The identification and characteristics of Phoebe zhennan buried wood

ABSTRACT The subject of this study is the structure and composition of buried Phoebe zhennan wood. Through comparative studies of the anatomy and composition with modern undegraded wood, the objective was to understand any changes that have taken place in the P. zhennan buried wood samples. The P. zhennan buried wood can be identified by wood structure characteristics and volatile components analysis. It is required that the microstructural features are identical to those of modern P. zhennan wood; simultaneously, the volatile components of the wood must contain six characteristic compounds with the same peak retention time. The P. zhennan buried wood sample which was used in the experiment was dated 8035–7945 BP (95. 4% probability). Further research showed that the cell wall of P. zhennan buried wood had been damaged, the hemicellulose was heavily degraded but there was no obvious degradation of crystalline cellulose. Moisture was present mainly as free water and large amounts of mineral elements such as Fe, and Ni were detected in the ash of P. zhennan buried wood. Both the buried and modern wood of P. zhennan were acidic.

Gas chromatography using ice-coated fused silica columns: study of adsorption of sulfur dioxide on water ice

The well established technique of gas chromatography is used to investigate interactions of sulfur dioxide with a crystalline ice film in a fused silica wide bore column. Peak shape analysis of SO2 chromatograms measured in the temperature range 205–265 K is applied to extract parameters describing a combination of three processes: (i) physisorption of SO2 at the surface, (ii) dissociative reaction with water and (iii) slow uptake into bulk ice. Process (ii) is described by a dissociative Langmuir isotherm. The pertinent monolayer saturation capacity is found to increase with temperature. The impact of process (iii) on SO2 peak retention time is found to be negligible under our experimental conditions.By analyzing binary chromatograms of hydrophobic n-hexane and hydrophilic acetone, the premelt surface layer is investigated in the temperature range 221–263 K, possibly giving rise to irregular adsorption. Both temperature dependencies fit simple van't Hoff equations as expected for process (i), implying that irregular adsorption of acetone is negligible in the investigated temperature range. Adsorption enthalpies of −45 ± 5 and −23±2 kJ mol−1 are obtained for acetone and n-hexane.The motivation of our study was to assess the vertical displacement of SO2 and acetone in the wake of aircraft by adsorption on ice particles and their subsequent sedimentation. Our results suggest that this transport mechanism is negligible.

Gas-Chromatography using ice coated fused silica-columns: Study of adsorption of sulfur dioxide on water-ice

The well-established technique of gas chromatography is used to investigate interactions of sulfur dioxide with a crystalline ice film in a fused silica wide-bore column. Peak shape analysis of SO2 chromatograms measured in the temperature range 205–265 K is applied to extract parameters describing a combination of three processes: (i) physisorption of SO2 at the surface; (ii) dissociative reaction with water; (iii) slow uptake into bulk ice. Process (ii) is described by a dissociative Langmuir isotherm. The pertinent monolayer saturation capacity is found to increase with temperature. The impact of process (iii) on SO2 peak retention time is found to be negligible under our experimental conditions. By analyzing binary chromatograms of hydrophobic n-hexane and hydrophilic acetone, the premelt surface layer is probed in the temperature range 221–263 K possibly giving rise to irregular adsorption. Both temperature dependencies fit simple van't Hoff equations as expected for process (i), implying that irregular adsorption of acetone is negligible in the probed temperature range. Adsorption enthalpies of −45 ± 5 kJ mol−1 and −23 ± 2 kJ mol−1 are obtained for acetone and n-hexane. Our study was motivated to assess the vertical displacement of SO2 and acetone in the wake of aircraft by adsorption on ice particles and their subsequent sedimentation. Our results suggest that this transport mechanism is negligible.

Using reverse phase high performance liquid chromatography as an alternative to resin fractionation to assess the hydrophobicity of natural organic matter

Resin fractionation is the most widely used technique to isolate and characterize natural organic matter (NOM) based on its hydrophobicity and hydrophilicity, however, it is also recognized as a time consuming technique. This paper describes the use of reverse phase high performance liquid chromatography (RPHPLC) as a rapid assessment technique to determine the hydrophobicity/hydrophilicity of NOM. The optimum column separation condition was achieved and without the need for concentrating the sample prior to analysis and with good reproducibility of the peak retention time and the peak area. The characterization results were further compared with the traditional resin fractionation technique using DAX-8 and XAD-4 resins. The results demonstrated that the polarities defined by the two methods were different but consistent and also that the fractions absorbed onto XAD-4 were less hydrophobic than those absorbed onto DAX-8. The difference in definition between resin fractionation and RPHPLC were further investigated.

Quantitative Determination of Saccharides in Dietary Glyconutritional Products by Anion-Exchange Liquid Chromatography with Integrated Pulsed Amperometric Detection

A new technique for the assay of carbohydrates is described in which separation and quantification of neutral saccharides, aminosaccharides, glycuronic acids, and disaccharides may be accomplished in less than 50 min of total run time. This method involves optimized anion-exchange liquid chromatography coupled with integrated pulse amperometric detection. Complex carbohydrates from various sources, including dietary supplements, were hydrolyzed in a dilute solution of trifluoroacetic acid, freeze-dried, and reconstituted in water containing 2-deoxygalactose as the internal standard. The solution was filtered and separated on CarboPac PA20 column. The eluted saccharides were detected by oxidation on a gold electrode with quadruple-pulsed integrated amperometry. The calibration plots for the saccharides were linear with an average correlation coefficient of 0.999. Method precisionc regarding peak retention time and resolution used in the peak identifications was verified. With this method, previously difficult-to-separate saccharides, such as galactosamine, glucosamine, and N-acetylglucosamine, were successfully resolved from the neutral saccharides rhamnose, arabinose, and galactose. Mannose was also resolved from xylose, and de-acetylation of aminosaccharides prior to separation was not necessary. This technique provides an accurate and efficient means to assay carbohydrates in dietary supplements, which new federal regulations will soon mandate.

Determination of Trace 2,4-Dichlorophenoxyacetic Acid in Fresh Produce by Gas Chromatography with Boron Trichloride/2- Chloroethanol Derivatization

2,4-Dichlorophenoxyacetic acid (2,4-D) residues in fresh produce is officially analyzed as its methyl ester form by gas chromatography with electron capture detection (GC-ECD). Because of safety concerns with diazomethane, the reagent used to form methyl esters, a less toxic and dangerous reagent, BCI3/2-chloroethanol, was considered. With this alternative reagent, the detecting product is a 2-chloroethyl ester. Compared with the methylester, the 2-chloroethylester has a longer retention time and a better signal-to-noise ratio for trace level analysis by GC-ECD. However, the reagent produces too many unwanted background peaks. If peak retention time is the only information available to identify the residue in case of litigation, the presence of too much background noise increases the ambiguity of identification. Therefore, confirmation by interpretation of the mass spectrum and determination of the compound structure is necessary to ensure the validity of the method. Ten commodities were fortified with 2,4-D at 0.1 ppm. Recoveries of 2-chloroethyl esters and methyl esters were 91 and 92%, respectively. The method is safe, simple, and robust.

Liquid Chromatographic Method for Determining the Percent of Olestra in Lipid Samples

A liquid chromatographic (LC) method has been developed to determine the percent of olestra in lipid samples. To achieve the highest degree of accuracy, this method requires the use of an olestra standard with the same molecular composition as the olestra in the lipid sample to be analyzed. Samples were analyzed by reversed-phase LC using an evaporative light-scattering detector. Chromatography was performed with a 5 μm octadecylsilane- Zorbax column that separates olestra from other lipophilic components. Three types of olestra standards (soybean-oil olestra, unheated cottonseed- oil olestra, and heated cottonseed-oil olestra), each analyzed in soybean oil, showed linearity when the amount of olestra injected ranged from 20 to 160 fig (r= 0.9996). The area under the olestra peak (retention time 3.5 to 4.9 min) was used to quantify the amount of olestra in olestra-lipid samples, by comparing the olestra area for the sample with that of the standard using a curve derived by linear regression. The method was evaluated using 3 types of olestra blended with soybean oil and varying the percent of olestra in the olestra-lipid blend from 5 to 90%. Recovery of olestra from these olestra-lipid blends varied from 99.2 to 106.0%, demonstrating excellent accuracy, with method precision expressed as the coefficient of variation, 0.9%. Each error estimate was derived from 5 parallel determinations. With proper validation (e.g., running an olestra-free blank for each lipid matrix), this method provides a rapid, accurate, and precise technique for measuring the percent of olestra in lipids extracted from olestra-formulated foods and in olestra-lipid blends.