PubMed Health⌕ Search

Biomedical subjects

J Henion

Publications and source records attributed to J Henion.

At least 19 recordsLinked to original sources
PubMed1997

Quantitative capillary electrophoresis/ion spray tandem mass spectrometry determination of EDTA in human plasma and urine.

A quantitative method has been developed for the determination of EDTA in human plasma and urine. The samples are prepared with automated anion-exchange solid-phase extraction using 100 microL of human plasma. The extracts are analyzed by capillary electrophoresis/mass spectrometry using selected reaction monitoring in the negative ion mode. Large-volume injections (10% of the CE capillary volume) are used to improve the concentration level of detection via field-amplified sample injection. The first reported validation of a CE/MS/MS technique was carried out for this method. Using a 13C stable-label isotope for the internal standard, the lower level of detection and lower level of quantitation were determined to be 7.3 and 14.6 ng/mL EDTA in human plasma, respectively. The injection precision had a relative standard deviation (RSD) of 6.1%. The intra-assay precision was less than 15% RSD. The intra-assay accuracy was less than +/- 12% bias from the nominal concentration. The interassay precision was less than 18% RSD and the interassay accuracy was less than +/- 9% bias from the nominal concentration.

Blood Chemical Analysis↗
PubMed1997

Quantitative multi-residue determination of beta-agonists in bovine urine using on-line immunoaffinity extraction-coupled column packed capillary liquid chromatography-tandem mass spectrometry.

This report demonstrates the potential of on-line immunoaffinity extraction and coupled column packed capillary liquid chromatography-ion spray tandem mass spectrometry for multi-residue determination of five beta-agonists, clenbuterol, mabuterol, mapenterol, methylclenbuterol, and tolubuterol, in bovine urine using an automated column switching system. Trace enrichment and preliminary sample cleanup was performed on-line using bovine urine diluted with phosphate-buffered saline. The column switching process involves trapping the target analytes onto a mini-bore immunoaffinity column, whereupon the target analytes are released from the immunoaffinity column onto a trapping column and subsequently eluted onto a packed capillary analytical column. The latter packed capillary column was used to provide the optimum sensitivity for ion spray LC-MS-MS analyses. The three-column system consists of a 2.0 mm I.D. immunoaffinity column, a 1 mm I.D. reversed-phase trapping column and a 320 microm I.D. packed capillary analytical column. Both qualitative and quantitative results are presented for the multi-residue determination of the target beta-agonists from the complex urinary matrix. Using tolubuterol as an internal standard, the quantitative data showed good linear response within the concentration ranges studied. Lower levels of quantitation were 50 part per trillion (ppt) for clenbuterol and methylclenbuterol, 20 ppt for mabuterol and 10 ppt for mapenterol. The bovine renal elimination is described using the technique for one of the beta-agonists, clenbuterol. The concentration of clenbuterol was detectable 15 days after the cessation of oral administration.

Adrenergic beta-Agonists↗
PubMed1997

Microsample determination of lovastatin and its hydroxy acid metabolite in mouse and rat plasma by liquid chromatography/ionspray tandem mass spectrometry.

A sensitive and specific method was developed and validated to quantitate lovastatin and its hydroxy acid in mouse and rat plasma. This method employs a solid-phase extraction procedure to isolate lovastatin and its hydroxy acid metabolite from the biological matrices (0.1 ml of mouse or rat plasma). The reconstituted extracts were analyzed by liquid chromatography/ionspray tandem mass spectrometry (LC/MS/MS). Simvastatin and simvastatin hydroxy acid were used as internal standards for lovastatin and lovastatin hydroxy acid, respectively. The assay has a lower limit of quantitation (LLQ) of 0.50 ng ml-1 in mouse and rat plasma for both lovastatin and its hydroxy acid based on 0.1 ml aliquots of plasma. The intra- and inter-assay precision (RSD), calculated from quality control (QC) samples, was < 7% for lovastatin and < 6% for lovastatin hydroxy acid in both matrices. The inter-assay accuracy as determined from QC samples was less than 6% for lovastatin and less than 8% for lovastatin hydroxy acid in both matrices. The overall recovery of lovastatin was 54% in mouse plasma and 55% in rat plasma, and the overall recovery of lovastatin hydroxy acid was 100% in mouse plasma and 67% in rat plasma.

Animals↗
PubMed1997

Quantitative determination of Orlistat (tetrahydrolipostatin, Ro 18-0647) in human plasma by high-performance liquid chromatography coupled with ion spray tandem mass spectrometry.

A rapid, sensitive and specific analytical method was developed and validated to quantify tetrahydrolipostatin (Orlistat, Ro 18-0647) in human plasma in order to provide pharmacokinetic data from clinical trials. This method employs a preliminary plasma protein precipitation step followed by a simple, one-step liquid-liquid extraction procedure to isolate Ro 18-0647 and its pentadeuterated internal standard, Ro 18-0647-d5, from the biological matrix. Reconstituted extracts were analyzed by liquid chromatography/ion spray tandem mass spectrometry (LC/MS/MS) in the selected reaction monitoring (SRM) mode. Chromatography was carried out using a 2 mm i.d. x 50 mm Deltabond Phenyl column. The eluent was acetonitrile-2 mM ammonium acetate (90:10). The retention time of the analyte was 1.2 min and chromatographic run times were less than 1.5 min. No interferences from anticoagulants, collection devices or endogenous constituents of the plasma were observed. The assay has a lower limit of quantitation (LLQ) of 0.20 ng ml-1 in plasma and a lower limit of detection (LLD) of 0.10 ng ml-1 plasma, based on 1 ml aliquots. The capability to detect 0.025 ng ml-1 in plasma has also been demonstrated. The calibration graphs were linear from 0.20 to 10 ng ml-1. The assay was initially validated with a linear range of 0.20-1.0 ng ml-1. This range was later extended and validated to an upper level of quantitation of 10 ng ml-1. Intra- and inter-assay precision studies showed a mean variability of less than 10%. The recovery, inter-assay precision and accuracy of the method were within acceptable bioanalytical standards. The assay has been shown to reliably provide automated, unattended sample analysis for approximately 150 samples per day. In an additional series of tests, Ro 18-0467 was shown to be stable under conditions that might be encountered during the analysis of samples from clinical trials. This LC/MS/MS assay procedure for Ro 18-0647 in human plasma has proven to be robust, sensitive, specific, accurate and reproducible. This method has been used to analyze over 5000 study samples.

Calibration↗
PubMed1997

Determination of ethylenediaminetetraacetic acid as the nickel chelate in environmental water by solid-phase extraction and capillary electrophoresis/tandem mass spectrometry.

An automated extraction procedure using solid-phase extraction (SPE) disk technology was developed for the qualitative and quantitative determination of ethylenediaminetetraacetic acid (EDTA) in water samples. The procedure involves conversion of all free and chelated EDTA present into the nickel EDTA chelate followed by extraction on strong anion exchange extraction disks, A 5 mL water sample is extracted and concentrated to 30 microL. This extract is then analyzed by capillary electrophoresis (CE) using ion spray-tandem mass spectrometry (MS) for selective detection. An amine-coated capillary column is used to separate anions using negative voltage and high electroosmotic flow. A self-aligning liquid junction is used as the CE/MS interface. The sample is injected using field amplification for enhanced concentration detection limits down to 0.15 microgram/L. This detection limit is about five times lower than any report we have found in the literature and provides the unique specificity afforded by mass spectrometry. Total sample preparation and run time was forty minutes per sample, including evaporation steps and capillary rinsing between runs. A tray of 24 vials, including samples and standards, was analyzed for these experiments and was easily finished within one day. These experiments demonstrate that CE/MS can be a rugged, quantitative technique, which, with proper sample preparation and focusing techniques, can compete with the concentration sensitivity of established analytical methods.

Chelating Agents↗
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↗
PubMed1996

On-line immunoaffinity extraction-coupled column capillary liquid chromatography/tandem mass spectrometry: trace analysis of LSD analogs and metabolites in human urine.

An on-line immunoaffinity extraction-coupled column capillary liquid chromatography/tandem mass spectrometry (IAE/LC/LC/MS/MS) method is described. The system involves three columns, a 2.1-mm-i.d. protein G immunoaffinity column with noncovalently immobilized antibody specific to the analytes of interest, a packed capillary trapping column, and a packed capillary analytical column. With use of a short packed capillary trapping column, the protein G column could be operated at flow rates of 2.5-4 mL/min while the packed capillary analytical column was maintained at a flow rate of 3.5 microL/min. Human urine diluted 1:1 with phosphate-buffered saline was pumped directly onto the immunoaffinity column without pretreatment and was analyzed by electrospray mass spectrometry following the column switching process. Sample handling and transfer procedures were eliminated. The system was optimized and evaluated for the determination of LSD, its analogs, and metabolites in spiked human urine at low part-per-trillion (ppt) levels using mass spectrometric detection. LSD-positive human urine specimens from LSD users were also analyzed. Concentrations as low as 2.5 ppt of LSD and several of its analogs were detected in spiked human urine using IAE/LC/LC/MS/MS/. This is 20-fold below our previous limit of detection using solid phase extraction and LC/MS/MS.

Chromatography, Liquid↗
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↗
PubMed1994

Determination of trace impurities of peptides and alkaloids by capillary electrophoresis-ion spray mass spectrometry.

Two different mixtures have been analyzed by CE-UV-MS using selected ion monitoring (SIM) conditions to evaluate whether this technique can detect trace impurities in such mixtures. The first mixture consisted of two bioactive peptide analogues which included Lys-bradykinin (kallidin) and Met-Lys-bradykinin. The presence of 0.1% Lys-bradykinin was detected by SIM CE-MS but not by CE-UV at the 0.1% level as it migrated from the capillary column prior to the major component, Met-Lys-bradykinin. The second mixture consisted of two antibacterial alkaloids, berberine and palmatine. The presence of 0.15% palmatine was detected by CE-UV and SIM CE-MS at the 0.15% level as it migrated from the capillary column following the major component, berberine. These results suggest that SIM CE-MS offers the necessary separation efficiencies and sensitivity to provide a complementary analytical determination of trace components in such sample mixtures.

Alkaloids↗
PubMed1994

Determination of carbofuran by on-line immunoaffinity chromatography with coupled-column liquid chromatography/mass spectrometry.

Development of a new technology for combined on-line sample preparation and analyte confirmation is presented. This technology involves the use of antibodies for trace analyte extraction and enrichment directly from a complex matrix. The antibodies are used in columns designed for use with ordinary high-pressure liquid chromatographic equipment. The immunoaffinity columns are combined with conventional reversed-phase LC columns by use of column-switching techniques and coupled directly to an atmospheric pressure ionization quadrupole ion trap mass spectrometer equipped with a pneumatically assisted electrospray (ion spray) interface. A column of aldehyde-activated silica was used to prepare a column specific to carbofuran. This column demonstrated excellent specificity toward carbofuran and showed no binding of another, unrelated compound, fluometuron. Direct extraction and detection of carbofuran was demonstrated at low levels (40 pg/mL) in spiked water, but the real utility of immunoaffinity chromatography (IAC) is demonstrated by the on-line extraction and detection of carbofuran from a chemically complex, crude potato extract. Samples extracted using an IAC column indicate that superior purification is obtained with IAC in comparison with samples pumped directly onto a reversed-phase trapping column. A detection limit for carbofuran of approximately 2.5 ng/g of potato was obtained using an atmospheric pressure ionization quadrupole ion trap mass spectrometer.

Carbofuran↗
PubMed1993

A quest for oleandrin in decayed human tissue.

This forensic case taught us several lessons. First, there is a need for improved sample cleanup and treatment of severely decayed tissue samples when trace determinations of target analytes are needed. With the exception of a few reports the literature is lacking in information with regard to the most modern sample preparation techniques. Second, the coupling of LC/LC with tandem MS provides an effective means of "on-line" samples cleanup for complex sample matrices. The improvements in selectivity shown in Figure 3 reveal the analytical power available when these techniques are combined. Third, once we decided to use LC/LC/MS/MS, we were able to analyze more than 50 samples in a semi-automated fashion over approximately three days. The reliability and ruggedness of the combined techniques and equipment suggest this approach may have merit for common applications in which large numbers of biological samples (e.g., plasma and urine) must be analyzed. As a postscript, when this project was completed we proposed that the use of antibodies for isolating oleandrin and its relatives might be a more selective means for trace enrichment of the target analytes. For example, a high-pressure immunoaffinity column could have been coupled on line as column 1 in Figure 4. After pumping a relatively high volume of aqueous tissue extract through an immunoaffinity column during trapping and trace enrichment conditions, the column could be rinsed with phosphate-buffered saline. Then the pH could be lowered to unfold the antibody protein and allow release of the trapped analyte from this column with subsequent trapping on column 2 in Figure 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Mass spectrometric investigations of drug-receptor interactions.

Mass spectrometric (MS) detection of biologically important noncovalent complexes is reviewed within the scope of on-going studies on this topic from this laboratory. The merits of ion spray MS and tandem MS are demonstrated in this area with examples that show systemic studies of several receptor-ligand, enzyme-substrate, and enzyme-product complexes associated with both an established well-characterized biological system (lysozyme hydrolysis of N-acetylglucosamine) and an important modern receptor-ligand complex (FKBP-FK-506 and FKBP-rapamycin). These examples and recent applications of negative ion MS and MS/MS with DNA adducts, heme-globin complexes, and antibiotic-binding proteins suggest an exciting new area of applications for MS that have not been previously available to investigators.

Animals↗
PubMed1992

High-performance anion-exchange chromatography coupled with mass spectrometry for the determination of carbohydrates.

Methodology has been developed to couple high-performance anion-exchange chromatography (HPAE) with mass spectrometry utilizing the ion spray liquid chromatography/mass spectrometry (LC/MS) interface. Anion micro-membrane suppression (AMMS) has been used to remove the high concentrations of NaOH and NaOAc (10-400 mM total [Na+]) necessary for the separation of mixtures of monosaccharides and oligosaccharides. Post-suppressor addition of CH3CN/H2O solutions containing NH4OAc or LiOAc provided low-nanomole detection of the monosaccharides by selected ion monitoring of the cationized adducts. Maltooligosaccharide mixtures (three to seven residues) were separated and detected by the HPAE/AMMS LC/MS system in the full-scan mode. Low declustering potentials (35 V) in the LC/MS API source afforded intact singly and doubly charge ammoniated and diammoniated adducts of the sugars. Higher declustering potentials (65 V) produced abundant fragmentation of the ammoniated adducts. The corresponding lithiated and dilithiated species produced intact molecule ion species at higher declustering potentials. The endo H-released oligomannose species from RNase B were determined by the HPAE/AMMS LC/MS system as ammoniated adducts and resulting fragment ions with a high declustering potential (95 V) in the full-scan mode.

Carbohydrates↗
PubMed1989

Rapid determination of methandrostenolone in equine urine by isotope dilution liquid chromatography-tandem mass spectrometry.

Urine samples were spiked with [17-methyl-2H3]methandrostenolone as internal standard and extracted with a mixture of dichloromethane and cyclohexane. The organic phase was concentrated and injected onto a short octyl-silica column (30 mm x 4.6 mm I.D.) for separation of methandrostenolone and 17-epimethandrostenolone. The effluent from the column was connected to a Sciex TAGA 6000E triple quadrupole mass spectrometer equipped with an atmospheric pressure ion source for sampling of ions generated by a heated pneumatic nebulizer with corona discharge ionization. This ion source produced abundant [M + H]+ ions and a weak fragment ion due to loss of water. The protonated molecular ions at m/z 301 and 304 for methandrostenolone, 17-epimethandrostenolone and the internal standard were transmitted to the second quadrupole for collision-induced dissociation. Quantification was obtained by selected reaction monitoring of three daughter ions. Methandrostenolone and 17-epimethandrostenolone were separated by liquid chromatography, but gave identical mass spectra. The method detection limit by injection of a urine extract corresponding to 2.8 ml urine was 180 pg/ml at the 99% confidence level. The precision (relative standard deviation) was 3% at the 16 ng/ml level and the linear dynamic range was at least 3 orders of magnitude. Screening for unknown metabolites in urine after administration of methandrostenolone to horses and humans was accomplished by a parent ion scan of m/z 121, a fragment corresponding to the intact A-ring of the steroids.

Animals↗
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↗