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At least 1,081 records · Page 60Linked to original sources
PubMed2000

Capillary electrochromatography-electrospray ionization mass spectrometry for the qualitative investigation of the drug etodolac and its metabolites in biological samples.

On-line coupling of capillary electrochromatography (CEC) with electrospray ionization (ESI) mass spectrometry (MS) was used for the qualitative investigation of the biotransformation of the non-steroidal anti-inflammatory drug etodolac. The coupling of this electro-driven separation technique with mass spectrometry allowed us to demonstrate the presence of different metabolites of etodolac extracted from human urine.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1988

High-performance liquid chromatographic assay for the simultaneous monitoring of mefloquine and its acid metabolite in biological samples using protein precipitation and ion-pair extraction.

A high-performance liquid chromatographic (HPLC) method is presented for the simultaneous determination of mefloquine and its acid metabolite in plasma and whole blood. Plasma and whole blood are deproteinized with a combination of zinc and acetonitrile before extraction. Mefloquine and its acid metabolite are extracted simultaneously at pH 4 by methyl tert.-butyl ether, where mefloquine is extracted as an ion pair with heptanesulphonate. After evaporation of the organic phase, the residue is dissolved in mobile phase and injected on to the chromatographic column. A reversed-phase column (Spherisorb ODS-1) is used with acetonitrile-phosphate buffer (0.1 mol/l, pH 2.5) (42:58) containing 40 mmol/l perchlorate as the mobile phase. N,N-Dioctylamine was added to the mobile phase to give a concentration of 0.1% and the pH was adjusted to 2.3-2.7 with concentrated phosphoric acid. The method permits the determination of 0.10 mumol/l (30 ng/ml) mefloquine and its acid metabolite in plasma. The coefficient of variation was 5-6% at the therapeutic level (mefloquine 1-4 mumol/l, its carboxylic metabolite 2-6 mumol/l) in 0.5-ml samples. An alternative method is also described with a similar clean-up procedure that uses protein precipitation with zinc-acetonitrile as a sample pretreatment for therapeutic monitoring of mefloquine and metabolite in plasma and whole blood. Using this method, 0.25 mumol/l mefloquine and its metabolite can be determined. The results from the two methods correlate well.

Animals↗
PubMed1980

Determination of methenamine in biological samples by gas-liquid chromatography.

Methenamine (hexamethylenetetramine), a urinary disinfectant, was determined in human plasma and urine by gas-liquid chromatography with a short (10 m) open-bore glass capillary column (split ratio 1:20) and nitrogen-selective detector. An almost quantitative recovery (92.1%) was achieved by simple dilution of water-containing samples (0.5 ml) with acetone (4.5 ml). After centrifugation an aliquot (2 microliter) of the supernatant was injected into the gas chromatograph. Selectivity and sensitivity of the nitrogen detector allowed the quantitation of unchanged methenamine in plasma and urine up to 24 h after a single therapeutic dose of 1 g. Reproducibility of the method was 7.6 and 2.1% (C.V.) in serum and urine, respectively. The time required for the analysis of one sample was approx. 2 min. Due to the simple extraction and short analysis time it was possible to analyze the samples concurrently with sample taking. Absorption of standard tablets and an enterosoluble preparation of methenamine hippurate was compared.

Adult↗
PubMed1980

Analysis of salsolinol and salsoline in biological samples using deuterium-labelled internal standards and gas chromatography--mass spectrometry.

Salsolinol and salsoline were labelled with deuterium using an acidic exchange reaction in 2HCl--2H2O. Two deuterium atoms were incorporated in both compounds. The deuterium-labelled salsolinol and salsoline were used as internal standards to determine picomol amounts of the corresponding unlabelled compound in the urine, cerebrospinal fluid, brain and liver. The salsolinol was purified on alumina and salsoline collected in the effluent. The compounds were analysed as their pentafluoropropionyl derivatives by gas chromatography on a 1% OV-17 column and were selectively detected with electron-impact mass spectrometry at the molecular ions M+ and M+--15. With human urine the precision of the methods were +/- 4.9% (coefficient of variation, n = 10) for salsolinol and +/- 2.2% for salsoline at a level of 0.100 nmol/ml. Administration of salsolinol to rats intraperitoneally (0.4 mmol/kg) resulted in levels of 1--2 nmol/g in striatum and limbic forebrain after 2 h, whereas the corresponding liver values were about 550 nmol/g. Control animals showed salsolinol values in liver of about 2 nmol/g and in striatum and limbic forebrain 1 nmol/g tissue.

Animals↗
PubMed1980

Quantitative analysis of histamine in biological samples by gas chromatography--mass spectrometry.

A mass fragmentographic method for the quantitative analysis of histamine in the supernatant from antigen-challenged leukocytes, whole blood, and urine is described. Histamine labeled with two 15N atoms was synthesized and added to the sample as an internal standard. N alpha-Heptafluorobutyryl-N tau-ethoxycarbonylhistamine was prepared for mass fragmentographic analysis and the molecular ions at m/z 379 and 381 were used for monitoring histamine and 15N2-labeled histamine, respectively. The quantitation limit of histamine was 2 ng by this method. The experimental error of the method was less than 7% at the level of 5 ng in the supernatant from antigen-challenged leukocytes. The value obtained by this method correlated well with that from radioisotopic enzymatic assay (r=0.990).

Gas Chromatography-Mass Spectrometry↗
PubMed1990

Analysis of diethylstilbestrol, dienestrol and hexestrol in biological samples by immunoaffinity extraction and gas chromatography-negative-ion chemical ionization mass spectrometry.

A method has been developed for the detection of diethylstilbestrol, together with dienestrol and hexestrol, using extraction with a single immunoaffinity column containing antibodies raised against diethylstilbestrol, followed by gas chromatography-negative-ion chemical ionization mass spectrometry. Immunoaffinity columns were prepared by coupling immunoglobulin G fractions obtained from rabbit antisera with a Sepharose matrix. The immunizing agent was synthesized by introducing a carboxyl group into the diethylstilbestrol molecule and coupling this product to bovine serum albumin. The columns were used for immunoadsorption of diethylstilbestrol and other estrogens, after dilution of samples with phosphate buffer, and were eluted with acetone-water (95:5 v/v). A derivatization method suitable for gas chromatographic-mass spectrometric analysis of diethylstilbestrol and other estrogens was developed using pentafluorobenzyl bromide and ethanolic potassium hydroxide as reagents. The derivatives obtained were detectable at the sub-picogram level using gas chromatography with negative-ion chemical ionization mass spectrometry. Recoveries of cis- and trans-diethylstilbestrol, dienestrol and hexestrol from the immunoaffinity columns, determined after extraction from urine, plasma and buffer, ranged from 28 to 96%. The sensitivity for diethylstilbestrol in urine samples was ca. 10 ppt. The method was applied to the analysis of urine from calves given a single dose of 10 mg of diethylstilbestrol. Free and glucuronic acid conjugated diethylstilbestrol decreased with time, but their ratio was variable.

Animals↗
PubMed1989

Determination of the enantiomeric composition of salsolinol in biological samples by high-performance liquid chromatography with electrochemical detection.

The enantiomers of salsolinol were completely separated as diastereoisomeric derivatives, after reaction with S-1-(1-naphthyl)ethyl isothiocyanate, by reversed-phase high-performance liquid chromatography and quantified by electrochemical detection. Good calibration curves were obtained for the quantification and determination of the enantiomeric composition of salsolinol in human urine. The sensitivity and specificity to the assay also permit the determination of the enantiomeric composition of salsolinol in food such as dried bananas and chocolate.

Cacao↗
PubMed1989

Determination of free amino acids in biological samples: problems of quantitation.

An automatic on-line high-performance liquid chromatographic method was developed to study the effects of various precipitating agents and delayed deproteinization procedures on the estimation of plasma levels of amino acids. The optimized method for analysis is based on pre-column derivatization with o-phthalaldehyde in the presence of 2-mercaptoethanol. The separation of 25 amino acids is accomplished within 45 min on a 5-microns C18 column, using a multi-step gradient with two solvents. The method is sensitive and reproducible, and the relationship between the fluorescence intensity and concentration is linear for each amino acid over a wide concentration range.

Adult↗