Ionic Strength Measurement via pH Buffer Titration

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Solution Overview

Problem

Current methods for determining the ionic strength of dilute natural water sources, such as rivers and lakes, are unreliable due to variable ion concentrations, making it challenging to model the behavior of pollutants and nutrients effectively.

Innovation Solution

A method involving multiple stages of pH adjustment using buffers and spectroscopic measurement to calculate ionic strength, where a pH indicator is added to the aqueous sample, and the pH is adjusted with acids or bases to achieve equilibrium, allowing for precise determination of ionic strength through the ratio of total alkalinity to buffer concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductivity measurements are used to determine ionic strength, then the method is simple and quick, but the measurement is highly unreliable in dilute natural water sources due to variable ion concentrations

Engineering Contradiction:
Improveionic strength measurement reliabilityVSAvoidmeasurement method complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the measurement parameter from conductivity to pH. By measuring pH before and after adding a known amount of buffer, the method determines ionic strength through pH change rather than direct conductivity measurement, achieving reliable results in dilute solutions where conductivity methods fail

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces a buffer solution as an intermediary substance. The buffer acts as a mediator that reacts with the water sample, and the pH change caused by this reaction is used to calculate ionic strength, providing a more reliable measurement approach for dilute natural waters

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If multiple stages of pH adjustment with buffers are performed, then ionic strength determination becomes accurate and reliable, but the measurement process becomes more complex and time-consuming

Engineering Contradiction:
Improveionic strength determination precisionVSAvoidmeasurement time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary pH adjustment by adding a buffer before the main measurement. This preliminary action establishes a known starting condition and allows the system to reach equilibrium more efficiently during the actual measurement, improving precision without excessive time loss

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent uses pH measurement as feedback to determine when equilibrium is reached. By continuously monitoring pH changes after buffer addition and comparing against expected values, the method ensures accurate ionic strength determination while providing a clear endpoint criterion to minimize measurement time

Inventive Principle:
Principle #23Feedback

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

This approach provides a reliable and portable method for accurately measuring ionic strength in dilute aqueous solutions, overcoming the limitations of conductivity measurements and enabling better understanding of pollutant and nutrient behavior in natural water bodies.

Implementation Method 1

adding a pH indicator to a portion of the aqueous sample; measuring a pH of the aqueous sample, wherein the aqueous sample comprises a pH indicator

Methodology Applied
Scientific EffectpH indicator color change: Photochromism

Implementation Method 2

adding an amount of a buffer to the portion of the aqueous sample to obtain a pHfinal; calculating the I value from a ratio of a total alkalinity of the aqueous sample to a total concentration of the buffer

Methodology Applied
Scientific EffectBuffer equilibrium:

Data Source

PatentUS11808710B2Methods and systems for determining an ionic strength of a dilute aqueous solution
Publication Date: 2023.11.07 UNIV OF SOUTH FLORIDA

AI summary

Disclosed herein are methods for measuring the ionic strengths of the natural water sources. Also disclosed herein are systems used to measure an ionic strength of the natural water sources. More specifically disclosed herein are methods and systems utilizing spectroscopic pH measurements and calculations of the ionic strength as a function of the measured pH.