Adsorption-calorimetric determination of the surface energy of dispersed oxides

A new method is proposed for the determination of the surface free energy σ_S and interfacial free energy σ_SL, based on their linear dependence on the specific heat of wetting of dispersed materials by water. The σ_S and σ_SL values of Silochrome, silica gel, and γ-aluminum oxide were determined first by this method. The obtained results are compared with data obtained from the similarity method and the empirical relationship between σ_S and the surface pressure. It is demonstrated that the methods can be used to determine σ_S for the investigated sorbents. Conclusions about the hydrophilicity-hydrophobicity of their surface were reached on the basis of the results. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 75–80, March–April, 2007.     

The effect of treating air samples with magnesium perchlorate for water removal during analysis for non-methane hydrocarbons

A comparison has been made between two cryogenic preconcentration - high resolution gas chromatography techniques for the analysis of non-methane hydrocarbons in ambient air, one involving treatment of air samples with magnesium perchlorate to remove water, the other involving analysis without treatment. Recoveries of C₁-, C₂-, and C₃-substituted benzenes in treated samples were 80%, 50%, and 50%, respectively. Incomplete recovery of C₇-C₉ n-1-olefins was also observed. C₂-C₈ hydrocarbons and C₂-C₆ n-1-olefins were recovered with greater than 90% efficiency. Analyses of certified audit samples containing a mixture of C₂-C₈ aliphatic and aromatic hydrocarbons at the 20 ppbv level in humidified zero-grade air indicated that the accuracy of the technique for untreated air samples was approximately 90%. The use of magnesium perchlorate for water removal cannot be recommended for the analysis of non-methane hydrocarbons in ambient air.     

Simultaneous analysis of all five organic priority pollutant fractions

Acrolein, acrylonitrile, volatile organics, base/neutral extractables, acid extractables, and pesticide fraction organics are analyzed in a single chromatographic run. This is accomplished by injecting the extractable organics, then applying a cryogenic focus to the front of the column, and desorbing the volatile components. The column utilized for this procedure is a fused silica open tubular (FSOT) column coated with the liquid phase SE-54. Minimum detection limits of this procedure by electron impact GC/MS are shown to be? 1 μg/liter in tests conducted on actual water samples.     

Antimicrobial Sol–Gel Coatings

The preparation and the releasing behavior of modified silica coatings, containing embedded biocides on textiles, were compared and assessed with regard to application parameters like antimicrobial efficacy, wash-out and long-term behavior. For this, silica layers with embedded silver, silver salts and biocidal quaternary ammonium salts (cetyltrimethylammoniumbromid and octenidine) were investigated. Both the growth of fungi and bacteria can be inhibited by coatings with embedded biocides. Especially by using octenidine, an excellent long-term inhibition of fungi growth can be reached.     

有序介孔氧化硅膜的制备及结构研究

本文介绍了在α-Al₂O₃中空纤维载体上制备担载有序氧化硅膜的方法。应用LXRD、HRTEM、TG-DTA、SEM、氮气吸附等测试手段对膜的结构、形貌进行了表征。LXRD和HRTEM结果显示所制备的非担载膜具有高度有序的二维六方结构。SEM分析发现担载膜表面完整、无缺陷。气体渗透实验表明中空纤维担载膜具有一定的气体选择性，在0.1 MPa下对H₂/N₂和CH₄/N₂的分离因子分别为2.80和1.65，气体透过膜孔的扩散由努森机制所控制。等温氮气吸附实验显示：500 ℃热处理后非担载膜的比表面积为548.84 m²·g^-1，孔容为0.57 mL·g^-1。     

Capillary electrochromatography with 1.5 μm ODS-modified non-porous silica spheres

Summary The particle realization of electrochromatography on capillaries packed with 1.5 μm ODS-modified non-porous silica spheres is demonstrated. In order to realize stable separation conditions it is crucial to add sodium dodecylsulphate (SDS) to the mobile phase and to pressurize both buffer vials at 10 bar. The presence of SDS stabilizes the current and makes the electro-osmotic flow in the packing more uniform so that no air bubbles are generated at high field strengths. The capillary columns are extremely efficient and on a 24 cm long column about 120,000 plates can be generated (a reduced plate height of about 1.3). The columns are very stable and no loss in efficiency was found after using a column continuously for two months.     

Some applications of capillary gas chromatography in the chemical industry

About three years ago, fused silica capillary columns were introduced in the Quality Control Laboratory of the Shell refinery/chemical complex at Pernis. In general, long, thick-film, wide-bore capillary columns are used together with low split ratios and hydrogen as carrier gas. These conditions enable the analysis of relatively large sample amounts, resulting in low detection limits for the minor components without overloading by the major components, while still maintaining a satisfactory resolution. A number of applications are shown, such as the analysis of complex mixtures, the determination of trace impurities and the analysis of residual volatiles in polymers.     

氨基酸和多肽在碱性硅胶载体上的固相衍生研究

为进行复杂体系中痕量生理活性物质 (如氨基酸和多肽等 )的高灵敏度分析 ,往往需要对其进行柱前或柱后的荧光衍生 -高效液相色谱或毛细管电泳分析 [1] .在一个存在着竞争反应的体系中 ,为保证样品有足够的反应产率 ,往往需使衍生试剂过量很多 ,这就使得衍生后的样品中必然含有高浓度的衍生试剂及其水解后形成的副产物 ,从而大大地干扰了分离与分析 .为解决这一问题 ,通常可采取溶剂萃取[2～ 5] 或加入 1 -金刚烷胺 [6 ,7] 或羟胺 [8,9] 等方法除去过量试剂 .但这些额外的处理使衍生方法更加烦琐 ,有时还导致收率的降低 .也有使用固相化的衍…     

Planarity selectivity in supercritical fluid and liquid chromatography using octadecylsilane-modified silicas with carbon dioxide

Summary The influence of column temperature and pressure on the planarity selectivity of encapsulated and polymeric octadecylsilane-modified silicas was examined using carbon dioxide mobile phase in supercritical fluid and liquid chromatography. The use of liquid carbon dioxide was found to enhance remarkably the molecular planarity recognition capability of the polymeric stationary phase compared with supercritical conditions. The influence of pressure and temperature on selectivity was seen to be significant with the polymeric phase but less with the encapsulated. It seems that pressure and temperature change the morphology of the polymeric phase to a greater extent than the encapsulated one.