Collision-induced dissociation analysis of negative atmospheric ion adducts in atmospheric pressure corona discharge ionization mass spectrometry.

Collision-induced dissociation (CID) experiments were performed on atmospheric ion adducts M + R formed between various types of organic compounds M and atmospheric negative ions R(-) [such as O2(-), HCO3(-), COO(-)(COOH), NO2(-), NO3(-), and NO3(-)(HNO3)] in negative-ion mode atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. All of the M + R adducts were fragmented to form deprotonated analytes M - H and/or atmospheric ions R(-), whose intensities in the CID spectra were dependent on the proton affinities of the M - H and R(-) fragments. Precursor ions M + R for which R(-) have higher proton affinities than M - H formed M - H as the dominant product. Furthermore, the CID of the adducts with HCO3(-) and NO3(-)(HNO3) led to other product ions such as M + HO and NO3(-), respectively. The fragmentation behavior of M + R for each R(-) observed was independent of analyte type (e.g., whether the analyte was aliphatic or aromatic, or possessed certain functional groups).