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T Wachs

Publications and source records attributed to T Wachs.

8 recordsLinked to original sources
PubMed1997

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.

Animals↗
PubMed1996

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.

Adrenergic beta-Agonists↗
PubMed1995

Kinetic monitoring of enzymatic reactions in real time by quantitative high-performance liquid chromatography-mass spectrometry.

The study of enzyme kinetics under steady-state conditions represents a common and very useful method for investigating the mechanisms of enzymatic reactions. We report the use of mass spectrometry (MS) coupled with HPLC for the kinetic analysis of enzymatic reactions in real time. The hydrolysis of dinucleotides with bovine pancreatic ribonuclease A (RNase A) and the substrate-specific hydrolysis of lactose with beta-galactosidase can be monitored using ion-spray (pneumatically assisted electrospray) mass spectrometry as a sensitive and specific detector for the native substrates. The resulting data can be used to calculate both KM and Vmax for each system. Kinetic parameters obtained for RNase A and beta-galactosidase paralleled those obtained by conventional techniques. These findings suggest the possibility of developing alternative techniques, based on mass spectrometric detection, for performing kinetic analyses of enzymatic processes where no simple spectrophotometric assay is feasible. In addition to enabling the determination of kinetic parameters for authentic substrates, and not chromogenic analogs, such assays would also be useful in situations where very high sensitivity and specificity are desired.

Animals↗
PubMedDate not supplied

Recent developments in electrospray mass spectrometry including implementation on an ion trap.

Mass spectrometry (MS) may be the ultimate detection technique when combined with modern condensed phase separation sciences. The technique combines sensitivity with excellent specificity, so the pharmaceutical analyst can obtain definitive information regarding components separated in a mixture. Thus, mass spectrometric detection not only provides evidence of a chromatographic peak, but it also provides important information including molecular weight and structural information enabling identification of the components. The coupling of an atmospheric pressure ionization (API) mass spectrometer to most of the separation science techniques offers a simpler alternative from earlier non-routine, less sensitive systems where the vacuum systems struggled to handle the liquid effluent from these systems. Contemporary sensitive and analytically rugged API systems can be operated unattended for extended periods of time thus reducing the cost per sample to a reasonable value especially given the wealth of information provided. Although the mass spectrometer is more complicated than conventional spectroscopic detectors, present day API systems effectively decouple the liquid-phase separation inlet from the high-vacuum system where mass analysis occurs. The ability to form gas-phase ions at atmospheric pressure and sample primarily the analyte ions into the mass spectrometer promises a bright future for combining on-line condensed phase separation science techniques with mass spectrometry. The increasing ease of performing these experiments offers new analytical opportunities for pharmaceutical laboratories.

Carbohydrate Sequence↗
PubMedDate not supplied

Urokinase administration in pediatric patients with occluded central venous catheters.

The effectiveness of urokinase in declotting central venous catheters was retrospectively assessed in a pediatric population of 63 patients ranging in age from 4 days to 22 years (mean, 6.4 years). Results of treatment from 103 episodes of catheter occlusion were evaluated. Urokinase was instilled into occluded single-lumen catheters and into each lumen of double-lumen catheters, as well as into occluded implanted ports. Patency was restored to 101 of 103 occluded catheters, with no side effects observed subsequent to clearance of the catheters with the urokinase infusion. Significant cost savings were seen using urokinase to restore patency as compared to the cost of replacing the catheter. These data clearly support the use of urokinase in a pediatric population as a safe and cost-effective alternative to catheter replacement in cases of thrombotic occlusion.

Adolescent↗