Biomedical subjects

R Dams

Publications and source records attributed to R Dams.

At least 19 recordsLinked to original sources

PubMed2002

Direct determination of methylmercury and inorganic mercury in biological materials by solid sampling-electrothermal vaporization-inductively coupled plasma-isotope dilution-mass spectrometry.

This paper reports on the use of solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry (SS-EIV-ICPMS) for the direct and simultaneous determination of methylmercury and inorganic mercury in biological materials. The main advantage of this fast and sensitive method is that no sample preparation is required. In this way, the sample throughput can be considerably increased, problems of contamination and analyte losses are kept to a minimum and, even more important, the original chemical form of the different analyte species in the solid samples is preserved. To achieve this goal, a solid sample is inserted into a graphite furnace of the boat-in-tube type and is subsequently submitted to an appropriate temperature program, leading to the separate vaporization of methylmercury and inorganic mercury, which are transported into the ICP by means of an argon carrier gas. The separation was accomplished within 75 s. For the quantification of the two peaks, species-unspecific isotope dilution was used. For this purpose, a stable flow of argon loaded with gaseous Hg isotopically enriched in 200Hg was generated using a permeation tube that was constructed in-house. Its emission rate was determined by collecting the mercury released during a given time interval on a gold-coated silica absorber, after which the amount collected was released by heating of the absorber and determined by cold vapor atomic absorption spectrometry (CVAAS) and cold vapor atomic fluorescence spectrometry (CVAFS). A reference material from the Canadian National Research Council (NRC) (TORT-2) was used to assess the accuracy of the method. For the application of the method to samples with diverse mercury contents, the spike/sample ratio can be optimized by varying the emission rate of the permeation tube simply by adapting its temperature. To prove the feasibility of this approach, two reference materials (BCR 463 and DORM-2) with a methylmercury content more than 10 times higher than that of TORT-2 were also analyzed. The detection limits obtained for 1 mg of sample (2 ng g(-1) and 6 ng g(-1) for methylmercury and inorganic mercury, respectively) were found to be sufficiently low for this kind of application and are competitive when compared to other techniques.

Animals↗

PubMed2002

Simultaneous determination of in total 17 opium alkaloids and opioids in blood and urine by fast liquid chromatography-diode-array detection-fluorescence detection, after solid-phase extraction.

A fast liquid chromatographic method with tandem diode array-fluorescence detection for the simultaneous determination of in total 17 opium alkaloids and opioids is presented. Blank blood and urine samples (1 ml) were spiked with different concentrations of a standard mixture, as well as with the internal standard, butorphanol (2000 ng/ml). After solid-phase extraction, based on weak cation exchange (Bond Elut CBA SPE columns), the extracts were examined by HPLC-DAD-FL. By using a "high-speed" phenyl column (53 x 7.0 mm I.D., particle size 3 microm) eluted with a gradient system (A: water-methanol (90:10, v/v), B: methanol, both containing 25 mM triethylammoniumformate (pH(A) = 4.5)) all compounds could be baseline separated within 12 min. The method was validated and its applicability was demonstrated by the analysis of real-time forensic cases.

Chromatography, High Pressure Liquid↗

PubMed2001

Heroin impurity profiling: trends throughout a decade of experimenting.

Heroin is still one of the most frequently abused drugs of today. All over the world, law enforcement agencies try to eradicate the illicit production and trafficking of this potent and highly addictive narcotic. To this aim, important information is provided by physical and chemical toxicological analysis of confiscated samples, with special attention for the identification and the quantification of minor components, such as the impurities related to the origin and manufacturing. By combining these data complex characterisations, i.e. impurity profiles, chemical signatures or fingerprints, can be obtained and used for comparative analysis. This review focuses on heroin impurity profiling during the 1990s, proclaimed by the United Nations as the 'Decade for Eradicating Drug Abuse'. Special attention will be given to the new trends in analytical techniques as well as in data handling strategies, so called chemometrics, to produce these profiles. The latter can be used in comparative analysis of seized heroin samples for tactical (batch-to-batch comparison) and strategic (origin determination) intelligence purposes.

Chemistry Techniques, Analytical↗

PubMed2001

Non-ideal behaviour of free vanadate on a Superose 12 size-exclusion column. Application to in vivo 48V-labelled rat spleen homogenate.

Seven chromatographic columns were evaluated for the recovery of 48V-radiolabelled vanadate. Further, the behaviour of vanadate (H2VO4-) was studied on a size-exclusion column Superose 12 as a function of (a) buffer salt molarity, (b) different buffer salts, (c) different buffers and (d) organic solvents added to the buffer. As opposed to the unsatisfactory recovery of V-compounds on other columns, we recovered the vanadium quantitatively. We observed that in most cases vanadate eluted after the total volume of the Superose 12 column. This indicates a non-ideal behaviour of vanadate. However, through this non-ideal behaviour it was possible to separate low-molecular-mass bound (Mr<5000) and unbound vanadium which would not be possible under normal behaviour. A possible explanation for this non-ideal behaviour of vanadium is put forward. The method has been successfully applied for the fractionation of different vanadium species in rat spleen homogenate.

Animals↗

PubMed2001

Stir bar sorptive extraction-thermal desorption-capillary gas chromatography-mass spectrometry applied to the analysis of polychlorinated biphenyls in human sperm.

Stir bar sorptive extraction (SBSE) on polydimethylsiloxane (PDMS) was applied to the enrichment of polychlorinated biphenyls (PCBs) from human sperm. The seven Ballschmiter PCBs were used as model compounds. The extracted PCBs were then thermally desorbed from the stir bar and analysed on-line by capillary gas chromatography (CGC) with mass spectrometric detection (MS). Method development started with the analysis of PCBs spiked in water. Methanol had to be added to the samples in order to reduce the influence of glass adsorption on recovery and reproducibility. Recoveries in water for all PCBs varied around 50-60% and were limited for low molecular mass (MM) PCBs by polarity changes in the sample due to methanol addition and for high MM PCBs by non-equilibrium conditions. Matrix suppression by the lipophilic medium lowered the recoveries in the sperm samples proportional with PCB polarity. The method was validated and although limits of detection (LOD) for the individual congeners were in the sub-ppt level (<pg/ml), the limit of quantification (LOQ) was set at 10 ppt (10 pg/ml).

Gas Chromatography-Mass Spectrometry↗

PubMed2001

Determination of rare earth elements in environmental matrices by sector-field inductively coupled plasma mass spectrometry.

In the framework of an international certification campaign, sector-field inductively coupled plasma mass spectrometry (sector-field ICP-MS) was used for the accurate determination of the rare earth elements in five candidate reference materials: aquatic plant, calcareous soil, mussel tissue, river sediment, and tuna muscle. All samples were taken into solution by use of microwave-assisted or mixed microwave-assisted / open beaker acid digestion. Subsequently, the samples were appropriately diluted and subjected to ICP-MS analysis. Except for Sc, all the elements involved were determined at low mass resolution (R = 300). For Sc, application of a higher resolution setting (R = 3,000) was required to separate the analyte signal from those of several molecular ions which gave rise to spectral overlap at low mass resolution. Some of the heavier REE can also suffer from spectral overlap attributed to the occurrence of oxide ions (MO+) of the lighter REE and Ba. This spectral overlap could be successfully overcome by mathematical correction. Matrix effects were overcome by use of two carefully selected internal standards, such that external calibration could be used. On each occasion, a geological reference material was analyzed as a quality-control sample and the reliability of all results obtained was additionally checked by means of chondrite normalization. For tuna muscle the content of all REE was below the limit of detection. For calcareous soil and river sediment, low to sub microg g(-1) values were observed, whereas the REE content of aquatic plant and mussel tissue was considerably lower (low to sub ng g(-1)). Overall, the results obtained were in excellent agreement with the average values, calculated on the basis of all "accepted" values, obtained in different laboratories using different techniques.

Journal Article↗

PubMed2001

A fatal case of serotonin syndrome after combined moclobemide-citalopram intoxication.

We present a case involving a fatality due to the combined ingestion of two different types of antidepressants. A 41-year-old Caucasian male, with a history of depression and suicide attempts, was found deceased at home. Multiple containers of medication, the MAO-inhibitor moclobemide (Aurorix), the SSRI citalopram (Cipramil), and the benzodiazepine lormetazepam (Noctamid) as active substance, as well as a bottle of whiskey were present at the scene. The autopsy findings were unremarkable, but systematic toxicological analysis (EMIT, radioimmunoassay, high-performance liquid chromatography-diode-array detection [HPLC-DAD], gas chromatography-nitrogen-phosphorus detection, and gas chromatography-mass spectrometry) revealed the following: ethanol (0.23 g/L blood, 0.67 g/L urine), lormetazepam (1.65 microg/mL urine), cotinine (0.63 microg/mL blood, 5.08 microg/mL urine), caffeine (1.20 microg/mL urine), moclobemide (and metabolites), and citalopram (and metabolite). There upon, we developed a new liquid chromatographic separation with optimized DAD, preceded by an automated solid-phase extraction, for the quantitation of the previously mentioned antidepressive drugs. The results obtained for blood and urine, respectively, were as follows: Ro 12-5637 (moclobemide N'-oxide) not detected and 424 microg/mL; Ro 12-8095 (3-keto-moclobemide) 2.26 microg/mL and 49.7 microg/mL; moclobemide 5.62 microg/mL and 204 microg/mL; desmethylcitalopram 0.42 microg/mL and 1.22 microg/mL; and citalopram 4.47 microg/mL and 19.7 microg/mL. The cause of death was attributed to the synergistic toxicity of moclobemide and citalopram, both antidepressants, which, by intentional or accidental combined ingestion, can produce a potentially lethal hyperserotoninergic state. Based on the history of the case and pharmacology of the drugs involved, the forensic pathologists ruled that the cause of death was multiple drug intoxication, resulting in a fatal "serotonin syndrome," and that the manner of death was suicide.

Adult↗

PubMed2000

Comparison of phenyl-type columns in the development of a fast liquid chromatographic system for eighteen opiates commonly found in forensic toxicology.

We report a precise and reliable method for the detection of 18 of the most commonly found opiates on the Belgian legal and illicit market, by ion-exchange, reversed-phase high-performance liquid chromatography, using a conventional phenyl-type analytical column (150x4.6 mm I.D., particle size 5 microm) and diode-array detection. We also describe a performance (efficiency and sensitivity) comparison of this column to a recently developed "high-speed" column (53x7.0 mm I.D., particle size 3 microm) packed with the same stationary phase, and used under slightly adjusted flow and gradient conditions. The final method, using the "high-speed" column, showed a significant reduction (55%) in analysis time without loss of resolution and sensitivity.

Buffers↗

PubMed2000

Multielement analysis of polyethylene using solid sampling electrothermal vaporization ICP mass spectrometry

Next to laser ablation (LA) also electrothermal vaporization (ETV) from a graphite furnace as a means of sample introduction opens possibilities for direct analysis of solid samples using inductively coupled plasma mass spectrometry (ICPMS). In this paper, it is demonstrated that solid sampling ETV-ICPMS is very well suited for the determination of metal traces in polyethylene. A limited multielement capability is often cited as an important drawback of ETV-ICPMS. However, by studying the effect of monitoring an increasing number of mass-to-charge ratios on the signal profile (integrated signal intensity and repeatability) of selected analyte elements, the multielement capability of (solid sampling) ETV-ICPMS was systematically evaluated, and the results obtained suggest that, with a quadrupole-based ICPMS instrument, at least 11 elements can be determined "simultaneously" (from the same vaporization step), in essence without compromising the sensitivity or the precision of the results obtained. In this work, the "simultaneous" determination of Al, Ba, Cd, Cu, Mn, Pb, and Ti in a polyethylene candidate reference material has been accomplished, despite the large variation in analyte concentration (from 5 ng/g for Mn to 500 microg/g for Ti) and in furnace behavior (volatility) they exhibit. To avoid premature losses of Cd during thermal pretreatment of the samples, Pd was used as a chemical modifier. Two different calibration methods--external calibration using an aqueous standard solution and single standard addition--were studied and the results obtained were compared with those obtained using neutron activation analysis (NAA) and/or with the corresponding (candidate) certified values (if available). Single standard addition was shown to be preferable (average deviation between ICPMS result and reference value < 3%), although--except for Ba--acceptable results could also be obtained with external calibration.

Journal Article↗

PubMed2000

Feasibility study on the characterization of thin layers by charged-particle activation analysis

The purpose of this feasibility study was to investigate the possibilities and limitations of Charged-Particle Activation Analysis (CPAA) as a thin layer characterization method, i.e., the determination of the mass thickness or the composition of a thin layer. Therefore industrially important layers of sputtered Al, AlOx, TiQx (all three from the packaging industry), YBa2Cu3O6+delta, and Y2O3-stabilized ZrO2 (both superconducting industry) on different substrates were analyzed, and thereby the accuracy, the detection limits, and the precision of the method were studied. To test the accuracy, the same materials were also analyzed with neutron activation analysis (NAA) and inductively coupled plasma mass spectrometry (ICPMS). The results of CPAA compared with the results of NAA and ICPMS showed no significant difference at the 95% confidence level. The detection limits expressed as mass thickness were about 10-2 microg cm-2 or expressed as thickness 0.04 nm for a monatomic layer of Al. The experiments showed that the precision of the method depends only on the counting statistics. Generally we can conclude that CPAA is an absolute method for the characterization of "thin" layers, with respect to composition and mass thickness determinations.

Journal Article↗

PubMed2000

Collaborative evaluation of the analytical state-of-the-art of platinum, palladium and rhodium determinations in road dust.

In order to control the quality of platinum, palladium and rhodium determinations in road dust, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a project, the final aim of which is to certify a road dust reference material for its contents of platinum group elements. The first part of this project consisted of an interlaboratory study, which aimed to test the feasibility of the preparation of a candidate road dust reference material and to detect and remove most of the pitfalls observed in platinum, palladium and rhodium determinations. This paper presents the main results of this interlaboratory study carried out prior to the certification campaign. The concordance of the data obtained by the participating laboratories for the three elements was considered to reflect the state-of-the-art and was encouraging enough to decide on the organization of a certification campaign to be conducted during the year 2000. The progress made with respect to the analytical state-of-the-art for these elements will be of great benefit to the quality of measurements carried out in environmental monitoring in this particular field.

Dust↗

PubMed1998

Determination of the uptake of [Pt(NH3)4](NO3)2 by grass cultivated on a sandy loam soil and by cucumber plants, grown hydroponically.

Two cultivation experiments were carried out in order to answer the question to what extent platinum can enter the food chain by accumulation in plants, when the platinum is present in a bio-available form: (i) cucumber plants (Cucumis sativus) were grown hydroponically in nutrient solutions containing [Pt(NH3)4](NO3)2 (from 0.5 to 50 micrograms Pt/l solution); and (ii) a water-soluble platinum compound--[Pt(NH3)4](NO3)2--was added in increasing amounts to a sandy loam soil (from 0.5 to 50 mg Pt/kg soil) and rye grass (Lolium perenne) was grown on it. The roots on the one hand and the green plant fractions in the other hand of the cucumber plants and the rye grass were digested using a high-pressure asher. The platinum concentration was determined by means of a quadrupole-based (VG PQ I) or a double focusing sector field ICP-mass spectrometer (Finnigan MAT, Element), depending on the platinum concentration in the sample solution. The detection limit for platinum obtained with the VG PQ I was observed to be 6 ng/1, while with the 'Element' the detection limit could be improved to 0.5 ng/1 Pt. Accumulation factors were calculated as the ratio of the platinum concentration in the plant to that in the soil or the nutrient solution. The grass grown on spiked soil accumulated platinum only to a slight degree (accumulation factors between 0.008 and 0.032). The hydroponically grown cucumber plants, however, strongly accumulated it (accumulation factors of 11-42 in the shoot and 1700-2100 in the roots). There are three possible causes for the large differences in the accumulation factors: (i) Cucumber plants are dicotyledons; grass, however, is a monocotyledon. Other cultivation experiments already showed that dicotyledons accumulate metals to a higher extent than monocotyledons. (ii) In the grass cultivation experiment, the platinum compound was only added once to the sandy loam soil, namely 2 days before grass was cultivated on it. The nutrient solutions of the cucumber plants were changed twice a week. Consequently, the total amount of platinum that the plants were exposed to during the cultivation of the cucumber plants was higher than during the cultivation of the grass. (iii) Immobilization of the platinum compound in the soil most likely occurred.

Biological Availability↗

PubMed1997

Synthesis of 6-methyl[11C]-2'-deoxyuridine and evaluation of its in vivo distribution in Wistar rats.

In this study, 6-methyl-2'-deoxyuridine, an artificial nucleoside, was labeled with 11C in the methyl position. Tissue distribution of 6-methyl[11C]-2'-deoxyuridine was investigated in normal Wistar rats and compared to the behavior of the natural nucleoside [methyl-11C]thymidine. High renal clearance, up to at least 20% of the injected activity, was noticed during the 20 min period following injection. Tissue distribution as determined by dynamic PET studies of both 11C-labeled nucleosides was significantly different for most of the organs.

Animals↗

PubMed1996

Determination of low amounts of platinum in environmental and biological materials using thermospray nebulization inductively coupled plasma-mass spectrometry.

A description is given of the experimental arrangement for thermospray nebulization of discrete liquid samples (100 microl) into an inductively coupled plasma-mass spectrometer (ICP-MS). The determination of ultratrace levels of platinum in environmental and biological materials is described. This method comprises an off-line sample enrichment by adsorptive chromatography, elution with ethanol and subsequent analysis of the evaporated eluate. The quantification of the concentration was performed with isotope dilution. The recovery, precision, accuracy and detection limit of the method are discussed.

Journal Article↗

PubMed1996

Non-spectral interferences encountered with a commercially available high resolution ICP-mass spectrometer.

Results of a systematic study concerning non-spectral interferences observed with a commercially available high resolution ICP-mass spectrometer are reported and compared to observations made with a quadrupole-based instrument. In general, matrix effects were observed to be to a large extent comparable for both instruments used. In all cases, the matrix-induced signal suppression or enhancement was seen to depend in a regular way on the mass number of the nuclides monitored. In most cases, the ionization potential of the nuclides has little or no influence on the extent of suppression or enhancement. For As, Se and Te, the introduction of 2.5% ethanol, 0.5 mol/l H(2)SO(4), or to a lesser extent 0.5 mol/l H(3)PO(4), leads to an exceptional increase in the signal intensity for both instruments. Registration of signal behaviour plots (signal intensity as a function of the nebulizer gas flow rate) in different matrices revealed that both the height of the plot and the optimum nebulizer gas flow rate are a function of the matrix composition. Finally, no indication was found that the acceleration of the extracted ions over 8000 V with the high resolution instrument would lead to an alleviation of space charge effects when compared to a quadrupole-based ICP-mass spectrometer.

Journal Article↗

PubMed1996

[Methyl-carbon-11] thymidine for in vivo measurement of cell proliferation.

UNLABELLED: [Methyl-11C]thymidine and PET provide an in vivo, noninvasive, quantitative approach for studying nucleoside uptake in cells on condition that the fraction of metabolites in the total accumulated activity is known. METHODS: Using an animal model (Wistar rats), two independent approaches were followed. In the first approach, total accumulated activity in rapidly dividing tissue after intravenous injection of [methyl-11C]thymidine, respectively, [methyl-11C]thymine (first metabolite), was compared. In the second approach, the liver was surgically isolated to avoid thymidine catabolism. RESULTS: After injection of [methyl-11C]thymidine, tissue activity consists of both labeled thymidine and metabolites, while after injection of [methyl-11C]thymine, it consists only of metabolites. The fraction of metabolites ranged from 9% to 44%. Comparing the specific activity with and without liver function yielded similar results. The calculated amount of metabolites was about 10%. CONCLUSION: In spite of the intense in vivo catabolism, major activity in rapidly dividing tissue consists of [methyl-11C]thymidine.

Animals↗

PubMed1995

Measurement of [methyl-carbon-11]thymidine and its metabolites in head and neck tumors.

UNLABELLED: We made routine measurements of [methyl-11C]thymidine and its metabolites in human venous blood in 13 patients with head and neck tumors. METHODS: Patients underwent PET imaging 10-30 min after bolus injection. Venous samples were collected at various intervals and water-soluble 11C-metabolites were analyzed with semipreparative HPLC on a C18 column with isotonic phosphate solution as an eluant. RESULTS: After rapid clearance, total radioactivity remained constant at a level of about 1.2% of the initial injected activity. CONCLUSION: In this group of patients with head and neck cancers, our results show that kinetic differences in various 11C-metabolites are small.

Adult↗

PubMed1994

Determination of strontium in human whole blood by ICP-AES.

The determination of strontium in human blood samples by ICP-AES is described. For the analysis no chemical separations were required after microwave destruction. A mean value of 11.4 +/- 0.83 micrograms/l is found for normal whole blood. The limit of detection of the method is 0.3 microgram/l. As a possible application the enhancement of the strontium level in blood of human beings who died from drowning is examined.

Cadaver↗