Timothy Wachs

Simple modification of a commercial mass spectrometer for metastable data collection

Abstract The geometry of a Hitachi Perkin—Elmer RMU-7 double-focusing mass spectrometer was reversed by interchanging the positions of ion source and electron multiplier. The high metastable resolution of the modified instrument (150 for narrow peaks) resulted in 57 new transitions found for n-decane. Because of the mode of operation, reproducible peak shapes and intensities can be obtained.

Design and applications of a self-aligning liquid junction-electrospray interface for capillary electrophoresis-mass spectrometry

A simple self-aligning liquid junction-electrospray interface for coupling a capillary electrophoresis (CE) system to an atmospheric pressure ionization (API) mass spectrometer (CE-MS) was developed. In contrast to previous liquid junction interfaces, the self-aligning liquid junction interface simplifies the precise alignment of the CE capillary and the sprayer needle and uses a positive make-up flow. Several capillary CE-MS applications were run using both the self-aligning liquid junction interface and the widely used sheath flow interface for comparison purposes. The electrospray stability of the self-aligning liquid junction interface is consistently better even when non-volatile electrolyte solutions are used. At first, some band broadening was obtained with the self-aligning liquid junction interface. Experiments with different CE buffer systems suggested that this band broadening was caused by the materials used in constructing the interface. By using a more inert material for the sprayer needle, the self-aligning liquid junction exhibits excellent electrophoretic resolution, comparable sensitivity, and higher signal-to-noise ratios when run under the same conditions as the sheath flow interface.

Quantitative ionspray liquid chromatographic/tandem mass spectrometric determination of reserpine in equine plasma

A method based on ionspray liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed for the determination of reserpine in equine plasma. A comparison was made of the isolation of reserpine from plasma by liquid-liquid extraction and by solid-phase extraction. A structural analog, rescinnamine, was used as the internal standard. The reconstituted extracts were analyzed by ionspray LC/MS/MS in the selected reaction monitoring (SRM) mode. The calibration graph for reserpine extracted from equine plasma obtained using liquid-liquid extraction was linear from 10 to 5000 pg ml-1 and that using solid-phase extraction from 100 to 5000 pg ml-1. The lower level of quantitation (LLQ) using liquid-liquid and solid-phase extraction was 50 and 200 pg ml-1, respectively. The lower level of detection for reserpine by LC/MS/MS was 10 pg ml-1. The intra-assay accuracy did not exceed 13% for liquid-liquid and 12% for solid-phase extraction. The recoveries for the LLQ were 68% for liquid-liquid and 58% for solid-phase extraction.

An improved mass spectrometer/computer system for collisional activation spectra☆

Abstract A reversed geometry double-focusing mass spectrometer used for measuring metastable ion and collisional activation (CA) spectra has been modified to include a special collision chamber, doubled ion-accelerating voltage, and a dedicated minicomputer. This results in a five-fold increase in sensitivity and a

Energy transfer in collisional activation of gaseous organic ions

2 increase in resolution. There is an additional large increase in resolution for peaks adjacent to the precursor ion due to the near elimination of off-focus scattering. Computer data acquisition and spectrum rescanning give the expected enhancement in signal/noise and increased efficiency in operation. A high-pressure ion source makes possible CA spectral studies of ion-molecule reaction products.

N nitrosamines and mutagens in rubber nursing nipples

Abstract The amounts of translational energy lost in the collisional activation (CA) of CH4+, CD4+, CH3+, and CD3+ to form the possible C(H,D)0–3+ products have been measured. These values are consistent with the gain in internal energy required to produce the observed decomposition in unimolecular reactions, as predicted by the quasi-equilibrium theory. Further, there appear to be marked differences in the distribution of internal energy values of CH4+ produced by electron ionization of CH4 and the distribution produced by CA of low energy CH4+ ions.

Occurrence of polycyclic aromatic hydrocarbons in municipal sewage sludge ashes

Aqueous extracts of four brands (eight types) of rubber nursing nipples purchased in the open market were analyzed for volatile N‐nitrosamines, diphenylamine, and mutagenic activity. N‐Nitrosodimethylamine, N‐nitrosodiethylamine, or N‐nitro‐sopiperidine were found in the aqueous extracts of the nipples and in the nipples themselves. All nipples analyzed contained one or more of the three volatile N‐nitrosamines. Diphenylamine was found to be continously released into aqueous extracts from most brands. Certain nipples produced a positive mutagenic response when incubated with Salmonella typhimurium (TA 100) in a modified liquid suspension test.

Electrospray Device for Coupling Microscale Separations and Other Miniaturized Devices with Electrospray Mass Spectrometry

Sludge ash residues from four cities that incinerate municipal sewage sludge were analyzed for isolated polycyclic aromatic hydrocarbons. Total amounts of PAHs in the ashes were in the range of 0.1–1μg/g. The ash containing the highest amount also exhibited the greatest variety of PAHs.