Journal of the Mass Spectrometry Society of Japan

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The gas phase affinities of a trimethylsilyl cation (a guest) to a series of permethylated monosaccharides and simple crown ethers (hosts) have been measured for the first time using the equilibrium method with ICR mass spectrometry. It was found that the gas phase complexation free energies (δΔG°_ICR) are mainly governed by the number of multiple binding (participating) oxygens in such complexation systems of the cyclic oxygen hosts toward a Me₃Si⁺ guest. A linear correlation was empirically observed between the present thermodynamic data (δΔG°_CIR) in the gas phase and the ln(RPI) quantities previously obtained from the complexations of the corresponding hosts toward a CH₃OCOCH₂NH₃⁺ guest using FAB mass spectrometry (RPI: relative peak intensity of the corresponding host-guest complex ions). Two approaches of the interconnection between the RPI values generated by FABMS and the relevant values introduced from the typical FAB ionization mechanism of a “gas collision model” and a “preformed ion model” were reported.

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An isolation procedure of microgram amounts of long-chain n-alkanes from crude oil using molecular sieve was examined for its applicability to stable carbon isotope analysis by gas chromatography/isotope ratio mass spectrometry (GC/IRMS).
The procedure examined is as follows: molecular sieve (type 5A, 200 mg) in 1 ml of isooctane solvent are mixed with a saturated hydrocarbon fraction extracted from an appropriate amount (approx. 20 mg) of crude oil and stayed at room temperatures for more than 3 hours. Long-chain n-alkanes are isolated by extraction with n-hexane after dissolution of the resulting molecular sieve with 47% hydrofluoric acid solution. The recoveries were 90±6% for C₁₅~C₃₄ n-alkanes when their total amounts applied do not exceed 1.4 mg. No effect of the isolation procedure on carbon isotope ratios of n-alkanes was observed.

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