Unexpected adduct ion formation under chemical ionization conditions

✍ Scribed by Donald G. Musson; Magnus M. Halldin; Deiji Karashima; Neal Castagnoli Jr.

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 559 KB
• Volume: 13
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/bms.1200130605

✦ Synopsis

As part of our efforts to characterize the in uiuo metabolic fate of the antihypertensive agent a-methyldopa, we have examined the urine of a-methyldopa-treated rats with the aid of a direct insertion probe chemical ionization mass spectral assay. The mass spectrum of the sample obtained by chromatographic purification followed by treatment with ethanolic hydrochloric acid and pentafluoropropionic anhydride displayed an intense ion at m / z 812, consistent with the f3-ethoxy-N,O,O,O-tetrakispentafluoropropionyl derivative of 6-hydroxy-a-methylnorepinephrine, a potential aromatic hydroxylation product of the known a-methyldopa metabolite a-methylnorepinephrine. Comparison of this spectrum with the spectrum obtained with the corresponding synthetic L-hydroxya-methylnorepinephrine, however, ruled out this possibility. A more thorough examination of the mass spectral data established that the ion at m / z 812 observed with the metabolic species was due to the formation of an unexpected adduct ion between a known metabolite of a-methyldopa and an impurity ion formed from a common constituent of urine. This paper summarizes the characterization of this adduct ion.