Research Interests:
Research Interests:
ABSTRACT Up to now the direct analysis of reactive gases has not been investigated sufficiently. A continuously running sampling system has been developed for the direct determination of the iron concentration in hydrogen chloride. Atomic... more
ABSTRACT Up to now the direct analysis of reactive gases has not been investigated sufficiently. A continuously running sampling system has been developed for the direct determination of the iron concentration in hydrogen chloride. Atomic emission spectra were generated by using a medium power microwave induced plasma with a rectangular type cavity. Different parameters were optimized, e.g., the design of discharge tubes, gas flow, forward power and volume of sample gas. In order to characterize the plasma, the excitation and gas temperatures have been determined. The calibration was carried out by means of a certified gas reference sample containing pentacarbonyliron in argon. The detection limit was found to be 0.25 µg l–1 of iron in argon (T= 25 °C) with a reproducibility of 6%(n= 10).
Research Interests:
The investigation of microbial extracellular polymeric substances (EPS) is helpful for the implementation of analytical methods which are suitable for biofilm analysis in order to understand the architecture and function of biofilms. A... more
The investigation of microbial extracellular polymeric substances (EPS) is helpful for the implementation of analytical methods which are suitable for biofilm analysis in order to understand the architecture and function of biofilms. A procedure for the qualitative and quantitative determination of various monosaccharides, oligosaccharides and uronic acids as important components of the carbohydrate fraction of microbial EPS by high-performance liquid chromatography (HPLC) and refractive index (RI)/UV detection is presented. Porous graphitic carbon and lead-form cation-exchanger have been examined as stationary phases. Therefore, two complementary HPLC methods are presented. To simulate the conditions of hydrolysis, the influences of various salts, acids and alkalis as matrix components have been investigated. Furthermore, the dependencies on the pH value and temperature of the mobile phase have been thoroughly studied. The results showed that the lead-form cation-exchanger is suitable for the separation of the neutral monosaccharides. However, for direct analysis after acidic hydrolysis with H(2)SO(4), HCl or trifluoroacetic acid, an additional purification step, e.g., precipitation or lyophilization, is necessary when the cation-exchanger is used. With the exception of hydrolysis with HCl, the porous graphitic carbon stationary phase can be used without any further purification step and is appropriate for the separation of uronic acids and their gamma-lactones. Additionally, the separation of a single monosaccharide and its derivatives is possible. Analytical parameters including the sensitivities, repeatabilities, limits of detection and limits of quantification of both HPLC methods using the RI detector are presented. The optimized method has been applied for the characterization of alginates and is also suitable for other extracellular polysaccharides in biofilms.
Research Interests: Engineering, Chemistry, Biofilms, Chromatography, Medicine, and 15 moreBiological Sciences, Calibration, Refractive Index, Pseudomonas aeruginosa, High Performance Liquid Chromatography, CHEMICAL SCIENCES, Analytical Method, Time Factors, Reproducibility of Results, Pseudomonas Aeruginosa, Sensitivity and Specificity, Hydrolysis, Cation Exchange, Acid hydrolysis, and limit of detection
Research Interests:
ABSTRACT An analytical procedure is described for the determination of iron, nickel, chromium and manganese in gaseous hydrogen chloride by means of a modified atomic absorption spectrometer. An automated sampling system allows a ‘quasi’... more
ABSTRACT An analytical procedure is described for the determination of iron, nickel, chromium and manganese in gaseous hydrogen chloride by means of a modified atomic absorption spectrometer. An automated sampling system allows a ‘quasi’ on-line monitoring of the investigated gas. The introduction of the gas was regulated by a magnetic valve, which is connected to the autoprobe of the spectrometer and to a control unit. Typical parameters, e.g., the temperature programme and the gas injection volume, were optimized. Different types of calibration were carried out using element standard solutions, standard additions of gaseous standards and standard solutions, as well as gaseous standards. The detection limit for the described procedure was 39 pg for iron, 8.7 pg for nickel, 1.1 pg for chromium and 0.4 pg for manganese (temperature = 25 °C) using the standard calibration with element standard solutions. The reproducibility of the absorbance signals for the elements in gaseous hydrogen chloride varies between 5.3 and 13%(n= 10).
Research Interests:
Research Interests:
Research Interests:
ABSTRACT Sections are included on (a) the determination of solid contaminants in air and other gases (with sub-sections on filtration, dissolution of the particles on the filters, impactors and impingers, and (b) analytical methods. A... more
ABSTRACT Sections are included on (a) the determination of solid contaminants in air and other gases (with sub-sections on filtration, dissolution of the particles on the filters, impactors and impingers, and (b) analytical methods. A table is included of elements (or groups of elements) with their matrices and applicable sample collection, sample treatment and analytical methods and references. (85 references).
Research Interests:
Up to now the analysis of aqueous samples by ion mobility spectrometry is a challenge due to the lack of suitable sample introduction systems. But just the introduction of asymmetric field strengths leading to a higher selectivity and... more
Up to now the analysis of aqueous samples by ion mobility spectrometry is a challenge due to the lack of suitable sample introduction systems. But just the introduction of asymmetric field strengths leading to a higher selectivity and sensitivity, this technique is of growing interest for on-site analysis of contaminated water. In this work, first results for the preparation of
Research Interests:
Research Interests:
Research Interests:
Research Interests:
A non-thermal plasma generated between two parallel-plate electrodes submerged in water was studied in this work. The surface of one of the stainless-steel electrodes (the cathode) was coated with a ceramic layer of Al2O3. This reactor... more
A non-thermal plasma generated between two parallel-plate electrodes submerged in water was studied in this work. The surface of one of the stainless-steel electrodes (the cathode) was coated with a ceramic layer of Al2O3. This reactor cell was connected to a water cycle and the discharge was carried out in a closed loop and therefore an equilibrium was established during discharge. The dependence of hydrogen peroxide formation as an indicator for the generation of most important oxidative species OH radicals on the pulse repetition rate, the solution conductivity and the pH of the solution was investigated. The highest yield of H2O2 (3.5 mg L−1) was obtained at 20 pps in a NaCl solution with a conductivity of 400 µS cm−1 and pH 7 in 90 min. The maximum energy efficiency of ∼0.1 g kWh−1 H2O2 was obtained. The surface of the coated electrodes, before and after applying of electrical discharges, was analysed by scanning electron microscopy. During the discharge process, the coating was destroyed and the formation of H2O2 decreased to 10% after discharging of nearly 35 h.
Research Interests:
The analytical potential of a non-dispersive atomic fluorescence spectrometer with a tantalum coil atomizer for gas monitoring are investigated. The analytical procedure for the determination of iron in argon, introduced as iron... more
The analytical potential of a non-dispersive atomic fluorescence spectrometer with a tantalum coil atomizer for gas monitoring are investigated. The analytical procedure for the determination of iron in argon, introduced as iron pentacarbonyl, is suggested as a first step of reactive gas monitoring. Parameters optimized include the atomization temperature and duration time and the atom residence time in the atomizer. These parameters are optimized by varying the charge voltage and condenser capacity. The detection limit achieved for iron is 4 ng l–1 of gas. The relative standard deviation sr= 0.03.
Research Interests:
Research Interests:
Research Interests:
This work presents a strategy to correlate the results from gas chromatography coupled ion mobility spectrometry (GCxIMS) and mass spectrometry (GC-MS) to enable a simpler and cheaper analysis of flavor compounds in e-liquids. The use of... more
This work presents a strategy to correlate the results from gas chromatography coupled ion mobility spectrometry (GCxIMS) and mass spectrometry (GC-MS) to enable a simpler and cheaper analysis of flavor compounds in e-liquids. The use of the retention index for GCxIMS measurements was validated for its application to correlate results with GC-MS data. The easy detection of the GCxIMS for substances at concentrations as low as 1 μg/L can therefore be combined with the identification power of the MS. The use of the MS' mass signals and wide-spread availability of mass spectra libraries reduces the effort necessary to choose the correct reference standards for the identification of unknown substances. Between both detectors, correlating of the retention time indices was achieved for ± 1%. 2-Alkanones were used as an alternative reference point for the IMS and the well-established alkanes for the MS. The application on flavor compounds in e-liquids shows equal or better results than those presented for more complex, hardware-based correlations like line splitting. Additionally, the inverted reduced mobility combined with the retention index of a non-polar column enables simple extrapolation for the confirmation of expected substances as well as the use in a transferable database. For the first time, this comprehensive application allows an extensive, simplified, and cheap identification of flavor compounds in e-liquids by GCxIMS and GC-MS.
Research Interests:
Research Interests:
Research Interests: Engineering, Chemistry, Chromatography, Mass Spectrometry, Medicine, and 10 moreBiological Sciences, Escherichia coli, Isoprene, Gas Chromatography, Pseudomonas aeruginosa, CHEMICAL SCIENCES, Bacterial growth, Gas Chromatography/mass Spectrometry, Analytical and Bioanalytical Chemistry, and Pseudomonas Aeruginosa
Research Interests:
An analytical procedure is described for the determination of boron in dichlorosilane by means of ICP-AES. A modified sampling and gas introduction system allows on-line monitoring of the investigated gas. The calibration of the procedure... more
An analytical procedure is described for the determination of boron in dichlorosilane by means of ICP-AES. A modified sampling and gas introduction system allows on-line monitoring of the investigated gas. The calibration of the procedure was carried out by standard additions of gaseous diborane/argon [c(B2H6) = 10.4 µl l−1] and dichlorosilane. The detection limit was found to be 0.63 µg boron g−1 of dichlorosilane.
Research Interests:
ABSTRACT The analysis of reactive gases, especially the determination of heavy metals, is of increasing importance because of their use in the production of semiconductors. Owing to the increasing requirement for high purity gases,... more
ABSTRACT The analysis of reactive gases, especially the determination of heavy metals, is of increasing importance because of their use in the production of semiconductors. Owing to the increasing requirement for high purity gases, efficient methods of analysis have to be developed for the determination of metallic contaminants. Up to now some analytical procedures have been described, but no reliable method for the on-line monitoring of reactive gases has been established. In this publication, an analytical procedure is described for the determination of iron in gaseous hydrogen chloride by means of a modified atomic absorption spectrometer. A gas inlet was realized by a special graphite capillary. The sampling was carried out by a modified ‘bypass-backflush-balancing’ gas injection system as described previously by Schram. Typical parameters, e.g., ashing and atomization temperature, the temperature programme and the gas injection volume were optimized. The calibration was carried out using iron standard solutions. The detection limit for the described procedure was 0.7 ng ml–1 iron (temperature = 25 °C). The reproducibility of the absorbance signals for iron in hydrogen chloride was 4%(n= 6).
Research Interests:
Research Interests:
Research Interests:
New regulations on the use of flavor compounds in tobaccoless electronic cigarettes require comprehensive analyses. Gas chromatography coupled ion mobility spectrometry is on the rise as an analytical technique for analyzing volatile... more
New regulations on the use of flavor compounds in tobaccoless electronic cigarettes require comprehensive analyses. Gas chromatography coupled ion mobility spectrometry is on the rise as an analytical technique for analyzing volatile organic compounds as it combines sensitivity, selectivity, and easy usage with a full-range screening. A current challenge is the quantitative GCxIMS-analysis. Non-linear calibration methods are predominantly used. This work presents a new calibration method using linearization and its corresponding fit based on the relation between the reactant and analyte ions from the chemical ionization. The analysis of e-liquids is used to compare the presented calibration with an established method based on a non-linear Boltzmann fit. Since e-liquids contain matrix compounds that have been shown to influence the analyte signals, the use of internal standards is introduced to reduce these effects in GCxIMS-analysis directly. Different matrix mixtures were evaluated...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In aquatic environments, microbial biofilms influence the fate of organic pollutants by sorption, accumulation and biodegradation. A growing interest is focused on understanding whether or not biofilm can be used for tracing organic... more
In aquatic environments, microbial biofilms influence the fate of organic pollutants by sorption, accumulation and biodegradation. A growing interest is focused on understanding whether or not biofilm can be used for tracing organic pollutants in water streams. By absorption, biofilms accumulated on solid surfaces in water streams, could be used as passive sampler systems for tracking point sources of polycyclic aromatic hydrocarbons (PAH). This systematic monitoring approach would be of great benefit to monitor and prevent pollution in water streams. In this regard, the sorption properties of microbial biofilms need to be taken into further consideration. Due to the nature of the point sources of pollution and to the dominant dynamic conditions in water streams, the fast desorption kinetics of the accumulated pollutant out from the biofilm matrix may be the crucial limitation to this approach. For this reason, it is necessary to measure the memory of biofilms for target pollutants....
Sample preparation is an important step in chemical analysis process. The present article gives an overview about the Cloud point extraction as a technique for sample preparation for trace element analysis. Cloud point extraction steps,... more
Sample preparation is an important step in chemical analysis process. The present article gives an overview about the Cloud point extraction as a technique for sample preparation for trace element analysis. Cloud point extraction steps, mechanism, advantages, disadvantages and some applications have been discussed.
Background Fluid warming, recommended for fluid rates of > 500 ml h-1, is an integral part of patient temperature management strategies. Fluid warming devices using an uncoated aluminium containing heating element have been reported to... more
Background Fluid warming, recommended for fluid rates of > 500 ml h-1, is an integral part of patient temperature management strategies. Fluid warming devices using an uncoated aluminium containing heating element have been reported to liberate aluminium resulting in critical aluminium concentrations in heated fluids. We investigated saline solution (0.9%), artificially spiked with organic acids to determine the influence of fluid composition on aluminium release using the uncoated enFlow® device. Additionally, the Level1® as a high volume fluid warming device and the ThermoSens® device were investigated with artificial spiked fluid at high risk for aluminum release and a clinically used crystalloid solution. Results Saline solution spiked with lactate more than acetate, especially at a non neutral pH, led to high aluminium release. Next to the enFlow® device, aluminium release was observed for the Level1® device, but not for the coated ThermoSens®-device. Conclusion Uncoated alu...
Research Interests:
This work presents a strategy to correlate the results from gas chromatography coupled ion mobility spectrometry (GCxIMS) and mass spectrometry (GC-MS) to enable a simpler and cheaper analysis of flavor compounds in e-liquids. The use of... more
This work presents a strategy to correlate the results from gas chromatography coupled ion mobility spectrometry (GCxIMS) and mass spectrometry (GC-MS) to enable a simpler and cheaper analysis of flavor compounds in e-liquids. The use of the retention index for GCxIMS measurements was validated for its application to correlate results with GC-MS data. The easy detection of the GCxIMS for substances at concentrations as low as 1 μg/L can therefore be combined with the identification power of the MS. The use of the MS' mass signals and wide-spread availability of mass spectra libraries reduces the effort necessary to choose the correct reference standards for the identification of unknown substances. Between both detectors, correlating of the retention time indices was achieved for ± 1%. 2-Alkanones were used as an alternative reference point for the IMS and the well-established alkanes for the MS. The application on flavor compounds in e-liquids shows equal or better results than those presented for more complex, hardware-based correlations like line splitting. Additionally, the inverted reduced mobility combined with the retention index of a non-polar column enables simple extrapolation for the confirmation of expected substances as well as the use in a transferable database. For the first time, this comprehensive application allows an extensive, simplified, and cheap identification of flavor compounds in e-liquids by GCxIMS and GC-MS.
Research Interests:
Abstract Pesticides are compounds which can affect human, environmental and aquatic system health. Therefore, the detection and determination of these compounds at trace level concentrations is of great importance. In this study selected... more
Abstract Pesticides are compounds which can affect human, environmental and aquatic system health. Therefore, the detection and determination of these compounds at trace level concentrations is of great importance. In this study selected pesticides out of four classes were investigated as target analytes: Dichlorovos as an insecticide, terbutryn as herbicide, cybutryne from the group of biocides and quinoxyfen as an example of fungicides. A direct immersion solid phase micro extraction (SPME) Arrow-GC–MS method was developed and validated for fully automated microextraction of the target compounds from aqueous samples. In this regard, the most important experimental parameters of the extraction: Extraction time, extraction temperature, pH, ionic strength of the sample and the Arrow type, were studied and optimized. In addition, the developed method was compared with the conventional SPME, regarding sensitivity, relative recovery and precision. The limit of detection values of SPME Arrow were between 0.68 and 544 ng L-1 for dichlorvos and quioxyfen, respectively, and significantly less than similar values obtained from conventional SPME (4.63 and 4400 ng L-1 for the same compounds). For all investigated pesticides, recovery rates ranged between 90 and 116% for the Arrow as well as 85 and 107% for the classical SPME fiber. Relative standard deviations (RSD %) were 4.3–7.8 and 3.5–11.8 for the Arrow and classic SPME, respectively. Also, coefficient of determination (R2) range was within the range of 0.993–0.999 for SPME Arrow and 0.990–0.996 for classic SPME.
Research Interests:
Research Interests:
Cystic fibrosis (CF) is an autosomal recessive inherited disease which leads to a production of thickened mucus in the airways. These conditions are conducive to poly-microbial infections, like chronic lung infection, in which Pseudomonas... more
Cystic fibrosis (CF) is an autosomal recessive inherited disease which leads to a production of thickened mucus in the airways. These conditions are conducive to poly-microbial infections, like chronic lung infection, in which Pseudomonas aeruginosa (P. aeruginosa) is the major pathogenic bacterium colonizing CF lungs at the end of the lifetime of CF patients. This in vitro study uses a P. aeruginosa biofilm model under partly cystic fibrosis conditions, with a sampling of volatile extracellular metabolites. The gas sampling was done with thin-film microextraction (TFME) and commercial polydimethylsiloxane (PDMS) films, whereas the analysis of loaded films was done by gas chromatography coupled to quadrupole mass spectrometry and thermodesorption (TD-GC-qMS). For this purpose, two commercially available films were characterized by means of thermogravimetry coupled to a qMS with atmospheric pressure photo ionization (TG-APPI-qMS), regarding homogeneity and temperature stability. The ...
Research Interests:
Research Interests:
Research Interests:
SummaryThe use of fluid‐warming systems is recommended for infusion rates > 500 ml.h−1 to avoid peri‐operative hypothermia. Some fluid‐warming devices use disposable aluminium‐heated plates for heat transfer, but there is no protective... more
SummaryThe use of fluid‐warming systems is recommended for infusion rates > 500 ml.h−1 to avoid peri‐operative hypothermia. Some fluid‐warming devices use disposable aluminium‐heated plates for heat transfer, but there is no protective coating to separate the fluid from the heated aluminium surface. It is unknown if this could promote release of aluminium into infusion fluids. We investigated a coated (Fluido compact) and an uncoated (enFlow) fluid‐warming device using normal saline or balanced electrolyte solution as infusion fluids, pumped through the heated disposables at flow rates of 2, 4 and 8 ml.min−1 for 60 min each. Aluminium concentrations in the fluid samples were analysed using graphite furnace atomic absorption spectrometry. With saline the coated and uncoated devices yielded aluminium concentrations below the level of quantification (< 128 μg.l−1). Similarly, balanced electrolyte solution in the coated device yielded aluminium concentrations < 128 μg.l−1. Howe...
Research Interests:
Objectives: The detection of microbial volatile organic compounds or host response markers in the exhaled gas could give an earlier diagnosis of ventilator-associated pneumonia. Gas chromatography-ion mobility spectrometry enables... more
Objectives: The detection of microbial volatile organic compounds or host response markers in the exhaled gas could give an earlier diagnosis of ventilator-associated pneumonia. Gas chromatography-ion mobility spectrometry enables noninvasive, rapid, and sensitive analysis of exhaled gas. Using a rabbit model of ventilator-associated pneumonia we determined if gas chromatography-ion mobility spectrometry is able to detect 1) ventilator-associated pneumonia specific changes and 2) bacterial species-specific changes in the exhaled gas. Design: Experimental in vivo study. Setting: University research laboratory. Subjects: Female New Zealand White rabbits. Interventions: Animals were anesthetized and mechanically ventilated. To induce changes in the composition of exhaled gas we induced ventilator-associated pneumonia via endobronchial instillation of either Escherichia coli group (n = 11) or Pseudomonas aeruginosa group (n = 11) after 2 hours of mechanical ventilation. In a control gro...
Research Interests:
Direct inlet probe (DIP) was used as an introduction and a pre-separation step for atmospheric pressure photoionization time-of-flight ion mobility spectrometry (APPI-TOF-IMS) for the first time. IMS is an analytical technique used to... more
Direct inlet probe (DIP) was used as an introduction and a pre-separation step for atmospheric pressure photoionization time-of-flight ion mobility spectrometry (APPI-TOF-IMS) for the first time. IMS is an analytical technique used to separate and identify ionized molecules in the gas phase and under atmospheric pressure based on their mobility. The utilization of DIP prior to IMS gives the possibility to introduce the analytes into the gas phase and provides an additional separation based on their vapor pressure. The proof-of-principle study was done on example of eight polycyclic aromatic hydrocarbons (PAHs) with the ring number from 2 to 5, namely naphthalene, fluorene, anthracene, phenanthrene, pyrene, fluoranthene, benzo[a]pyrene, and benzo[k]fluoranthene. All these compounds are included in EPA priority pollutant list. Moreover, benzo[a]pyrene and benzo[k]fluoranthene are marked by EPA as probably carcinogen compounds and also included into SCF and EU lists. To increase the se...
Research Interests:
Research Interests: Engineering, Chemistry, Chromatography, Mass Spectrometry, Medicine, and 12 moreFood Analysis, Biological Sciences, Ion mobility spectrometry, Volatile Organic Compounds, Terpenes, Gas Chromatography, TERPENE, CHEMICAL SCIENCES, Cosmetics, Gas Chromatography/mass Spectrometry, Analytical and Bioanalytical Chemistry, and Equipment Design
A laser-induced fluorescence (LIF) was used as a complimentary detection system for time-of-flight ion mobility spectrometry (TOF-IMS). A LIF detection system is potentially faster than a conventional electrometer detector and can provide... more
A laser-induced fluorescence (LIF) was used as a complimentary detection system for time-of-flight ion mobility spectrometry (TOF-IMS). A LIF detection system is potentially faster than a conventional electrometer detector and can provide additional (to usual for IMS drift time) analytical information, namely wavelength of fluorescence maxima and fluorescence lifetime. Therefore, better discrimination ability can be expected. Additionally, the combination of IMS and LIF operates at atmospheric pressure. This allows fluorescence measurements of specified ions and ion clusters, which would not survive in a mass spectrometer. An IMS drift cell of open design with both the electrometer and LIF detectors was designed. The feasibility of IMS-LIF was demonstrated on the example of the Xanthene dye Rhodamine 6G (R6G). Electrospray was used as an ionization source. The release and desolvation of R6G ions from the electrospray with following IMS-LIF analysis were demonstrated. The effects of ...
Research Interests:
Research Interests:
Research Interests:
In this study, a systematic spectroscopic characterization of a low-temperature plasma (LTP) probe operated with He/N2 gas mixtures is carried out.
Research Interests:
Research Interests:
In this study, we demonstrate that the combination of an enzymatic method (based on Colilert-18 medium) and gas chromatography-differential mobility spectrometry (GC-DMS) can reduce the time required for detection of coliform bacteria... more
In this study, we demonstrate that the combination of an enzymatic method (based on Colilert-18 medium) and gas chromatography-differential mobility spectrometry (GC-DMS) can reduce the time required for detection of coliform bacteria (including Escherichia coli) from 18 to 2.5 h. The presented method includes the incubation (~2.5 h) of the sample containing coliform bacteria in Colilert-18 medium. The incubation time of 2.5 h is required for the activation of the β-galactosidase enzyme. Produced during the incubation biomarker o-nitrophenol (ONP) can be detected by means of GC-DMS within just 200 s. The detection limit for ONP was 45 ng (on-column). The method developed in this work provides significantly shorter analysis time compared with standard methods, and can be potentially adapted to the field conditions. Therefore, this method is a promising tool for an early detection of coliform bacteria (including E. coli). Graphical Abstract Fast detection of coliform bacteria by means of GC-DMS.