Improved method for quantifying levoglucosan and related monosaccharide anhydrides in atmospheric aerosols and application to samples from urban and tropical locations

An improved analytical method was developed and validated for the determination of the monosaccharide anhydrides levoglucosan, mannosan, and galactosan in atmospheric aerosol samples. The method uses an external recovery standard, extraction in dichloromethane, trimethylsilylation, addition of an internal standard (1-phenyl dodecane), and analysis by gas chromatography with flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC/MS). As external recovery standard, we selected 1,2,3-trihydroxyhexane, which has a similar polarity as the monosaccharide anhydrides; furthermore, it was ensured that the trimethylsilylation step leads to complete derivatization into trimethylsilyl ethers. The reproducibility of the combined trimethylsilylation and analysis of levoglucosan was about 2% for standard solutions, whereas the precision of the entire method for the sum of all three monosaccharide anhydrides (MAs) in real aerosol filter samples was about 5%. The method was applied to aerosol samples from urban and tropical locations. The atmospheric concentration of the MAs in fine (<2.5 microm) aerosols at a primary forest site in Rond?nia, Brazil, was on average 2.15 microg m(-3) during the dry season when intensive biomass burning occurs, which was almost 400 times higher than during the wet (nonburning) season. Urban total aerosols collected in Gent, Belgium, showed an average atmospheric concentration of MAs of 0.56 microg m(-3) for the winter season, which was a factor of 20 higher than for the summer season. The carbon in the MAs accounted on average for about 5.1% and 1.8% of the organic carbon in the Brazilian dry season and Gent winter aerosols, respectively. Levoglucosan was the major MA, with a relative abundance in the range of 76-93%.     

Comparison of bioactive compounds,antioxidant and antiproliferative activities of Mon Thong durian during ripening

The aim of this investigation was to compare the bioactive and nutrient compounds, fatty acids, and antioxidant and antiproliferative activities of Mon Thong durian at different stages of ripening. It was found that the total polyphenols, flavonoids, flavanols, ascorbic acid, tannins and the antioxidant activity determined by four assays (CUPRAC, DPPH, ABTS and FRAP) differed in immature, mature, ripe and overripe samples. The content of polyphenols and antioxidant activity were the highest in overripe durian, flavonoids were the highest in ripe durian, and flavanols and antiproliferative activity were the highest in mature durian (p < 0.05). FTIR spectra of polyphenols, HPLC profiles of fatty acids, the antioxidant and antiproliferative activities can be used as indicators to characterise different stages of durian ripening.     

Increasing shelf life of strawberries (Fragaria ssp) by using a banana starch-chitosan-Aloe vera gel composite edible coating

Strawberries are among the most consumed fruits in the world, however, they are highly susceptible to both microbial and fungal contamination during storage. In this study, we used composite films made from banana starch-chitosan and Aloe vera gel (AV gel) at different AV gel concentrations. Our results show that AV gel inclusion can significantly reduce fungal decay, increasing strawberries shelf life up to 15 day of storage at the highest AV gel concentration (20%), while maintaining their physicochemical properties, such as colour and firmness. Weight loss was reduced 5% with respect of the uncoated fruit. Our results can be attributed to the limited water vapour transfer allowed by the edible coating, this is the result of the crosslinking effect of the different AV gel and starch molecules that allows a more controlled decay of the strawberries in commercial storage conditions.     

The influence of French fries processing on the glycoalkaloid content in coloured-fleshed potatoes

French fries made from coloured-fleshed potatoes may be interesting alternative to the traditional snacks for consumers. However, potatoes contain glycoalkaloids (TGA), so potato tubers and obtained fried snacks should be subjected to comprehensive examination. The aim of this study was to determine the effect of different stages of French fries processing on the content of TGA (α-solanine and α-chaconine) in the red- and blue-fleshed potatoes, in semi-products and ready-to-eat products. It was stated that during the processing of French fries prepared from coloured-flesh potato varieties significantly decreased the content of TGA (α-solanine and α-chaconine) in the samples obtained at different stages of the process compared to the raw material. Potatoes with blue-fleshed of Vitelotte variety and red-fleshed of Highland Burgundy Red variety can be used to French fries processing due to their low content of TGA (in unpeeled and peeled potatoes). However, Blue Congo variety with blue-fleshed should not be applied to French fries processing, because of high TGA content in raw material and first of all in peeled potatoes flesh. The peeling process of coloured-fleshed potatoes decreased in TGA content on average by about 50 %, cutting process on average by about 53 %, whereas blanching on average by about 58 % compared with the raw material. The highest decrease in TGA content was caused by frying process. The mean values were about 97.5 % in ready-to-eat French fries. In French fries after I and II steps of frying, the ratio α-solanine to α-chaconine was lower (1.0:2.0) than in unpeeled potatoes (1.0:2.3).     

Hydroxydicarboxylic acids: markers for secondary organic aerosol from the photooxidation of alpha-pinene

Detailed organic analysis of fine (PM2.5) rural aerosol collected during summer at K-puszta, Hungary from a mixed deciduous/coniferous forest site shows the presence of polar oxygenated compounds that are also formed in laboratory irradiated alpha-pinene/NOx/air mixtures. In the present work, two major photooxidation products of alpha-pinene were characterized as the hydroxydicarboxylic acids, 3-hydroxyglutaric acid, and 2-hydroxy-4-isopropyladipic acid, based on chemical, chromatographic, and mass spectral data. Different types of volatile derivatives, including trimethylsilyl ester/ether, methyl ester trimethylsilyl ether, and ethyl ester trimethylsilyl ether derivatives were measured by gas chromatography/mass spectrometry (GC/MS), and their electron ionization (El) spectra were interpreted in detail. The proposed structures of the hydroxydicarboxylic acids were confirmed or supported with reference compounds. 2-Hydroxy-4-isopropyladipic acid formally corresponds to a further reaction product of pinic acid involving addition of a molecule of water and opening of the dimethylcyclobutane ring; this proposal is supported by a laboratory irradiation experiment with alpha-pinene/NOJ0 air. In addition, we report the presence of a structurally related minor alpha-pinene photooxidation product, which was tentatively identified as the C7 homolog of 3-hydroxyglutaric acid, 3-hydroxy-4,4-dimethylglutaric acid. The detection of 2-hydroxy-4-isopropyladipic acid in ambient aerosol provides an explanation for the relatively low atmospheric concentrations of pinic acid found during daytime in forest environments.     

Evidence for the existence of organosulfates from beta-pinene ozonolysis in ambient secondary organic aerosol

The formation of organosulfates from the gas-phase ozonolysis of beta-pinene in the presence of neutral or acidic sulfate particles was investigated in a series of indoor aerosol chamber experiments. The organosulfates were analyzed using high-performance liquid chromatography (LC) coupled to electrospray ionization-time-of-flight mass spectrometry (MS) in parallel to ion trap MS. Organosulfates were only found in secondary organic aerosol from beta-pinene ozonolysis in the presence of acidic sulfate seed particles. One of the detected organosulfates also occurred in ambient aerosol samples that were collected at a forest site in northeastern Bavaria, Germany. beta-Pinene oxide, an oxidation product in beta-pinene/O3 and beta-pinene/NO3 reactions, is identified as a possible precursor for the beta-pinene-derived organosulfate. Furthermore, several nitroxy-organosulfates originating from monoterpenes were found in the ambient samples. These nitroxy-organosulfates were only detected in the nighttime samples, suggesting a role for nighttime chemistry in their formation. Their LC/MS chromatographic peak intensities suggest that they represent an important fraction of the organic mass in ambient aerosols, especially at night.     

Characterization of hydrocarbon emissions from green sand foundry core binders by analytical pyrolysis

Analytical pyrolysis was conducted to study a relative comparison of the hydrocarbon and greenhouse gas emissions of three foundry sand binders as follows: (a) conventional phenolic urethane resin, (b) biodiesel phenolic urethane resin, and (c) collagen-based binder. These binders are used in the metal casting industry for making cores that are used to create internal cavities within castings. In this study, the core samples were flash pyrolyzed in a Curie-point pyrolyzer at 920 degrees C with a heating rate of about 3000 degrees C/sec. This simulated some key features of the fast heating conditions that the core binders would experience at the metal-core interface when molten metal is poured into green sand molds. The core samples were also pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temperature to 1000 degrees C with a heating rate of 30 degrees C/min, and this simulated key features of the slow heating conditions that the core binders would experience at distances that are further away from the metal-core interface during casting cooling. Hydrocarbon emissions from flash pyrolysis were analyzed with a gas chromatography-flame ionization detector, while hydrocarbon and greenhouse gas (CO and CO2) emissions from TGA pyrolysis were monitored with mass spectrometry. The prominent hazardous air pollutant emissions during pyrolysis of the three binders were phenol, cresols, benzene, and toluene for the conventional phenolic urethane resin and biodiesel resin, and they were benzene and toluene for the collagen-based binder. It was also found that volatile organic compound and polycyclic aromatic hydrocarbon emissions considerably decreased in order from conventional phenolic urethane resin to biodiesel resin to collagen-based binder. These results have shown some similarity with those for stack emission testing conducted at demonstration scale and/or full-scale foundries, and the similar trends in the two sets of results offered promise that bench-scale analytical pyrolysis techniques could be a useful screening tool for the foundries to compare the relative emissions of alternative core binders and to choose proper materials in order to comply with air-emission regulations.     

Stability of chlorine dioxide in aqueous solution

Chlorine dioxide in unbuffered aqueous solution at pH 9 and 25°C decomposes to chlorate, chlorite, chloride and oxygen by coupled slow and rapid reactions. The initiation of the second rapid decomposition depends on the initial chlorine dioxide concentration and ionic strength of the solution. Chloride ion has a catalytic and inhibiting effect, changing the product distribution to a 1:1 molar ratio of chlorate and chlorite, thus increasing the oxidizing potential of chlorine dioxide. In buffered solutions at pH 8.8 the reaction is pseudo-second order, yielding chlorate and chlorite as products.     

Improving the Property–Function Tuning Range of Thiophene Materials via Facile Synthesis of Oligo/Polythiophene‐S‐Oxides and Mixed Oligo/Polythiophene‐S‐Oxides/Oligo/Polythiophene‐S,S‐Dioxides

A platform is described for the first time for the facile synthesis of oligo‐ and polythiophene‐S‐oxides and the corresponding ‐S,S‐dioxides in short times, mild conditions, high yields. Employing ultrasound assistance, brominated thiophenes are selectively mono‐ or dioxygenated at room temperature. These building blocks are then combined with metalated thiophenes via microwave‐assisted cross‐coupling reactions through a “Lego‐like” strategy to afford unprecedented oligo/polythiophene‐S‐oxides and mixed ‐S‐oxides/‐S,S‐dioxides. It is demonstrated that depending on the number, type, and sequence alternation of nonoxygenated, monooxygenated, and dioxygenated thiophene units a very wide property–function tuning can be achieved spanning from frontier orbital energies and energy gaps, to charge transport characteristics and supramolecular H‐bonding interactions with specific proteins inside live cells.