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Biomedical subjects

W Weinmann

Publications and source records attributed to W Weinmann.

At least 19 recordsLinked to original sources
PubMed2001

Fast confirmation of 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THC-COOH) in urine by LC/MS/MS using negative atmospheric-pressure chemical ionisation (APCI).

A fast method using automated solid-phase extraction (SPE) and short-column liquid-chromatography coupled to tandem mass-spectrometry (LC/MS/MS) with negative atmospheric-pressure chemical ionisation (APCI) has been developed for the confirmation of 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THC-COOH) in urine samples. This highly specific method which combines chromatographic separation and MS/MS-analysis can be used for the confirmation of positive immunoassay results with a NIDA cut-off of 15ng/ml. The conjugates of THC-COOH were hydrolysed prior to SPE, and a standard SPE was performed using C18-SPE columns. No derivatisation of the extracts was needed as in GC/MS analysis, and the LC run-time was 6.5min by gradient elution with a retention time of 2.4min. Linearity of calibration was obtained in the range between 0 and 500ng/ml (correlation coefficient R(2)=0.998). Using linear regression (0-50ng/ml) the limit of detection (LOD) was 2.0ng/ml and the limit of quantitation (LOQ) was 5.1ng/ml; day-to-day reproducibility and precision were tested at 15 and 250ng/ml and were 13.4ng/ml+/-3.3% and 255.8ng/ml+/-4.5%, respectively.

Chromatography, Liquid↗
PubMed2001

Tune compounds for electrospray ionisation/in-source collision-induced dissociation with mass spectral library searching.

Haloperidol, paracetamol, metronidazole and metamizole have been tested as tune compounds for electrospray ionisation in-source collision-induced dissociation MS (ESI-CID-MS) with two different mass spectrometers (Sciex API 365 and Agilent 1100 MSD SL). The different electrospray sources of API 365 and MSD 1100 SL consist of an orifice with nitrogen curtain gas and a capillary interface, respectively. In-source CID occurs in both interfaces in front of the skimmers, which separate a region with a vacuum of approximately 300 Pa and the high vacuum (<10(-3) Pa). Comparison of the breakdown curves of selected tune compounds, depending on collision energy (orifice or fragmentor voltage), showed, that very similar fragmentation can be obtained with both instruments, when adjusting the fragmentor voltage of the MSD 1100 SL to higher values than the orifice voltage of the API 365. For three energy levels--low, medium and high--the corresponding voltages were 20, 50 and 80 V for the API 365 and 110, 190, 230 V for the MSD 1100 SL. These voltages resulted in the most similar spectra for haloperidol and paracetamol with both instruments. The comparison of ESI-CID-MS of all tune compounds at three energy levels showed, that - despite variations in relative ion abundances - all significant ions were present in one of the three CID spectra. Therefore, mass spectral library searching of an ESI-CID-MS library set-up with one of the two instruments should be possible with the other instrument after adjusting the CID energies by means of at least two tune compounds such as haloperidol and paracetamol, metronidazole or metamizole.

Acetaminophen↗
PubMed2001

Prevalence of nicotine consumption in drug deaths.

One hundred consecutive drug death victims autopsied at the Institute of Forensic Medicine, University of Freiburg, between 1995 and 1997 were studied retrospectively as to whether the drug users had also consumed nicotine. The study included histological examination of the lung tissue for smoker cells and radioimmunological as well as GC-MS assays of the urine for cotinine, the primary metabolite of nicotine. It was found that 98 out of 100 drug victims had consumed nicotine in addition to illicit drugs or replacements. Yellowish-brown discolorations on the middle and index fingers were discernible in 44 drug victims, whereas fresh or scarred burns due to glowing cigarettes were found in six deceased drug consumers. Diseases of the bronchial system typical of heavy smokers were seen in 35 cases. Siderophages could be demonstrated in 17 of the 100 drug deaths.

Adolescent↗
PubMed2001

Tuning compounds for electrospray ionization/in-source collision-induced dissociation and mass spectra library searching.

Tuning compounds for positive and negative electrospray ionization (ESI) were tested for the tuning of in-source collision-induced dissociation (ESI/CID) with three types of SCIEX API instruments (API 365, 2000 and 3000) in the single-quadrupole mode. The vacuum interfaces of these instruments differ slightly in geometry, but the principles of ionization and solvent evaporation by nebulizer and curtain gases, orifice and skimmer are identical. For comparison of in-source CID, breakdown curves of haloperidol, paracetamol, metronidazole and metamizole were acquired by increasing the orifice voltages. The API 2000 and 3000 required higher orifice voltages than did the API 365 to induce a similar degree of fragmentation of the protonated or deprotonated molecules to characteristic fragment ions. This increase of orifice voltage could be demonstrated with each of the four compounds tested by a shift of the maxima of the breakdown curves to higher orifice voltages. A procedure with three collision energy (CE) levels for drug identification with a mass spectra library set up with an API 365 therefore required an adjustment of the orifice voltages to higher values when being transferred to an API 2000 or API 3000. The corresponding orifice voltages for the three instruments were 20/50/80 V (API 365), 30/90/130 V (API 2000) and 40/80/120 V (API 3000). However, a change in orifice voltage of +/-10 V (with the API 2000 and 3000) hardly influenced the fit values of a library search for each single CE level. For adjusting orifice voltages with different instruments, a tuning procedure with haloperidol and paracetamol is presented. With this tuning procedure an ESI/CID mass spectra library set up for API 365 and API 150 could also be used for drug identification with an API 2000 and an API 3000 with good library search results.

Chromatography, High Pressure Liquid↗
PubMed2001

Post-mortem detection and identification of sildenafil (Viagra) and its metabolites by LC/MS and LC/MS/MS.

The highly putrefied corpse of an 80-year-old man was found in the apartment which he had rented to a prostitute. A package of Viagra 25 was found beside the corpse and three tablets were missing. Autopsy revealed severe coronary artery sclerosis as well as signs of previous myocardial infarctions. For the detection and identification of sildenafil and three metabolites in urine and tissue samples, solid-phase extraction, LC/MS and MS/MS methods were developed. Blood was not available for toxicological analysis due to the putrefaction. For method development, urine from a volunteer who had ingested 25 mg sildenafil was collected over 8 h, and three metabolites were identified by MS/MS. These metabolites were also found in the victim's urine. These findings prove that sildenafil was taken some time prior to death, but the causality of sildenafil intake and fatal cardiac failure could not be proven, since no blood was available for analysis. However, the administration of sildenafil was contraindicated due to several previous myocardial infarctions.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Identification of selected psychopharmaceuticals and their metabolites in hair by LC/ESI-CID/MS and LC/MS/MS.

Hair samples of patients of psychiatry and hair samples of suicide cases were analysed by liquid-chromatography/ionspray-mass spectrometry (LC/MS) for antidepressants and neuroleptics. Electrospray ionisation (ESI) with in-source collision induced dissociation (ESI/CID) and tandem-mass spectrometry (MS/MS) were used for drug and metabolite identification. Mass spectra library searching was performed using an ESI/CID mass spectra library and a MS/MS spectra library. Furthermore, extracted ion chromatograms were used for the detection of N-desmethyl-metabolites, which were also identified by their fragment-ion spectra. Three examples using these methods are shown: The tricyclic antidepressant maprotiline, the selective serotonin receptor inhibitor (SSRI) citalopram and their desmethylmetabolites as well as the neuroleptic pipamperone were detected and identified in hair extracts. For extraction powdered hair was treated by ultrasonication in methanol and solid-phase extraction was used for sample clean-up prior to LC/MS or MS/MS analysis. These examples demonstrate the power of LC/MS and LC/MS/MS for the detection and identification of drugs in hair extracts using full-scan mode and ESI/CID with library searching or using highly selective LC/MS/MS-analysis with library searching or in multiple reaction monitoring mode.

Antidepressive Agents, Second-Generation↗
PubMed2000

Simultaneous determination of THC-COOH and THC-COOH-glucuronide in urine samples by LC/MS/MS.

A fast method using liquid-liquid extraction and HPLC/tandem-mass spectrometry (LC/MS/MS) was developed for the simultaneous detection of 11-Nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid beta-glucuronide (THC-COOH-glucuronide) and 11-Nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in urine samples. This highly specific method, which combines chromatographic separation and MS/MS analysis, can be used for the confirmation of positive immunoassay results even without hydrolysis of the sample or derivatisation of extracts. Liquid-liquid extraction was optimised: with ethylacetate/diethylether (1:1, v/v) THC-COOH-glucuronide and THC-COOH could be extracted in one step. Molecular ions of the glucuronide (MH(+), m/z 521) and THC-COOH (MH(+), m/z 345) were generated using a PE/SCIEX turboionspray source in positive ionisation mode; specific fragmentation was performed in the collision cell of an API 365 triple-quadrupole mass spectrometer and yielded major fragments at m/z 345 (for THC-COOH-glucuronide) and m/z 327 as well as m/z 299 for both cannabinoids. Chromatographic separation was performed using a reversed-phase C8 column and gradient elution with 0.1% formic acid/1 mM ammonium formate and acetonitrile/0.1% formic acid. Retention times were 22.2 min for the glucuronide and 26.8 min for THC-COOH. After enzymatic hydrolysis of urine samples with beta-glucuronidase/arylsulfatase (37 degrees C, 5 h), THC-COOH-glucuronide was no longer detectable by LC/MS/MS in urine samples. However, the THC-COOH concentration was increased. For quantitation of THC-COOH, THC-COOH-D(3) was added to the urine samples as internal standard prior to analysis. From the difference of THC-COOH in the native urine and urine after enzymatic hydrolysis, molar concentration ratios of THC-COOH-glucuronide/THC-COOH in urine samples of cannabis users were determined and found to be between 1.3 and 4.5.

Chromatography, High Pressure Liquid↗
PubMed2000

Identification of lorazepam and sildenafil as examples for the application of LC/ionspray-MS and MS-MS with mass spectra library searching in forensic toxicology.

A mass spectra (MS) library using in-source collision induced dissociation (ESI-CID) as well as a tandem-mass spectra (MS-MS) library with product ion spectra of drugs has recently been developed with a triple-quadrupole ionspray mass spectrometer [1,2]. For the ESI-CID MS library, single-quadrupole mode and for the MS-MS library triple-quadrupole mode have been used. These mass spectra libraries were applied successfully for the general-unknown screening for drugs and metabolites in serum and urine with liquid-chromatography-mass spectrometry (LC-MS) using a PE/SCIEX API 365 with a turboionspray source. As examples, the identification of lorazepam and lorazepam-glucuronide in a serum extract and the identification of sildenafil and alkyloxidated sildenafil in urine are presented here.

Databases, Factual↗
PubMed2000

Automated solid-phase extraction and two-step derivatisation for simultaneous analysis of basic illicit drugs in serum by GC/MS.

A combination of automated solid-phase extraction (SPE) and subsequent two-step derivatisation has been developed for the simultaneous analysis of basic drugs of abuse and cocaine metabolites in serum samples. Substances included in this procedure are morphine, codeine, methadone, cocaine, benzoylecgonine, methylecgonine, amphetamine, methamphetamine, MDMA, MDEA and MDA. SPE with mixed-mode cartridges (RP-C8 and cation-exchange) was fully automated with a Zymark RapidTrace SPE robot. GC/MS analysis was performed after derivatisation with a new two-step reaction by trifluoroacetic anhydride and 2,2,3,3,3-pentafluoropropanol. High recoveries (> 85%) with high reproducibility (CV 1.1-3.8%) were found for all drugs. High correlation coefficients (r > 0.998) were obtained due to the addition of deuterated standards prior to extraction. Experience obtained over 2 years of applying this method to drug analysis in serum is discussed.

Automation↗
PubMed1999

Spectrophotometric evaluation of postmortem lividity.

Under low ambient temperatures normally bluish postmortem lividity adopts a bright red or pink colour due to resaturation of haemoglobin with O2. The most important differential diagnosis in the presence of pink hypostasis is carbon monoxide poisoning. To answer the question if objective measuring methods allow differentiation of hypostasis with regard to cold exposition or carbon monoxide poisoning, spectrophotometric measurements were performed and the colorimetric measures as well as the spectral reflectance curves of the postmortem lividity were determined. The colorimetric measures CIE-L*a*b* showed similar values for all bright red livores mortis; differentiation between CO intoxication and cold exposition was not possible. Reflectance curves of pink hypostasis after cold storage showed the typical pattern of O2-rich blood with reflectance minima at wavelengths 541 nm and 576 nm and a reflectance maximum at 560 nm. Pink hypostasis because of carbon monoxide poisoning showed a shift of the reflectance maximum toward 555 nm and a flattened curve in all cases with COHb concentrations exceeding 52%, whereas these changes were not regularly observed with lower COHb levels.

Adolescent↗
PubMed1999

Screening for drugs in serum by electrospray ionization/collision-induced dissociation and library searching.

Factors influencing in-source collision-induced dissociation (ESI/CID) of organic molecules in a Perkin-Elmer/SCIEX ionspray source have been investigated. Breakdown curves of four drugs and organic compounds were acquired by monitoring the intensities of MH+ and specific fragment ions while ramping the orifice voltage. Haloperidol, diazepam, 1,4-acetamido-acetoxybenzene and diacetamido-1,2-benzene were found to be substances with characteristic breakdown curves, with maximums and points of intersection at orifice voltages between 20 and 70 V. The breakdown curves of haloperidol were used for comparison of ESI/CID with ionspray and turboionspray sources on three PE/SCIEX-API instruments. Using standardized source parameters and mass resolution, very similar fragmentation graphs were obtained for haloperidol with all instruments. Infusion of varying concentrations of haloperidol (0.1 to 10 micrograms/mL with ionspray, and 0.01 to 1 microgram/mL with turboionspray) yielded comparable breakdown curves. With turboionspray, a preconcentration of the aerosol occurred, yielding higher ion abundances. Solvent pH and the ratio of aqueous ammonium formate/acetonitrile had minor effects on the degree of fragmentation of haloperidol in a wide range. With these preconditions, a currently expanding mass spectral library of 400 drugs was set up by liquid chromatography/mass spectrometry with alternating orifice voltages (20, 50, and 80 V, respectively) in a looped experiment. An example of drug identification in a patient's serum with library search is shown.

Chromatography, High Pressure Liquid↗
PubMed1998

Lethal monointoxication by overdosage of MDEA.

A 19-year-old man died after the intake of ten tablets of Ecstasy containing 3,4-methyl-enedioxy-N-ethylamphetamine (MDEA) as the main active ingredient. According to an eyewitness the symptoms of intoxication were strong sweating, sudden aggressiveness followed by hallucinations, subsequent failure of motoric coordination, severe spasms of arms and back, complete depression of the respiratory system, unconsciousness, and collapse. Resuscitation by an emergency doctor failed. Major autopsy findings were severe vascular congestion of all internal organs, liquid post-mortem blood, numerous subpleural and subepicardial petechial haemorrhages. By GC/MS analysis, MDEA was found in large amounts in serum (12 mg/l in femoral vein, 22 mg/l in heart blood serum), urine (201 mg/l), brain (18 to 28 mg/l) and in other tissue samples. Scalp-hair was highly positive for MDEA (17 ng/mg). Besides MDEA and its metabolites only trace amounts of MDMA could be found in urine and blood; no other drugs were detected. It can be concluded that the cause of death was a monointoxication by overdosage of MDEA.

Adult↗
PubMed1994

Isolation of hydrophobic lipoproteins in organic solvents by pressure-assisted capillary electrophoresis for subsequent mass spectrometric characterization.

Two capillary electrophoretic (CE) separation techniques with either simultaneous solvent flow induced by hydrostatic pressure or CE followed by low pressurization with helium were developed for the analysis of extremely hydrophobic proteins, such as the lung surfactant protein SP-C. For both related procedures, buffer solutions containing up to 70% of 2-propanol were used for the capillary electrophoretic separation. This high concentration of organic co-solvent, needed to solubilize the protein, dramatically reduces the electroosmotic flow (EOF) in aminopropyltrimethoxysilane-treated fused-silica capillaries. Because the EOF was insufficient to elute the separated analytes from the capillary, two "pressure-assisted" CE techniques were developed. An additional flow to elute the separated analytes was produced either by raising the inlet of the capillary or by helium pressure. Using the pressurization procedure a baseline separation of the SP-C protein and its dimeric complex was obtained in a 55-minute electrophoretic run, followed by pressure elution of the analyte to the detector. The present combination of pressurization and capillary electrophoresis does not require any detergents or involatile buffer additives, which are usually needed to solubilize extremely hydrophobic lipoproteins. It is therefore applicable to on-line coupling with electrospray mass spectrometry for the direct structural characterization of hydrophobic proteins.

Amino Acid Sequence↗
PubMed1994

Capillary electrophoresis combined with 252Cf plasma desorption and electrospray mass spectrometry for the structural characterization of hydrophobic polypeptides using organic solvents.

Capillary electrophoresis (CE) conditions have been developed for the separation of hydrophobic polypeptides, such as fatty acid-acylated peptides, and their subsequent structural identification by 252Cf plasma desorption (PDMS) and electrospray mass spectrometry (ESMS). Salt- and detergent-free aqueous acetic acid buffers containing up to 20% 2-propanol or 25% acetonitrile were employed for CE separations of hydrophobic peptides with (i) untreated, and (ii) 3-aminopropyltrimethoxysilane-derived fused silica capillaries. For both capillary types, electroosmotic flow rates suitable for sample isolation and transfer were determined, and CE separations of polypeptide mixtures were compared for aqueous buffers containing 2-propanol or acetonitrile. For the mass spectrometric identification of CE-separated peptides, a sheath flow sample isolation method was developed for subsequent transfer to PDMS. This procedure enabled the efficient isolation of peptide fractions for PDMS analysis, or alternative microanalytical techniques.

Amino Acid Sequence↗
PubMed1993

Structural characterization of polypeptides and proteins by combination of capillary electrophoresis and (252)Cf plasma desorption mass spectrometry.

An efficient and sensitive method for the isolation and transfer of peptides and proteins from capillary zone electrophoresis separation for subsequent analysis by 252Cf plasma desorption mass spectrometry was developed. Sample isolation on to nitrocellulose-coated targets for mass spectrometric analysis is performed by using a stainless-steel microtube pre-filled with aqueous buffer solution, to which the capillary end is connected, and the peptide is collected by applying a suitable transfer voltage according to the separation voltage. Low-and sub-picomolar sample amounts were isolated with high transfer efficiency and reproducibility, without the necessity for independent determination of electroosmotic flow-rates. Plasma desorption mass spectra of several peptides and proteins showed predominantly intact molecular ions; however, for several peptides partial oxidative modification was found which can be accounted for by the electrophoretic separation and/or transfer conditions. First applications to peptides and proteins show the feasibility of this off-line combination for primary structure characterization, such as by in situ chemical modification and enzymatic proteolysis reactions on the sample target prior to mass spectrometric analysis.

Amino Acid Sequence↗
PubMed1983

Safety and potency aspects in the preparation of an experimental HBsAg vaccine.

No experimental setting is available to exclude residual infectivity in HBsAg vaccines derived from human plasma. Thus, safety can be achieved only by means of their preparation. To reduce infectivity of the starting material, only plasma from healthy anti-HBe positive donors was used. In the FRG, 50% of all healthy HBsAg carriers with anti-HBe have a suitable serum level of 5 to 20 micrograms/ml. The purification procedure removed hepatitis B virus by a factor greater than 10(4). The purified product contained only the HBsAg proteins and no serum protein, as shown by SDS gel electrophoresis. The pure HBsAg was treated with formalin 1:500 at 37 degrees C for 4 days. A loss of 30 to 50% antigenicity was tolerated to achieve the highest possible destruction of known and unknown infectious agents. After inactivation, the HBsAg was bound to aluminium hydroxide gel. The gel was washed repeatedly to remove the formalin. Doses of 40 micrograms or 20 micrograms absorbed HBsAg protein were given to greater than 2500 persons without serious side effects. In greater than 97% anti-HBs was formed with a median titer of 1900 I.U./ml.

Follow-Up Studies↗