Jürgen Efer
Leipzig University
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Featured researches published by Jürgen Efer.
Journal of Chromatography A | 2002
Arndt Asperger; Jürgen Efer; Therese Koal; W. Engewald
An integrated on-line SPE-HPLC-MS/MS system has been developed for the rapid analysis of various trace level priority pesticides in surface and drinking water. Eleven pesticides were included in this study, with various phenylureas, triazines and organophosphorous species among them. Use of turbulent-flow chromatography columns (TFC, 50 x 1 mm, 30-50 microm particle size) as extraction cartridges enables fast on-line SPE at high sampling flow-rate (5 ml/min). Polymeric and carbon based TFC columns (Oasis HLB, Cyclone, Hypercarb) allow complete extraction with good recoveries from water volumes up to 50 ml. On-line coupling to HPLC is performed with re-mixing of the organic TFC eluate with water in front of the analytical column to ensure efficient band focussing. For fast HPLC analysis, a short monolithic column is applied in combination with highly selective API-MS/MS detection. Matrix effects on the APCI-MS/MS signal were found to be reduced by the system to an acceptable minimum. Limits of detection, determined for 10-ml samples of river water were in the range between 0.4 and 13 ng/l typically, except trifluralin (approximately 280 ng/l), which is less susceptible to ionization under atmospheric pressure conditions. At an enriched water volume of 10 ml, the whole SPE-HPLC-MS/MS procedure requires less than 14 min. The method was successfully applied to the analysis of drinking and surface water samples taken from several sampling sites around the city of Leipzig, Germany. Concentrations measured (maximum: 16 ng/l simazine in river water) were far below the concentration limits scheduled by law.
Journal of Chromatography A | 2000
André Schreiber; Jürgen Efer; W. Engewald
The coupling of high-performance liquid chromatography (HPLC) and atmospheric pressure ionisation mass spectrometry (API-MS) seems to be the method of choice if good separation and selective detection of semi-volatile, thermolabile, and polar substances is required. Libraries of mass spectra will make the identification of unknown substances in complex environmental samples easier and more user-friendly. Unfortunately, existing GC-MS libraries are not applicable to HPLC-API-MS analysis. Thus, new and extensive mass spectral libraries were constructed. Several investigations of chromatographic (composition and salt concentration of the eluent) as well as mass spectrometric (orifice voltage) parameters and a few applications of real environmental samples are used to discuss the possibilities and limits of these libraries.
Journal of Chromatography A | 2001
Arndt Asperger; Jürgen Efer; Therese Koal; W. Engewald
The API-MS signal response of several pesticides (atrazine, simazine, isoproturon, diuron, chlorfenvinphos, chlorpyrifos, alachlor, trifluralin) depending on the flow-rate of eluent entering the MS interface was investigated. The investigations were based on API-MS-MS analyses of standard pesticide mixtures in the flow injection mode (FIA) at systematically varied eluent flow-rates using both an ESI interface (Turboionspray) and a heated nebulizer type APCI source. In the result, the individual compounds included in this study showed significant differences in their signal response behaviour depending on the flow-rate of eluent applied. The most hydrophobic compounds among the investigated pesticides (chlorpyrifos and trifluralin) showed drastic losses of sensitivity with increasing eluent flow-rate in both ESI and APCI, while more hydrophilic compounds like atrazine, simazine and isoproturon showed the expected signal response (concentration-sensitive in ESI, mass-flow-sensitive in APCI) at least within a certain range of flow-rates (200-600 microl/min in ESI, 200-2000 microl/min in APCI). These findings lead to the conclusion that application of a programmed HPLC eluent flow-rate may be advantageous to achieve maximum sensitivity of API-MS detection for all pesticides of interest. This is exemplified by the implementation of a flow gradient into an online SPE-HPLC-APCI-MS/MS method for improved analysis of pesticides in drinking water.
Journal of Chromatography A | 1999
W. Engewald; J Teske; Jürgen Efer
The application of programmed temperature vaporisation (PTV) in capillary gas chromatographic analysis is reviewed. The development of the different strategies as well as the state of the art are described. As the analytes are normally enriched in the PTV insert, the quoted papers are subdivided depending on whether the enrichment was carried out from organic solvents, from water or from gaseous media. Furthermore, the possibilities of PTVs for on-line coupling with sample preparation methods or other separation techniques and their use as thermoreactors are mentioned.
Chromatographia | 2003
Therese Koal; Arndt Asperger; Jürgen Efer; W. Engewald
SummaryA new system has been developed for rapid on-line SPE-LC-MS-MS analysis of a wide spectrum of trace level pesticides in drinking and surface water. The system employs a serial arrangement of two different turbulent flow columns (TFC; polymer based column in front, carbon based column back) for rapid extraction (Turbulent flow solid phase extraction; TFSPE) from small sample volumes (10 mL) at high flow rates (5 mL min−1). Purely organic eluent is used for TFC elution, and the effluent is re-mixed with water in a mixing chamber in front of the HPLC column to provide efficient analyte focusing. This methodology allows to use a short monolithic LC column for the following fast on-line LC-APCI-MS-MS analysis.This approach gives quantitative results for nearly 30 pesticide species (triazines, phenyl ureas, organophosphorous pesticides and others) in less than 14 min and, thus, allows considerably increased sample throughput. The method is well reproducible, robust and extremely sensitive achieving detection limits between 0.1 and 1 ng L−1. As the comparison of internal and external calibration methods showed, potential matrix effects on the quality of the results are managed by the method in a very effective manner.Real pesticide concentrations determined in drinking water and surface water samples showed significant temporal variations but were constantly below the concentration limit for individual pollutants of 100 ng L−1.
Journal of Chromatography A | 1999
W. Engewald; J Teske; Jürgen Efer
The introduction of large sample volumes in capillary gas chromatography using programmed temperature vaporisers (PTV) is reviewed. The development of the different strategies as well as the state of the art are described. As the analytes are normally enriched in the insert in large-volume PTV injection, the quoted papers are subdivided depending on whether the enrichment was carried out from organic solvents, from water or from gaseous media. Furthermore, the possibilities of PTVs for online coupling with sample preparation methods or other separation techniques and their use as thermoreactors are mentioned.
Journal of Chromatography A | 1996
Uta Lewin; Jürgen Efer; W. Engewald
Electrochemical detection (ED) in the oxidative and reductive mode was applied to the analysis of nitroaromatics, nitramines, aminoaromatics and nitrophenols in groundwater samples from the surroundings of a former ammunition plant. Settings for working potential and eluent composition were optimized in terms of detection limit, linearity and selectivity. The results were compared with those obtained by UV detection and the advantages of combined UV-ED detection for the analysis of complex samples are shown.
Chromatographia | 1998
J Teske; Jürgen Efer; W. Engewald
SummaryThe potential of large-volume PTV injection was studied for the analysis of triazine herbicides in water samples. Direct water injection and in-vial extraction were described and compared. Detection limits were between 0.01–0.02 μg L−1 and relative standard deviations were <9%. Both methods are suitable for the analysis of triazines at ppt-level, although in-vial extraction is favourable for water samples with relatively large amounts of matrix components.
Chromatographia | 1997
U. Lewin; L. Wennrich; Jürgen Efer; W. Engewald
SummaryA method was developed for the determination of nitrobenzoic acids and nitrophenols as well as of diaminoaromatics and was applied to the analysis of water samples from the former ammunition plant at Elsnig (Saxony, Germany).The procedure is based on a preseparation into a neutral, an acidic and a basic fraction by multi-step extraction at different pH values followed by HPLC analysis with UV and electrochemical detectors, coupled in series.Applying optimized enrichment conditions, all investigated compounds were extracted from spiked distilled water with recoveries >80% and variation coefficients <7%. Similar results were obtained with spiked ground water samples.After enrichment, all compounds can be analysed by HPLC with UV detection at concentrations below 100 ngL−1. The electrochemical detector (ELCD) allowed a selective and sensitive detection of the nitrophenols and especially of the diaminoaromatics and, therefore, provides, some advantages in the analysis of real samples.
Umweltwissenschaften Und Schadstoff-forschung | 1993
W. Engewald; Thomas Knobloch; Jürgen Efer
ZusammenfassungMittels adsorptiver Anreicherung an hydrophoben Adsorbentien, Thermodesorption und kapillargaschromatographischer Analyse wurden flüchtige organische Verbindungen in den Rauchgasen aus dem Hausbrand von Braunkohlebriketts aus dem Lausitzer Revier bestimmt. 152 Verbindungen konnten sicher identifiziert und quantitativ erfaßt werden. Die auf die Menge des eingesetzten Brennmaterials bezogenen Emissionsfaktoren der nachgewiesenen Einzelverbindungen wurden ermittelt und gestatten erstmals eine auf konkreten Meßwerten basierende Abschätzung der aus dem Hausbrand heimischer Braunkohle resultierenden Belastung der Stadt Leipzig mt flüchtigen organischen Verbindungen.AbstractVolatile organic compounds were determined in stack-gas emissions from the residential burning of brown-coal briquets using adsorptive enrichment on hydrophobic adsorbents, thermal desorption and capillary-gas chromatographic analysis. 152 compounds were identified and quantified.Quantitative emission factors of the identified individual compounds were determined in relation to the amount of the fuel used. These factors permit assessment of the pollution of the city of Leipzig with volatile organic compounds resulting from the burning of indigenous lignite.