E-cigarette liquids: Constancy of content across batches and accuracy of labeling.

AIMS: To assess whether bottles of refill liquids for e-cigarettes were filled true to label, whether their content was constant across two production batches, and whether they contained impurities. METHODS: In 2013, we purchased on the Internet 18 models from 11 brands of e-liquids. We purchased a second sample of the same models 4months later. We analyzed their content in nicotine, anabasine, propylene glycol, glycerol, ethylene glycol and diethylene glycol, and tested their pH. RESULTS: The median difference between the nicotine value on the labels and the nicotine content in the bottles was 0.3mg/mL (range -5.4 to +3.5mg/mL, i.e. -8% to +30%). For 82% of the samples, the actual nicotine content was within 10% of the value on the labels. All models contained glycerol (median 407mg/mL), and all but three models contained propylene glycol (median 650mg/mL). For all samples, levels of anabasine, ethylene glycol and diethylene glycol were below our limits of detection. The pH of all the e-liquids was alkaline (median pH=9.1; range 8.1 to 9.9). The measured content of two batches of the same model varied by a median of 0% across batches for propylene glycol, 1% for glycerol, 0% for pH, and 0.5% for nicotine (range -15% to +21%; 5th and 95th percentiles: -15% and +10%). CONCLUSIONS: The nicotine content of these e-liquids matched the labels on the bottles, and was relatively constant across production batches. The content of propylene glycol and glycerol was also stable across batches, as was the pH.

Employing bacterial microcompartment technology to engineer a shell-free enzyme-aggregate for enhanced 1,2-propanediol production in Escherichia coli.

Bacterial microcompartments (BMCs) enhance the breakdown of metabolites such as 1,2-propanediol (1,2-PD) to propionic acid. The encapsulation of proteins within the BMC is mediated by the presence of targeting sequences. In an attempt to redesign the Pdu BMC into a 1,2-PD synthesising factory using glycerol as the starting material we added N-terminal targeting peptides to glycerol dehydrogenase, dihydroxyacetone kinase, methylglyoxal synthase and 1,2-propanediol oxidoreductase to allow their inclusion into an empty BMC. 1,2-PD producing strains containing the fused enzymes exhibit a 245% increase in product formation in comparison to un-tagged enzymes, irrespective of the presence of BMCs. Tagging of enzymes with targeting peptides results in the formation of dense protein aggregates within the cell that are shown by immuno-labelling to contain the vast majority of tagged proteins. It can therefore be concluded that these protein inclusions are metabolically active and facilitate the significant increase in product formation.

Laboratory-scale evaluation of a combined soil amendment for the enhanced biodegradation of propylene glycol-based aircraft de-icing fluids.

A combined soil amendment was tested in microcosm experiments with an aim to enhance the aerobic biodegradation of propylene glycol (PG)-based aircraft de-icing fluids during and following the infiltration of contaminated snowmelt. A key objective under field conditions is to increase degradation of organic pollutants in the surface soil where higher microbial activity and plant rhizosphere effects may contribute to a more efficient biodegradation of PG, compared to subsoil ground layers, where electron acceptors and nutrients are often depleted. Microcosm experiments were set up in Petri dishes using 50 g of soil mixed with appropriate additives. The samples contained an initial de-icing fluid concentration of 10,000 mg/kg soil. A combined amendment using calcium peroxide, activated carbon and 1 x Hoagland solution resulted in significantly higher degradation rates for PG both at 4 and 22 degrees C. Most probable numbers of bacteria capable of utilizing 10,000 mg/kg de-icing fluid as a sole carbon source were about two orders of magnitude higher in the amended soil samples compared to unamended controls at both temperatures. The elevated numbers of such bacteria in surface soil may be a source of cells transported to the subsoil by snowmelt infiltration. The near-surface application of amendments tested here may enhance the growth of plants and plant roots in the contaminated area, as well as microbes to be found at greater depth, and hence increase the degradation of a contaminant plume present in the ground.

Bioaugmentation to degrade the organic de-icers acetate and monopropylene glycol at low temperatures.

Two de-icers, potassium acetate and monopropylene glycol (MPG), used widespread as a runway and wing de-icer respectively, can exert high BOD in the surrounding waters. A bioaugmentation approach to degrade these de-icer compounds in the drainage water prior to discharge has been tested. A microbial consortium originating from soil was enriched at low temperatures (4 degrees C) in order to adapt to wintertime conditions. With 0.05 g CDW/L of biocatalyst, maximum specific removal rates up to 1.46 and 3.33 g acetate/g CDW d at 4 degrees C were achieved with and without biostimulation respectively. An acetate:MPG mixture of 1:3 at a total COD concentration of 0.80 and 1.20 g/L was degraded in 12 days by 83 and 70% respectively. Bioaugmentation in the field over a period of 25 days showed a removal of 88% MPG compared to 46% in the control. These results demonstrate that bioaugmentation of airport runoff water can be successfully applied to prevent organic de-icer compounds from entering the receiving surface waters.

Comparison of biodegradation of poly(ethylene glycol)s and poly(propylene glycol)s.

The biodegradation of poly(ethylene glycol)s (PEGs) and poly(propylene glycol)s (PPGs), both being major by-products of non-ionic surfactants biodegradation, was studied under the conditions of the River Water Die-Away Test. PEGs were isolated from a water matrix using solid-phase extraction with graphitized carbon black sorbent, then derivatized with phenyl isocyanate and determined by HPLC with UV detection. PPGs were isolated from a water matrix by liquid-liquid extraction with chloroform, then derivatized with naphthyl isocyanate and determined by HPLC with fluorescence detection. The primary biodegradation of both PEGs and PPGs reached approximately 99% during the test. The tests show different biodegradation pathways of PEG and PPG. During PEG biodegradation, their chains are shortened leading to the formation of ethylene glycol and diethylene glycol. During PPG biodegradation, no short-chained biodegradation products were found.

Isolation of poly(propylene glycol)s from water for quantitative analysis by reversed-phase liquid chromatography.

Procedures for the isolation of poly(propylene glycol)s (PPGs) from a water matrix have been developed. Solid-phase extraction with an octadecylsilica cartridge and elution with methanol or with a graphitised carbon black cartridge and elution with a mixture of dichloromethane-methanol (4:1) or liquid-liquid extraction with chloroform were all suitable for model samples. However, only liquid-liquid extraction was suitable both for model and real environmental samples. Methods for reversed-phase liquid chromatographic determination of PPGs based on derivatisation and ultraviolet or fluorescence detection have been developed. Four derivatisation agents [3,5-dinitrobenzoyl chloride, phenyl isocyanate, 1-naphthoyl chloride and 1-naphthyl isocyanate (NIC)] were tested. Only NIC was found to give good reproducibility as well as a satisfactory detection limit. Finally, a method with liquid-liquid extraction with chloroform, derivatisation with NIC and liquid chromatographic separation with fluorescence detection was established. The developed method shows a highly correlated linearity of the analytical signals of particular homologues within a wide concentration range (approximately from 0.01 to 10 mg l(-1)). The precision of measurements is satisfactory for homologues having 5-9 oxypropylene subunits and becomes worse with an increase in the number of oxypropylene subunits. The limit of detection is 2 microg l(-1) for the majority of homologues. The method is suitable for the isolation and quantitative determination of PPGs in river water samples and as a tool for biodegradation testing.

Biodegradation of propylene glycol and associated hydrodynamic effects in sand.

At airports around the world, propylene glycol (PG) based fluids are used to de-ice aircraft for safe operation. PG removal was investigated in 15-cm deep saturated sand columns. Greater than 99% PG biodegradation was achieved for all flow rates and loading conditions tested, which decreased the hydraulic conductivity of the sand by 1-3 orders of magnitude until a steady-state minimum was reached. Under constant loading at 120 mg PG/d for 15-30 d, the hydraulic conductivity (K) decreased by 2-2.5 orders of magnitude when the average linear velocity of the water was 4.9-1.4 cm/h. Variable PG loading in recirculation tests resulted in slower conductivity declines and lower final steady-state conductivity than constant PG feeding. After significant sand plugging, endogenous periods of time without PG resulted in significant but partial recovery of the original conductivity. Biomass growth also increased the dispersivity of the sand.

[Preparation of gas chromatographic capillary columns with beta-cyclodextrin polymer stationary phase modified with methyl phenyl silicone(OV-17)].

An insoluble beta-cyclodextrin polymer cross-linked with epichlorohydrin was prepared. beta-Cyclodextrin polymer (0.26 g) was treated for 0.5 h by a ultrasonator in the mixed solvent (10 mL) of isopropyl ether, methylene dichloride and benzene with a volume ratio 2:1:2, and a 26 g/L colloidal stationary liquid was prepared. It was coated on a fused silica capillary by superdynamic coating method. The capillary column was of high column efficiency of above 3,000/m with good thermal stability and moderate polarity. Enantiomers of xylene, dichlorobenzene, alpha-pinene, beta-pinene, ethyl lactate, alpha-phenyl ethanol, 1, 2-propanediol, alpha-lonone, methyl alpha-chloropropionate and gamma-valerolactone were separated on the capillary column. The experimental results showed that beta-cyclodextrin polymer treated by a ultrasonator is a capillary chromatographic stationary phase with good performance and high selectivity.