Ultraviolet photodissociation and collision-induced dissociation for qualitative/quantitative analysis of low molecular weight compounds by liquid chromatography-mass spectrometry.

Collision-induced dissociation (CID) is the most wildly used fragmentation technique for qualitative and quantitative determination of low molecular weight compounds (LMWC). Ultraviolet photodissociation (UVPD) has been mainly investigated for the analysis of peptides and lipids while only in a limited way for LMWC. A triple quadrupole linear ion trap instrument has been modified to allow ultraviolet photodissociation (UVPD) in the end of the q2 region enabling various workflows with and without data-dependent acquisition (DDA) combining CID and UVPD in the same LC-MS analysis.

UVPD spectroscopy of differential mobility-selected prototropic isomers of protonated adenine.

Two prototropic isomers of adenine are formed in an electrospray ion source and are resolved spatially in a differential mobility spectrometer before detection in a triple quadrupole mass spectrometer. Each isomer is gated in CV space before being trapped in the linear ion trap of the modified mass spectrometer, where they are irradiated by the tuneable output of an optical parametric oscillator and undergo photodissociation to form charged fragments with / 119, 109, and 94. The photon-normalised intensity of each fragmentation channel is measured and the action spectra for each DMS-gated tautomer are obtained.

Electronic spectroscopy of differential mobility-selected prototropic isomers of protonated -aminobenzoic acid.

-Aminobenzoic acid (PABA) was electrosprayed from mixtures of protic and aprotic solvents, leading to formation of two prototropic isomers in the gas phase whose relative populations depended on the composition of the electrospray solvent. The two ion populations were separated in the gas phase using differential mobility spectrometry (DMS) within a nitrogen-only environment at atmospheric pressure. Under high-field conditions, the two prototropic isomers eluted with baseline signal separation with the -protonated isomer having a more negative CV shift than the -protonated isomer, in accord with previous DMS studies.

UVPD Spectroscopy of Differential Mobility-Selected Prototropic Isomers of Rivaroxaban.

Two ion populations of protonated Rivaroxaban, [CHClNOS + H], are separated under pure N conditions using differential mobility spectrometry prior to characterization in a hybrid triple quadrupole linear ion trap mass spectrometer. These populations are attributed to bare protonated Rivaroxaban and to a proton-bound Rivaroxaban-ammonia complex, which dissociates prior to mass-selecting the parent ion. Ultraviolet photodissociation (UVPD) and collision-induced dissociation (CID) studies indicate that both protonated Rivaroxaban ion populations are comprised of the computed global minimum prototropic isomer.

Measuring Electronic Spectra of Differential Mobility-Selected Ions in the Gas Phase.

We describe the modification of a commercially available tandem differential mobility mass spectrometer (DMS) that has been retrofitted to facilitate photodissociation (PD) of differential mobility-separated, mass-selected molecular ions. We first show that a mixture of protonated quinoline/isoquinoline (QH/iQH) can be separated using differential mobility spectrometry. Efficient separation is facilitated by addition of methanol to the DMS environment and increased residence time within the DMS.

How Hot Are Your Ions in Differential Mobility Spectrometry?

Ions can experience significant field-induced heating in a differential mobility cell. To investigate this phenomenon, the fragmentation of several -substituted benzylpyridinium "thermometer" ions (R = OMe, Me, F, Cl, H, CN) was monitored in a commercial differential mobility spectrometer (DMS). The internal energy of each benzylpyridinium derivative was characterized by monitoring the degree of fragmentation to obtain an effective temperature, , which corresponds to a temperature consistent with treating the observed fragmentation ratio using a unimolecular dissociation rate weighted by a Boltzmann distribution at a temperature .

Extending the Ion Capacity of a Linear Ion Trap Using Nonlinear Radio Frequency Fields.

Mass selective axial ejection (MSAE) from a low pressure linear ion trap (LIT) is investigated in the presence of added auxiliary nonlinear radio frequency (rf) fields. Nonlinear rf fields allow ions to be ejected with high sensitivity at large excitation amplitudes and reduced deleterious effects of space charge. These permit the operation of the LIT at ion populations considerably larger than the space charge limit usually observed in the absence of the nonlinear fields while maintaining good spectral resolution and mass accuracy.

Boundary-activated dissociation in a low pressure linear quadrupole ion trap in the presence of nonlinear DC fields.

Boundary-Activated Dissociation (BAD) of multiple charge ions has been investigated in a low pressure linear ion trap (LIT) in the presence of nonlinear DC fields. Nonlinear DC fields allowed ions to be stored for a long duration at working points beyond the βy = 0 stability boundary of the regular quadrupole fields. The ions reached large stable radial amplitude trajectories gaining high kinetic energies from the drive RF field.

Tandem ion trap design with enhanced mass analysis capabilities for large populations of ions.

A new arrangement consisting of two separate radio frequency (rf) quadrupole ion traps is used to analyze large populations of ions over a wide mass-to-charge (m/z) range. The setup consists of an "accumulation" trap that is maintained at a higher pressure than the second high-performance "analyzer" trap. The two traps are scanned simultaneously, with a mass difference between that determines the residence time and mass range of ions in the analytical trap.

Performance enhancements of mass selective axial ejection from a linear ion trap.

Mass selective axial ejection (MSAE) of ions from a linear ion trap (LIT) takes advantage of the rf fringing fields at the end of the linear quadrupole to convert radial ion excitation into axial ejection. Ions gain radial amplitude via a mass selective resonance excitation process and are ejected axially over an electrostatic DC barrier. The extraction efficiency and resolution are determined by the length and shape of the extraction region in the vicinity of the exit aperture.