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Analysis of thiocyanates and isothiocyanates by ammonia chemical ionization gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1016/0021-9673(93)80426-9
AuthorSearch for: 1; Search for:
Affiliation
  1. National Research Council of Canada. NRC Plant Biotechnology Institute
FormatText, Article
Abstract
Under NH₃-chemical ionization (CI) conditions alkyl thiocyanates give mass spectra which show only the adduct ions (M + NH₄)⁺ (base peak) and (M + NH₄. NH₃)⁺. Allyl thiocyanate and aromatic thiocyanates show fragmentation similar to the corresponding isothiocyanates but still produce (M+NH₄)⁺ as base peak and (M+NH₄.NH₃)⁺ as a prominent ion. These properties allow the thiocyanates to be easily distinguished from isothiocyanates whose NH₃-CI mass spectra indicate considerable fragmentation but little, or no, adduct ion formation. The isothiocyanates are further characterized by relatively abundant M⁺ and (M + H)⁺ ions in spectra of the C₁-C₅ alkyl isomers and the ion at m/z 115 as base peak for the longer-chain alkyl isothiocyanates. Thiocyanates and isothiocyanates can also be differentiated on the basis of their gas-phase Fourier transform (FT) IR spectra. The spectra of isothiocyanates are dominated by a very intense absorption band at ca. 2060 cm⁻¹ (-NCS) similar to that seen in liquid film spectra. Thiocyanates, in contrast, show only weak absorption at ca. 2165 cm⁻¹. Due to their weak interaction with infrared, aromatic thiocyanates are difficult to detect by this technique. Allyl thiocyanate is a special case. Under normal GC-FT-IR conditions it quickly isomerizes to Allyl isothiocyanate. Allyl thiocyanate was only detected in admixture with Allyl isothiocyanate, with light-pipe temperatures below 100°C.
Publication date
PublisherElsevier
In
  • Journal of Chromatography A 648, no. 2 (October 1993): 433–443.
LanguageEnglish
Peer reviewedYes
Identifier0021967393804269
NRCC-37329
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Record created2023-11-06
Record modified2023-11-06
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