Biomedical subjects

T Kraemer

Publications and source records attributed to T Kraemer.

25 records · Page 2Linked to original sources

PubMed1997

Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) in toxicological analysis. Studies on the detection of clobenzorex and its metabolites within a systematic toxicological analysis procedure by GC-MS and by immunoassay and studies on the detection of alpha- and beta-amanitin in urine by atmospheric pressure ionization electrospray LC-MS.

GC-MS is the method of choice for toxicological analysis of toxicants volatile in GC while non-volatile and/or thermally labile toxicants need LC-MS for their determination. Studies are presented on the toxicological detection of the amphetamine-like anorectic clobenzorex in urine by GC-MS after acid hydrolysis, extraction and acetylation and by fluorescence polarization immunoassay (FPIA, TDx (meth)amphetamine II). After ingestion of 60 mg of clobenzorex, the parent compound and/or its metabolites could be detected by GC-MS for up to 84 h or by FPIA for up to 60 h. Since clobenzorex shows no cross-reactivity with the used immunoassay, the N-dealkylated metabolite amphetamine is responsible for the positive TDx results. The intake of clobenzorex instead of amphetamine can be differentiated by GC-MS detection of hydroxyclobenzorex which is detectable for at least as long as amphetamine. In addition, the described GC-MS procedure allows the simultaneous detection of most of the toxicologically relevant drugs. Furthermore, studies are described on the atmospheric pressure ionization electrospray LC-MS detection of alpha- and beta-amanitin, toxic peptides of amanita mushrooms, in urine after solid-phase extraction on RP-18 columns. Using the single ion monitoring mode with the ions m/z 919 and 920 the amanitins could be detected down to 10 ng/ml of urine which allows us to diagnose intoxications with amanita mushrooms.

Amanitins↗

PubMed1997

Analytical development for low molecular weight xenobiotic compounds.

Specific and sensitive detection or precise quantification of xenobiotics in biosamples (e.g. blood, urine, saliva, sweat, hair) are great challenges in analytical toxicology. GC-MS is the most sensitive, specific and universal analytical method for low mass xenobiotics. Precise quantification can be performed using the selected ion mode (SIM) and stable isotopes as internal standards. Negative chemical ionization (NCI) can improve severalfold the sensitivity for the determination of compounds with electronegative sites (e.g. halogens). For screening and identification of most of the basic and neutral drugs (e.g. drugs of abuse, psychotropics, hypnotics, analgesics, cardiacs) in urine, a systematic toxicological analysis procedure (STA) was developed using GC-MS after acid hydrolysis, extraction and acetylation. for detection of acidic xenobiotics (e.g. anticoagulants, ACE inhibitors, diuretics, antirheumatics) in urine, a further GC-MS procedure was developed using extractive alkylation. For the detection of non-volatile xenobiotics (e.g. toxic peptides like alpha- and beta-amanitin or phase II metabolites) electrospray LC-MS procedures were developed. The procedures and examples show that in analytical toxicology GC-MS is the method of choice for low mass xenobiotics while LC-MS is that for non-volatiles.

Chromatography, High Pressure Liquid↗

PubMed1992

Toxicological detection of selegiline and its metabolites in urine using fluorescence polarization immunoassay (FPIA) and gas chromatography-mass spectrometry (GC-MS) and differentiation by enantioselective GC-MS of the intake of selegiline from abuse of methamphetamine or amphetamine.

Selegiline (R(-)-N-methyl-N-(1-phenyl-2-propyl)-2-propinylamine), a selective MAO-B inhibitor used as an antiparkinsonian, is excreted in urine as N-desmethyl selegiline (norselegiline), R(-)-methamphetamine (R(-)-MA), R(-)-amphetamine (R(-)-AM) and their conjugated p-hydroxy derivatives. We found that the fluorescence polarization immunoassays (FPIA) TDx amphetamine/methamphetamine II (AM/MA II) and TDx amphetamine class (AM class) lead to positive results for up to 2 days after a single oral dose of 10 mg selegiline (detection limit: 0.1 mg/l, each). Every urine specimen from long term selegiline patients (10 mg/day) showed positive TDx results during the selegiline regimen. Positive TDx results were confirmed using gas chromatography-mass spectrometry (GC-MS). Selegiline metabolites, particularly MA, could be detected in urine for up to 7 days after intake of a single oral dose of 10 mg selegiline (detection limit: 0.01 mg/l for MA and AM). Norselegiline, the only specific selegiline metabolite, was only detectable for about 12 h. Moreover, norselegiline was not detected in all urine samples from long term selegiline patients (10 mg/day). Since differentiation of selegiline intake from MA/AM abuse by detecting norselegiline was not possible in most cases, an enantioselective GC-MS procedure was developed. It allowed differentiation of the enantiomers of the selegiline metabolites and thereby separation of selegiline intake (only R(-)-enantiomers) from methamphetamine and/or amphetamine abuse (racemates or S(+)-enantiomers). After derivatization with S(-)-N-trifluoroacetyl-prolyl chloride (TPC), the two enantiomers of MA and AM were each separated as diastereomers employing the routinely used achiral GC capillary.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗

PubMedDate not supplied

Screening procedure for detection of non-steroidal anti-inflammatory drugs and their metabolites in urine as part of a systematic toxicological analysis procedure for acidic drugs and poisons by gas chromatography-mass spectrometry after extractive methylation.

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used as analgesic and anti-rheumatic drugs, and they are often misused. A gas chromatographic-mass spectrometric (GC-MS) screening procedure was developed for their detection in urine as part of a systematic toxicological analysis procedure for acidic drugs and poisons after extractive methylation. The compounds were separated by capillary GC and identified by computerized MS in the full-scan mode. Using mass chromatography with the ions m/z 119, 135, 139, 152, 165, 229, 244, 266, 272, and 326, the possible presence of NSAIDs and their metabolites could be indicated. The identity of positive signals in such mass chromatograms was confirmed by comparison of the peaks underlying full mass spectra with the reference spectra recorded during this study. This method allowed the detection of therapeutic concentrations of acemetacin, acetaminophen (paracetamol), acetylsalicylic acid, diclofenac, diflunisal, etodolac, fenbufen, fenoprofen, flufenamic acid, flurbiprofen, ibuprofen, indometacin, kebuzone, ketoprofen, lonazolac, meclofenamic acid, mefenamic acid, mofebutazone, naproxen, niflumic acid, phenylbutazone, suxibuzone, tiaprofenic acid, tolfenamic acid, and tolmetin in urine samples. The overall recoveries of the different NSAIDs ranged between 50 and 80% with coefficients of variation of less than 15% (n = 5), and the limits of detection of the different NSAIDs were between 10 and 50 ng/mL (S/N = 3) in the full-scan mode. Extractive methylation has proved to be a versatile method for STA of various acidic drugs, poisons, and their metabolites in urine. It has also successfully been used for plasma analysis.

Acids↗

PubMedDate not supplied

The antispasmodic drug mebeverine leads to positive amphetamine results by fluorescence polarization immunoassay (FPIA)--studies on the toxicological analysis of urine by FPIA and GC-MS.

Mebeverine (Duspatal, MB), an antispasmodic drug, is the veratric acid ester of 4-[ethyl-[2-(4-methoxyphenyl)-1-methylethyl]amino]butan-1-ol (MB-OH), which is a N-substituted ethylamphetamine derivative. MB is metabolized via ester hydrolysis to MB alcohol (MB-OH) and veratric acid. N-Dehydroxybutylation leads to methoxyethylamphetamine (MO-EA) and, after O-demethylation, to hydroxy EA (HO-EA). N-Bisdealkylation leads to p-methoxyamphetamine (PMA). MO-EA and PMA are also known as designer drugs. Fluorescence polarization immunoassay (FPIA) and gas chromatographic-mass spectrometric studies on the toxicological analysis of MB after ingestion of a single 405-mg oral dose of MB were performed. We could show that intake of MB leads to positive FPIA results for amphetamine. The N-dehydroxybutyl metabolites of MB, MO-EA, HO-EA, and the bis-dealkyl metabolite PMA should be responsible for the positive immunoassay results. Using our systematic toxicological analysis procedure, every positive amphetamine immunoassay could be explained by detection of MO-EA, HO-EA, and/or PMA. Misinterpretation of the origin of MO-EA, HO-EA, or PMA can be avoided by detecting the specific (non-dehydroxybutylated) metabolites of MB, which are excreted for a much longer time after ingestion.

Amphetamine↗

PubMedDate not supplied

Concentrations and ratios of amphetamine, methamphetamine, MDA, MDMA, and MDEA enantiomers determined in plasma samples from clinical toxicology and driving under the influence of drugs cases by GC-NICI-MS.

Enantiomers of amphetamine (AM), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxyethylamphetamine (MDEA) exhibit different pharmacological properties. This may be important for the interpretation of analytical results. Plasma samples were analyzed using validated negative ion chemical ionization gas chromatography-mass spectrometry procedures. The results for clinical toxicology cases, divided into screening (SCR) and intoxication (ITX) cases, and those of driving under the influence of drugs (DUID) cases were compared. The concentrations of all enantiomers, except R-(-)-MDA and R-(-)- and S-(+)-MA, in the SCR samples were lower than in ITX and DUID samples. Differences between concentrations in ITX and DUID samples were only significant for both enantiomers of AM (DUID higher). These findings suggested impairment in drugged drivers. Different enantiomer ratios (R vs. S) were found for AM between DUID and SCR samples, for MDMA between ITX and SCR samples, and for MDA between DUID and ITX and DUID and SCR samples. Higher MDMA enantiomer ratios in SCR compared to ITX samples are in accordance with a previously described increase of those ratios over time, possibly allowing differentiation of recent from nonrecent ingestion. Pharmacokinetic analysis of a MDMA poisoning yielded elimination half-lives of 6.0 h for R-(-)-MDMA and 4.1 h for S-(+)-MDMA. The enantiomer ratios rose exponentially over time.

3,4-Methylenedioxyamphetamine↗

PubMedDate not supplied

Toxicological detection of ibuprofen and its metabolites in urine using gas chromatography-mass spectrometry (GC-MS).

Ibuprofen, (R,S)-2-(4-isobutylphenyl)propionic acid, is a non-opioid analgesic which is prescription-free available in pharmacies since 1989. Consequently, use and misuse of this analgesic strongly increased. For diagnosis of an abuse or an intoxication a GC-MS procedure was developed for the toxicological detection of ibuprofen in urine after extraction at pH 5 and methylation. For screening, mass chromatography with the masses m/z 220, 161 (methylated ibuprofen), 178, 119 (methylated hydroxy ibuprofen) and 264, 145 (methylated carboxy ibuprofen) was used to indicate the presence of these compounds in urine. The identity of the peaks underlying full mass spectra was confirmed by comparison with the reference spectra using computer library search. After ingestion of one single oral dose of 400 mg ibuprofen, the parent compound could be detected for 27 to 34 h, hydroxy ibuprofen for 34 to 40 h and carboxy ibuprofen for 5 to 6 d. Using this procedure ibuprofen which was taken even several days ago could be detected.

Biotransformation↗