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At least 955 records · Page 53Linked to original sources
PubMed1993

Identification and quantitation of intact diastereoisomeric benzodiazepine glucuronides in biological samples by high-performance liquid chromatography.

A rapid and simple high-performance liquid chromatographic method for the simultaneous detection of intact glucuronides of different benzodiazepines is described. Separation of the diastereomers of the following benzodiazepine glucuronides can be achieved on a reversed-phase column (octadecyl or select B): oxazepam, nordiazepam, temazepam, lorazepam and 3-hydroxyprazepam. If the sample contains both S-lorazepam and R-temazepam glucuronides, or both S-temazepam and nordiazepam glucuronides, further separation on a beta-cyclodextrin column is required. The detection limit ranges between 5 and 10 ng of glucuronides per ml of plasma or urine, respectively.

Benzodiazepines↗
PubMed1994

Determination of oxytocin in biological samples by isocratic high-performance liquid chromatography with coulometric detection using C18 solid-phase extraction and polyclonal antibody-based immunoaffinity column purification.

A specific high-performance liquid chromatographic (HPLC) method is described for the reliable quantitation of oxytocin using culture media supernatants. The procedure employs solid-phase extraction, antibody-based immunoaffinity purification and isocratic HPLC with dual channel coulometric detection (ED). The lower limit of detection for this cyclic nonapeptide was 40 pg (40 fmol). Due to its relative simplicity, specificity and precision, the HPLC-ED of oxytocin is an accurate and attractive alternative to many existing quantitative methods.

Amino Acid Sequence↗
PubMed1994

Simple and sensitive determination of 2,3-butanediol in biological samples by gas chromatography with electron-capture detection.

2,3-Butanediol was quantitatively oxidized into diacetyl by reaction with MnO4- at 20 degrees C for 30 min under neutral conditions. The reaction of diacetyl with 4,5-dichloro-1,2-diaminobenzene afforded 6,7-dichloro-2,3-dimethyl-quinoxaline (DCDMQ), which was extracted with n-hexane and determined by gas chromatography with electron-capture detection. As an internal standard 1,2-cyclohexanediol was used. The detection limit of DCDMQ (or 2,3-butanediol) was 10 fmol/microliter in the extract, and the determination limit of DCDMQ (or 2,3-butanediol) was at least from 50 fmol/microliter to 20 pmol/microliter in the extract. Recoveries from normal rat urine and rat liver homogenate were 97.8 +/- 3.4% and 98.4 +/- 2.9%, respectively. The method is very simple and sensitive and is applicable to the determination of 2,3-butanediol in normal rat tissues.

Animals↗
PubMed1994

Enantioselective gas chromatographic assay with electron-capture detection for amlodipine in biological samples.

A sensitive enantioselective gas chromatographic assay has been developed for amlodipine, 2-[(2-aminoethoxy)-methyl]-4-(2-chlorophenyl)-3-ethoxycarbonyl-5- methoxycarbonyl-6-methyl-1,4-dihydropyridine, a calcium channel blocking therapeutic agent. The assay involves conversion of the (+)-(R)- and (-)-(S)-enantiomers of amlodipine into their acyl derivatives with the chiral reagent (+)-(S)-alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride (Mosher's reagent). Peak separation after chromatography of the diastereomers was larger than 85%, and the lower limit of detection in blood plasma was 0.02 ng/ml for each enantiomer. The method has been used for the measurement of amlodipine enantiomers in human, rat and dog plasma, and in various organs of the rat.

Adult↗
PubMed1995

Determination of d-amphetamine in biological samples using high-performance liquid chromatography after precolumn derivatization with o-phthaldialdehyde and 3-mercaptopropionic acid.

An HPLC method is described for the determination of amphetamine using fluorometric detection after derivatization with o-phthaldialdehyde and 3-mercaptopropionic acid. This procedure is more sensitive (detection limit 370 fmol in microdialysate buffer standards, 1.5 pmol in extracted plasma and tissue samples) than most of the previous methods described for the determination of amphetamine with HPLC-fluorescence detection. Due to the stability of the derivative it is also suitable for autosampling after manual derivatization. Investigators currently using o-phthaldialdehyde derivatization and fluorometric detection for amino acid determination should be able to rapidly implement this method.

3-Mercaptopropionic Acid↗
PubMed1994

Determination of L-asparagine in biological samples in the presence of L-asparaginase.

The antileukaemic efficacy of L-asparaginase is related to the ability of the enzyme to induce the complete disappearance from plasma of L-asparagine, an amino acid essential to lymphoblastic leukaemia cells. It is not feasible to monitor L-asparagine plasma levels in patients under L-asparaginase treatment using the usual analytical procedures as the enzyme continues the hydrolysis of L-asparagine after blood sampling and during plasma extraction. A method was therefore developed for the determination of L-asparagine in patients receiving L-asparaginase. Sulphosalicylic acid is added to blood samples to deproteinize and inactivate L-asparaginase rapidly. The samples are then analysed by HPLC using a Novapack C18 column and fluorescence detection. With the same method L-asparagine is determined in blood cells and, by difference, plasma levels are calculated. This method is highly specific and sufficiently simple and sensitive for clinical use.

Asparaginase↗
PubMed1995

High-performance liquid chromatography using electrochemical detection for the determination of prazosin in biological samples.

For the quantitation of prazosin a sensitive high-performance liquid chromatographic (HPLC) method was developed. This HPLC analysis method uses an electrochemical detection technique for the identification and quantitation of prazosin. In this assay the serum samples were deproteinized by using a simple acetonitrile precipitation technique that was followed by n-hexane extraction. Prazosin in the deproteinized serum sample was separated by an isocratic elution with an ODS Hypersil HPLC column (150 x 4.6 mm) using a mobile phase consisting of 0.05 M Na2HPO4-acetonitrile (60:40), pH 8.4. Prazosin that was eluted from the column was detected using a Coulochem II electrochemical detector. The precision of this assay method was assessed by performing inter- and intra-assay analyses by spiking prazosin free fetal bovine serum samples with 20 and 40 ng/ml concentrations of prazosin. In the intra-assay the recovery was 95.40 +/- 4.82% and 97.80 +/- 3.40%, respectively, for 20 and 40 ng/ml concentrations of prazosin that were used to spike the serum samples. This electrochemical detection HPLC assay method could be very useful in monitoring plasma levels of prazosin.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1996

Determination of trovafloxacin, a new quinolone antibiotic, in biological samples by reversed-phase high-performance liquid chromatography.

A simple, accurate and precise high-performance liquid chromatographic method was developed and validated for the determination of trovafloxacin, a new quinolone antibiotic, in serum and urine. Following solid-phase extraction, chromatographic separation was accomplished using a C18 column with a mobile phase consisting of 0.04 M H3PO4-acetonitrile-tetrabutylammonium hydroxide-0.005 M dibutyl amine phosphate (D-4) reagent (83:16.85:0.05:0.1, v/v), pH 3. Trovafloxacin and the internal standard (a methyl derivative of trovafloxacin) were detected by ultraviolet absorbance at 275 nm. The lower limit of quantification for trovafloxacin was 0.1 microgram/ml and the calibration curves were linear over a concentration range of 0.1 to 20.0 micrograms/ml (r2 = 0.9997). The average recoveries were greater than 70% for both trovafloxacin and internal standard. The intra-day and inter-day coefficients of variation were generally less than 5% in urine and serum over the concentration range of 0.1 to 20.0 micrograms/ml. Human serum samples could be stored for up to 12 months at -20 degrees C and urine samples could be stored up to 18 months at -80 degrees C.

Anti-Infective Agents↗
PubMed1996

Determination of 1-O-acyl-2-acetyl-sn-glyceryl-3-phosphorylcholine, platelet-activating factor and related phospholipids in biological samples by high-performance liquid chromatography--tandem mass spectrometry.

Combining normal-phase HPLC separation and tandem mass spectrometric detection, using an ion-spray HPLC-MS interface, a quantitative method for acyl-platelet activating factor (acyl-PAF), platelet-activating factor (PAF) and related phospholipids was developed. Mass spectra, positive ions, showed intense [M+H]+ ions; collision-induced dissociation of protonated molecular ions gave characteristic daughter ions corresponding to the polar head. Detection limits of 0.1-0.3 ng injected were obtained by multiple reaction monitoring. Samples of human endothelial cells treated with compounds modulating the levels of acyl-PAF and PAF have been analyzed by the present technique, proving that this approach is suitable for biochemical studies.

Cells, Cultured↗
PubMed1987

Two tricyclic antidepressant poisonings: levels of amitriptyline, nortriptyline and desipramine in post-mortem biological samples.

Two deaths due to amitriptyline and desipramine overdoses are reported. The first case deals with a 20-year-old Caucasian male who was found dead at his residence. Toxicological analysis of the blood, urine, liver and kidney revealed the presence of amitriptyline (1.7 mg/l, 0.13 mg/l, 36.0 mg/kg and 98.0 mg/kg) and nortriptyline (0.66 mg/l, 0.74 mg/l, 12.0 mg/kg and 37.0 mg/kg). The gastric content contained only 220 mg of amitriptyline. The urine also contained norverapamil, which was consistent with previous verapamil therapy. The second case involved a 19-year-old Caucasian male who attempted suicide earlier and was on desipramine medication. The blood, urine, liver and gastric content disclosed the presence of desipramine in the concentrations of 14.2 mg/l, 33.7 mg/l, 112.5 mg/kg and 180 mg, respectively. The levels of these tricyclics analyzed by high pressure liquid chromatography were in agreement with the levels reported in the literature. Though with the amitriptyline poisoning no significant anatomic changes were noted, the desipramine-caused death was further supported by the multisystem vascular congestion and ischemic changes consistent with cardiopulmonary failure.

Adult↗
PubMed1988

Wide-bore capillary column gas chromatography in toxicological analysis of biological samples from multidrug overdoses fatalities.

Fatalities from multidrug overdoses account for 25% of the total number of all poisoning fatalities and as such deserve greater attention from researchers than single drug overdoses. High resolution, good sensitivity, and repeatability provided by gas chromatography (GC) with wide-bore capillary silica and glass columns make GC particularly useful for identification and quantitative analysis of drugs in toxicological screening of autopsy specimens. Results of toxicological findings in three deaths from multidrug overdoses (methaqualone, doxepine, methotrimeprazine, pernazine-aspirin, paracetamol, codeine-morphine, diazepam) occurring in routine medical practice are reported.

Adult↗
PubMed1989

A simple gas chromatographic identification and determination of 11 CNS stimulants in biological samples. Application on a fatality involving phendimetrazine.

A method is presented for the simultaneous identification and quantification of several CNS stimulants, including amphetamine in plasma and urine by GC/FID using mephentermine as an internal standard. No derivation is necessary and after a single alkaline extraction, GC analysis for the 11 compounds tested is achieved in 23 min. The lower limit of detectability was found to be 4 ng/ml for amphetamine in plasma. This method is sensitive, reproducible, selective and applicable in forensic and clinical toxicological analyses. Toxicological findings, after a fatality involving phendimetrazine are presented as an application of the procedure.

Adult↗
PubMed1993

Positive- and negative-ion mass spectrometry of diphenylmethane antihistaminics and their analogues and rapid clean-up of them from biological samples.

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra are presented for 15 compounds of diphenylmethane antihistaminics and their analogues, and each fragmentation pathway was analyzed. In the PIEI mode, molecular peaks were very small or missing for most compounds. Peaks at m/z 58, due to a dimethylaminomethyl group liberated, constituted base peaks in five compounds. Peaks at m/z 165 and/or 167, due to diaromatic rings plus a methyl group, appeared in most compounds. In the PICI mode, peaks due to M+H and M+C2H5 appeared in all compounds. Peaks due to diaromatic rings plus a methyl or ethyl group constituted base peaks in five compounds, which had an ether bond in their structures. In the NICI mode, anions at m/z M-H appeared in most compounds. Peaks at m/z 35 were observed for compounds having a chlorine group in their structures. Detection limits for total ion monitoring of these compounds were 20-50 ng on column in the PIEI mode, 100-200 ng in the PICI mode and 500-1000 ng in the NICI mode. A rapid and simple clean-up procedure of these drugs with use of Sep-Pak C18 cartridges is also presented. The drugs could be detected by gas chromatography with DB-1 and DB-17 capillary columns with satisfactory separation from impurities in their underivatized forms. The recovery of the drugs, which had been added to whole blood and urine, was more than 60% except for meclizine.

Benzhydryl Compounds↗
PubMed1984

Fully-automated assay by liquid chromatography for routine drug monitoring in body fluids--method development with biological samples.

A fully-automated liquid chromatograph based on alternated pre-column enrichment technique has been developed for routine drug monitoring of body fluids using a column switching technique. Advantages of the method include the facility of direct injection of the body fluid onto the chromatograph and the simultaneous detection of both polar and non-polar metabolites under isocratic or gradient elution conditions.

Journal Article↗
PubMed1986

Determination of dihydroxyphenylalanine and dihydroxyphenylacetic acid in biological samples by coupled-column liquid chromatography with dual coulometric-amperometric detection.

Adrenaline, noradrenaline, dopamine and dihydroxyphenylalanine in brain tissue and dihydroxyphenylacetic acid in plasma have been determined by direct injection of brain homogenates or plasma into a liquid chromatographic system comprising three columns, one packed with a boronic acid gel and two with reversed-phase material. The catecholamines and dihydroxyphenylalanine were selectively adsorbed on the boronic acid gel and separated by ion-pair chromatography on the reversed-phase columns. DOPAC was determined in a modified system without the addition of ion-pairing reagents. The catechols were detected by coulometry or amperometry with two working electrodes, operated in the oxidative-reductive mode. The reductive signal was used for quantification. The limits of determination were 0.05 nmol g(-1) with 40 mg brain tissue and 2 nmol 1(-1) with 0.5 ml plasma for DOPA and DOPAC respectively. The limit of quantification of DA and DOPAC in urine was about 0.1 micromol l(-1).

Journal Article↗