Miniaturised air sampling techniques for analysis of volatile organic compounds in air

Growing concern about the effects of atmospheric pollutants on climate and human health has accelerated the development of novel analytical methods, including sampling systems, for the determination of atmospheric volatile organic compounds (VOCs). Miniaturised air sampling (MAS) techniques have attracted wide attention in the past two decades due to their advantages (ease of operation, time-integrated sampling, small/no organic solvent consumption, and potential for automation). This review focuses on the latest developments in these techniques, including needle trap microextraction (NTME), in-tube extraction (ITEX), sorption trap, solid-phase microextraction (SPME fibre, SPME Arrow, and retracted SPME fibre), thin-film microextraction (TFME), solid-phase dynamic extraction (SPDE), and stir bar sorptive extraction (SBSE). Further, their benefits, drawbacks, and applicability to air sampling are discussed. The applications of MAS techniques for the analysis of atmospheric air, indoor air, breath air, and emissions of plants and foods are summarised and discussed.Peer reviewe

Problems Caused by Moisture in Gas Chromatographic Analysis of Headspace SPME Samples of Short-Chain Amines

Volatile amines are usually problematic compounds in sampling, sample pretreatment and gas chromatographic analysis due to their chemical characteristics (polarity, basicity and reactivity). Headspace solid-phase microextraction (SPME) Arrow sampling of aqueous samples were proven to be complicated since moisture in the headspace was also sorbed into the SPME sorbent and resulted in distorted or split peaks for the volatile amines. This was the case especially with old used sorbents not so much with the new ones. Volume of the water sample, sampling conditions, quality of the SPME sorbent and desorption conditions greatly influenced the concentration of water in the headspace and in the sorbent phase. This, in turn, affected the length of the water film in the column which determined the degree of peak splitting and distance between the split amine peaks (water film trapped part of the amine molecules). Addition of the salt to the sample solution and additional drying of the SPME sorbent after the sampling were shown to effectively decrease the amount of water in the headspace and in the sorbent phase. This combined effect of salt addition and drying step resulted in much better peak shapes and intensities for the amines. In the best cases, the peak splitting for the volatile amines could in this way be completely avoided.Peer reviewe

Research on a Joint Leadership Model for Early Childhood Education in Finland

This article presents the results of a study assessing the quality of joint leadership in Early Childhood Education and Care (ECEC) in the city of Hämeenlinna, Finland. The assessment was carried out through an online survey in August 2015. The study’s respondents were ECEC centre directors and teachers in Hämeenlinna. The results indicated that the teachers did not consider the joint leadership model to be as yet entirely successful, but the directors were more satisfied. The challenges of this model focused on the different dimensions of joint leadership, namely time, interaction, situation, and diversity. To develop joint leadership, the following conditions are necessary: time for reflection, discussion, and the clarification of practices and structures; permanency in interactions, communication, and relationships; the vertical distribution of leadership between directors and teachers; and the commitment of all stakeholders

Nontargeted evaluation of the fate of steroids during wastewater treatment by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Emerging organic contaminants in wastewater are usually analyzed by targeted approaches, and especially estrogens have been the focus of environmental research due to their high hormonal activity. The selection of specific target compounds means, however, that most of the sample components, including transformation products and potential new contaminants, are neglected. In this study, the fate of steroidal compounds in wastewater treatment processes was evaluated by a nontargeted approach based on comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. The potential of the nontargeted approach to generate comprehensive information about sample constituents was demonstrated with use of statistical tools. Transformation pathways of the tentatively identified compounds with steroidal four-ring structure were proposed. The purification efficiency of the wastewater treatment plants was studied, and the distribution of the compounds of interest in the suspended solids, effluent water, and sludge was measured. The results showed that, owing to strong adsorption of hydrophobic compounds onto the solid matter, the steroids were mostly bound to the suspended solids of the effluent water and the sewage sludge at the end of the treatment process. The most abundant steroid class was androstanes in the aqueous phase and cholestanes in the solid phase. 17 beta-estradiol was the most abundant estrogen in the aqueous phase, but it was only detected in the influent samples indicating efficient removal during the treatment process. In the sludge samples, however, high concentrations of an oxidation product of 17 beta-estradiol, estrone, were measured.Peer reviewe

Terminology for analytical capillary electromigration techniques (IUPAC Recommendations 2003)

This paper presents terms and definitions for capillary electromigration techniques for separation, qualitative and quantitative analysis and physico-chemical characterization. Names and descriptions for such techniques (e.g., capillary electrophoresis and capillary electrochromatography) as well as terms for the phenomenon of electroosmotic flow are included

Kinetics and interaction studies of anti-tetraspanin antibodies and ICAM-1 with extracellular vesicle subpopulations using continuous flow quartz crystal microbalance biosensor

Continuous flow quartz crystal microbalance (QCM) was utilized to study binding kinetics between EV subpopulations (exomere- and exosome-sized EVs) and four affinity ligands: monoclonal antibodies against tetraspanins (anti-CD9, anti-CD63, and anti-CD81) and recombinant intercellular adhesion molecule-1 (ICAM-1) or CD54 protein). High purity CD9+, CD63+, and CD81+ EV subpopulations of <50 nm exomeres and 50-80 nm exosomes were isolated and fractionated using our recently developed on-line coupled immunoaffinity chromatography - asymmetric flow field-flow fractionation system. Adaptive Interaction Distribution Algorithm (AIDA), specifically designed for the analysis of complex biological interactions, was used with a four-step procedure for reliable estimation of the degree of heterogeneity in rate constant distributions. Interactions between exomere-sized EVs and anti-tetraspanin antibodies demonstrated two interaction sites with comparable binding kinetics and estimated dissociation constants Kd ranging from nM to fM. Exomeres exhibited slightly higher affinity compared to exosomes. The highest affinity with anti-tetraspanin antibodies was achieved with CD63+ EVs. The interaction of EV subpopulations with ICAM-1 involved in cell internalization of EVs was also investigated. EV - ICAM-1 interaction was also of high affinity (nM to pM range) with overall lower affinity compared to the interactions of anti-tetraspanin antibodies and EVs. Our findings proved that QCM is a valuable label-free tool for kinetic studies with limited sample concentration, and that advanced algorithms, such as AIDA, are crucial for proper determination of kinetic heterogeneity. To the best of our knowledge, this is the first kinetic study on the interaction between plasma-derived EV subpopulations and anti-tetraspanin antibodies and ICAM-1.Peer reviewe

Atomistic MD simulation reveals the mechanism by which CETP penetrates into HDL enabling lipid transfer from HDL to CETP

Peer reviewe

Quaternary ammonium-functionalized silica sorbents for the solid-phase extraction of aromatic amines under normal phase conditions

Quaternary ammonium-functionalized silica materials were synthesized and applied for solid-phase extraction (SPE) of aromatic amines, which are classified as priority pollutants by US Environmental Protection Agency. Hexamethylenetetramine used for silica surface modification for the first time was employed as SPE sorbent under normal phase conditions. Hexaminium-functionalized silica demonstrated excellent extraction efficiencies for o-toluidine, 4-ethylaniline and quinoline (recoveries 101–107%), while for N,N-dimethylaniline and N-isopropylaniline recoveries were from low to moderate (14–46%). In addition, the suitability of 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica as SPE sorbent was tested under normal phase conditions. The recoveries achieved for the five aromatic amines ranged from 89 to 99%. The stability of the sorbent was evaluated during and after 150 extractions. Coefficients of variation between 4.5 and 10.2% proved a high stability of the synthesized sorbent. Elution was carried out using acetonitrile in the case of hexaminium-functionalized silica and water for 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent. After the extraction the analytes were separated and detected by liquid chromatography ultraviolet detection (LC-UV). The retention mechanism of the materials was primarily based on polar hydrogen bonding and π–π interactions. Comparison made with activated silica proved the quaternary ammonium-functionalized materials to offer different selectivity and better extraction efficiencies for aromatic amines. Finally, 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent was successfully tested for the extraction of wastewater and soil samples.M.-L.R. and J.-P.M. would like to thank the Academy of Finland Centre of Excellence program (project. no.1118615) for financial support, and L.V. thanks “Generalitat Valenciana” (Spain) for her post-doctoral grant. In addition, financial support was provided by Kempe Foundations as well as Knut and Alice Wallenberg Foundations (J.-P.M.)