Browsing by Subject "Indoor air"
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(2022)This paper features two parts; a literature review discussing the recent development in using electrochemical gas sensors for pollutant detection and the use of sensor nodes in real-life locations, and an experimental section focusing on the kinetic study of nitrogen containing compounds utilizing in-tube extraction device. Growing interest towards personal safety have led to development of low-cost electrochemical sensors for personal safety, indoor air quality and leak detection applications. Heterojunctions and light illumination have emerged as an effective way to improve sensor performance, but the selectivity of electrochemical sensors remains relatively poor. Multiple sensors can be combined to create ‘E-noses’ which significantly improve the selectivity and compound identification. These E-noses have been deployed in some indoor locations, either being stationary in sensor networks or moved around by a robot or drone. All approaches have benefits and caveats associated to them, with the differences between individual sensors limiting sensor network use, and slow response and recovery times limiting the use of moving sensors. A novel micropump system was constructed to be used in the active air sampling together with in tube extraction (ITEX) and thermal desorption gas-chromatography (TD-GC-MS). The repeatability of this method was tested in a kinetic study of 10 selected nitrogen containing compounds in a custom-built permeation chamber. The breakthrough times and volumes of the compounds were investigated. Kinetic modelling was successful for 9 out of the 10 compounds with 1 compound behaving significantly different from the rest. The breakthrough times were always over 20 minutes and breakthrough volumes were around the 1000 ml region. Reproducibility was tested with multiple ITEX’s and samples were taken from five indoor locations. Three of the tested compounds were found in some of the samples.
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(2019)Monitoring of indoor air quality (IAQ) is important because IAQ is directly related to human health and comforts. The purpose of this study was to develop a non-targeted approach for the screening of organic compounds present in indoor air. The sampling was done using cryogenic active and passive samplers, and the separation and analysis were done by using a liquid chromatograph coupled with a triple quadrupole mass spectrometer (LC-QQQ-MS). First, experimental design for sampling by variables, cooling temperature and sampling period was made and optimized to -15 ˚C and 120 minutes respectively to ensure efficient sample collection. For mass spectrometry in both positive and negative ionization modes, the ion source parameters, gas temperature, gas flow, nebulizer pressure and capillary voltage were optimized to 300 ˚C, 10 L/min, 45 psi and 4000 V respectively to enable as much detector response as possible facilitating detection and analysis of the compounds in the sample. The concentration of compounds in the raw sample being very low, one important step was to optimize the sample preparation method to enrich the sample for smooth detection and further analysis. Since the sample was collected in the form of condensate water, different sample preparation methods such as evaporation, liquid-liquid extraction (LLE) and solid-phase extractions (SPEs) with different cartridges were adopted for preconcentration. Comparing the outcomes from different sample preparation methods, it was found that sequential SPE using C2 and C18 cartridges gives maximum compound recovery, e.g., 1.5 and 2.6 times compared to evaporation and LLE respectively in positive ion mode, and 2.6 and 4.1 times in negative ion mode. Therefore, this methodology was adopted to analyze the condensate water samples from two sick houses in Finland. The results from the sick houses were compared with a reference house having no sick building syndrome (SBS) to look for potential compounds causing health issues. The data analysis was done using MZmine 2.3.4 software. Additionally, tandem mass spectrometric (MS/MS) acquisition parameters were optimized and product ions were determined as the initial step of identification of compounds in the sample of the first house. The methods developed in this work would be useful to analyze various natural samples including the analysis of outdoor air also.
Now showing items 1-2 of 2