Formation of complexes between alkyl polyglycosides and potato starch

The formation of complexes between soluble potato starch and three commercial alkyl polyglycosides has been studied by means of surface tension measurements at 37 degrees C. All surfactants assayed form complexes with starch, the quantity of bound surfactant being proportional to the amount of starch present in the solution. For all alkyl polyglycoside-starch systems tested, there is a direct proportional relationship between the bound and total surfactant concentrations, so that the formation of the surfactant-starch complex continues until the minimum surface tension is reached without detectable starch saturation prior to the occurrence of surfactant micelles. Binding isotherms and Scatchard plots support the idea that alkyl polyglycosides are bound to amylose by positive cooperative binding and to amylopectin by non-cooperative Langmuir-type binding.     

几种乙酸铵离心法测定土壤阳离子交换量的方法探讨

乙酸铵离心交换法测定酸性和中性土壤阳离子交换量是经典方法,但此方法的蒸馏过程繁琐、时间长、效率低。本文引用纳氏试剂分光光度法测定土壤CEC值,并将结果与乙酸铵离心法常用的几种传统测定方法进行了实验对比和总结。通过对国家标准样品及实际土壤样品的CEC值测定,纳氏试剂比色法的精密度在2-4%之间,准确度与经典方法一致。与传统滴定法比较,取代了蒸馏的步骤,测定方法简单,干扰少,结果可靠,可操作性强。     

Oil in Louisiana's estuarine environments: A development model

Coastal erosion, accelerated by sea level rise, and subsidence are major Louisiana issues. With current sea-level-rise projections, coupled with the state's eroding barrier islands and coastal wetlands, the region's estuarine environments are in jeopardy of being lost, redefined, or permanently altered. As the coast erodes, Louisiana is endangered of losing valuable wetland's habitat. In addition, if the barrier islands disappear, the region's wetland-oriented oil and gas wells and associated infrastructure will be at risk to open Gulf conditions. If this should occur, each well, pipeline, and storage battery represents a potential environmental catastrophe.     

Controlled Fabrication of Cd-Bi Nanoparticles via Sonochemical Method

IntroductionMetal or alloy nanoparticles,because of their con-spicuous physicochemical properties,have been widelyapplied to various fields such as electronics,catalysis,magnetism,and corrosion-resistant materialsfields[1—4].It has been estimated that the particle sizeand the properties of nanoparticles depend strongly onthe specific method of fabrication and the applied ex-periment conditions,which makes the controlled syn-thesis of nanomaterials become an increasingly activeand important ar…     

素理想完全分裂的一个判别法则

本文给出了数域K内一个素理想在K的有限次正规扩域L内完全分裂的一个判别法则。     

Effect of Light on the Electrokinetic Behavior of TiO(2) Particles in Contact with Cr(VI) Aqueous Solutions

The electrokinetic behavior of titanium dioxide particles (Degussa P25, mainly composed of anatase) put in contact with chromium(VI) aqueous solutions is highly sensitive to light exposure under normal laboratory conditions. In the dark, adsorption of Cr(VI) gives rise to substantial decrements in the mobilities, especially in the acidic branch, and, at higher concentrations, to shifts in the isoelectric point (pH(piep)) to lower values, as expected for anionic chemisorption. A two-mode adsorption model accounts qualitatively for the results. Under light, pH(piep) shifts in the opposite direction as the Cr(VI) concentration increases. A maximum value is attained at [Cr(VI)] approximately 10(-3) mol dm(-3), pH(piep) 8.2, which coincides with values reported for hydrous chromium(III) oxides. At higher concentrations, Cr(VI) adsorption defines a shift of pH(piep) to lower values. It is concluded that light absorption by titanium dioxide promotes the reduction of Cr(VI) and the surface precipitation of the hydrous Cr(III) oxide. The values of pH(piep) for partially covered surfaces are well described by a simple model of surface ionization derived earlier. FTIR/ATR analysis of the surfaces supports this interpretation, and further suggests that one of the modes of Cr(VI) adsorption implies surface dimerization to yield adsorbed dichromate. Copyright 2000 Academic Press.     

A Robust, Environmentally Benign Catalyst for Highly Selective Hydroformylation

By a sol-gel process a rhodium complex containing a diphosphane with a large natural P-Rh-P bite angle is covalently anchored in a silica matrix (see picture). The immobilized catalyst is a very selective hydroformylation catalyst that is completely and conveniently separated from the product and can be reused in numerous cycles.     

Hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) determination of cocaine and its metabolites benzoylecgonine, ecgonine methyl ester, and cocaethylene in hair samples

This study reports the development and validation of a method using hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) for the analysis of cocaine and its metabolites benzoylecgonine (BE), ecgonine methyl ester (EME), and cocaethylene (CE) in hair samples. Decontamination was performed as follows: Firstly, the aliquot of hair was briefly rinsed with 2 mL dichloromethane, then was washed three times with 10 mL 0.01 M phosphate buffer, pH 6, for 15 min, followed by 2 mL 2-propanol for less than 2 min, and, finally, a last rinse with 2 mL dichloromethane was again done. Cocaine compounds were extracted from 10 mg of hair by incubation with 2 mL 0.1 M HCl at 50 °C for 12 h and purified by solid phase extraction with Oasis MCX cartridges. Analysis was performed by LC-MS/MS using an Atlantis HILIC silica chromatographic column. The method was fully validated. Linearity was established over the concentration range 0.020–10.0 ng/mg for cocaine (COC), 0.010–10.0 ng/mg for BE and CE, and 0.005–2.0 ng/mg for EME, and the correlation coefficients were all >0.99. Extraction efficiency was >70% for all analytes. Limits of detection were 0.0005 ng/mg for CE and 0.001 ng/mg for the other analytes (COC, BE, and EME). Lower limits of quantification were the lowest points of the calibration curves with acceptable accuracy and precision (coefficient of variation ≤20%). Intra- and inter-day imprecision ranged between 1.5% and 9.5% and 0.7% and 12.6%, respectively. Intra- and inter-day inaccuracy ranged from 0.5% to 12.3% and from 0.7% to 7.1%, respectively. With regard to matrix effects, suppression was <27.5% in all cases. The method was applied to the analysis of several samples derived from forensic cases.