Relative Response Factor Determination in LC-ELSD Analysis

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Solution Overview

Problem

Current methods for determining relative response factors in chromatographic analysis are time-consuming and require standards of known concentrations, which are not always available, and alternative techniques like NMR are expensive and limited in detecting low concentrations or closely related molecules.

Innovation Solution

A method using liquid chromatographic separation combined with molar concentration-based detection and mass concentration-based detection to determine relative response factors, eliminating the need for isolating impurities and generating calibration curves, and allowing for accurate quantification of substances without requiring standards of known concentrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If calibration curve-based technique is used to determine relative response factors, then accurate correction for detector responsiveness differences is achieved, but the process becomes time-consuming and requires standards of known concentrations which are not always available

Engineering Contradiction:

Improveaccuracy of impurity quantificationVSAvoidtime required for determining relative response factors

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent extracts the impurity compounds from the complex mixture through chromatographic separation, isolating them in individual peaks that can be detected and quantified without requiring external standards. This extraction approach allows determination of relative response factors directly from the separated components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs a universal detection approach using mass spectrometry that can detect and quantify both API and impurity compounds simultaneously based on their mass-to-charge ratios. This multi-functional detection system eliminates the need for compound-specific calibration curves while maintaining accurate quantification across different substances.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If NMR is used to determine relative response factors, then universal and quantitative detection is achieved, but the cost increases and detection of low concentration compounds becomes difficult

Engineering Contradiction:

Improveuniversality of detection methodVSAvoiddetection sensitivity for low concentration compounds

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent replaces the NMR mechanical detection system with a mass spectrometry-based detection system. This substitution maintains the universality of detection across different compounds while significantly improving sensitivity for low concentration impurities through mass-to-charge ratio detection and selective ion monitoring.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If standards of known concentrations are used for calibration, then accurate relative response factors can be calculated, but the requirement for such standards becomes a limiting factor when they are not available

Engineering Contradiction:

Improveaccuracy of relative response factor determinationVSAvoidavailability and preparation of standard samples

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent implements a self-service approach where the analytical system determines relative response factors using the sample components themselves as references. The API peak serves as an internal reference against which impurity peaks are compared, eliminating the need for external standard preparations while maintaining measurement accuracy.

Inventive Principle:

Principle #25Self-service

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 enables efficient and accurate determination of relative response factors, improving the precision of mass balance calculations in pharmaceutical stability studies by correcting for detector responsiveness differences between APIs and impurities, thereby ensuring accurate quantification and mass balance without the need for extensive calibration or expensive equipment.

Implementation Method 1

liquid chromatographic separation of a sample

Methodology Applied

Scientific EffectChromatography: Chromatography

Implementation Method 2

molar concentration-based detection

Methodology Applied

Scientific EffectAbsorbance detection: Absorption Spectroscopy

Implementation Method 3

mass concentration-based detection

Methodology Applied

Scientific EffectEvaporative light scattering detection: Evaporation

Data Source

PatentUS10422775B2Methods for determining relative response factors for impurity analysis using liquid chromatography with absorbance and evaporative light scattering detection

Publication Date: 2019.09.24 WATERS TECHNOLOGY CORP

AI summary

Methods and systems for determining relative response factors for liquid chromatography using both molar concentration-based detection and mass concentration-based detection are described herein. A method includes determining a relative response factor for a compound based on the ratio of a molar-based peak area for the compound to the logarithm of the mass-based peak area for the compound and based on the ratio of a molar-based peak area for a reference compound divided by the logarithm of the mass-based peak area for the reference compound.