NMR Terephthalic Acid Measurement Solvent System
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Solution Overview
Problem
Current methods for measuring terephthalic acid content in polyesters or their decomposition products, such as liquid chromatography, are time-consuming and fail to accurately quantify terephthalic acid due to peak overlap in NMR measurements.
Innovation Solution
A method using a solvent mixture of chloroform, 2,2,2-trifluoroethanol, and an organic base, with optional 1,1,1,3,3,3-hexafluoro-2-propanol, to separate and measure terephthalic acid peaks via nuclear magnetic resonance spectroscopy targeting hydrogen atoms, optimizing the mixing ratio for effective separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If liquid chromatography is used to measure terephthalic acid content, then measurement precision is improved, but measurement time increases to several tens of minutes per sample and several hours for overall quantification
Solution Approach 1:
The patent replaces liquid chromatography (mechanical separation system) with nuclear magnetic resonance spectroscopy (magnetic field-based detection system). This substitution enables rapid measurement of terephthalic acid content in polyesters and decomposition products, reducing measurement time from several hours to a fraction of that time while maintaining quantification accuracy through characteristic peak identification in the NMR spectrum.
2Loss of time
If conventional NMR measurement is used, then measurement time is reduced, but measurement precision deteriorates because the peak of terephthalic acid cannot be found and cannot be measured due to peak overlap
Solution Approach 1:
The patent extracts the problematic peak overlap issue by introducing a specific solvent system (deuterated chloroform with 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol) that chemically shifts the NMR peaks. This solvent modification separates the terephthalic acid peak from overlapping peaks, enabling accurate detection and quantification of terephthalic acid content in the polyester sample.
Solution Approach 2:
The patent changes the chemical environment parameters by using a specific mixed solvent system with deuterated chloroform, 2,2,2-trifluoroethanol, and 1,1,1,3,3,3-hexafluoro-2-propanol. This parameter change in the NMR measurement conditions alters the chemical shifts of the proton signals, thereby separating the terephthalic acid peak from overlapping peaks and enabling accurate measurement.
3Reliability
If startup and shutdown operations are included in liquid chromatography measurement, then measurement completeness is improved, but device complexity and operational time increase significantly
Solution Approach 1:
The patent replaces liquid chromatography with NMR spectroscopy, eliminating the need for complex startup and shutdown operations. The NMR instrument requires no sample preparation or system conditioning, allowing direct measurement of polyester samples in deuterated solvent, thereby simplifying the operational procedure while maintaining measurement reliability.
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
Enables rapid and accurate measurement of terephthalic acid content in polyesters or their decomposition products, overcoming the limitations of peak overlap and reducing measurement time significantly.
Implementation Method 1
measuring the amount of terephthalic acid in the sample liquid through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms
Data Source
AI summary
In a first step, a sample liquid is fabricated by mixing a sample formed of a polyester or decomposition products of a polyester into a solvent. The solvent used here contains chloroform and 2,2,2-trifluoroethanol and has an organic base added thereto. The organic base is at least one of a primary amine, a secondary amine, a tertiary amine and a heterocyclic amine. In a second step, the amount of terephthalic acid in the sample liquid is measured through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms