle:
Principle #2Taking out (Extraction)

3Adaptability or versatility

If enzymatic methods are used to specifically analyze the concentration of acetic acid, then the specificity is improved, but the methods require very expensive and unstable reagents, long analysis times, present many interferences, and have low reproducibility

Engineering Contradiction:
Improvespecificity for acetic acidVSAvoidreproducibility and reagent stability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces expensive and unstable enzymatic reagents with a stable, non-consumable sensor system. The metal oxide semiconductor sensor coated with ionic liquid can be reused multiple times without degradation, eliminating the need for frequent reagent replacement while maintaining specificity for acetic acid measurement and improving reproducibility

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

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 optical method using a kinetic calibration of optically pH-sensitive probes in a heterogeneous phase allows for the direct, fast, and cost-effective measurement of total and volatile acidity in real samples, unaffected by humidity or other volatile compounds, with a response time of seconds and high sensitivity to pH changes of 0.01 units.

Implementation Method 1

measuring a change in an optical property of the optically pH-sensitive material produced by a reaction in heterogenous phase between the free hydronium ions (H3O+) present in the sample and the optically pH-sensitive material

Methodology Applied
Scientific EffectpH-sensitive optical detection: Absorption Spectroscopy

Data Source

PatentEP4667914A1Optical kinetic method for the determination of total or volatile acidity
Publication Date: 2025.12.24 UNIV DE GRANADA
  • EP4667914A1 patent drawingFigure 1
  • EP4667914A1 patent drawingFigure 2~3
  • EP4667914A1 patent drawingFigure 4~5(C)

AI summary

The present invention refers to an optical kinetic method for the determination of the total or volatile acidity of a sample, which comprises: - a) carrying out a kinetic calibration of an optically pH-sensitive material - b) contacting a sample with the optically pH-sensitive material, - c) measuring a change in an optical property of the optically pH-sensitive material produced by a reaction in heterogenous phase between the free hydronium ions (H3O+) of the sample and the optically pH-sensitive material, during a constant reaction time, - d) detecting a signal corresponding to the change in the optical property, an its use in the industry, for example, in the food industry.