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Related Concept Videos

Mass Spectrometry: Complex Analysis01:21

Mass Spectrometry: Complex Analysis

910
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...
910
Chemical Shift: Internal References and Solvent Effects01:17

Chemical Shift: Internal References and Solvent Effects

833
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...
833
Inductive Effects on Chemical Shift: Overview01:27

Inductive Effects on Chemical Shift: Overview

1.3K
The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
1.3K
Inductively Coupled Plasma-Mass Spectrometry (ICP-MS): Interferences01:20

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS): Interferences

650
Inductively coupled plasma–mass spectrometry (ICP–MS) is a highly selective and sensitive technique for accurate elemental analysis. Though the analysis of ICP–MS mass spectra is comparatively straightforward, it is affected by spectroscopic and non-spectroscopic interferences. Spectroscopic interferences arise when the plasma contains ionic species with an m/z value the same as the analyte ion. Spectroscopic interference can be categorized as isobaric, polyatomic ions, and...
650
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.1K
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...
1.1K
NMR Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

1.7K
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
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Updated: Sep 20, 2025

Identification and Quantification of Decomposition Mechanisms in Lithium-Ion Batteries; Input to Heat Flow Simulation for Modeling Thermal Runaway
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Updates to the Inverted Library Search Algorithm for Mixture Analysis.

Arun S Moorthy1, Stephen S Tennyson1, Edward Sisco1

  • 1National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.

Journal of the American Society for Mass Spectrometry
|June 8, 2022
PubMed
Summary
This summary is machine-generated.

This study enhances an algorithm for identifying mixture components using mass spectrometry. Improved methods increase accuracy and explainability, particularly for real-world samples like seized drugs.

Keywords:
ILSAmass spectrometrymixture analysissearch algorithmsseized drug analysis

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Area of Science:

  • Analytical Chemistry
  • Mass Spectrometry
  • Chemical Analysis

Background:

  • Identifying components in chemical mixtures is a significant challenge.
  • The Inverted Library Search Algorithm (ILSA) was previously developed for mixture analysis using in-source collision induced dissociation (is-CID) mass spectra.
  • Real-world samples often present noisy mass spectra, complicating analysis.

Purpose of the Study:

  • To present advancements to the Inverted Library Search Algorithm.
  • To improve the accuracy and explainability of mixture component identification.
  • To enhance the algorithm's performance with noisy mass spectra from real-world samples.

Main Methods:

  • The study refines the Inverted Library Search Algorithm.
  • Updated compound matching strategies are implemented to enhance result explainability.
  • Spectral filtering techniques are introduced to manage noisy mass spectra.

Main Results:

  • The enhanced algorithm demonstrates improved performance in identifying mixture components.
  • Updated matching strategies provide clearer explanations for identified compounds.
  • Spectral filtering effectively handles noisy data, improving reliability for practical applications.

Conclusions:

  • The refined Inverted Library Search Algorithm offers significant improvements for mixture analysis.
  • These advancements make the algorithm more robust and applicable to complex, real-world samples.
  • The updated methods contribute to more reliable identification of components in challenging mass spectral data.