Differentiation of regioisomers of sulfobenzoic acid by traveling-wave ion mobility mass spectrometry.

An ion mobility mass spectrometry (IM-MS) investigation using a Synapt G2 mass spectrometer was conducted to separate anions generated from the three regioisomers of sulfobenzoic acid. The results revealed that the differences in arrival time distributions (ATDs) were inadequate to differentiate the isomers unambiguously. However, the ATD profiles of the product ions, generated by fragmenting the respective mass-selected m/z 201 precursor ions in the Trap region of the three-compartment traveling-wave ion guide of the Synapt G2 mass spectrometer, were distinctly different, enabling definitive differentiation of the isomers.

Dependence of Collision-Induced Mass Spectra of Protonated Michler's Ketone on the Nature of LC-MS Mobile Phase.

Michler's ketone (MK) is a dimethylamino ketone that undergoes facile protonation under electrospray-ionization conditions to produce an ion of / 269. Initial LC-MS results showed that the collision-induced dissociation (CID) spectra of the / 269 ion depend heavily on the composition of the chromatographic mobile phase. Subsequent ion-mobility separation of the mass-selected / 269 ion revealed that protonated MK exists as two tautomeric forms.

Impact of Ambient Vapors on Spectra of 4-Nitroaniline Recorded under Atmospheric Solids Analysis Probe (ASAP) Mass Spectrometric Conditions.

Thermally desorbed 4-nitroaniline (4-NA), upon atmospheric pressure chemical ionization (APCI), generates gaseous ions for its protonated species. The APCI mass spectrum recorded under mild in-source ion-activating conditions from 4-NA showed a peak at / 139, whereas that acquired under high ion-activating conditions showed two additional peaks at / 122 (OH loss) and 92 (NO loss). The spectrum changed instantaneously when acetonitrile vapor was introduced to the source.