TY - JOUR A1 - Tahri, K. A1 - Tiebe, Carlo A1 - Bougrini, M. A1 - Saidi, T. A1 - El Alami El Hassani, N. A1 - El Bari, N. A1 - Hübert, Thomas A1 - Bouchikhi, B. T1 - Characterization and discrimination of saffron by multisensory systems, SPME-GC-MS and UV-Vis spectrophotometry N2 - Different electronic sensor systems coupled with multivariate data analysis were applied to characterize and classify seven saffron samples and to verify their declared geographical origin. The proposed electronic sensing consists of a low-cost electronic nose (E-nose) based on metal oxide semiconductor sensors and a voltammetric electronic tongue (VE-tongue) based on voltammetric sensors. The ability of multivariable analysis methods such as Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Support Vector Machines (SVMs) to classify the saffron samples according to their geographical origin have been investigated. Both PCA and HCA have shown an overlapping of E-nose responses. Moreover, the SVM analysis of the E-nose database reached a 66.07% success rate in the recognition of the saffron sample odour. On the other hand, good discrimination has been reached using PCA and HCA in the VE-tongue characterization case, besides a 100% accuracy in the saffron flavour recognition was attained. To validate the proposed electronic sensing systems, analytical chemical methods such as SPME-GC-MS and UV-Vis spectrophotometry were used. These analytical methods could be helpful tools to identify the composition of volatile compounds of the analysed saffron samples. Moreover, UV-Vis spectrophotometry was also used to determine the non-volatile profile of the samples from different geographic origins. It is demonstrated that the electronic sensing systems' findings are in a satisfactory correlation with the analytical methods. In the light of these results, we might say that the electronic systems offer a fast, simple and efficient tool to recognize the declared geographical origin of the saffron samples. KW - Electronic nose KW - Voltammetric electronic tongue KW - SPME-GC-MS KW - UV-vis spectrophotometry KW - Saffron KW - Geographic differentiation KW - Multivariable analysis PY - 2015 DO - https://doi.org/10.1039/C5AY01986A SN - 1759-9660 SN - 1759-9679 VL - 7 IS - 24 SP - 10328 EP - 10338 PB - RSC Publ. CY - Cambridge AN - OPUS4-35174 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Detjens, Marc A1 - Hübert, Thomas A1 - Tiebe, Carlo A1 - Banach, Ulrich T1 - Temperature influence on coulometric trace humidity measurement N2 - Planar coulometric sensors were tested in humidified synthetic air at various gas temperatures. Generated frost point temperature in the gas ranged from -30 °C to -60 °C and were measured by coulometric sensors and in addition by a calibrated dew point hygrometer. The gas temperatures, which were measured by a calibrated Pt100 sensor, were set to -20 °C, 0 °C, 23 °C, 40 °C, 50 °C, and 60 °C during the experiments. Empiric nonlinear functions were calculated between the generated humidity and the sensor signals. In comparison to the measured signals at 23 °C, the sensor signals were lower at the other gas temperatures. The measurements at 60 °C showed indistinct results due to a great signal noise. The response behavior of the sensors was similar at 23 °C, 40 °C and 50 °C. In contrast to that, the sensors reacted slowly at a gas temperature of -20 °C and 0 °C. In summary, with coulometric sensors it was possible to measure continuously trace humidity with an expanded uncertainty below 2 K. T2 - IEEE Sensors 2017 CY - Glasgow, Scotland, UK DA - 30.10.2017 KW - Response behavior KW - Coulometric sensors KW - Trace humidity measurement KW - Temperature influence KW - Chemical reaction PY - 2017 SN - 978-1-5386-4056-2 SP - 1308 EP - 1310 PB - IEEE CY - Piscataway, NJ, USA AN - OPUS4-43241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Detjens, Marc A1 - Hübert, Thomas A1 - Tiebe, Carlo A1 - Banach, Ulrich T1 - Coulometric trace humidity measurement in technical gases N2 - Trace humidity was measured by using miniaturized planar coulometric sensors in technical gases such as hydrogen, nitrogen, helium, nitrous oxide, and synthetic air. Frost point temperatures tf in the gases ranged from −60 °C to −30 °C, which is equivalent to a vapour mole fraction xv from 10 μmol mol−1 to 376 μmol mol−1. In addition, the generated humidity was determined by using a precision dew point hygrometer as reference. Nonlinear calibration functions were calculated that correlated electric current (sensor signal) and reference humidity. Parameters of functions were tested with one-way analysis of variances (ANOVA) to prove if all used sensors had a similar behavior in the same gas during experiments. Results of ANOVA confirmed that averaged functions can be applied for trace humidity measurement in nitrogen, helium, nitrous oxide, and synthetic air. The calculated functions were negligibly different for nitrogen, helium, and synthetic air. In humidified nitrous oxide, a minor change of parameters was observed due to lower electrical currents. In total contrast to that, the measured sensor signals were significantly higher in humidified hydrogen and each sensor required its own calibration function. The reason was a recombination effect that favoured multiple measurements of water molecules. Nevertheless, it was possible to measure continuously trace humidity in all tested gases by using coulometric sensors with an expanded uncertainty below 2 K (k = 2). KW - ANOVA KW - Trace humdity measurement KW - Coulometric sensors KW - Chemical sensors KW - Measurement uncertainty PY - 2018 DO - https://doi.org/10.1063/1.5008463 SN - 0034-6748 SN - 1089-7623 VL - 89 IS - 8 SP - 085004, 1 EP - 8 PB - American Institute of Physics (AIP) CY - Maryland (USA) AN - OPUS4-45956 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tiebe, Carlo A1 - Detjens, Marc A1 - Banach, Ulrich A1 - Hübert, Thomas T1 - Measurement uncertainty of coulometric trace humidity sensors N2 - Especially trace amounts of water vapour in gases can be reliably determined by coulometric trace humidity sensors. The principle of these sensors is based on water vapour absorption in a hygroscopic layer and its subsequent electrolytic decomposition. The calibration of sensors was performed in the humidity range, expressed as frost point temperature, from −30°C to −80°C . This range is equivalent to volume fractions smaller than 376 µL·L−1. Generated humidity was measured with coulometric sensors and a chilled dew point hygrometer that was used as reference. An empirical non-linear function was found between sensor signal and measured reference humidity. This function consists of two parameters with a measurement uncertainty. Both calibration parameters were checked by means of one-way analysis of variance. It showed that gas specific function can be used for humidity measurement in nitrogen, hydrogen, dinitrogen monoxide, compressed and synthetic air. It is possible to determine trace humidity in all tested gases with an expanded uncertainty less than 2.1 K (coverage factor k=2 ) regarding frost point temperature. KW - Trace humidity KW - Coulometric sensor KW - Measurement uncertainty KW - ANOVA PY - 2018 DO - https://doi.org/10.1515/teme-2018-0031 SN - 0171-8096 VL - 85 IS - 12 SP - 746 EP - 753 PB - De Gruyter CY - Oldenbourg AN - OPUS4-45959 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tahri, K. A1 - Tiebe, Carlo A1 - El Bari, N. A1 - Hübert, Thomas A1 - Bouchikhi, B. T1 - Geographical classification and adulteration detection of cumin by using electronic sensing coupled to multivariate analysis N2 - The objective of this work is to report the improvement obtained in the discrimination of complex aroma and taste with subtle differences in odor and flavor, by the use of fast suitable procedures for the cases of measurements in the field demanding decision-making in real time. The proposed electronic sensing systems, formed by an E-nose and VE-tongue, were used to discriminate cumin cultivars from different geographical origins, as well as to quantify the cumin adulteration percentages by using unsupervised and supervised chemometric tools. Thus, the results obtained are sufficiently encouraging as a starting point for the development of new electronic sensing systems with more improvement such the reliability of the sensors’ performance as well as the chemometric tools in order to deal with a complex dataset. KW - VE-tongue KW - E-nose KW - Chemometric tools KW - Cumin discrimination KW - Geographical origins KW - Adulteration detection PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-409735 DO - https://doi.org/10.1016/j.protcy.2017.04.102 SN - 2212-0173 VL - 27 SP - 240 EP - 241 PB - Elsevier B.V. AN - OPUS4-40973 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shabir Mahr, Muhammad A1 - Hübert, Thomas A1 - Sabel, Martin A1 - Schartel, Bernhard A1 - Bahr, Horst A1 - Militz, H. T1 - Fire retardancy of sol-gel derived titania wood-inorganic composites N2 - Sol–gel technology was applied in tailoring novel wood-made-inorganic composites with improved thermal and fire properties. In practice, composites materials were prepared by impregnating pine sapwood wood with nano-scaled precursor solutions derived from titanium(IV) isopropoxide followed by a thermal curing process. Thermal and fire properties were evaluated by thermal analysis and cone calorimetry, whereas flammability was specified by oxygen index (LOI) and UL 94 test. Peak heat release rates were moderately reduced indicating fire retardance potential in terms of flame spread attributed to the appropriate protection layer action of the titania-based depositions. LOI (oxygen index) values of these composites were increased up to 38 vol.% in comparison to 23 vol.% for untreated wood. The flame retardancy performance depends on the fire scenario and is strongly influenced by wood loading and crackfree deposition of the titania layers inside the composite. PY - 2012 DO - https://doi.org/10.1007/s10853-012-6628-3 SN - 0022-2461 SN - 1573-4803 VL - 47 IS - 19 SP - 6849 EP - 6861 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-26235 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Usmani, S. A1 - Voss, L. A1 - Stephan, Ina A1 - Hübert, Thomas A1 - Kemnitz, E. T1 - Improved Durability of Wood Treated with Nano Metal Fluorides against Brown-Rot and White-Rot Fungi N2 - Low-water soluble metal fluorides such as magnesium fluoride (MgF2) and calcium Fluoride (CaF2) were evaluated for decay protection of wood. Initially, the biocidal efficacy of nano metal fluorides (NMFs) against wood destroying fungi was assessed with an in-vitro agar test. The results from the test showed that agar medium containing MgF2 and CaF2 was more efficient in preventing fungal decay than stand-alone MgF2 or CaF2. These metal fluorides, in their nanoscopic form synthesized using fluorolytic sol-gel synthesis, were introduced into the sapwood of Scots pine and beech wood and then subjected to accelerated ageing by leaching (EN 84). MAS 19F NMR and X-ray micro CT images showed that metal fluorides were present in treated wood, unleached and leached. Decay resistance of Scots pine and beech wood treated with NMFs was tested against Wood destroying fungi Rhodonia placenta and Trametes versicolor in accordance with EN 113. Results revealed that mass losses were reduced to below 3% in wood treated with the combination of MgF2 and CaF2. It is concluded that NMFs provide full protection to wood even after it has been leached and can be used as wood preservatives in outdoor environments. KW - Nanoparticles KW - Fluoride KW - Wood protection KW - Fluorolytic sol-gel synthesis KW - Brown-rot fungi KW - White-rot fungi KW - Basidiomycetes PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543877 DO - https://doi.org/10.3390/app12031727 VL - 12 IS - 3 SP - 1 EP - 11 PB - MDPI AN - OPUS4-54387 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shabir Mahr, Muhammad A1 - Hübert, Thomas A1 - Schartel, Bernhard A1 - Bahr, Horst A1 - Sabel, Martin A1 - Militz, H. T1 - Fire retardancy effects in single and double layered sol-gel derived TiO2 and SiO2-wood composites N2 - Sol–gel derived TiO2 and SiO2-wood inorganic composites are prepared by direct vacuum infiltration of silicon and titanium alkoxide based precursors in pine sapwood in one or two cycles followed by a controlled thermal curing process. The resulting flame retardancy effect is investigated under two different fire scenarios using cone calorimetry and oxygen index (LOI). Heat release rates (HRR) especially the values for the second peak, are reduced moderately for all single layered composites. This effect is more pronounced for double layered composites where HRR was reduced up to 40 % showing flame retardancy potential in developing fires. Beside this, smoke release was lowered up to 72 % indicating that these systems had less fire hazards compared to untreated wood, whereas no meaningful improvement is realized in terms of fire load (total heat evolved) and initial HRR increase. However impressively, the LOI of the composites were increased up to 41 vol% in comparison to 23 vol% for untreated wood displaying a remarkable flame retardancy against reaction to a small flame. An approximate linear interdependence among the fire properties and the material loading as well as fire residue was observed. A residual protection layer mechanism is proposed improving the residue properties for the investigated composites. KW - Wood KW - Sol-gel KW - Composite materials KW - Cone calorimeter KW - Fire retardance KW - Flammability PY - 2012 DO - https://doi.org/10.1007/s10971-012-2877-5 SN - 0928-0707 SN - 1573-4846 VL - 64 IS - 2 SP - 452 EP - 464 PB - Kluwer Academic Publ. CY - Dordrecht AN - OPUS4-27618 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Tiebe, Carlo A1 - Stephan, Ina T1 - Detection of fungal infestations of wood by ion mobility spectrometry N2 - During their growth on wood many fungi produce characteristic volatile organic compounds as secondary metabolites. These microbial volatile organic compounds (MVOCs) can be used as indicators of fungal growth even when such growth is concealed. In order to investigate the formation of these volatile metabolites on building materials, specimens of pine sapwood on agar media colonized by the dry-rot fungus Serpula lacrymans and a mixture of six moulds were examined. MVOCs from this fungal growth were studied over a period of up to half a year by ion mobility spectrometry (IMS) headspace analysis using a sensitive, portable IMS mini-device. The IMS headspace spectra from the growing fungal specimens obtained during this time span are differed from non-incubated wood specimens and indicate the presence of a mixture of MVOCs. The composition and amount of volatile metabolites of the fungi changed during cultivation. This was confirmed by a principal component analysis (PCA). Identification of different MVOCs in the headspace according to drift time and the mobility of ionized gaseous species in reference to GC-MS investigations were proposed. It was concluded that IMS can be used as a rapid and sensitive on-site method to indicate actively growing fungi concealed within wood. KW - Dry rot KW - Serpula lacrymans KW - Moulds KW - Concealed infestation KW - Ion mobility spectrometry KW - Fungal detection PY - 2011 DO - https://doi.org/10.1016/j.ibiod.2011.03.008 SN - 0964-8305 VL - 65 IS - 5 SP - 675 EP - 681 PB - Elsevier CY - Barking AN - OPUS4-23994 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shabir Mahr, Muhammad A1 - Hübert, Thomas A1 - Stephan, Ina A1 - Militz, H. T1 - Decay protection of wood against brown-rot fungi by titanium alkoxide impregnations N2 - Decay resistance of pine sapwood treated with titanium alkoxide solutions was tested against the brown-rot fungi Coniophora puteana and Poria placenta for exposure times of 10 and 16 wk. In practice, wood-specimens were vacuum-impregnated by alcoholic solutions of titanium alkoxide with concentrations in the range of 5–16 mass % (solid content in solution) and subsequently cured under different humidity conditions. Results reveal that treated wood degraded up to 5% in comparison to untreated one that deteriorated 38% and 50%, respectively against both wood-decay fungi. Even full protection (mass loss below 3%) was achieved against brown rot with titanium alkoxide solution containing solid content of around 5 mass% with a weight percentage gain (WPG) of 9 mass%. With increased concentration, fungal resistance decreased slightly which was associated with more cracks and imperfections formed in the deposited layers of titanium dioxide in the adjacent wood matrix. Thermal analysis verified that a considerable amount of precursor remained in the wood structure as un-hydrolyzed organic residues. These organics, being bioactive, had the tendency to induce similar fungicidal effects as those of conventional fungicides. The amount of organic residues is correlated with the decay resistance of the tested samples. In a prolonged decay test, mass losses of 16-wk incubated samples do not show behavior different from that of the wood samples incubated for 10 wk. This result implies that the decay protection is permanent and confirms further the fungicidal activity of titanium-alkoxide-treated wood. KW - Precursor solutions KW - Sol-gel process KW - Equivalent solid content KW - Brown rot KW - Coniophora puteana KW - Poria placenta KW - Fungal colonization KW - Biocidal effect PY - 2013 DO - https://doi.org/10.1016/j.ibiod.2012.04.026 SN - 0964-8305 VL - 77 SP - 56 EP - 62 PB - Elsevier Ltd. CY - Barking AN - OPUS4-27622 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shabir Mahr, Muhammad A1 - Hübert, Thomas A1 - Stephan, Ina A1 - Bücker, Michael A1 - Militz, H. T1 - Reducing copper leaching from treated wood by sol-gel derived TiO2 and SiO2 depositions N2 - The antileaching efficacy of sol-gel-derived TiO2- and SiO2-based precursors has been evaluated through laboratory leaching trials with pine sapwood in two different ways. In a one-step process, wood was vacuum impregnated by the precursor solutions containing CuCl2. The copper (Cu) emission rates of the sol-gel-based impregnated woods were up to 70% lower than that of wood treated with pure CuCl2 solution at the same level of concentration. More improvement (80%) could be achieved in a two-step process, in which sol-gel precursors were introduced into an already CuCl2-treated wood. The refinement was attributed to several effects. In the one-step approach, Cu was embedded in the TiO2/SiO2 gels formed in the wood texture. During a two-step impregnation, gel layers that were formed in the wooden interior acted as an effective diffusion barrier. The sol-gel impregnations made wood more hydrophobic; therefore, the low amount of water that penetrated the cell wall was less efficient to leach out Cu. KW - Copper leachability KW - SiO2-based gel KW - Sol-gel treatment of wood KW - TiO2-based gel KW - Wood impregnation KW - Wood protection PY - 2013 DO - https://doi.org/10.1515/hf-2012-0105 SN - 0018-3830 SN - 1437-434X VL - 67 IS - 4 SP - 429 EP - 435 PB - De Gruyter CY - Berlin AN - OPUS4-28892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -