Predicting Conductivity of Complex Buffer Solutions

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Solution Overview

Problem

Current methods cannot accurately predict the conductivity of complex buffer solutions, which are combinations of strong and weak electrolytes, due to the complex nature of these mixtures and the need to account for ion activities.

Innovation Solution

A method is developed to predict the conductivity of liquid mixtures, specifically buffer solutions, by calculating the exact concentrations of ions, determining their molar conductivities using the Kohlrausch equation, and summing these values to obtain the total conductivity, with predetermined Kohlrausch coefficients obtained through data fitting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If commercial software is used to calculate pH of buffer solutions, then pH calculation is automated, but conductivity prediction remains impossible due to complex nature of buffer solutions

Engineering Contradiction:
ImprovepH calculation automationVSAvoidconductivity prediction capability
Core Design Contradiction:
Extent of automationVSAdaptability or versatility

Solution Approach 1:

The patent segments the complex buffer solution into individual ionic species and applies the Kohlrausch equation to each ion separately. By calculating the contribution of each ion to the total conductivity and summing these contributions, the method achieves conductivity prediction for complex mixtures that cannot be treated as a single entity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces the Kohlrausch coefficient as a key parameter that relates ionic concentration to molar conductivity. By using this parameter and the square-root concentration dependence relationship, the method transforms the complex conductivity prediction problem into a manageable calculation involving individual ionic contributions.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If predetermined Kohlrausch coefficient values are used for calculating molar conductivities, then conductivity prediction becomes feasible, but measurement precision may be affected by approximation

Engineering Contradiction:
Improveconductivity prediction feasibilityVSAvoidconductivity prediction accuracy
Core Design Contradiction:
Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent performs preliminary determination of Kohlrausch coefficients through fitting to measured conductivity data before using these coefficients for prediction. This preliminary calibration step ensures that the predetermined values are optimized for the specific buffer system, improving both feasibility and accuracy of subsequent predictions.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The method incorporates feedback by fitting the Kohlrausch coefficients to measured conductivity data, creating a self-calibrating system. The predetermined values are not arbitrary but are derived from experimental data, allowing the model to adjust to the specific characteristics of different buffer solutions and improve prediction accuracy.

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 allows for accurate prediction of buffer solution conductivity, enabling better control in buffer formulation and in-line dilution systems, and can be used in screening experiments and indirect pH determination.

Implementation Method 1

calculating for each ionic species of said plurality of species the molar conductivity by the formula: Λ=Λ0−K×Sqrt(c) wherein Λ is the molar conductivity, Λ0 is the molar conductivity at infinite dilution, c is the concentration of the ionic species, K is the Kohlrausch coefficient

Methodology Applied
Scientific EffectKohlrausch equation:

Implementation Method 2

for each pair of species derived from a weak electrolyte, solving a respective equilibrium equation to calculate from said predetermined recipe the actual molar concentration of each such species, including all ionic species derived from the weak electrolyte, at equilibrium in the liquid solution

Methodology Applied
Scientific EffectChemical equilibrium:

Data Source

PatentUS11670402B2Method for predicting the conductivity of a liquid mixture
Publication Date: 2023.06.06 CYTIVA SWEDEN AB
  • US11670402B2 patent drawing

AI summary

In a method of preparing a liquid solution by mixing ingredients according to a predetermined recipe, wherein at least one pair of species of the liquid solution is derived from a weak electrolyte and corresponds to an acid-base pair, the conductivity of the liquid solution is predicted by:(i) for each pair of species derived from a weak electrolyte, solving a respective equilibrium equation to calculate the actual molar concentration of each such species at equilibrium in the liquid solution,(ii) calculating for each ionic species of said plurality of species the molar conductivity by the formula:Λ=Λ0−K×Sqrt(c)wherein Λ is the molar conductivity, Λ0 is the molar conductivity at infinite dilution, c is the concentration, and K is the Kohlrausch coefficient, and wherein K and Λ0 are predetermined values for K and Λ0 for each ionic species,(iii) calculating the conductivity κ for each ionic species by the formula:κ=c×Λand(iv) adding up the conductivities determined in step (iii) for the different ionic species to obtain a predicted conductivity of the liquid solution. A computer program product comprises instructions for causing a computer to perform the method steps.