Volatilization Research Papers - Academia.edu (original) (raw)

Partition coefficients, Kfat, from air to human fat and to rat fat have been collected for 129 volatile organic compounds, VOCs. A linear free energy relationship, LFER, correlates the 129 values of logKfat with R2=0.958 and a standard... more

Partition coefficients, Kfat, from air to human fat and to rat fat have been collected for 129 volatile organic compounds, VOCs. A linear free energy relationship, LFER, correlates the 129 values of logKfat with R2=0.958 and a standard deviation, S.D., of 0.194 log units. Use of training and test sets gives a predictive assessment of around 0.20 log units. Combination

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available... more

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available for assessing risks to benthic invertebrates due to VOCs in sediment. More strongly hydrophobic organic chemicals are frequently assessed by using the equilibrium partitioning (EqP) approach, which predicts the bioavailable fraction of chemical (the concentration dissolved in pore water) from the sediment-sorbed fraction, assuming that partitioning is at equilibrium. As typically applied, the EqP approach is ineffective for assessing VOCs in sediment, because the standard EqP equation fails to account for the contribution of dissolved chemical to the total chemical concentration in sediment. For chemicals with low organic carbon-water partition coefficients (KOCs), this results in nonsensical sediment-quality benchmarks that are more conservative (i.e., lower) than benchmarks calculated by assuming 100% bioavailability. A modified EqP equation is presented that accounts for the dissolved fraction of total chemical concentrations in sediment. Results of the standard and modified EqP equations converge with increasing KOC and are essentially identical at log KOC values exceeding approximately 3.5.

Abstract: Cyanoacrylate fuming is a widely used forensic tool for the development of latent fingerprints, however the mechanistic details of the reaction between the fingerprint residue and the cyanoacrylate vapor are not well... more

Abstract: Cyanoacrylate fuming is a widely used forensic tool for the development of latent fingerprints, however the mechanistic details of the reaction between the fingerprint residue and the cyanoacrylate vapor are not well understood. Here the polymerization of ethyl-cyanoacrylate vapor by sodium lactate or alanine solutions, two of the major components in fingerprint residue, has been examined by monitoring the time dependence of the mass uptake and resultant polymer molecular weight characteristics. This data provides insight into the molecular level actions in the efficient development of latent fingerprints by superglue fuming. The results show that the carboxylate moiety is the primary initiator of the polymerization process and that a basic environment inhibits chain termination while an acidic environment promotes it. The results also indicate that water cannot be the primary initiator in this forensic technique.

Application of compound-specific stable isotope approaches often involves comparisons of isotope enrichment factors (ε). Experimental determination of ε-values is based on the Rayleigh equation, which relates the change in measured... more

Application of compound-specific stable isotope approaches often involves comparisons of isotope enrichment factors (ε). Experimental determination of ε-values is based on the Rayleigh equation, which relates the change in measured isotope ratios to the decreasing substrate fractions and is valid for closed systems. Even in well-controlled batch experiments, however, this requirement is not necessarily fulfilled, since repetitive sampling can remove a significant fraction of the analyte. For volatile compounds the need for appropriate corrections is most evident, and various methods have been proposed to account for mass removal and for volatilization into the headspace. In this study we use both synthetic and experimental data to demonstrate that the determination of ε-values according to current correction methods is prone to considerable systematic errors even in well-designed experimental setups. Application of inappropriate methods may lead to incorrect and inconsistent ε-value...

Effects of wetting and drying conditions on micromeritic, mechanical and disintegration properties of microcrystalline cellulose (MCC) pellets were evaluated. Extrusion/spheronization and three drying methods (fluidized bed, microwaves,... more

Effects of wetting and drying conditions on micromeritic, mechanical and disintegration properties of microcrystalline cellulose (MCC) pellets were evaluated. Extrusion/spheronization and three drying methods (fluidized bed, microwaves, and freeze drying) were applied using two wetting liquids (water or water-isopropanol 60:40 w/w) and three MCC types: (standard, silicified, and modified). Additionally, the effects of drying method were compared on highly porous pellets prepared by the incorporation and extraction of pore former (NaCl). It was found that the drying method has the greatest effect on the pellet size and porosity followed by the wetting liquid. The modification of MCC resulted in reduced water retention ability, implying hornification, increased porosity, reduced resistance to deformation and tensile strength of pellets. The disintegration time also decreased markedly due to the modification but only in the low porosity range <37%. Silicification increased greatly the disintegration time of the low porosity pellets (<14%). Combination of water-isopropanol, freeze drying and modified MCC gave the greatest increase in pellet size and porosity. The increase in pellet porosity caused exponential reduction in the resistance to deformation, tensile strength and disintegration time, as expected. Compared to fluidized bed, the freeze drying resulted in 20-30% higher porosity for pellets prepared without pore former and 6% for those with pore former, indicating the possibility of preparing highly porous pellets by employing freeze drying.

Volatiles were isolated from the dried inner bark of Tabebuia impetiginosa using steam distillation under reduced pressure followed by continuous liquid-liquid extraction. The extract was analyzed by gas chromatography and gas... more

Volatiles were isolated from the dried inner bark of Tabebuia impetiginosa using steam distillation under reduced pressure followed by continuous liquid-liquid extraction. The extract was analyzed by gas chromatography and gas chromatography-mass spectrometry. The major volatile constituents of T. impetiginosa were 4-methoxybenzaldehyde (52.84 microg/g), 4-methoxyphenol (38.91 microg/g), 5-allyl-1,2,3-trimethoxybenzene (elemicin; 34.15 microg/g), 1-methoxy-4-(1E)-1-propenylbenzene (trans-anethole; 33.75 microg/g), and 4-methoxybenzyl alcohol (30.29 microg/g). The antioxidant activity of the volatiles was evaluated using two different assays. The extract exhibited a potent inhibitory effect on the formation of conjugated diene hydroperoxides (from methyl linoleate) at a concentration of 1000 microg/mL. The extract also inhibited the oxidation of hexanal for 40 days at a level of 5 microg/mL. The antioxidative activity of T. impetiginosa volatiles was comparable with that of the well-known antioxidants, alpha-tocopherol, and butylated hydroxytoluene.

A retention index (RI) database containing 250 volatile compounds was created on a polar stationary phase column and validated for food aroma characterisation. Precision of the retention indices (RIs) was assessed by performing replicated... more

A retention index (RI) database containing 250 volatile compounds was created on a polar stationary phase column and validated for food aroma characterisation. Precision of the retention indices (RIs) was assessed by performing replicated injections of a representative number of volatiles under the same experimental conditions: differences lower than 1 U were observed for all the compounds. Robustness was evaluated by carrying out injections of the same set of volatile compounds under different experimental conditions, i.e. program temperature, column batches and instrumentation. Excellent results were obtained with a maximum difference in the RI values of 10 U. The capabilities of the created database for food aroma characterisation were finally evaluated by analysing the volatile fractions of different food matrices such as dry sausages, cheese and bread. A great number of volatile compounds were identified in the analysed samples on the basis of their RI, thus proving the usefuln...