Unique Usage of a Classical Selective Homodecoupling Sequence for High-Resolution Quantitative ¹H NMR.

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Nuclear Magnetic Resonance (NMR)

Background:

• Proton NMR (¹H NMR) is crucial for chemical analysis.
• Spectral overlaps from ¹H-¹H spin coupling can limit accuracy in purity assays.
• Existing methods may struggle with complex mixtures or high-purity compounds.

Purpose of the Study:

• To develop and validate a classical selective homodecoupling technique for ¹H NMR purity assays.
• To improve the accuracy and reliability of purity determination by overcoming spectral interferences.
• To demonstrate the method's utility in analyzing both high-purity reference materials and samples with structurally similar impurities.

Main Methods:

• Implementation of classical selective homodecoupling in a ¹H NMR purity assay.
• Inclusion of dummy irradiation to mitigate irradiation bias.
• Validation using National Metrology Institute of Japan Certified Reference Materials (NMIJ CRMs) of diethyl phthalate and dipropyl phthalate.

Main Results:

• The method successfully resolved spectral overlaps caused by ¹H-¹H spin coupling.
• Purity assay biases were within 0.27% for high-purity diethyl phthalate (99.98%).
• Accurate purity determination (98.39%) was achieved for dipropyl phthalate (98.41%) containing methyl propyl phthalate, outperforming conventional methods (99.13%).

Conclusions:

• Classical selective homodecoupling is an effective technique for enhancing ¹H NMR purity assay accuracy.
• The method provides reliable results even in the presence of spectral overlaps and structurally similar impurities.
• This approach offers a valuable tool for precise quantitative analysis in analytical chemistry.