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Proton (¹H) NMR: Chemical Shift

Proton (¹H) NMR: Chemical Shift

Organic molecules primarily contain carbon and hydrogen atoms. While all the hydrogen isotopes are NMR-active, protium or hydrogen-1 is the most abundant. It has a significant energy separation between its nuclear spin states due to its large gyromagnetic ratio. As per Boltzmann's distribution, an increase in the energy separation implies a greater excess population of nuclei available for excitation, resulting in a strong NMR absorption signal.
Absorption signals of all the protium nuclei in a...

¹H NMR of Labile Protons: Deuterium (²H) Substitution

¹H NMR of Labile Protons: Deuterium (²H) Substitution

This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.

¹H NMR of Labile Protons: Temporal Resolution

¹H NMR of Labile Protons: Temporal Resolution

Protons bonded to heteroatoms such as nitrogen and oxygen exhibit a range of chemical shift values. This is due to the varying degree of hydrogen bonding between the proton and the heteroatom in other molecules. The extent of hydrogen bonding affects the electron density around the proton, thereby giving different chemical shift values for the protons in the proton NMR spectrum.
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...

¹H NMR Signal Integration: Overview

¹H NMR Signal Integration: Overview

The intensity of a signal, which can be represented by the area under the peak, depends on the number of protons contributing to that signal. The area under each peak is shown as a vertical line called an integral, with the integral value listed under it, as seen in the proton NMR spectrum of benzyl acetate. Each integral value is divided by the smallest integral value to obtain the ratio of the number of protons producing each signal. The ratio reveals the relative number of protons and not...

Chemical Shift: Internal References and Solvent Effects

Chemical Shift: Internal References and Solvent Effects

In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...

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Related Experiment Video

Updated: Jun 1, 2026

Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins

Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins

Published on: September 23, 2021

Concentration Measurement by Proton NMR Using the ERETIC Method.

S Akoka¹, L Barantin, M Trierweiler

¹Laiem - Upres-A CNRS 6006, Faculté des Sciences, Université de Nantes, 2 rue de la houssinière - BP 92208, 44322 Nantes Cedex 3, France, and Inserm U316 Faculté de Médecine, Université de Tours, 2bis Bd tonnellé, 37032 Tours Cedex, France.

Analytical Chemistry

|June 14, 2011

Summary

The Electronic REference To access In vivo Concentrations (ERETIC) method offers accurate and precise absolute concentration determination in (1)H NMR. This electronic reference method demonstrates excellent stability and requires only monthly calibration for reliable results.

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Area of Science:

Analytical Chemistry
Nuclear Magnetic Resonance Spectroscopy

Background:

Absolute concentration determination is crucial in quantitative analysis.
Traditional methods often require internal standards added to the sample.

Purpose of the Study:

To evaluate the accuracy and precision of the ERETIC method for (1)H high-resolution NMR.
To assess the stability and calibration requirements of the ERETIC method.

Main Methods:

Utilized the ERETIC method to generate a reference signal for concentration determination.
Compared ERETIC results with an internal reference standard (trimethylamine hydrochloride).
Analyzed D(2)O solutions of sodium lactate at varying concentrations.

Main Results:

ERETIC method showed comparable standard deviations (<1% of the mean) to internal referencing.
ERETIC exhibited slightly better accuracy than the internal reference method.
The method demonstrated good stability over 56 hours and monthly intervals (3% standard deviation).

Conclusions:

The ERETIC method provides accurate and precise absolute concentration measurements in (1)H NMR.
ERETIC offers advantages such as no sample addition and flexible reference signal placement.
The method is stable and requires infrequent calibration, making it a reliable quantitative tool.