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Related Concept Videos

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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Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
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A low-cost internal standard loader for solid-phase sorbing tools.

F M Vivaldi1, S Reale1, S Ghimenti1

  • 1Department of Chemistry and Industrial Chemistry, University of Pisa, via Giuseppe Moruzzi 13, 56124 Pisa, Italy.

Journal of Breath Research
|August 11, 2023
PubMed
Summary
This summary is machine-generated.

A new portable system reliably generates and dispenses deuterated toluene (8D-Toluene) as an internal standard for gaseous sample analysis. This enhances analytical precision for techniques like breath analysis, ensuring stable concentrations for up to three weeks.

Keywords:
breath analysisinternal standardneedle trap microextractionquality controlsolid phase extraction

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Area of Science:

  • Analytical Chemistry
  • Environmental Science
  • Biomedical Engineering

Background:

  • Solid-phase sorption is crucial for preconcentrating and storing gaseous analytes.
  • Internal standards (ISs) are vital for reducing variability and enhancing the reliability of analytical methods.
  • Accurate and reproducible generation of gaseous internal standards is essential for robust analytical workflows.

Purpose of the Study:

  • To develop and validate a portable system for generating and loading gaseous 8D-Toluene as an internal standard.
  • To assess the system's performance with various solid-phase sorption techniques for gaseous sample analysis.
  • To ensure the stability and reproducibility of the internal standard in canisters for potential breath analysis applications.

Main Methods:

  • Development of a microcontroller-controlled portable system with a digital mass flow controller for precise flow rate adjustment.
  • Utilizing a rotary encoder or an Android app for setting flow rate and sample volume.
  • Testing the system with needle trap microextraction, solid-phase extraction, and thin-film microextraction.
  • Quantification of 8D-Toluene concentration using selected-ion flow-tube mass spectrometry and gas chromatography-mass spectrometry.

Main Results:

  • The system demonstrated excellent airflow control with variability below 1% across a flow rate range of 5-200 ml min-1.
  • The variability in dispensed 8D-Toluene concentration was less than 3%, leading to intra- and inter-day precision below 15% for loaded amounts.
  • No carry-over was detected in the loader, and the 8D-Toluene concentration remained stable in Silonite canisters for up to three weeks at room temperature.

Conclusions:

  • The developed portable system provides a reliable and reproducible method for generating and loading gaseous internal standards.
  • This system significantly improves the precision and reliability of solid-phase sorption techniques for gaseous sample analysis, including breath analysis.
  • The stability and ease of use of the system make it a valuable tool for various applications requiring accurate gaseous sample collection and analysis.