Electron ionization and electrospray ionization mass spectrometric study of a series of isomeric N-chloro(or bromo)benzyl-substituted (E)-2'(3'- or 4')-hydroxy-4-stilbazole halides

The electron ionization (EI) mass spectra and electrospray ionization (ESI) mass spectra of a series of isomeric N-chlorobenzyl- and N-bromobenzyl-substituted (E)-2'(3' or 4')-hydroxy-4-stilbazole chlorides and bromides (1-12) were recorded. The fragmentation pathways of all of the compounds and the characteristic fragment ions formed by EI-MS were studied by means of B/E and B(2)/E constant linked-scanning techniques. The formation of ions originating from preionization reactions, characteristic of quaternary halides under EI-MS conditions, such as the elimination of chloro- or bromobenzyl halides, dehydrohalogenation or substitution reactions, is explained. As soft ionization methods cause no such degradation reactions, the ESI-MS spectra of the studied compounds were also obtained for comparison. We thus demonstrated the applicability of EI-MS even in cases when preionization takes place, as long as such secondary processes are properly accounted for.

Direct quantitation of antiseptic quaternary ammonium compounds by fast atom bombardment mass spectrometry

The medicinally important quaternary ammonium salts benzyldimethyltetradecylammonium chloride (BDTA), cetylpyridinium chloride and benzethonium chloride, all afford, under fast atom bombardment (FAB) mass spectrometric conditions, abundant and persistent [M-Cl]+ species usefully amenable to quantitative analysis with the aid of thioglycerol as a liquid FAB matrix. The use of BDTA as an internal standard allowed a direct, precise and accurate determination of cetylpyridinium and benzethonium chlorides, either as pure samples or in dosage forms, in the concentration range 0.05-2 mg/ml.

Preparation of semisynthetic (+)-tubocurarine chloride

Semisynthetic (+)-tubocurarine chloride (II) was prepared by monoquaternization of (+)-tubocurine. The method involved treating (+)-tubocurine with a 0.5 M equivalent of hydrochloric acid prior to quaternization with methyl iodide, followed by neutralization and iodide-chloride ion-exchange. Column chromatography and crystallization procedures were utilized for pure semisynthetic II preparation. The neuromuscular junction blocking activities of the semisynthetic and commercial II were determined by the in vivo cat hypoglossal nerve-tongue muscle preparation. No delectable differences among physical constants, spectral data, and neuromuscular junction blocking activities were noted between the commercial product and the semisynthetic II. This result substantiates the chemical and biological data for the well-accepted new formula for II. The unexplained M + n14 mass spectral peaks shown by the curare-type bases are characteristic of the molecular species rather than a result of contaminants.