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Isoprene is a substantial contributor to the global secondary organic aerosol (SOA) burden, with implications for public health and the climate system. The mechanism by which isoprene-derived SOA is formed and the influence of environmental conditions, however, remain unclear. We present evidence from controlled smog chamber experiments and field measurements that in the presence of high levels of nitrogen oxides (NO ₓ = NO + NO ₂) typical of urban atmospheres, 2-methyloxirane-2-carboxylic acid (methacrylic acid epoxide, MAE) is a precursor to known isoprene-derived SOA tracers, and ultimately to SOA. We propose that MAE arises from decomposition of the OH adduct of methacryloylperoxynitrate (MPAN). This hypothesis is supported by the similarity of SOA constituents derived from MAE to those from photooxidation of isoprene, methacrolein, and MPAN under high-NO ₓ conditions. Strong support is further derived from computational chemistry calculations and Community Multiscale Air Quality model simulations, yielding predictions consistent with field observations. Field measurements taken in Chapel Hill, North Carolina, considered along with the modeling results indicate the atmospheric significance and relevance of MAE chemistry across the United States, especially in urban areas heavily impacted by isoprene emissions. Identification of MAE implies a major role of atmospheric epoxides in forming SOA from isoprene photooxidation. Updating current atmospheric modeling frameworks with MAE chemistry could improve the way that SOA has been attributed to isoprene based on ambient tracer measurements, and lead to SOA parameterizations that better capture the dependency of yield on NO ₓ.

This article provides an overview of the state-of-the-art and future trends of the application of LC-high resolution mass spectrometry to the environmental analysis of polar micropollutants. Highly resolved and accurate hybrid tandem mass spectrometry such as quadrupole/time-of-flight and linear ion trap/orbitrap technology allows for a more reliable target analysis with reference standards, a screening for suspected analytes without reference standards, and a screening for unknowns. A reliable identification requires both high resolving power and high mass spectral accuracy to increase selectivity against the matrix background and for a correct molecular formula assignment to unknown compounds. For the identification and structure elucidation of unknown compounds within a reasonable time frame and with a reasonable soundness, advanced automated software solutions as well as improved prediction systems for theoretical fragmentation patterns, retention times, and ionization behavior are needed. [graphic removed]

Recent progress in the laboratory has been a result of improvements in rapid analytical techniques. An update of the applications of lateral flow tests (also called immunochromatographic assay or test strip) is presented in this review manuscrit. We emphasized the description of this technology in the detection of a variety of biological agents and chemical contaminants (e.g. veterinary drugs, toxins and pesticides). It includes outstanding data, such as sample treatment, sensitivity, specificity, accuracy and reproducibility. Lateral flow tests provide advantages in simplicity and rapidity when compared to the conventional detection methods. Overview of study using colored particles as label in lateral flow tests for the detection of pathogen agents and chemical contaminants. Data were obtained from a literature survey. The total number of published reports considered in this figure was seventy two

Cyclic olefin polymers (COPs) are increasingly popular as substrate material for microfluidics. This is due to their promising properties, such as high chemical resistance, low water absorption, good optical transparency in the near UV range and ease of fabrication. COPs are commercially available from a range of manufacturers under various brand names (Apel, Arton, Topas, Zeonex and Zeonor). Some of these (Apel and Topas) are made from more than one kind of monomer and therefore also known as cyclic olefin copolymers (COCs). In order to structure these materials, a wide array of fabrication methods is available. Laser ablation and micromilling are direct structuring methods suitable for fast prototyping, whilst injection moulding, hot embossing and nanoimprint lithography are replication methods more appropriate for low-cost production. Using these fabrication methods, a multitude of chemical analysis techniques have already been implemented. These include microchip electrophoresis (MCE), chromatography, solid phase extraction (SPE), isoelectric focusing (IEF) and mass spectrometry (MS). Still much additional work is needed to characterise and utilise the full potential of COP materials. This is especially true within optofluidics, where COPs are still rarely used, despite their excellent optical properties. This review presents a detailed description of the properties of COPs, the available fabrication methods and several selected applications described in the literature.

A method for the simultaneous determination of seven commonly used artificial sweeteners in water is presented. The analytes were extracted by solid phase extraction using Bakerbond SDB 1 cartridges at pH 3 and analyzed by liquid chromatography electrospray ionization tandem mass spectrometry in negative ionization mode. Ionization was enhanced by post-column addition of the alkaline modifier Tris(hydroxymethyl)amino methane. Except for aspartame and neohesperidin dihydrochalcone, recoveries were higher than 75% in potable water with comparable results for surface water. Matrix effects due to reduced extraction yields in undiluted waste water were negligible for aspartame and neotame but considerable for the other compounds. The widespread distribution of acesulfame, saccharin, cyclamate, and sucralose in the aquatic environment could be proven. Concentrations in two influents of German sewage treatment plants (STPs) were up to 190 μg/L for cyclamate, about 40 μg/L for acesulfame and saccharin, and less than 1 μg/L for sucralose. Removal in the STPs was limited for acesulfame and sucralose and >94% for saccharin and cyclamate. The persistence of some artificial sweeteners during soil aquifer treatment was demonstrated and confirmed their environmental relevance. The use of sucralose and acesulfame as tracers for anthropogenic contamination is conceivable. In German surface waters, acesulfame was the predominant artificial sweetener with concentrations exceeding 2 μg/L. Other sweeteners were detected up to several hundred nanograms per liter in the order saccharin [almost equal to] cyclamate > sucralose. [graphic removed]

The study on the photostability of six UV filters in aqueous solution was combined with investigations on the phytotoxicity of the produced degradation mixtures. During the exposure to artificial sunlight over 72 h, the degradation of three of the UV filters evaluated was observed with half-lives between 20 and 59 h. The structural changes of iso-amylmethoxy-cinnamate (IAMC), ethylhexyl-methoxy-cinnamate (EHMC), and 4-methylbenzyliden camphor (4-MBC) occurred during irradiation were consistent with isomerisation and polymerization (IAMC and EHMC) whereas 2-ethylhexyl-4-(dimethylamino)benzoate (OD-PABA) was degraded. The analysis of the UV filters and their degradation products was performed by stir bar sorptive extraction (SBSE) followed by thermodesorption-gas chromatography-mass spectrometry (TD-GC-MS) or liquid desorption-liquid chromatography-mass spectrometry (LD-LC-MS). The phytotoxicological potential of the UV filters was examined in vitro by evaluating reproduction inhibition of the chlorophyte microalgae Scenedesmus vacuolatus. Excess toxicity was calculated by comparing experimental derived median efficiencies after log-logistic modeling to predict effects assuming narcotic mode of action. Benzophenone-3 (BP-3) showed 43-fold higher toxicity than theoretically predicted and a more specific mode of action was assumed. The other UV filters tested indicated toxicity in the range of modeled narcosis. For IAMC, EHMC, and OD-PABA the phytotoxicity of their photodegradation mixtures was followed over time. Phytotoxicity decreased directly with the reduction of the parent substance from the solution. Five of the tested UV filters do not represent a risk at least for algae. Octocrylen and 4-MBC were found to be photostable but few toxic to algae. EHMC, IAMC, and OD-PABA were fast degraded during UV radiation and the phytotoxicity of the corresponding degradation mixtures was low and decreased onward during exposure. Thus, for the UV filters studied, it could be confirmed that sunlight can account noticeably for decontamination and detoxification of contaminated water. However, due to its potential accumulation in combination with a specific mode of action, BP-3 may imply probable environmental risks at least to algae. This study emphasizes the need of a combined chemical and toxicological evaluation for a reliable risk assessment concerning degradation processes exemplified here for UV-protecting agents.

Recent developments in chromatographic supports and instrumentation for liquid chromatography (LC) are enabling rapid and highly efficient separations. Various analytical strategies have been proposed, for example the use of silica-based monolithic supports, elevated mobile phase temperatures, and columns packed with sub-3 μm superficially porous particles (fused core) or with sub-2 μm porous particles for use in ultra-high-pressure LC (UHPLC). The purpose of this review is to describe and compare these approaches in terms of throughput and resolving power, using kinetic data gathered for compounds with molecular weights ranging between 200 and 1300 g mol −1 in isocratic and gradient modes. This study demonstrates that the best analytical strategy should be selected on the basis of the analytical problem (e.g., isocratic vs. gradient, throughput vs. efficiency) and the properties of the analyte. UHPLC and fused-core technologies are quite promising for small-molecular-weight compounds, but increasing the mobile phase temperature is useful for larger molecules, for example peptides. Figure Recent progress in HPLC technology to increase throughput and resolving power

Hollow fiber liquid-phase microextraction (HF-LPME) offers an efficient alternative to classical techniques for sample preparation and preconcentration. Features include high selectivity, good enrichment factors, and improved possibilities for automation. HP-LPME relies on the extraction of target analytes from aqueous samples into a supported liquid membrane (SLM) sustained in the pores of the wall of a porous hollow fiber, and then into an acceptor phase (that can be aqueous or organic) in the lumen of the hollow fiber. After extraction, the acceptor solution is directly subjected to a chemical analysis. HP-LPME can be performed in either the 2- or 3-phases mode. In the 2-phase mode, the organic solvent is present both in the porous wall and inside the lumen of the hollow fiber. In the 3-phase mode, the acceptor phase can be aqueous and this results in a conventional 3-phase system compatible with HPLC or capillary electrophoresis. Alternatively, the acceptor solution is organic and this represents a 3-phase extraction system with two immiscible organic solvents that is compatible with all common analytical instruments. In HP-LPME methods based on the use of SLMs, the mass transfer occurs by passive diffusion, and high extraction yields as well as efficient extraction kinetics are obtained by applying a pH gradient. In addition, active transport can be performed by using carrier or applying an electrical potential across the SLM. Due to high analyte preconcentration, excellent sample clean-up, and low consumption of organic solvent, HF-LPME has a large application potential in areas such as drug analysis and environmental monitoring. This review focuses on the fundamentals of extraction principles, technical implementations, and future trends in HF-LPME. Figure Schematic diagram of three-phase HF-LPME based of two immiscible organic solvent

We report the use of paper-based microfluidic devices fabricated from a novel polymer blend for the monitoring of urinary ketones, glucose, and salivary nitrite. Paper-based devices were fabricated via photolithography in less than 3 min and were immediately ready for use for these diagnostically relevant assays. Patterned channels on filter paper as small as 90 μm wide with barriers as narrow as 250 μm could be reliably patterned to permit and block fluid wicking, respectively. Colorimetric assays for ketones and nitrite were adapted from the dipstick format to this paper microfluidic chip for the quantification of acetoacetate in artificial urine, as well as nitrite in artificial saliva. Glucose assays were based on those previously demonstrated (Martinez et al., Angew Chem Int Ed 8:1318–1320, 1 ; Martinez et al., Anal Chem 10:3699–3707, 2 ; Martinez et al., Proc Nat Acad Sci USA 50:19606–19611, 3 ; Lu et al., Electrophoresis 9:1497–1500, 4 ; Abe et al., Anal Chem 18:6928–6934, 5 ). Reagents were spotted on the detection pad of the paper device and allowed to dry prior to spotting of samples. The ketone test was a two-step reaction requiring a derivitization step between the sample spotting pad and the detection pad, thus for the first time, confirming the ability of these paper devices to perform online multi-step chemical reactions. Following the spotting of the reagents and sample solution onto the paper device and subsequent drying, color images of the paper chips were recorded using a flatbed scanner, and images were converted to CMYK format in Adobe Photoshop CS4 where the intensity of the color change was quantified using the same software. The limit of detection (LOD) for acetoacetate in artificial urine was 0.5 mM, while the LOD for salivary nitrite was 5 μM, placing both of these analytes within the clinically relevant range for these assays. Calibration curves for urinary ketone (5 to 16 mM) and salivary nitrite (5 to 2,000 μM) were generated. The time of device fabrication to the time of test results was about 25 min. Paper-based microfluidic chip illustrating the colorimetric detection of salivary nitrite. Color intensities were quantified using a flatbed scanner and image manipulation software and plotted against concentration to produce calibration curves for the assay

In vitro α-glucosidase inhibition assays and ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray ionization tandem mass spectrometry (ultrafiltration LC-DAD-ESI-MSn) were combined to screen α-glucosidase inhibitors from hawthorn leaf flavonoids extract (HLFE). As a result, four compounds were identified as α-glucosidase inhibitors in the HLFE, and their structures were confirmed to be quercetin-3-O-rha- (1-4)-glc-rha and C-glycosylflavones (vitexin-2“-O-glucoside, vitexin-2”-O-rhamnoside and vitexin) by high-resolution sustained off resonance irradiation collision-induced dissociation (SORI-CID) data obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). Several other C-glycosylflavones (vitexin, isovitexin, orientin, isooriention) and their aglycones apigenin and luteolin were evaluated by in vitro assays, and were found to possess strong α-glucosidase inhibitory activities as well. Moreover, the substituent groups on the flavones had a great impact on the enzyme inhibition activity. C-3′-OH of the B-ring of flavones in particular increased the α-glucosidase inhibition activity, whereas C-glycosylations at C-6 or C-8 of the A ring weakened the inhibition activity. Screening and Structural Characterization of α-Glucosidase Inhibitors from Hawthorn Leaf Flavonoids Extract by Ultrafiltration LC-DAD-MSn and SORI-CID FTICR MS.