Ulrich Banach

Electronic Noses for the Quality Control of Spices

Abstract Spices are parts of plants, which are added to foodstuffs due to their natural flavoring. Their flavor is usually stimulated by a great number of volatile organic compounds. As natural products, the quality varies due to origin, seasons as well as processing and requires quality control. In addition to established methods, such as sensory and chemical analysis, electronic nose analysis has been developed to characterize various quality parameters of spices. Electronic noses are deployed for the discrimination between different types, provenience, and quality of spices. Furthermore, aroma intensity, aging effects, and mold infestation have been investigated. Electronic noses are used to characterize the impact of processing spices by milling or irradiation. Spice mixtures have been investigated in order to detect adulterations. In most cases, the deployment of electronic noses is performed in combination with other methods for reference such as sensory or chemical analysis.

Measurement uncertainty of coulometric trace humidity sensors

Abstract 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-30\hspace{0.1667em}^\circ \mathrm{C} to − 80 ° C-80\hspace{0.1667em}^\circ \mathrm{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 = 2k=2) regarding frost point temperature.

P4.02 - Novel sensor for long-term monitoring of ammonia in gas phase

Because ammonia and its reaction products can cause considerable damage to human health and ecosystems, there is a need for reliably operating and reversibly interacting sensor materials to monitor traces of gaseous ammonia in ambient air, which at best can be used on-site for in-the-field measurements. Herein, the development of a sensor material for gaseous ammonia in the lower ppm to ppb range using optical fluorescence as transduction mechanism is presented. A fluorescent dye, which shows reversible fluorescence enhancement in the presence of ammonia is incorporated into a polymer matrix, the latter to ensure the accumulation of ammonia. The sensor material is integrated into a prototype of a miniaturized sensor device, facilitating long-term operation. To calibrate the optical sensor system a gas standard generator, producing standard gas mixtures, is used, leading to a sensitivity down to lower ppm concentrations of ammonia.

P2.5.1 Long-Term Stability of the Low Energy Hydrogen Sensor

A silicon MIS-structure prepared with thin layers of the super-ionic conductor LaF3 and Pd is used to detect hydrogen. The sensor is able to detect hydrogen in a concentration range from below one ppm to the lower flammable limit in air which is 4 vol.-%. The chip operates at room temperature which results in an extremely low energy consumption compared to other hydrogen sensors. Only once per day a short heating pulse is necessary to reactivate the sensor chip. In cooperation with the BAM, a long-term experiment was carried out. The duration of the measurement was about three months, with a hydrogen exposure every two weeks. The sensor signal remained stable over the measured period.