ATMOSPHERIC PRESSURE THERMAL DISSOCIATION CHEMICALIONIZATION MASS SPECTROMETRY: MASS SPECTROMETRICANALYSES OF POLYCYCLIC AROMATIC HYDROCARBONS ANDAMINO-ACIDS BY DIRECT SAMPLING IN AMBIENT AIR

摘要

A novel concept to use the radical cation created by thermal dissociation of phenyldiazonium chloride for direct chemical ionization of both non-polar and polar compounds atrnatmospheric pressure was presented. An atmospheric pressure thermal dissociation chemicalrnionization (APTDCI) source was constructed and characterized by using phenyldiazoniumrnchloride as thermal dissociation reagent and toluene as analyte. Under the optimized workingrnconditions, a series of polycylic aromatic hydrocarbons (PAHs) such as naphthalene, anthracene,rntriphenylene and benz[ ] α -anthracene were ionized in APTDCI source to give dominant peakrncorresponding to radical cation or protonated molecules when H-acid diazonium salt was used asrnreagent in MS spectra, demonstrating the basic performance of the APTDCI source for non-polarrncompounds. The detection limit of benz[ ] α -anthracene was 10 fg. Serine, an amino acid ofrnsignificant importance in life evolution, was employed as an example to show the capability ofrnAPRDCI source for the polar compounds. It was deduced that APRDCI could be applied to ionizernanalytes, both non-polar and polar compounds, in atmospheric pressure without complicatedrnsample pretreatment. All the data were validated in tandem mass spectra of interested ions inrnLTQ mass spectrometer by collision-induced dissociation. The mechanism of thermal dissociationrnchemical ionization was discussed briefly.