High-pressure gas phase femtosecond laser ionization mass spectrometry.

We describe a novel ion source for analytical mass spectrometry based on femtosecond laser ionization at pressures at and above atmospheric and characterize its performance when coupled to a tandem quadrupole/time-of-flight mass spectrometer. We assess source saturation limits, ionization and sampling efficiencies, the effective ionization volume, and limits of detection. We demonstrate 100% efficient ionization for a set of organic compounds and show that the degree of ion fragmentation over a range of laser powers is favorable compared to electron impact ionization, especially in that a substantial parent ion signal is always observed.

Ultraviolet photodissociation of protonated pharmaceuticals in a pressurized linear quadrupole ion trap.

Ultraviolet photodissociation (UVPD) was evaluated as a technique for generating ion fragmentation information that is alternative and/or complementary to the information obtained by collision-induced dissociation (CID). Ions trapped in a pressurized linear ion trap were dissociated using a 355 nm or a 266 nm pulsed laser. Comparisons of UVPD and CID spectra using a set of aromatic chromophore-containing compounds (desmethyl bosentan, haloperidol, nelfinavir) demonstrated distinct characteristic fragmentation patterns resulting from photodissociation.

A useful binary matrix for visible-MALDI of low molecular weight analytes.

In this work, a new absorbing candidate, rhodamine (R) 575, is described, which forms the basis of a binary matrix operating at 532 nm. Analyte ionization is found to be much more efficient when the dye is combined with a proton donor such as hydrochloric acid or alpha-cyano-4-hydroxycinnamic acid, or a proton acceptor such as sodium hydroxide. This makes the matrix more generic than many others that have been tried.

Formation of (bn-1 + H2O) ions by collisional activation of MALDI-formed peptide [M + H]+ ions in a QqTOF mass spectrometer.

Collisional activation of [M + H](+) parent ions from peptides of n amino acid residues may yield a rearrangement that involves loss of the C-terminal amino acid residue to produce (b(n-1) + H(2)O) daughters. We have studied this reaction by a retrospective examination of the m/z spectra of two collections of data. The first set comprised 398 peptides from coat protein digests of a number of plant viruses by various enzymes, where conditions in the tryptic digests were chosen so as to produce many missed cleavages.

Applications of a matrix-assisted laser desorption/ionization orthogonal time-of-flight mass spectrometer. l. Metastable decay and collision-induced dissociation for sequencing peptides.

The use of a high-performance orthogonal time-of-flight (o-TOF) mass spectrometer for sequence analysis is described. The mass spectrometer is equipped with a matrix-assisted laser desorption/ionization (MALDI) source that operates at elevated pressure, 0.01-1 Torr.