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Biomedical subjects

A S Christophersen

Publications and source records attributed to A S Christophersen.

47 records · Page 3Linked to original sources
PubMed1987

Identification of opiates in urine by capillary column gas chromatography of two different derivatives.

A capillary gas chromatographic method is described for the identification and confirmation of morphine, codeine, ethylmorphine and 6-monoacetylmorphine in urine. The method was useful for forensic purposes, as morphine and 6-monoacetylmorphine could be measured together with the legal drugs codeine and ethylmorphine. The legal non-prescription drug pholcodine could be detected together with the metabolites normorphine and norcodeine. After extraction and evaporation the opiates were derivatized with either N,O-bis(trimethylsilyl)trifluoroacetamide or pentafluoropropionic anhydride, and both types of derivative were chromatographed on a non-polar capillary column with a nitrogen-phosphorus selective detector. The use of two chemically different derivatives was found to be necessary for the unequivocal identification of all opiates of interest, which were not all separated as a single derivative. If a mixture of opiates was subjected to the two different derivatization agents, the derivatives were eluted in a different order. This improved considerably the selectivity of opiate analysis in urine. Particularly difficult samples would require mass spectrometric confirmation.

Buffers↗
PubMed1987

Oral administration of codeine in the presence of ethanol: a pharmacokinetic study in man.

Three healthy male volunteers were given a codeine (1 mg/kg) solution in the absence and presence of ethanol in a cross-over designed study. The blood ethanol concentration was kept at approximately 16 mM for 8 hrs. Blood samples were taken at several occasions during the first day after the codeine administration. Urine was sampled during three days. There were no significant differences in the area under serum concentration versus time curve in the absence and presence of ethanol with respect to free codeine, total codeine and total morphine. The fraction of codeine glucuronized in serum (approximately 94%), the maximum serum concentration of free (0.34 microM) and total codeine (6.3 microM), the time to reach the maximum serum concentration values (approximately 65 min.) were also similar in the absence and presence of ethanol. The accumulated percentage of the codeine dose given which was found as codeine and morphine and their conjugates in the urine ranged from 50 to 91 percent in the different subjects. The accumulated percentage of the administered codeine dose found as free morphine in the urine, was significantly lower in the ethanol exposed individuals (0.18 +/- 0.03%) compared to the controls (0.39 +/- 0.09%). The percentage of the codeine dose found in the urine in the control situation as free codeine (5.2 +/- 2.2%) was not statistically different from the amount found in the urine after ethanol treatment (4.3 +/- 2.0%). The percentage glucuronized morphine (95.3 +/- 0.4%) and codeine (91.9 +/- 2.2%) in the urine in the absence of ethanol was similar to glucuronized morphine (95.3 +/- 2%) and codeine (93.1 +/- 3%) after ethanol exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1980

Glass capillary column gas chromatography of barbiturates after flash-heater derivatization with dimethylformamide dimethylacetal.

Glass capillary column gas chromatography has been used for quantitative and qualitative analyses of barbiturates. The barbiturates are first converted into the corresponding acetal derivates by flash-heater derivatization, using dimethylformamide dimethylacetal as the derivatization reagent. The influence of the injection port temperature, the column temperature, the solvent used to dissolve the substances and the reagent dilution were studied in order to obtain the optimal response with good reproducibility. Calibration graphs in the concentration range 5--50 micrograms/ml were evaluated and the relative standard deviations for the quantitative analyses were calculated. High sensitivity was obtained when extracts from plasma containing phenobarbital in the low therapeutic concentration range were analysed using the described derivatization technique.

Barbiturates↗
PubMed1977

Determination of hydrochlorothiazide in serum by high-pressure liquid chromatography.

A quantitative high-pressure liquid chromatographic method has been developed for the analysis of hydrochlorothiazide in serum in therapeutical concentrations. The method is based on gel filtration of the sera on Sephadex G-15, extraction of the protein-free fraction of the effluent with ethyl acetate and injection of a methanol solution of the drug extract on a reversed-phase column packed with Spherisorb ODS (particle size, 10 mum). The mobile phase is 15% methanol in water. The detection limit is 50 ng/ml of serum. Serum samples from patients receiving hydrochlorothiazide have been analysed by the described method at different hours postdose.

Chromatography, Gel↗
PubMedDate not supplied

Tetrahydrocannabinol stability in whole blood: plastic versus glass containers.

The stability of tetrahydrocannabinol (THC) in whole blood during storage was investigated. Two types of containers were used: plastic tubes (polystyrene) and glass vials. Freshly drawn blood was spiked with 10 pmol THC/mL and stored for four days at room temperature (20 degrees to 25 degrees C). The material was kept for four weeks at -20 degrees C. Blood samples from 16 persons apprehended by the police on suspicion of cannabis smoking were collected into the two types of containers and stored frozen (-20 degrees C) until analysis. THC was quantified by capillary column gas chromatography/electron impact mass spectrometry (GC/EI-MS) combined with selected ion monitoring (SIM). Deuterium-labeled THC (THC-d3) was used as internal standard (IS) and was added to the samples immediately prior to extraction. The THC level remained unchanged in glass vials. Samples from the plastic containers had lost 60 to 100% of their THC during storage. In 13 authentic samples, the THC level in blood from the plastic containers varied 0 to 87% from the level in the same blood stored in glass vials. The IS was undetectable in some of these samples.

Blood Specimen Collection↗
PubMedDate not supplied

Interference with analysis of amphetamine in blood by N-ethylbenzenamine from rubber septums.

When blood stored in glass vials sealed with natural rubber septums was screened for amphetamine, a contaminant was seen. The contamination originated from the rubber septums and was identified by GC/MS as N-ethylbenzenamine. Like amphetamine, N-ethylbenzenamine was extracted from strongly alkaline solutions. N-Ethylbenzenamine and amphetamine chromatographed with the same retention time on a packed Apiezon/KOH column and on nonpolar capillary columns. Separation was achieved on a medium polar capillary column. Trifluoroacetyl derivatives of amphetamine and N-ethylbenzenamine had the same retention time on a packed SP-2250 column, but separated on nonpolar capillary columns. The amounts of N-ethylbenzenamine found were high enough to give rise to significant false positive results if N-ethylbenzenamine was erroneously read as amphetamine. N-Ethylbenzenamine is believed to be formed by thermal decomposition of the vulcanizing agent zinc ethylphenyldithiocarbamate used in rubber production.

Amphetamine↗
PubMedDate not supplied

Determination of amphetamine and methamphetamine in blood by derivatization with perfluorooctanoyl chloride and gas chromatography/mass spectrometry.

A relatively simple method for quantitation of amphetamine and methamphetamine in blood was developed. Blood samples were extracted with cyclohexane, and the extracts were derivatized with perfluorooctanoyl chloride prior to gas chromatography/mass spectrometry. Selected ions were monitored at m/z 118 and 440 for amphetamine, m/z 118 and 454 for methamphetamine, and m/z 121 and 443 for the internal standard amphetamine-d3. The imprecision was less than 5% for amphetamine and less than 9% for methamphetamine. Limits of detection were 11 micrograms/L for amphetamine and 13 micrograms/L for methamphetamine, while limits of quantitation were 22 and 34 micrograms/L, respectively. Calibration curves were linear in the ranges 14-2700 micrograms/L and 15-3000 micrograms/L, respectively. Some drugs that were known or suspected to interfere with immunological or chromatographic methods for amphetamine and methamphetamine were tested for interference. None of the drugs tested interfered, except for a substance in putrefied blood samples, which was found to interfere with one ion (m/z 118) for amphetamine but not with the second ion.

Amphetamine↗
PubMedDate not supplied

Determination of benzodiazepines in human urine using solid-phase extraction and high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method has been developed and validated for the determination of benzodiazepines, on the market in Norway, and/or their metabolites in human urine. The following compounds were included: 7-aminonitrazepam, 7-aminoclonazepam, 7-aminoflunitrazepam, alprazolam, alpha-hydroxyalprazolam, oxazepam, 3-OH-diazepam, and n-desmethyldiazepam. The method includes hydrolysis of urine samples (0.5 mL) with beta-glucuronidase at 60 degrees C for 2 h before solid-phase extraction with a polymer-based mixed-mode column. The analytes were quantified in multiple reaction monitoring mode using two transitions. Deuterated analogues were used as internal standards for all analytes except 7-aminonitrazepam and alpha-hydroxyalprazolam, which were quantified using 7-aminoclonazepam-d(4) and alprazolam-d(5), respectively. The concentration range was 0.1-8.0 microM for 7-aminonitrazepam, 7-aminoclonazepam, 7-aminoflunitrazepam, alprazolam, and alpha-hydroxyalprazolam and 0.5-40 microM for the other compounds. The average recovery for the different analytes ranged from 56% to 83%. The between-day precision of the method was in the range of 3-12%. The limits of quantification were found to be between 0.002 and 0.01 microM for the different compounds. Comparison with other analytical methods was performed for method validation, using approximately 500 samples provided by the routine laboratory at the Norwegian Institute of Public Health. The LC-MS-MS method has proven to be robust and specific for the determination of benzodiazepines in urine. It has been routinely used for approximately 1800 samples in the past 7 months.

Benzodiazepines↗
PubMedDate not supplied

Drug analysis for control purposes in forensic toxicology, workplace testing, sports medicine and related areas.

This MiniReview describes the present guidelines for drug testing in forensic toxicology, workplace testing and doping control of athletes. Such guidelines are established to secure the chain of custody, from sample collection through analysis with screening, confirmation methods and interpretation, to the final report of results. Specifications for good laboratory practice, facility maintenance and quality assurance programs are described. The advantages and limitation of immunological drug assays and the necessity of specific chromatographic confirmation methods are discussed. The importance of correct interpretation of positive test results is illustrated. The effect of drug testing on the prevalence of drug abuse, accident rates and effectivity at the workplace is discussed.

Data Interpretation, Statistical↗