PubMed Health⌕ Search

Biomedical subjects

A Kettrup

Publications and source records attributed to A Kettrup.

At least 19 recordsLinked to original sources
PubMed2001

A capillary-based supersonic jet inlet system for resonance-enhanced laser ionization mass spectrometry: principle and first on-line process analytical applications.

A new supersonic jet inlet system for resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS), based on a fused-silica capillary with an integral nozzle has been developed. The new jet inlet system generates a supersonic molecular beam that originates in the center of the ion source of the time-of-flight mass spectrometer. Because of the design of the inlet system, high spatial overlap of sample and laser beam (i.e., increased detection sensitivity) and excellent jet beam qualities are achieved with good adiabatic cooling properties of analyte molecules (i.e., considerably enhanced optical selectivity of the REMPI process). Furthermore, the inlet is very robust and chemically inert and contains no moving parts. As a result of these properties, the new inlet is perfectly suited for field applications of jet-REMPI. A first field application of a mobile supersonic jet-REMPI mass spectrometer equipped with the novel inlet technique is reported; namely, the concentration of monochlorobenzene, which is an indicator for the formation and emission of toxic polychlorinated dibenzo-p-dioxins/furans, PCDD/F) was measured on-line in the flue gas of a waste incineration plant.

Journal Article↗
PubMed2001

A mobile mass spectrometer for comprehensive on-line analysis of trace and bulk components of complex gas mixtures: parallel application of the laser-based ionization methods VUV single-photon ionization, resonant multiphoton ionization, and laser-induced electron impact ionization.

A newly developed compact and mobile time-of-flight mass spectrometer (TOFMS) for on-line analysis and monitoring of complex gas mixtures is presented. The instrument is designed for a (quasi-)simultaneous application of three ionization techniques that exhibit different ionization selectivities. The highly selective resonance-enhanced multiphoton ionization (REMPI) technique, using 266-nm UV laser pulses, is applied for selective and fragmentationless ionization of aromatic compounds at trace levels (parts-per-billion volume range). Mass spectra obtained using this technique show the chemical signature solely of monocyclic (benzene, phenols, etc.) and polycyclic (naphthalene, phenathrene, indol, etc.) aromatic species. Furthermore, the less selective but still fragmentationless single photon ionization (SPI) technique with 118-nm VUV laser pulses allows the ionization of compounds with an ionization potential below 10.5 eV. Mass spectra obtained using this technique show the profile of most organic compounds (aliphatic and aromatic species, like nonane, acetaldehyde, or pyrrol) and some inorganic compounds (e.g., ammonia, nitrogen monoxide). Finally, the nonselective ionization technique laser-induced electron-impact ionization (LEI) is applied. However, the sensitivity of the LEI technique is adjusted to be fairly low. Thus, the LEI signal in the mass spectra gives information on the inorganic bulk constituents of the sample (i.e., compounds such as water, oxygen, nitrogen, and carbon dioxide). Because the three ionization methods (REMPI, SPI, LEI) exhibit largely different ionization selectivities, the isolated application of each method alone solely provides specific mass spectrometric information about the sample composition. Special techniques have been developed and applied which allow the quasi-parallel use of all three ionization techniques for on-line monitoring purposes. Thus, a comprehensive characterization of complex samples is feasible jointly using the characteristic advantages of the three ionization techniques. Laboratory applications show results on rapid overview characterization of mineral oil-based fuels and coffee headspace. The first reported field applications include timely resolved on-line monitoring results on automobile exhausts and of waste incineration flue gas.

Journal Article↗
PubMed2001

Migration of neutral solutes by double stepwise gradient elution in capillary electrochromatography.

Characteristics of electroosmotic flow (EOF) and the migration of neutral solutes under double stepwise gradient elution in capillary electrochromatography were studied systematically. EOF velocity proved to be the function of operation time changing with the introduction of the second mobile phase. Accordingly, the retention of components also changed. The migration of neutral solutes was studied under the following three situations; A, components eluted when the column was filled only with the first kind of mobile phase; B, solutes eluted still in the first kind of mobile phase while at that time two kinds of mobile phase coexisted in the column and C, samples eluted in the second kind of mobile phase. Equations to describe the retention times of components under these three kinds of conditions were deduced and applied to predict the retention times of 12 aromatic compounds. Relative errors between experimental and calculated values were below 5.0%, which proved the reliability of the equations. In addition, parameters that might affect the retention time of solutes, such as the transferring time of mobile phase vials, the capacity factors of components and EOF velocities two steps were studied systematically.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2001

Emission of nonchlorinated and chlorinated aromatics in the flue gas of incineration plants during and after transient disturbances of combustion conditions: delayed emission effects.

The profiles of different products of incomplete combustion (PIC) in the flue gas of a 1 MW pilot combustion facility were investigated under normal steady-state and disturbed combustion conditions. The behavior of emission profiles after disturbed combustion conditions was investigated in order to obtain a better understanding of emission memory effects. Highly time-resolved, quantitative on-line measurements of several aromatic species down to low ppbv or higher pptv concentrations were performed by a mobile resonance-enhanced multiphoton ionization time-of-flight mass spectrometer. Conventional analytical methods (gas chromatography-mass spectrometry and high-performance liquid chromatography) were also applied for measurement of polycyclic aromatic hydrocarbons (PAH) and polychlorinated dibenzo-p-dioxins and -furans (PCDD/F). The sampling point was located in the high-temperature region of the plant at the outlet of the post-combustion chamber at temperatures between 650 and 880 degrees C, prior to any emission reduction devices. The investigation pointed out that after a short phase of disturbed combustion conditions, e.g., due to process changes, transient puffs, or malfunctions, the composition of combustion byproducts in the flue gas can be changed drastically for a very long time ("memory emission" effect). It is suggested that carbonaceous layers, deposited on the inner walls in the high-temperature zone of the plant, might be responsible for the observed memory emission of some PAH species. Drastic changes in the profiles of the PCDD/F homologues were also observed during memory emission conditions. The PAH memory most likely is due to pyrolytic degradation of the carbonaceous layers, while the altered PCDD/F homologue pattern may be mediated by the high catalytic activity of the freshly formed deposit layers. Finally, it should be emphasized that a rich pattern of aromatic species, including PCDD/F, was found in a temperature regime well above the typical temperature window (approximately 300 degrees C) for de novo PCDD/F formation.

Air Pollutants↗
PubMed2001

Quantitative and qualitative precision improvements by effective mobility-scale data transformation in capillary electrophoresis analysis.

By transforming the time-based x-axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility-scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (mu eff-scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity-based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the mu eff-scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time-scale integration.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed2001

Application of coupled liquid chromatography-mass spectrometry in photolysis studies of the herbicide triflusulfuron-methyl.

The photochemical fate of the herbicide triflusulfuron-methyl in aqueous solution under UV light (lambda > 290 nm) was investigated. Nine photoproducts were detected and tentatively identified by LC/MS and LC/MS/MS analysis. The main routes of degradation involve the cleavage and/or contraction of the sulfonylurea bridge with the elimination of sulfur dioxide, which increases the acidity of the reaction medium. On the basis of the results obtained a photodegradation pathway is proposed.

Benzoates↗
PubMed2001

Partial-filling micellar electrokinetic chromatography and non-aqueous capillary electrophoresis for the analysis of selected agrochemicals.

Selected agrochemicals (s-triazines and phenoxy acids) have been investigated with partial-filling micellar electrokinetic chromatography (PFMEKC) and non-aqueous capillary electrophoresis (NACE). Because these two techniques are compatible for coupling of capillary electrophoresis with mass spectrometry, different conditions affecting the separation efficiency (reproducibility, method linearity) were systematically tested, and the results were compared with those from classical MEKC. The conditions tested included buffer molarity, pH, the concentrations of the organic modifier and surfactant, the applied voltage, the injection time of the sample, and the length of the partial-filling plug. The respective limits of detection (LOD) using UV-detection were determined. Reduction of the electrophoretic raw data using the mobility scale transformation (micro-scale) improved qualitative comparison of the electropherograms and the reproducibility of quantitative data (integrated peak area) thus extending this data treatment from CZE to other endoosmotic flow-driven CE-techniques such as PFMEKC and NACE.

Journal Article↗
PubMed2001

Bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans in the foodweb of Ya-Er Lake area, China.

Bioaccumulation of PCDD/F in the foodweb was investigated in the Ya-Er Lake area, which was heavily polluted by PCDD/F. The high concentrations of PCDD/F in sediment can be transferred and bioaccumulated by aquatic organisms and humans through various pathways. Benthonic invertebrate animals and aquatic plants with a lot of fibers in the root can accumulate PCDD/F from sediment and water. Snail (Bellamya aeruginosa), shrimp (Macrobranchium sp.) and freshwater mussel (Acuticosta chinensis (Lea)) took up PCDD/F from the water and maintained the emission patterns, whereas fish tended to selectively accumulate 2,3,7,8-substituted isomers. The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by PCDD/F due to ingestion of fish and other aquatic organisms from sediment. The residual concentration in breast milk depended on the original concentration of PCDD/F in the food. A resident in Ya-Er Lake area showed a daily intake of PCDD/F of about 9.14 pg TEQ/kg body weight/day. This is higher than the tolerable daily intake (TDI) for PCDD/F (1 pg TEQ/kg body weight/day), which was recommended by the World Health Organization (WHO).

Animals↗
PubMed2001

Mobility and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediment of Ya-Er Lake, China.

The sediment of Ya-Er Lake had been heavily polluted by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the former chloralkali industry. The total amounts of PCDD/Fs and I-TEQ decreased along the water flow direction and also decreased from top to bottom layers of sediment cores. Sediment of Pond 1 was dominated by PCDF. especially TCDF. In contrast, in the other four ponds, PCDD dominated in all layers and octachlorinated dibenzo-p-dioxin (OCDD) predominated in all of the homologues. When homologue profiles from sediments and water samples were compared using principal component analysis (PCA), the first two principal components represented 95.2% of the variance in the data. The first component explained 75.9% of the variance and the second one 19.3%. Two clusters were most distinct, presenting a shift in PCDD/Fs composition from PCDF to heptachlorinated dibenzo-p-dioxin (HpCDD) and OCDD in sediments and water from Pond I to Ponds 2-5. The pattern variation between Pond I and Ponds 2-5 in Ya-Er Lake was most likely due to the change of process in the chemical plant after the dams between the ponds were built. The results of the present study also showed that log Koc of PCDD/Fs calculated from data of sediment and water in the field were comparable with theoretical log Koc. The results also implied that the concentrations of PCDD/Fs in water and sediments could be predicted from each other by log Koc.

Benzofurans↗
PubMed2001

Leaching behaviour of wood treated with creosote.

The results of a laboratory investigation on the leaching behaviour of wood treated with creosote and of untreated wood are reported. A special leaching test derived from the German standard method DEV S4 test (DIN 38414) has been developed. Samples were leached in deionized water, in a solution buffered at pH 4.7 and in a solution of humic substances. The organic fraction of the leachate was extracted using liquid-liquid extraction. The extracts were analysed qualitatively with GC/MSD and quantified with GC/FID. The results were compared with those of Soxhlet-extracts from creosote-treated wood.

Chromatography, Gas↗
PubMed2001

Quantitative structure-property relationships (QSPRs) on direct photolysis of PCDDs.

By the use of partial least squares (PLS) method and 27 quantum chemical descriptors computed by PM3 Hamiltonian, a statistically significant QSPR were obtained for direct photolysis quantum yields (Y) of selected Polychlorinated dibenzo-p-dioxins (PCDDs). The QSPR can be used for prediction. The direct photolysis quantum yields of the PCDDs are dependent on the number of chlorine atoms bonded with the parent structures, the character of the carbonoxygen bonds, and molecular polarity. Increasing bulkness and polarity of PCDDs lead to decrease of log Y values. Increasing the frontier molecular orbital energies (Elumo and Ehomo) and heat of formation (HOF) values leads to increase of log Y values.

Carbon↗
PubMed2001

Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabolism and uptake of phenanthrene in wheat-solution-lava microcosm.

Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabolism and uptake of phenanthrene in wheat-solution-lava microcosm were studied using 14C-labeled phenanthrene. The mineralization and metabolism of phenanthrene were fast in such a system. At least 90% of the applied phenanthrene were transformed within 24 days. Only 0.3% of the applied 14C-activity were identified to be the parent phenanthrene. Most of the applied 14C-activity (70%) was recovered from wheat, in which ca. 70% were associated with wheat shoots (stems and leaves) and ca. 30% wheat roots. 33% and 20% of the applied 14C-activity had been constructed into wheat tissues of shoots and roots, respectively. The 14C-activity recovered in forms of CO2 and volatile organic chemicals (VOCs) was 12-16% and 4-5%, respectively. The major metabolites of phenanthrene were polar compounds (18% of the applied 14C) and only 2.1% were identified as non-polar metabolites. No phenanthrene was found in wheat shoots indicating that it could not be transported from roots to upper parts of the plant but in form of metabolites (mostly polar metabolites). Foliar uptake of 14C-activity via air in form of 14CO2 occurred. The presence of Tween-80 significantly enhanced the degradation of phenanthrene, which could be attributed to its increase of microbial activities in the system. Tween-80 also significantly (P < 0.05) reduced the phenanthrene level in wheat roots, which probably resulted from desorption of phenanthrene from root surface caused by the surfactant.

Adsorption↗
PubMed2001

Persistence of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in Ya-Er Lake area, China.

The concentrations of polychlorinaxed dibenzo-p-dioxins and dibenzofurans (PCDD/F) in surface sediment, soil, human hair, and fish muscle from Ya-Er Lake area, China, were analyzed. The results showed that there were very high concentrations of PCDD/F existing in these samples. The results also indicated that Ya-Er Lake, which received a large amount of waste water from a nearby chloroalkali plant, was heavily polluted by PCDD/F. The present study demonstrated that those congeners, which possess at least three chlorine atoms in the lateral position with a fourth chlorine atom in the neighborhood bond of the third single chlorine atom, such as 1,2,7,8-TCDF and 2,3,6,7-TCDF, were very resistant to biodegradation due to the "neighbor effect" of every two chlorine atoms. The present study suggested that human hair may be a suitable alternative bioindicator for detecting PCDD/F exposure.

Animals↗
PubMed2001

Is it possible to develop a QSPR model for direct photolysis half-lives of PAHs under irradiation of sunlight?

By the use of the partial least squares method and 11 fundamental quantum chemical descriptors computed from the PM3 Hamiltonian, a Quantitative Structure-Property Relationship model was obtained for direct photolysis half-lives of selected polycyclic aromatic hydrocarbons (PAHs) under irradiation of sunlight. Direct photolysis half-lives for some other PAHs without reported values were predicted. It was concluded from the model that the main factors affecting photolysis half-lives of PAHs under irradiation of sunlight are PAH absolute hardness and electronegativity, which are related to the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, (Elumo - Ehomo) and (Elumo + Ehomo), respectively. Increasing Ehomo and the average molecular polarizability (alpha) values of the PAHs leads to decrease of photolysis half-lives. Increasing (Elumo - Ehomo) and Elumo values of the PAHs leads to an increase of the PAH photolysis half-lives.

Environmental Pollutants↗
PubMed2001

Comparison of degradation reactions of Acid Yellow 61 in both oxidation processes of H2O2/UV and O3.

The comparison of degradation of Acid Yellow 61 as a model dye compound in both oxidation processes of H2O2/UV and O3 has been studied. When the decolorization rate of Acid Yellow 61 in both reactions presented similar, it was found there are some differences from the results of AOX removal and production of inorganic ions and organic acids. The results reveal that the H2O2/UV has beneficial effect on mineralization than O3 only for degradation of Acid Yellow 61 solution and it is possible for enhancement of method efficiency by taking longer reaction time and addition of high concentration of oxidants.

Benzene Derivatives↗
PubMed2000

Study of the copper distribution in contaminated soils of hop fields by single and sequential extraction procedures.

Hop growing in Bavaria requires the use of copper containing fungicides against mildew, which results in an accumulation of copper in the upper soils to concentrations of up to approximately 450 mg kg(-1). The naturally occurring concentration of copper is approximately 10-15 times lower. Several single and sequential extractions were performed in parallel to the determination of total copper content after aqua regia digestion. By these means copper mobility and retention, its availability to plants as well as its distribution in soils was assessed. Three agricultural soils and two soils from fallow land have been analysed to elucidate whether the copper distribution changes in relation to agricultural activities and to predict environmental risks due to the high copper concentrations. This work also focuses on the difficulties arising from different results when using single and sequential extraction procedures. EDTA, acetic acid, deionised water, ammonium nitrate and calcium chloride were used as single extractants for the functionally defined speciation. EDTA and acetic acid can be regarded as extractants for the plant-available species, while deionised water, NH4NO3 and CaCl2 only release electrostatically weakly bound metals to estimate the mobile species. The extraction behaviour of copper in these procedures is discussed with respect to the quantities extracted from the contaminated and non-contaminated soils. The studies indicate that no vertical copper translocation is observed in the ground, but the main amounts are highly available to plants. Sequential extraction procedures were used for operationally defined speciation, quantifying copper in specific soil phases. The 'five-step extraction scheme' first applied, suggested by the Standard Measurement and Testing Programme of the European Community, overestimated the amounts of copper bound to the residual phase. This was mainly due to the non-specific nature of the reagents for the organic/sulfidic and crystalline iron oxide fraction. A second reason could be the fact that this scheme was developed for sediment and not for soil analysis. Therefore, the sequential extraction has been applied using an adapted method of Zeien and Bruemmer, using different extractants for the two phases. The copper distribution was different, showing that approximately 40-50% of the total copper was bound to the organic fraction and approximately 15-30% could be extracted with the iron oxides. The amounts in the residual fraction were much lower. After comparing the results of the different extraction procedures the environmental behaviour of copper and its risks for plants, micro-organisms and groundwater is discussed in brief.

Agriculture↗