正已醇氧化成正已醛磷钨杂多酸催化剂的过氧化氢分解活性

详细讨论了磷钨杂多酸催化氧化正已醇生成正已醛反应中,在不同条件下氧化剂过氧化氢的分解活性及其动力学性质。结果表明,反应温度是影响过氧化氢分解的主要因素,温度低于70℃,分解反应进行平缓;温度一旦达到或超过80℃,则过氧化氢的分解速率迅速加快,2h的分解率达95.2%。有机溶剂及反应底物的加入,均对过氧化氢的分解反应始终保持其一级动力学性质。     

Catalytic Oxidation of Hexanol to Hexanal with H2O2 Over P-W Heteropoly Compounds

The syntheses of Keggin and Dawson-structural phospho-tungsto heteropoly compounds and their Peroxo-derivatives(PCWP), and the catalytic performance over this series of catalysts for the selective oxidation of hexanol to hexylaldehyde are reported. By means of IR, NMR and UV-DRS techniques the catalysts were characterized and a comparison of the structural properties of these catalysts before and after the reaction was made. The correlation between the catalytic performance and the structure of this series of catalysts was discussed as well.     

High-pressure (vapour + liquid) equilibria for ternary systems composed by {(E)-2-hexenal or hexanal + carbon dioxide + water}: Partition coefficient measurement

A new apparatus based on a static–analytic method assembled in this work was utilised to perform high-pressure (vapour + liquid) equilibria measurements of aqueous ternary systems. This work includes values of isothermal partition coefficients between CO₂ and water of two apple aroma constituents, (E)-2-hexenal and hexanal. Additionally, this work reports new experimental (vapour + liquid) equilibria measurements for the ternary systems (CO₂ + (E)-2-hexenal + water) and (CO₂ + hexanal + water), at fixed liquid phase composition (600 mg · kg⁻¹), at temperatures of (313, 323 and 333) K and at pressures from (8 to 19) MPa. Vapour liquid interphase was checked and monitored visually for all the systems studied in this work. No liquid immiscibility was observed at the composition, temperatures and pressures studied. In order to suggest reasonable operation conditions for fractionation of aromas with dense carbon dioxide, partition coefficients of the aroma compounds between CO₂ and water along with their separation factors from water were calculated. Partition coefficients of (E)-2-hexenal between CO₂ and water were in the range of (6 to 91) and where found to be near six times higher than those of hexanal (9 to 17). Very high separation factors from water were observed (∼10⁴) especially for (E)-2-hexenal. The highest separation factor, for both compounds, was found at a temperature of 313 K and pressures from (12 to 14) MPa.     

Solid-phase microextraction–gas chromatography–mass spectrometry method validation for the determination of endogenous substances: Urinary hexanal and heptanal as lung tumor biomarkers

Hexanal and heptanal are endogenous aldehydes coming from membrane lipid oxidation, found in lung cancer patients’ blood, and suggested as lung tumor biomarkers. Here the urinary matrix was investigated instead of blood and the difficulties related to the determination of endogenous substances in biological matrices were faced by developing an external calibration HS-SPME/GC/MS method. The methodology was validated according to international validation procedures and it was verified analyzing unknown biological samples from cancer patients and healthy subjects. Percentage accuracy and precision, ranging from −11.25 to 10.85% and from 0.45 to 4.46%, respectively, were obtained, together with limits of detection (LODs) and lower limits of quantification (LLOQs) of 0.11 and 0.23 pg μL⁻¹ for hexanal and of 0.10 and 0.21 pg μL⁻¹ for heptanal. Analytes percentage recoveries (66.3%, hexanal and 70.5%, heptanal) and stability were evaluated. No analytes degradation was found at room temperature, while the remarkable analytes loss found after 1 month storage suggests analyzing biological samples within a week from storage. Results coming from the analysis of unknown biological samples showed no evident differences of heptanal urinary excretion between lung cancer patients and healthy subjects (0.22–0.95 and 0.21–0.69 pg μL⁻¹, respectively), while hexanal urinary concentrations in cancer patients (0.24–4.36 pg μL⁻¹) were slightly higher than those found in control group ones (0.23–1.26 pg μL⁻¹). The obtained results highly suggest to do further investigations in order to collect statistically significant biological data to discriminate between the pathological state of lung cancer patients and physiological conditions of healthy subjects, using the simple, rapid and cheap method here reported for the quantification of urinary aldehydes.     

Measurement of Hexanal Production by Myoglobin-Induced Lipid Peroxidation Using a Miniature Incubator and Cryofocusing Inlet System with Gas Chromatography and Time-of-Flight Mass Spectrometry

A miniature incubator was used in combination with a cryofocusing inlet system and GC-TOFMS in order to determine the rate of hexanal production during myoglobin (Mb)-induced lipid peroxidation of phosphatidyl choline containing arachidonic acid. The cryofocusing inlet system allowed for rapid preconcentration of the volatile products of the peroxidation reaction, yielding a total analysis time for hexanal of less than 4 min. Each reaction was sampled repetitively, and the production of hexanal was determined in real time, as the reaction progressed. Myoglobin-induced lipid peroxidation produced hexanal linearly over 40 min, maximizing at an average concentration of 1 ppm after 60 min. In reaction mixtures containing basal levels of hexanal, presumably due to autoxidation occurring during storage, greater amounts of hexanal were formed at a faster rate of production, though the production was not linear for more than 15 min. The rapid preconcentration and nondestructive sampling are advantageous; the sampling time can be adjusted in order to detect and quantitate minor products, and the instrumentation can thus be used for full profiling of the volatile products of lipid peroxidation.     

兔肉腥味物质的提取与鉴定

兔肉腥味（风味）物质与组织结合紧密，使用十二烷基硫酸钠（SDS）可使腥味物质解离释放。应用改进的NPT技术提得未去势与去势兔肉中腥味物质，经气－质联谱比较分析，初步确定中级醛类尤其己醛是兔肉腥味物质的主导成分；两种卤代烷烃（1－氯十二烷和1－溴十三烷）可能是构成兔肉特殊气味的重要成分。     

正己醇(氧化)脱氢制正己醛的研究

制备尖晶石型复合氧化物CuAl2O4以及将其负载化,并进行正己醇制正己醛反应催化性能的评价.应用XRD及N2低温吸附等技术对其进行表征.研究结果表明,无论是在正己醇脱氢或氧化脱氢反应中,非负载型及氧化铝负载型CuAl2O4在280℃和LHSV(hexanol)=14.4mL·g-1·h-1时均有较好的催化性能.催化剂的预处理方法不同,对催化剂的氧化脱氢性能影响很大.     

Polydopamine/dialdehyde starch/chitosan composite coating for in-tube solid-phase microextraction and in-situ derivation to analysis of two liver cancer biomarkers in human blood

In order to highly enrich two liver cancer biomarkers (hexanal and 2-butanone) in human blood, in this study, natural nontoxic polydopamine/dialdehyde starch/chitosan (PD/DAS/CHI) coating material was synthesized and immobilized on the inner wall of polytetrafluoro-ethlyene (PTFE) tube. It was used to develop the method based on in-tube solid-phase microextraction (IT-SPME) with in-situ derivatization (ISD) coupled to high performance liquid chromatography for the determination of the above mentioned two liver cancer biomarkers in human blood. The simple, rapid and sensitive IT-SPME-ISD method can be finished within 11 min. Under optimum conditions, the limits of detection (LODs) were 1.4 and 1.6 nmol L⁻¹ for hexanal and 2-butanone, respectively. The relative recoveries from real human blood samples were in the range from 70% to 91% with the intra- and inter-day precisions less than 7.2%. Furthermore, this method was successfully applied for the analysis of hexanal and 2-butanone in blood samples from healthy people with 0.42 ± 0.05 and 0.34 ± 0.04 μmol L⁻¹, while liver cancer patients with 1.90 ± 0.07  μmol L⁻¹ and 0.91 ± 0.07 μmol L⁻¹, respectively. The t-test's results showed there is a statistically significant difference between the data from healthy persons and liver cancer patients. Hence, the developed method might be applied in the screening of suspected liver cancer patients.