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Zaventem, Belgium

Haunschmidt M.,Johannes Kepler University | Klampfl C.W.,Johannes Kepler University | Buchberger W.,Johannes Kepler University | Hertsens R.,JEOL Europe BV
Analytical and Bioanalytical Chemistry

A screening method for analyzing environmental waters contaminated with UV filters using direct analysis in real-time mass spectrometry (DART-MS) was developed. To demonstrate the suitability of DART-MS a test set of seven organic UV filters, namely benzophenone-3 (BP-3), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), 4-t-butyl-4′-methoxydibenzoylmethane (BM-DBM), homomethyl salicylate (HMS), 2-(ethylhexyl) salicylate (EHS), octocrylene (OC), and 4-methylbenzylidene camphor (4-MBC), was defined. In the first step, standard solutions of the analytes prepared in methanol were investigated in order to determine optimum parameters for the DART-MS. Because of the very low concentrations of UV filters expected in environmental water samples, a pre-concentration step using stir bar sorptive extraction was performed. DART-MS allows the direct, simple and rapid semi-quantitative analysis of the analytes enriched on the surface of the polydimethylsiloxane-coated stir bars. The optimized method provided calibration curves with correlation coefficients R>0.959, repeatability from 5% (for 4-MBC) to 30% (for BM-DBM) relative standard deviation and limits of detection lower than 40 ng L-1 for all analytes. Finally, real lake water samples from locations with typical leisure activities were analyzed. Results obtained with the developed DART-MS method were cross-checked by confirmatory analysis using thermodesorption gas chromatography mass spectrometry (TD-GC-MS). Thereby, it could be demonstrated that both analytical methods provide comparable concentrations for the UV filters in the lake water samples. © 2010 Springer-Verlag. Source

Eberherr W.,Johannes Kepler University | Buchberger W.,Johannes Kepler University | Hertsens R.,JEOL Europe BV | Klampfl C.W.,Johannes Kepler University
Analytical Chemistry

A novel hyphenated technique namely the combination of HPLC with direct analysis in real time (DART) mass spectrometry (MS) is presented. The coupling of HPLC to DART-MS was achieved by a simple interface design with a capillary end piece transferring the HPLC effluent to the ionization region of the DART. Flow rates (0.3-1.6 mL min-1) and inner diameters of the capillary (50-150 μm) were harmonized to provide a stable liquid jet. Ionization-related parameters optimized included positioning of the capillary end piece with respect to He outlet of the ionization source and the MS inlet, He heater temperature and He flow rate. Among DART-MS voltages, the grid electrode voltage proved to have the most pronounced effect on signal intensities. A major benefit of this setup is the possibility to employ (commonly not MS-compatible) HPLC eluents such as phosphate buffers up to a phosphate concentration of 120 mM even at typical HPLC flow rates such as 1 mL min-1 and above without negative side effects like contamination of the ion source or ion suppression. Experiments evaluating the correlation of signal intensity to mass-flow and concentration revealed that DART-MS can be seen as a mass flow sensitive detector. The usability of this hyphenated technique has been tested on the example of four parabenes (measured in the negative ion mode) as well as a set of pyrazine derivatives (measured in the positive ion mode). For the parabenes limits of detection (LOD) in the range of 20-55 μg L-1 and linear ranges from at least 200-10000 μg L-1 with correlation coefficients better than 0.997 were obtained. © 2010 American Chemical Society. Source

Hintersteiner I.,Johannes Kepler University | Hertsens R.,JEOL Europe BV | Klampfl C.W.,Johannes Kepler University
Journal of Liquid Chromatography and Related Technologies

Studies for the evaluation of a lab made liquid jet interface designed for the coupling of direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) with liquid-phase sample introduction systems such as flow injection analysis (FIA) or high performance liquid chromatography (HPLC) have been performed. Thereby a substantial influence of parameters like surface/volume ratio (determined by the inner diameter of the capillary employed) of the liquid jet as well as the composition of the eluent (with respect to the concentration of electrolyte and organic solvent) on signal intensities could be detected. Comparison of the developed interface with other more common interface types (based on electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization) was carried out on the example of a test mixture containing four parabens spiked into biological fluid samples. DART ionization proved superior when employed in combination with FIA as it was less affected by matrix effects resulting in ionization suppression. On the other hand if at least partial separation of the matrix/analytes was performed by using short chromatographic columns, the other ionization techniques turned out to be the better choice primarily due to their increased sensitivity. © 2014 Copyright Taylor & Francis Group, LLC. Source

Beissmann S.,Johannes Kepler University | Buchberger W.,Johannes Kepler University | Hertsens R.,JEOL Europe BV | Klampfl C.W.,Johannes Kepler University
Journal of Chromatography A

Direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) has been tested for its suitability as a detector for gradient elution HPLC. Thereby a strong dependency of signal intensity on the amount of organic solvent present in the eluent could be observed. Adding a make-up liquid (iso-propanol) post-column to the HPLC effluent greatly enhanced detection limits for early eluting compounds. Limits of detection achieved employing this approach were in the range of 7-27μgL-1 for the parabene test mixture and 15-87μgL-1 for the pharmaceuticals. In further investigations DART ionization was compared to several other widely used atmospheric pressure ionization methods with respect to signal suppression phenomena occurring in when samples with problematic matrices are analyzed. For this purpose extracts from environmental and waste water samples were selected as model matrices which were subsequently spiked with a set of six substances commonly present in personal care products as well as six pharmaceuticals at concentration levels between 100μgL-1 and 500μgL-1 corresponding to 100ngL-1 and 500ngL-1 respectively in the original sample. With ionization suppression of less than 11% for most analytes investigated, DART ionization showed similar to even somewhat superior behavior compared to atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization (APPI) for the Danube river water extract; for the more challenging matrix of the sewage plant effluent extract DART provided better results with ion suppression being less than 11% for 9 out of 12 analytes while values for APCI were lying between 20% and >90%. Electrospray ionization (ESI) was much more affected by suppression effects than DART with values between 26% and 80% for Danube river water; in combination with the sewage plant effluent matrix suppression >50% was observed for all analytes. © 2011 Elsevier B.V. Source

Haunschmidt M.,Johannes Kepler University | Buchberger W.,Johannes Kepler University | Klampfl C.W.,Johannes Kepler University | Hertsens R.,JEOL Europe BV
Analytical Methods

A method based on direct-analysis-in-real-time mass spectrometry (DART-MS) for the qualitative and semi-quantitative analysis of eight organic UV filters and four parabens in twelve cosmetic products with substantially different formulations (as cream, milk, lotion, oil, lipstick) was developed. All tested substances could be identified unambiguously in the investigated samples without any sample pre-treatment. Direct analysis of cosmetic products allows semi-quantitative determination of parabens. For UV filters no satisfactory results were obtained by direct analysis but all analytes could be quantified by simply dissolving the samples in methanol, addition of an internal standard and subsequent measurement of the solution by DART-MS without further pre-treatment. The results obtained using DART-MS were confirmed by a more established method namely gas chromatography with mass spectrometric detection (GC-MS). © 2011 The Royal Society of Chemistry. Source

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