Reference standards for negative ion mass spectrometry

Abstract

The negative ion mass spectra of phosphonitrile chlorides (PNCI,), (n23) are studied. Since this series of compounds give very intense negative [MI' and [M-CI]-ions, they can be used as good reference standards for negative ion mass spectrometry.Although studies on negative ion mass spectra have increased in number, reference standards which are required in high resolution negative ion mass spectrometry have been little sought for. In addition, reference standards for low resolution negative ion mass spectrometry are also desired, because the fact that the negative ion mass spectra of organic compounds are generally far simpler than the positive ones sometimes causes difficulty in counting. Although the negative ion mass spectrum of perfluorokerosine (PFK) has been reported,' the intensity of the ions is not strong enough.In the previous paper, the negative ion mass spectrum of sulphur was investigated and proved to be useful as a reference standard in the lower mass region up to m/e 256.' The spectrum consists mainly of [S,]-( n = 1-6) with additional minor peaks due to [S,]-and [SJ.In this study, the phosphonitrile chlorides (PNCl,), ( n I 3) (1) were found to be useful standard compounds for the higher mass region.

Vacuum nebulizing interface for direct coupling of micro-liquid chromatograph and mass spectrometer

“…With this interface, a more general system for LC-MS direct coupling can be established, where the wide range of flow rate of the solvent can be stably interfaced without any conventional splitting and even fairly involatile compounds can effectively be introduced into the ion source at relatively lower temperatures than those required for nonnebulizing direct introduction. Further, this device is also quite effective for sample introduction of polar and/or large molecules of which mass spectra are otherwise difficult to take (9). EXPERIMENTAL Nebulizing Interface.…”

“…In this case, testing solutes of interest are first dissolved in an appropriate solvent which becomes a good reagent gas for Cl, and then an aliquot of the solution is introduced into the coaxial capillary by a constant flow of the same solvent from a micro-feeder pump of the LC. With this technique, it was possible to take fairly stable Cl mass spectra of polyethyleneglycols up to m/e = 600, and many of the free amino acids, oligopeptides, and steroids (9), Further investigation along these lines is under way.…”