E-liquids generally contain four main components: nicotine, flavours, water and carrier liquids. The carrier liquid dissolves flavours and nicotine and vaporises at a certain temperature on the atomizer of the e-cigarette. Propylene glycol and glycerol, the principal carriers used in e-liquids, undergo decomposition in contact with the atomizer heating-coil forming volatile carbonyls. Some of these, such as formaldehyde, acetaldehyde and acrolein, are of concern due to their adverse impact on human health when inhaled at sufficient concentrations. The aim of this study was to correlate the yield of volatile carbonyls emitted by e-cigarettes with the temperature of the heating coil. For this purpose, a popular commercial e-liquid was machine-vaped on a third generation e-cigarette which allowed the variation of the output wattage (5-25W) and therefore the heat generated on the atomizer heating-coil. The temperature of the heating-coil was determined by infrared thermography and the vapour generated at each temperature underwent subjective sensorial quality evaluation by an experienced vaper. A steep increase in the generated carbonyls was observed when applying a battery-output of at least 15W corresponding to 200-250°C on the heating coil. However, when considering concentrations in each inhaled puff, the short-term indoor air guideline value for formaldehyde was already exceeded at the lowest wattage of 5W, which is the wattage applied in most 2nd generation e-cigarettes. Concentrations of acetaldehyde in each puff were several times below the short-term irritation threshold value for humans. Acrolein was only detected from 20W upwards. The negative sensorial quality evaluation by the volunteering vaper of the vapour generated at 20W demonstrated the unlikelihood that such a wattage would be realistically set by a vaper. This study highlights the importance to develop standardised testing methods for the assessment of carbonyl-emissions and emissions of other potentially harmful compounds from e-cigarettes. The wide variety and variability of products available on the market make the development of such methods and the associated standardised testing conditions particularly demanding.

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Electronic cigarettes have achieved growing popularity since their introduction onto the European market. They are promoted by manufacturers as healthier alternatives to tobacco cigarettes, however debate among scientists and public health experts about their possible impact on health and indoor air quality means further research into the product is required to ensure decisions of policymakers, health care providers and consumers are based on sound science. This study investigated and characterised the impact of 'vaping' (using electronic cigarettes) on indoor environments under controlled conditions using a 30m(3) emission chamber. The study determined the composition of e-cigarette mainstream vapour in terms of propylene glycol, glycerol, carbonyls and nicotine emissions using a smoking machine with adapted smoking parameters. Two different base recipes for refill liquids, with three different amounts of nicotine each, were tested using two models of e-cigarettes. Refill liquids were analysed on their content of propylene glycol, glycerol, nicotine and qualitatively on their principal flavourings. Possible health effects of e-cigarette use are not discussed in this work. Electronic cigarettes tested in this study proved to be sources for propylene glycol, glycerol, nicotine, carbonyls and aerosol particulates. The extent of exposure differs significantly for active and passive 'vapers' (users of electronic cigarettes). Extrapolating from the average amounts of propylene glycol and glycerol condensed on the smoking machine filter pad to the resulting lung-concentration, estimated lung concentrations of 160 and 220mgm(-3) for propylene glycol and glycerol were obtained, respectively. Vaping refill liquids with nicotine concentrations of 9mgmL(-1) led to vapour condensate nicotine amounts comparable to those of low-nicotine regular cigarettes (0.15-0.2mg). In chamber studies, peak concentrations of 2200μgm(-3) for propylene glycol, 136μgm(-3) for glycerol and 0.6μgm(-3) for nicotine were reached. Carbonyls were not detected above the detection limits in chamber studies. Particles in the size range of 20nm to 300nm constantly increased during vaping activity and reached final peak concentrations of 7×10(6)particlesL(-1). Moreover, the tested products showed design flaws such as leakages from the cartridge reservoirs. Possible long term effects of e-cigarettes on health are not yet known. E-cigarettes, the impact of vaping on health and the composition of refill liquids require therefore further research into the product characteristics. The consumers would benefit from harmonised quality and safety improvements of e-cigarettes and refill liquids.

The measurement of physicochemical properties of polydisperse complex biological samples, for example, extracellular vesicles, is critical to assess their quality, for example, resulting from their production and isolation methods. The community is gradually becoming aware of the need to combine multiple orthogonal techniques to perform a robust characterization of complex biological samples. Three pillars of critical quality attribute characterization of EVs are sizing, concentration measurement and phenotyping. The repeatable measurement of vesicle concentration is one of the keychallenges that requires further efforts, in order to obtain comparable results by using different techniques and assure reproducibility. In this study, the performance of measuring the concentration of particles in the size range of 50-300 nm with complementary techniques is thoroughly investigated in a step-by step approach of incremental complexity. The six applied techniques include multi-angle dynamic light scattering (MADLS), asymmetric flow field flow fractionation coupled with multi-angle light scattering (AF4-MALS), centrifugal liquid sedimentation (CLS), nanoparticle tracking analysis (NTA), tunable resistive pulse sensing (TRPS), and high-sensitivity nano flow cytometry (nFCM). To achieve comparability, monomodal samples and complex polystyrene mixtures were used as particles of metrological interest, in order to check the suitability of each technique in the size and concentration range of interest, and to develop reliable post-processing data protocols for the analysis. Subsequent complexity was introduced by testing liposomes as validation of the developed approaches with a known sample of physicochemical properties closer to EVs. Finally, the vesicles in EV containing plasma samples were analysed with all the tested techniques. The results presented here aim to shed some light into the requirements for the complex characterization of biological samples, as this is a critical need for quality assurance by the EV and regulatory community. Such efforts go with the view to contribute to both, setup reproducible and reliable characterization protocols, and comply with the Minimal Information for Studies of Extracellular Vesicles (MISEV) requirements.

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The use of face masks is among the measures taken to prevent person-to-person transmission of the virus (SARS-CoV-2) responsible for the coronavirus disease (COVID-19). Lately, concern was expressed about the possibility that carbon dioxide could build up in the mask over time, causing medical issues related to the respiratory system. In this study, the carbon dioxide concentration in the breathing zone was measured while wearing a surgical mask, a KN95 and a cloth mask. For the surgical mask, the concentration was determined under different conditions (office work, slow walking, and fast walking). Measurements were made using a modified indoor air quality meter equipped with a nondispersive infrared (NDIR) CO2 sensor. Detected carbon dioxide concentrations ranged from 2150 ± 192 to 2875 ± 323 ppm. The concentrations of carbon dioxide while not wearing a face mask varied from 500-900 ppm. Doing office work and standing still on the treadmill each resulted in carbon dioxide concentrations of around 2200 ppm. A small increase could be observed when walking at a speed of 3 km h-1 (leisurely walking pace). Walking at a speed of 5 km h-1 , which corresponds to medium activity with breathing through the mouth, resulted in an average carbon dioxide concentration of 2875 ppm. No differences were observed among the three types of face masks tested. According to the literature, these concentrations have no toxicological effect. Concentrations in the detected range can cause undesirable symptoms, such as fatigue, headache, and loss of concentration.

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This work proposes the use of multimodal mixtures of monodispersed silica nanoparticles (SiO2-NPs) standards for the simultaneous determination of size and concentration of SiO2-NPs in aqueous suspensions by asymmetric flow field-flow fractionation (AF4) coupled to inductively coupled plasma mass spectrometry (ICPMS). For such a purpose, suspensions of SiO2-NPs standards of 20, 40, 60, 80, 100, and 150 nm were characterized by transmission electronic microscopy (TEM), centrifugal liquid sedimentation (CLS), dynamic light scattering (DLS) and by measuring the Z-potential of the particles as well as the exact concentration of NPs by offline ICPMS. An online AF4-ICPMS method which allowed the separation of all the different sized SiO2-NPs contained in the mixture of standards was developed and the analytical figures of merit were systematically evaluated. The method showed excellent linearity in the studied concentration range (0.1-25 mg L(-1)), limits of detection between 0.16 and 0.3 mg L(-1) for smaller and greater particles, respectively, besides a satisfactory accuracy. AF4 calibration with particles with identical nature to those to be analyzed, also permitted accurate size determination in a pragmatic way. Similarly, by using prechannel calibration with NPs for mass determination it was possible to overcome common quantification problems associated with losses of material during the separation and size-dependent effects. The proposed methodology was successfully applied to the characterization in terms of size and concentration of aqueous test samples containing SiO2-NPs with monomodal size distributions.