Biomedical subjects

J Henion

Publications and source records attributed to J Henion.

45 records · Page 3Linked to original sources

PubMed1989

Determination of methandrostenolone and its metabolites in equine plasma and urine by coupled-column liquid chromatography with ultraviolet detection and confirmation by tandem mass spectrometry.

Monitoring steroid use requires an understanding of the metabolism in the species in question and development of sensitive methods for screening of the steroid or its metabolites in urine. Qualitative information for confirmation of methandrostenolone and identification of its metabolites was primarily obtained by coupled-column high-performance liquid chromatography-tandem mass spectrometry. The steroids and a sulphuric acid conjugate were isolated and identified by their daughter ion mass spectra in the urine of both man and the horse following administration of methandrostenolone. Spontaneous hydrolysis of methandrostenolone sulphate gave 17-epimethandrostenolone and several dehydration products. This reaction had a half-life of 16 min in equine urine at 27 degrees C. Mono- and dihydroxylated metabolites were also identified. Several screening methods were evaluated for detection and confirmation of methandrostenolone use including thin-layer chromatography and high-performance liquid chromatography. Coupled-column liquid chromatography was used for automated clean-up of analytes difficult to isolate by manual methods. The recovery of methandrostenolone was 101 +/- 3.3% (mean +/- S.D.) at 6.5 ng/ml and both methandrostenolone and 17-epimethandrostenolone were quantified in urine by ultraviolet detection up to six days after a 250-mg intramuscular dose to a horse. The utility of on-line tandem mass spectrometry for confirmation of suspected metabolites is also shown.

Animals↗

PubMed1988

The determination of protein, oligonucleotide and peptide molecular weights by ion-spray mass spectrometry.

The mass spectra of several compounds with molecular weights in the 2500-20,000 Da range were obtained with a quadrupole mass spectrometer equipped with an atmospheric pressure ion source. Average molecular weight determinations of mellitin (2846.4 Da), a synthetic oligonucleotide (4262.8 Da), myoglobin (16,950.4 Da) and on the subunits of beta-lactoglobulin (18,277.1 Da) requiring as little as 1 pmol of material were achieved with accuracies and precisions of +/- 1 Da. An ion-spray interface was used to produce ions via the ion evaporation process, producing mass spectra containing a series of multiply-charged molecular species. A simple method for calculating the molecular weight of unknown compounds from the spectra containing multiply-charged ions is described.

Lactoglobulins↗

PubMed1985

Quantitative secondary ion monitoring gas chromatography/mass spectrometry of diethylstilbestrol in bovine liver.

A procedure is described for the extraction of diethylstilbestrol (DES) from animal tissue for quantitative capillary gas chromatography/mass spectrometry (GC/MS). The procedure is based upon use of a strong anion exchange polystyrene divinylbenzene resin for sample purification. The recovery of DES from the resin clean up was 88% in the high parts per trillion (ppt) range. Criteria for identification of DES using selected ion monitoring (SIM) GC/MS are presented. Liquid chromatography/mass spectrometry (LC/MS) was used to investigate altered DES cis/trans ratios observed in biological extracts.

Animals↗

PubMed1983

Determination of drugs in biological samples by thin-layer chromatography-tandem mass spectrometry.

In this work thin-layer chromatography-tandem mass spectrometry (TLC-MS-MS) allowed detection and confirmation of caffeine and nicotine in human urine and of butorphanol, betamethasone, and clenbuterol in equine urine. In most cases of trace analysis of labile compounds the drugs could not be identified unless they were developed on a TLC plate, scraped from the plate and the TLC scrape eluted with a suitable organic solvent prior to MS-MS. Usually a sample prepared in this way still had several components in it, but was sufficiently cleaned up to allow collision-induced dissociation (CID) experiments to unequivocally identify the drug. In contrast, trace levels of labile drugs could not be identified by CID experiments either directly from the raw urine extracts or by thermally desorbing them from the TLC scrape.

Animals↗

PubMed1983

Micro LC/MS in drug analysis and metabolism studies.

LC/MS has become a routine research tool in some laboratories. Although no single approach to LC/MS presently is without limitations, each approach offers encouraging results and prompts continued improvements. The remaining hurdles appear to be the introduction of total LC effluent into the MS, increased sensitivity, and the ability to analyze higher molecular weight, polar molecules. The micro LC/MS results discussed in this paper offer an opportunity for significantly increased sensitivity by allowing total micro LC effluent introduction into the MS. It remains to be seen whether the development of micro LC column and equipment technology will allow practical micro LC/MS. It may someday provide improved separation of drugs, metabolites, and their conjugates from high levels of endogenous materials in reasonable time periods. Currently, the impressive efficiencies demonstrated for micro LC columns involve mixtures containing low molecular weight solutes that are perhaps more amenable to GC analysis. The analyst routinely involved with problem solving must deal with complex mixtures composed of components with large concentration differences. The future of micro LC, and hence micro LC/MS, will depend upon how well the technique helps solve problems. We believe the future is bright for micro LC/MS. The techniques may require some fine tuning of operating procedures, just as with capillary GC/MS, but certainly the potential for increased efficiency and sensitivity is worth the effort. Currently we are testing a new micro LC/MS DLI probe wherein the exit of the micro column is within 1 cm of the MS ion source [82]. The micro LC column is contained within the DLI probe and should offer the lowest dead volume and the least extracolumn effects yet achieved by LC/MS. Initial testing of this new probe is under way, and experimental results will be reported subsequently. The analytical potential of micro LC/MS is receiving considerable interest. Practical micro LC performance can provide increased capabilities to all types of LC/MS reported to date, and perhaps offer new insight into alternative methods of LC/MS not yet reported. We look forward to learning of these breakthroughs as they become available.

Animals↗

PubMed1982

On-line direct liquid introduction interface for micro-liquid chromatography/mass spectrometry: application to drug analysis.

We describe an integrated micro-liquid chromatograph/mass spectrometer (micro-LC/MS) system capable of performing routine determinations for 1--10 ng of drugs and their metabolites extracted from biological fluids. The micro-LC is constructed from conventional "high-performance" liquid-chromatographic instrumentation by using commercially available components. The mass spectrometer is operated in the chemical ionization mode. The direct liquid introduction micro-LC/MS interface can be constructed from commercially available materials. Chromatographic and mass spectral results demonstrate the ability of the micro-LC and micro-LC/MS system to separate and determine multiple components in standards of trace concentrations and in equine urinary extracts. The stability and sensitivity of this micro-LC/MS system are demonstrated through determinations of trichlormethiazide.

Animals↗

PubMed1980

Characterization of a mutagenic bacterial product in human feces.

Mutagens detectable with the Ames assay have been found in the feces of apparently healthy individuals and the incidence of this mutagenic activity was found to be greater in a population at high risk for colon cancer than in a population at low risk. A compound accounting for the mutagenic activity has been isolated by high performance liquid chromatography. Two closely related forms which behave identically chemically could be resolved. The compound was active on Salmonella typhimurium TA98 and TA100, had a characteristic ultraviolet absorption spectrum with maxima at about 320, 340, and 365 nm, fluoresced green in long wavelength ultraviolet light, and had the same mobility on the thin-layer chromatography as the mutagenic activity in a direct ether extract of feces. The compound was unstable in air but could be stabilized in the presence of butylated hydroxytoluene. Upon oxidation the compound lost its mutagenicity and its ultraviolet absorption spectrum underwent a blue shift so that the absorption maxima were at 295, 310, and 325 nm. Determination of the structure of the mutagen has been difficult since the compound was not volatile and production of a volatile derivative has not been successful. On thin-layer chromatography plates the compound reacted with reagents that detect chlorinated compounds. By thermal energy analysis it did not appear to contain a nitroso group. The compound increased in concentration upon anaerobic incubation of feces at 37 C and this increase was prevented by cold, air, and antimicrobial agents. This suggests to us that the fecal flora produces the compound.

Bacteria↗

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

Elucidation of LSD in vitro metabolism by liquid chromatography and capillary electrophoresis coupled with tandem mass spectrometry.

The in vitro metabolism of D-lysergic acid diethylamide (LSD) by human liver microsomes was investigated. Tandem mass spectrometric techniques, using precursor and neutral loss scans, were employed in the initial search for drug metabolites. The determination of LSD human liver in vitro metabolites was performed by high-performance liquid chromatography and capillary electrophoresis coupled with tandem mass spectrometry. Two new in vitro metabolites, lysergic acid ethylamide (LAE) and 2-oxo-LSD, were positively identified; their structures were established by comparing with reference standards. Several other possible in vitro metabolites detected were suggested to be mono- and trioxylated metabolites of LSD. The major metabolic route of LSD by human liver microsomes is deethylation. Some results with LSD-positive human urine are presented. Among the LSD-related compounds detected in human urine specimens, iso-LSD was present at the highest concentration, followed by nor-LSD and isonor-LSD. Low concentrations of LAE and iso-LAE were also found in these urine specimens.

Chromatography, Liquid↗