Fresh Dual Presaturation Method for Analyzing H₂O-Rich Samples Using Quantitative ¹H NMR.

Area of Science:

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

Background:

• Quantifying analytes in H2O-rich samples using 1H NMR is challenging due to water signal suppression.
• Conventional single presaturation (pre-SAT) methods can lead to significant underestimation of analyte concentrations.
• Accurate quantification is crucial for various applications, including metabolomics and quality control.

Purpose of the Study:

• To develop and validate a novel dual presaturation (pre-SAT) method for accurate 1H NMR quantification of analytes in H2O-rich samples.
• To assess the performance of the dual pre-SAT method compared to the conventional single pre-SAT method.
• To demonstrate the method's efficacy in quantifying specific analytes like glycine and maleic acid.

Main Methods:

• Implementation of a dual pre-SAT technique involving an additional dummy pre-SAT pulse with a tailored offset for each analyte.
• Utilizing D2O solutions with specific analytes (l-phenylalanine, l-valine, glycine, maleic acid) and an internal standard (DSS-d6).
• Comparative analysis of analyte quantification using single pre-SAT versus the proposed dual pre-SAT method.

Main Results:

• The dual pre-SAT method reduced the measured concentration decrease of phenylalanine from 48% (single pre-SAT) to less than 3%.
• Accurate quantification of glycine and maleic acid was achieved in a 10% D2O/H2O solution, with measured values closely matching preparation values.
• The method demonstrated high precision and accuracy, with expanded uncertainties (k=2) within acceptable limits.

Conclusions:

• The developed dual pre-SAT method significantly enhances the accuracy of 1H NMR quantification in H2O-rich matrices.
• This technique effectively suppresses residual HOD signals without compromising analyte signals.
• The dual pre-SAT method offers a robust solution for precise analyte determination in complex aqueous samples.