Time filter

Source Type

Vautz W.,Leibniz Institute for Analytical Sciences | Seifert L.,Leibniz Institute for Analytical Sciences | Liedtke S.,Leibniz Institute for Analytical Sciences | Hein D.,PAS Technology Deutschland GmbH
International Journal for Ion Mobility Spectrometry | Year: 2014

Ion mobility spectrometry (IMS) is a well-known analytical method for the detection of CWAs and explosives since many years. Coupling IMS to GC pre-separation, new application fields in medicine and biology could be opened, dealing with complex and humid mixtures. However, identification of unknowns in such a complex sample is challenging and can only be achieved by parallel GC/MS analysis, thus obtaining a proposal for the responsible compound for validation via reference substances by GC/IMS again. The available adsorption tools for such accompanying GC/MS analysis have their particular drawbacks (e.g. problematic quantification for SPME, high sample volumes for adsorption tubes). Therefore miniaturised adsorption needles (NeedleTrap) were applied to both GC/IMS and GC/MS for validation of their reproducibility. It could be demonstrated that the needles can even be used for appropriate quantification when the adsorbent and the sample volume are adapted properly to the concentration range, the compounds of interest and humidity of the sample. The method is very flexible with regard to the concentration range by variation of the sample volume (e.g. 20 mL for pptV, 10 mL for lower ppbV or 1 mL for ppmV) and with regard to the compounds of interest by application of common adsorption materials optimised for the relevant substance group. Such materials are available commercially in a broad variability. Therefore, the miniaturised adsorption needles are a helpful complementary sampling method for any GC/MS or GC/IMS investigations. © 2014 Springer-Verlag Berlin Heidelberg. Source

Trefz P.,University of Rostock | Kischkel S.,University of Rostock | Hein D.,PAS Technology Deutschland GmbH | James E.S.,Shinwa Chemical Industries Ltd. | And 2 more authors.
Journal of Chromatography A | Year: 2012

Combining advantages of SPE and SPME needle trap devices (NTD) represent promising new tools for a robust and reproducible sample preparation. This study was intended to investigate the effect of different packing materials on efficacy and reproducibility of VOC analysis by means of needle trap micro extraction (NTME). NTDs with a side hole design and containing different combinations of PDMS, DVB and Carbopack X and Carboxen 1000 and NTDs containing a single layer organic polymer of methacrylic acid and ethylene glycol dimethacrylate were investigated with respect to reproducibility, LODs and LOQs, carry over and storage. NTDs were loaded with VOC standard gas mixtures containing saturated and unsaturated hydrocarbons, oxygenated and aromatic compounds. Volatile substances were thermally desorbed from the NTDs using fast expansive flow technique and separated, identified and quantified by means of GC-MS. Optimal desorption temperatures between 200 and 290°C could be identified for the different types of NTDs with respect to desorption efficiency and variation. Carry over was below 6% for polymer packed needles and up to 67% in PDMS/Carboxen 1000 NTDs. Intra and inter needle variation was best for polymer NTDs and consistently below 9% for this type of NTD. LODs and LOQs were in the range of some ng/L. Sensitivity of the method could be improved by increasing sample volume. NTDs packed with a copolymer of methacrylic acid and ethylene glycol dimethacrylate were universally applicable for sample preparation in VOC analysis. If aromatic compounds were to be determined DVB/Carboxen 1000 and DVB/Carbopack X/Carboxen 1000 devices could be considered as an alternative. PDMS/Carbopack X/Carboxen 1000 NTDs may represent a good alternative for the analysis of hydrocarbons and aldehydes. NTME represents a powerful tool for different application areas, from environmental monitoring to breath analysis. © 2011 Elsevier B.V. Source

Mleth M.,University of Rostock | Schubert J.K.,University of Rostock | Groger T.,Helmholtz Center for Environmental Research | Sabei B.,University of Rostock | And 6 more authors.
Analytical Chemistry | Year: 2010

This study was intended to evaluate low-volume (20 mL) multibed needle trap (NTD) sampling combined with heart-cut gas chromatography/mass spectrometry (GC/ MS) and comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/TOFMS) for trace gas analysis under clinical conditions. NTDs, high-throughput automatic desorption and separation systems, were tested in vitro and within a study in 11 patients undergoing cardiac surgery with respect to reproducibility, reliability, and clinical applicability. NTDheart-cut GC/MS analysis of standard mixtures containing different volatile organic compounds (VOCs) yielded relative standard deviations (RSDs) from 4.0% to 18.5%. Substance adsorption was stable for 1 day if NTDs were closed on both ends and was stable for approximately 7.8 h when NTD tip ends had to be left open during autosampler storage. Even in the presence of high concentrations of contaminants linearity of heart-cut GC/MS was conserved. In patients' breath potential biomarkers could be determined even in the presence of very high concentrations of sevoflurane. Profiles of blood-borne biomarkers, intravenous drugs, and clinical contaminants were characterized. Comprehensive GC × GC/TOF-MS may be used as a screening tool for new biomarkers, if patterns are generated from deconvoluted normalized areas. Needle trap sampling in combination with hyphenated chromatographic techniques can thus be used to provide well-tailored solutions for complex problems occurring in clinical breath analysis. © 2010 American Chemical Society. Source

Trefz P.,University of Rostock | Rosner L.,PAS Technology Deutschland GmbH | Hein D.,PAS Technology Deutschland GmbH | Schubert J.K.,University of Rostock | Miekisch W.,University of Rostock
Analytical and Bioanalytical Chemistry | Year: 2013

Needle trap devices (NTDs) have shown many advantages such as improved detection limits, reduced sampling time and volume, improved stability, and reproducibility if compared with other techniques used in breath analysis such as solid-phase extraction and solid-phase micro-extraction. Effects of sampling flow (2-30 ml/min) and volume (10-100 ml) were investigated in dry gas standards containing hydrocarbons, aldehydes, and aromatic compounds and in humid breath samples. NTDs contained (single-bed) polymer packing and (triple-bed) combinations of divinylbenzene/Carbopack X/Carboxen 1000. Substances were desorbed from the NTDs by means of thermal expansion and analyzed by gas chromatography-mass spectrometry. An automated CO2-controlled sampling device for direct alveolar sampling at the point-of-care was developed and tested in pilot experiments. Adsorption efficiency for small volatile organic compounds decreased and breakthrough increased when sampling was done with polymer needles from a water-saturated matrix (breath) instead from dry gas. Humidity did not affect analysis with triple-bed NTDs. These NTDs showed only small dependencies on sampling flow and low breakthrough from 1-5 %. The new sampling device was able to control crucial parameters such as sampling flow and volume. With triple-bed NTDs, substance amounts increased linearly with increasing sample volume when alveolar breath was pre-concentrated automatically. When compared with manual sampling, automatic sampling showed comparable or better results. Thorough control of sampling and adequate choice of adsorption material is mandatory for application of needle trap micro-extraction in vivo. The new CO2-controlled sampling device allows direct alveolar sampling at the point-of-care without the need of any additional sampling, storage, or pre-concentration steps. © 2013 Springer-Verlag Berlin Heidelberg. Source

Discover hidden collaborations