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Related Concept Videos

Mass Spectrometry: Complex Analysis01:21

Mass Spectrometry: Complex Analysis

Mass spectrometry is an important technique for the identification of pure compounds. However, it has some limitations for the analysis of complex mixtures, often due to excessive fragmentation making the spectrum too complicated to decipher. Mass spectrometry can be combined with suitable separation methods in sequence, forming hyphenated methods, which are useful in the analysis of complex mixtures.
GC–MS is a powerful hyphenated method commonly used in forensics and environmental...
NMR Spectrometers: Overview01:20

NMR Spectrometers: Overview

NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
¹H NMR Signal Integration: Overview00:58

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 Effects01:17

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...

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Related Experiment Video

Updated: Jul 5, 2026

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
09:38

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures

Published on: January 7, 2019

Web server based complex mixture analysis by NMR.

Steven L Robinette1, Fengli Zhang, Lei Brüschweiler-Li

  • 1National High Magnetic Field Laboratory, University of Florida, Gainesville, Florida 32611, USA.

Analytical Chemistry
|April 22, 2008
PubMed
Summary
This summary is machine-generated.

This study introduces COLMAR query, an automated NMR strategy for identifying metabolites in complex mixtures. It efficiently screens NMR data against a spectral database, enabling robust compound identification.

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Last Updated: Jul 5, 2026

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
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Area of Science:

  • Analytical Chemistry
  • Biochemistry
  • Spectroscopy

Background:

  • Metabolomics relies on identifying and quantifying metabolites in biological samples.
  • Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for this purpose.
  • Existing methods require efficient strategies for analyzing complex NMR data.

Purpose of the Study:

  • To develop an automated NMR-based strategy for metabolite identification in complex mixtures.
  • To enhance the accuracy and efficiency of compound identification using NMR data.
  • To provide a publicly accessible tool for metabolomics analysis.

Main Methods:

  • An automated fingerprinting strategy, COLMAR query, was developed.
  • It screens NMR chemical shift lists and 1D NMR cross sections against the BioMagResDatabank (BMRB).
  • Local clustering selects cross peaks, and three algorithms (forward, reverse, bipartite matching) generate a consensus score for compound identification.

Main Results:

  • The COLMAR query strategy demonstrated robust compound identification for a metabolite model mixture.
  • The consensus score effectively combined results from different algorithms for reliable identification.
  • The approach was validated against the metabolomics BMRB.

Conclusions:

  • COLMAR query provides an efficient and robust NMR-based method for metabolite identification.
  • The developed public Web server facilitates the analysis of diverse metabolite mixtures.
  • This strategy advances automated compound identification in metabolomics research.