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J Wijsbeek

Publications and source records attributed to J Wijsbeek.

At least 19 recordsLinked to original sources
PubMed2000

SPEC disc solid-phase extraction for rapid broad-spectrum drug screening in urine.

Broad-spectrum drug screening requires that all relevant substances be isolated, detected, and identified, regardless of their structure and/or polarity. To this end, systematic solid-phase extraction (SPE) approaches for drug isolation from biological fluids are required. Because speed and cost effectiveness are key issues in analytical toxicology, we have evaluated a disc-format extraction device for this purpose and compared the latter with an existing packed-bed column-format method. The discs were SPEC.PLUS.C18AR/MP3 cartridges with 10-mL solvent reservoirs, providing hydrophobic and cation exchange interactions. Blank human urine was spiked at 2 microg/mL with a selection of acidic, neutral, and basic drugs representing a variety of relevant drug classes. Urine specimens (2 mL) were diluted with 2 mL 0.1 M phosphate buffer (pH 5.0) and then applied to the preconditioned disc. Washing was done with 1 mL water. Acidic and neutral drugs were eluted with 1 mL ethyl acetate/acetone (1:1), and basic drugs were eluted with 1 mL ammoniated ethyl acetate. The eluates were collected separately, evaporated down to about 0.1 mL, and analyzed by gas chromatography-flame-ionization detection to check cleanliness, recoveries, and reproducibilities. The discs showed good extraction properties for all drugs and were easy to handle. Recoveries were 75-100% with coefficients of variation of around 5%. The resulting eluates showed only a few matrix interferences. As compared to our standard SPE method with packed-bed columns, the disc procedure allowed reductions in elution volumes and total processing time of approximately 60-65%.

Barbiturates↗
PubMed1993

Reusability of Bond Elut Certify columns for the extraction of drugs from plasma.

The reusability of Bond Elut Certify columns for the extraction of toxicologically relevant drugs from plasma has been evaluated. Pentobarbital, hexobarbital, mepivacaine, trimipramine and clonazepam were selected as test drugs to represent various classes of drugs. The columns were regenerated immediately after an extraction by washing with methanol, hydrochloric acid (1%), water and methanol, sequentially. These regenerated columns were found to be reusable for plasma. More than 85% of the test drugs were recovered when the columns were used three times. However, the extraction power of the regenerated columns decreased slightly with the number of reuses, so that a column should not be used more than two or three times.

Animals↗
PubMed1993

Study of lot-to-lot reproducibilities of Bond Elut Certify and Clean Screen DAU mixed-mode solid-phase extraction columns in the extraction of drugs from whole blood.

The lot-to-lot reproducibilities of Bond Elut Certify and Clean Screen DAU columns are described. The recoveries of five test drugs obtained from twelve lots of Bond Elut Certify columns ranged from 84 to 104% with standard deviations of less than 9%. The recoveries of five test drugs obtained from six lots of Clean Screen DAU columns ranged from 81 to 103% with standard deviations of less than 7%. The 95% confidence intervals of the means as obtained by ANOVA demonstrate that there are no significant differences between the tested lots of Bond Elut Certify and Clean Screen DAU columns. Comparison of the two brands shows that both Bond Elut Certify and Clean Screen DAU columns are well acceptable for routine drug screening in systematic toxicological analysis, with a slightly higher overall recovery for the former.

Animals↗
PubMed1993

Semi-automated solid-phase extraction procedure for drug screening in biological fluids using the ASPEC system in combination with Clean Screen DAU columns.

The use of a semi-automated solid-phase extraction system (ASPEC) for the screening of drugs in plasma and urine on a single mixed-mode column (Clean Screen DAU) is described. The processes of column preconditioning, sample application, column wash, pH adjustment and elution of the drugs were accomplished by the ASPEC. After off-line evaporation, the residues were injected into a wide-bore capillary gas chromatograph. The recoveries of the tested drugs were in the range of 73-96%, with relative standard deviations less than 5% at a concentration level of 2 micrograms/ml.

Animals↗
PubMed1992

A single-column procedure on Bond Elut Certify for systematic toxicological analysis of drugs in plasma and urine.

A single-column solid-phase extraction procedure was developed for the screening of acidic, neutral, and basic drugs from plasma. The recoveries of all 25 tested drugs exceeded 82%. After the plasma had been diluted with phosphate buffer (pH 6.0), the drugs were extracted using a single Bond Elut Certify column. The acidic and most of the neutral drugs were eluted by acetone/chloroform (1:1) and the basic drugs were eluted by 2% ammoniated ethyl acetate. Some neutral drugs appeared in both fractions. The two fractions were collected separately and evaporated until approximately 100 microL of solvent remained in the tube. Both fractions were analyzed separately on a gas chromatograph equipped with a wide-bore capillary column and a flame ionization detector. The procedure could also be used for urine samples.

Animals↗
PubMed1988

Impact of urine matrix and isolation procedure on retention behaviour of basic drugs in thin-layer chromatography.

The influence of three different isolation procedures, namely liquid-liquid extraction, Extrelut column extraction and XAD-2 column extraction, and of the urine matrix on the standardised Rf values and variability of Rf values of some selected basic drugs was investigated. It appears that the liquid-liquid extraction may give a significant deviation of standardised Rf values in respect of pure drugs, which is dependent on the TLC system. For all three isolation procedures, the search window for substance identification by means of data collection based on standardised Rf values of pure drugs should be slightly wider after extraction than when using pure drugs. The TLC system cyclohexane-toluene-diethylamine (75:15:10, v/v/v) showed the best accuracy and precision of Rf values.

Journal Article↗
PubMed1988

[Analysis of residues of organochlorine compounds in plant drugs. 3. Identification of residues of polychlorobiphenyl compounds by comparison of gas chromatography on packed and capillary columns and GCMS coupling].

The identification of residues of polychlorinated biphenyls in a test sample of Flores Chamomillae could be achieved by the retention behavior at gas chromatographic analyses on packed and capillary columns compared with reference standard Clophen A 60, respectively as well as well by capillary GC/MS using single ion monitoring of substance-characteristic ion mass.

Chromatography, Gas↗
PubMed1986

Determination of carbisocaine, heptacaine and pentacaine in plasma by capillary gas chromatography with nitrogen-selective detection.

A gas-liquid chromatographic method is described for the determination of the local anaesthetics carbisocaine, heptacaine and pentacaine in plasma. A C(18) solid-phase extraction was used in a modification to increase selectivity. Following on-column derivatization with trimethylanilinium hydroxide, the analytes were determined by means of capillary gas chromatography and nitrogen-phosphorus selective detection. In comparison with flame ionization detection, the sensitivity of NPD was 20 times higher with a limit of determination in plasma of 10 ng ml(-1).

Journal Article↗
PubMed1986

Multicenter evaluation of ultrafiltration, dialysis, and thermal coagulation as sample pretreatment methods for the colorimetric determination of paraquat in blood and tissues.

Three methods of sample pretreatment for the rapid colorimetric determination of paraquat were compared: ultrafiltration, dialysis, and thermal coagulation. Spiked autopsy blood and tissue samples were examined in parallel in Groningen and Krakow and some samples were interchanged. All three methods gave recoveries between 87 to 102%; accuracy at the 20-mg/L level was within 10% of the target value and coefficients of variation in the 10 to 60-mg/L range were between 3 to 15%. Determinations in blood and liver in a fatal case of Gramoxone poisoning showed excellent agreement. Because of its reliability, speed, and simplicity, ultrafiltration is the method of choice.

Colorimetry↗
PubMed1986

[Plant drugs with residues of organochlorine compounds. 2. Identification of residues of DDT and its analogs by comparison of gas chromatography on packed and capillary columns and GC/MS coupling].

For the GC analysis of DDT isomers and metabolites in extracts of Flores Chamomillae end Radix Valerianae the separation on a packed QF-1/OV-17 column was compared with various capillary columns of the CP-Sil type. Identification of the individual compounds could be achieved by comparing the retention behavior, chemical transformation of DDT and DDE, as well as by capillary GC-MS using single ion monitoring of substance-characteristic ion mass. In this way, residues of p,p'-DDT, o,p'-DDE and p,p'-TDE could be identified.

Chromatography, Gas↗
PubMed1983

Capillary gas chromatography on fused silica columns with splitless injection: the determination of phenobarbital in blood plasma.

A method is described for the quantitative determination of phenobarbital in blood plasma by means of fused silica capillary columns and splitless sample introduction. Several factors that influence the splitless sample introduction are evaluated. Using a simple column isolation procedure without derivatization prior to GC analysis, recoveries over 80% were found with a precision corresponding with a standard deviation of about 5%. Concentrations ranged from 5-25 mg/l. With a flame ionization detector a detection limit of 0.5 mg/l was observed so that the procedure can also be useful for barbiturates with lower therapeutic plasma levels.

Chromatography, Gas↗
PubMed1983

Clinical pharmacokinetics of intramuscular thiazinamium methyl sulfate.

The disposition of the quaternary ammonium compound thiazinamium methyl sulfate is described after intramuscular injection in humans. The plasma concentration-time curves could be resolved into two exponential components, suggesting an open two-compartment model with absorption phase. Absorption was found to be extremely fast. Peak concentrations were always reached within 20 min, but in the majority of cases they were found to be between 6 and 10 min. Occasionally, the first sample (t = 3 min) proved to contain the highest concentration. Apparently the high solubility of the drug in the interstitial fluid is of prime importance for rapid absorption. Injection technique and the injection site seemed to be important for the final profile of the plasma concentration-time curve. Distribution was found to be very fast as well, with a half-life of approximately 20 min, and the apparent volume of distribution for the central compartment was about 40-60 l. Muscle activity and hence increased capillary blood flow during the distribution phase may result in a second peak in the plasma concentration-time curve. The distribution phase is followed by an elimination phase with a much longer half-life (mean value 375 min) and a volume of distribution of approximately 200-400 l. The total body clearance for thiazinamium methyl sulfate was found to be high (mean value about 800 ml/min), suggesting an active excretion process.

Adolescent↗
PubMed1982

Metabolism and excretion of the quaternary ammonium compound thiazinamium methylsulfate (Multergan) in man. I. Parenteral administration.

The quaternary ammonium compound thiazinamium was found to be metabolized by sulfoxidation solely. No ring hydroxylation products, nor demethylation products (e.g. promethazine) could be found. Thiazinamium sulfoxide was found both in urine and bile, but thiazinamium is-after parenteral administration - mainly excreted in the unchanged form. After intravenous injection about 40% of the dose was excreted, unchanged, in the urine. The excretion was very rapid and almost complete within eight hours. About 9% of the dose was excreted in the urine in the form of thiazinamium sulfoxide cations. After intramuscular injection virtually the same figures for urinary excretion were found. No correlation could be observed between urine production or pH and the amount of drug excreted in urine. In a study involving bile-fistula patients it was found that both thiazinamium cations and thiazinamium sulfoxide cations are excreted to a considerable extent in bile. The amount of unchanged drug in bile was almost equal to that in urine, but the amount of sulfoxide was slightly higher.

Bile↗
PubMed1982

Metabolism and excretion of the quaternary ammonium compound thiazinamium methylsulfate (Multergan) in man. II. Oral and rectal administration.

In this study it is shown that biotransformation of thiazinamium, when given orally, does not differ qualitatively from the pattern found after parenteral administration. However, quantitatively both the metabolism and excretion patterns are considerably different from those after intravenous injection. The renal clearance accounted for 256 +/- 136 ml.min-1 (mean +/- SD). This value is higher than glomerular filtration, which may be indicative of an active excretion process. Hepatic clearance (biotransformation and biliary excretion of unchanged cation) was 537 +/- 495 ml.min-1 (mean +/- SD). Hepatic clearance was found to correlate negatively with bioavailability. The ratio between unchanged drug and the only metabolite, the sulfoxide, in urine was about I:0.9. This is substantially different from that found after parenteral administration (ca. I:0.2), which may imply that a 'first-pass effect' occurs. It was estimated that ca. 50% of the absorbed amount was metabolized during the first liver passage. The fate of thiazinamium after rectal administration in Witepsol HI5 suppositories shows several similarities with that after oral administration. The ratio between unchanged drug and metabolite in urine in this case was ca. I:0.8, indicating that also after rectal administration a 'first-pass effect' occurs, now to a degree of ca. 35%.

Administration, Oral↗
PubMed1979

Isolation and determination of quaternary ammonium compounds by means of amberlite XAD-columns and thin layer chromatography.

The potentials of XAD-columns for the isolation of quaternary ammonium compounds from aqueous media have been investigated. When adequate amounts of counter ions (perchlorate, chloride, phosphate, nitrate) were added to the aqueous sample, to the column pretreatment fluid and to the aqueous washing fluid, most quaternary compounds investigated were retained on the column and could be recovered by elution with methanol. This approach proved also suitable for urine. Quantitation of quaternaries isolated in this way from urine samples could be performed on silicagel thin layer plates through visualization with iodine, followed by densitometric evaluation. For decamethonium detection limits were 0.1 micrograms/ml. Recoveries at the 1 micrograms/ml level were between 80--90% with variation coefficients of less than 10%.

Chromatography, Ion Exchange↗
PubMed1979

First-pass effect after rectal administration of thiazinamium methylsulfate.

The absorption and metabolism of the quaternary ammonium compound thiazinamium methylsulfate were studied in humans using plasma concentration data and urinary excretion measurements. After giving a dose of 150 mg in suppositories, the relative bioavailability was 5.8 +/- 3.2 (SD) % of the dose, comparable to the values obtained following oral administration. The degree of first-pass effect observed after rectal administration was comparable with that after oral administration.

Aged↗
PubMed1979

Isolation and determination of quaternary ammonium compounds by means of XAD-columns and thin layer chromatography.

The potentials of XAD-columns for the isolation of quaternary ammonium compounds from aqueous media have been investigated. When adequate amounts of counter ions (perchlorate, chloride, phosphate, nitrate) were added to the aqueous sample, to the column pretreatment fluid and to the aqueous washing fluid, most quaternary compounds investigated were retained on the column and could be recovered by elution with methanol. Quantitation of decamethonium isolated in this way from urine samples could be performed on silicagel thin layer plates through visualization with iodine, followed by densitometric evaluation. Detection limits were 0.1 microgram/ml. Recoveries at the 1 microgram/ml level were between 80-90% with variation coefficients of less than 10%.

Chromatography↗