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Related Concept Videos

Mass Spectrometry: Isotope Effect01:13

Mass Spectrometry: Isotope Effect

Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the mass differences between isotopes. Furthermore, the intensity of these signals is dependent on the...
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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High-throughput and Comprehensive Drug Surveillance Using Multisegment Injection-Capillary Electrophoresis-Mass Spectrometry
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Evaluation method for linking methamphetamine seizures using stable carbon and nitrogen isotopic compositions: a

Yuko T Iwata1, Kenji Kuwayama, Kenji Tsujikawa

  • 1National Research Institute of Police Science, 6-3-1, Kashiwanoha, Kashiwa, Chiba 277-0882, Japan.

Rapid Communications in Mass Spectrometry : RCM
|November 5, 2008
PubMed
Summary

Linking methamphetamine seizures is enhanced by combining stable isotope analysis with gas chromatographic impurity profiling. This dual approach improves accuracy in forensic investigations by corroborating evidence from drug samples.

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Area of Science:

  • Forensic Chemistry
  • Analytical Chemistry
  • Isotope Ratio Mass Spectrometry

Background:

  • Drug profiling is crucial for linking seized substances and supporting criminal investigations.
  • Gas chromatographic impurity profiling is a major method for drug analysis.
  • Stable isotope analysis offers complementary data for forensic investigations.

Purpose of the Study:

  • To evaluate a method for linking methamphetamine seizures.
  • To integrate stable carbon and nitrogen isotopic compositions with gas chromatographic impurity profiling.
  • To assess the effectiveness of this combined approach in forensic casework.

Main Methods:

  • Analysis of methamphetamine (MA) seizures using stable carbon and nitrogen isotope ratios (delta(13)C and delta(15)N).
  • Gas chromatographic impurity profiling of MA samples.
  • Hierarchical cluster analysis of impurity profiles.
  • Classification of MA seizures based on isotopic compositions in a delta(13)C-delta(15)N graph.
  • Determination of cluster size using pooled standard deviations (s(p)).

Main Results:

  • Impurity profiles were similar within linked seizure sets, aligning with investigative information.
  • MA seizures showed distinct isotopic compositions, classifying them into seven potential origin groups.
  • Isotopic composition clusters were consistently small (less than 6s(p)).
  • Linkages derived from isotopic compositions corroborated impurity profiling and investigative data.

Conclusions:

  • The complementary use of stable isotope analysis and impurity profiling effectively evaluates links between drug seizures.
  • This integrated method provides robust information for forensic investigations involving methamphetamine.
  • The study demonstrates the value of combining chemical and isotopic analyses for drug profiling.