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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 Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

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...
Inductively Coupled Plasma-Mass Spectrometry (ICP-MS): Interferences01:20

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

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 refractory oxide ion...
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...
Chromatographic Methods: Terminology01:18

Chromatographic Methods: Terminology

Chromatography is an analytical technique widely used in fields such as chemistry, biology, environmental science, and pharmaceuticals to separate the components of a mixture and identify substances between them. The process of chromatography is based on the interactions between two distinct phases: the stationary phase and the mobile phase. The stationary phase is fixed in place by a supporting material, while the mobile phase moves over it, carrying the solutes. As the mobile phase travels,...
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: Jun 26, 2026

Preparation of Human Tissues Embedded in Optimal Cutting Temperature Compound for Mass Spectrometry Analysis
09:09

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Published on: April 27, 2021

Retention time alignment algorithms for LC/MS data must consider non-linear shifts.

Katharina Podwojski1, Arno Fritsch, Daniel C Chamrad

  • 1Fakultät Statistik, Technische Universität Dortmund, 44221 Dortmund, Germany. katharina.podwojski@tu-dortmund.de

Bioinformatics (Oxford, England)
|January 30, 2009
PubMed
Summary
This summary is machine-generated.

Accurate retention time alignment in liquid chromatography-mass spectrometry (LC/MS) is crucial for proteomics. Algorithms that correct non-linear retention time shifts improve data alignment, enhancing biomarker discovery and drug development.

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Area of Science:

  • Proteomics
  • Biomarker Discovery
  • Drug Development

Background:

  • Liquid chromatography-mass spectrometry (LC/MS) is vital for analyzing protein mixtures.
  • Comparing hundreds of LC/MS runs in clinical studies requires sophisticated preprocessing.
  • Retention time (rt) alignment is a critical, non-trivial preprocessing step.

Purpose of the Study:

  • To evaluate and compare different retention time alignment algorithms.
  • To demonstrate the importance of correcting non-linear rt shifts.
  • To present and analyze new regression-based alignment methods.

Main Methods:

  • Developed and analyzed two versions of a regression-based alignment algorithm (linear and non-linear shifts).
  • Adapted an established shifting vector algorithm to correct non-linear shifts.
  • Conducted a simulation study to compare alignment performance.

Main Results:

  • Alignment procedures capable of estimating non-linear shifts yield superior results.
  • This improvement holds true even with minor non-linear deviations in retention time.
  • The new regression-based methods show strong performance in correcting rt shifts.

Conclusions:

  • Correcting non-linear retention time shifts is essential for accurate LC/MS data analysis.
  • Regression-based methods, particularly those estimating non-linear shifts, offer improved alignment.
  • The study provides valuable tools and insights for proteomic data preprocessing.