离子色谱测定铬酸钾中微量硫酸根和氯离子

建立了一种用于测定化学试剂铬酸钾中的微量硫酸根和氯离子抑制型离子色谱分析法.采用3.2 mmol/L碳酸钠和1.0 mmol/L碳酸氢钠溶液作为缓冲液,流速0.7 mL/min、4 mL/L稀硫酸水溶液作为抑制再生液,进样体积20 μL.该法建立的氯离子和硫酸根离子的线性范围分别为0.01 ～1.0 mg/L和0.1～10.0 mg/L,线性系数r均＞0.999,氯离子和硫酸根离子的检出限为0.5和5 μg/L(以溶液浓度计),精密度分别为2.15％和1.94％(n=8),加标回收率分别在99.2％～100.0％和97.9％～99.9％.该法操作简单、准确、快速.可以用于常规铬酸钾试剂中微量硫酸根和氯离子的定性与定量分析.     

离子色谱法检测铬酐中的痕量氯离子和硫酸根

建立了离子色谱法分离-抑制型电导检测铬酐中痕量氯离子和硫酸根的方法.方法先将铬酐溶于水,持续搅拌下滴加8.5%水合肼溶液将Cr(Ⅵ)还原为Cr(Ⅲ),同时生成氢氧化铬沉淀,离心过滤,取上清液过0.22 μm尼龙膜、H型阳离子交换柱后,以OH-选择性的IonPac AS11-HC阴离子交换分离柱分离,氢氧化钾淋洗液一步梯度洗脱,抑制型电导检测.方法对氯离子的线性范围在5～1 000 μg/L,线性相关系数为0.999 7,检出限(S/N=3)为2.96 μg/L;对硫酸根的线性范围在0.1～50 mg/L,线性相关系数为0.999 9,检出限为4.75 μg/L.方法成功用于铬酐中痕量氯离子和硫酸根的检测.对样品进行加标回收,氯离子的回收率为90%～115%,硫酸根的回收率为80%～105%.方法具有易于操作、选择性好、灵敏度高等特点.     

Higher levels of plasma cholesterol sulfate in patients with liver cirrhosis and hypercholesterolemia

An analytical method for the determination of cholesterol sulfate (CS) in plasma using gas-liquid chromatography was developed. We measured plasma CS concentrations in patients with liver cirrhosis and hypercholesterolemia as examples of disorders that involve aberrations in cholesterol metabolism. Patients with liver cirrhosis had plasma CS concentrations that were significantly higher than those of control subjects (444.6±51.7vs. 253.0±24.6 μg/dL, mean ±SE). The levels of other lipids were lower in cirrhotics, although the differences were not significant. There was no correlation between the levels of CS and sulfated bile acids in cirrhotic patients. CS levels in plasma were also higher in subjects with hypercholesterolemia (413.7±44.5 μg/gL) however, the ratio of CS to total cholesterol (TC) clearly differed between cirrhotics and hypercholesterolemic subjects (1.44±0.11×10⁻³,vs. 3.31 ±0.63×10⁻³;P<0.05). Both in subjects with hypercholesterolemia and in healthy controls, the CS/TC ratio was similar and CS accounted for roughly 0.14% of the TC concentration.     

Electrochemical behavior of magnesium alloys AZ91D,AZCe2, and AZLa1 in chloride and sulfate solutions

The influence of Cl⁻ and SO₄²⁻ on the electrochemical behavior of AZ91D, AZCe2, and AZLa1 was studied. For all alloys, there was a current plateau in the anodic polarization curves in Na₂SO₄ solutions. In 0.5% NaCl solution, there was a small current plateau, whereas there was none in the 3.5% and 5% NaCl solutions. This indicated that SO₄²⁻ is less aggressive than Cl⁻. The range of the current plateau decreased with increasing SO₄²⁻ concentration. For all alloys, the high frequency capacitive loop in the Nyquist plots decreased with increasing concentration consistent with the decrease in corrosion resistance with increasing Cl⁻ and SO₄²⁻ concentration.     

Determination of optimal pre-treatment conditions for ethanol production from olive-pruning debris by simultaneous saccharification and fermentation

Ethanol generation from lignocellulose materials provides an alternative energy-production system. This study investigates the effect of pre-treatment conditions: maximum temperature (range 423.15-483.15 K) and sulfuric-acid concentration (interval 0.002-0.059 kmol/m³) on fuel-ethanol production from simultaneous saccharification and fermentation (SSF) of olive-pruning debris by Saccharomyces cerevisiae IR2-9a (a thermal acclimatized microorganism, 313.15 K). The influence of these two variables was determined by using a response-surface methodology. Cellulose percentage in pre-treated solids reached a maximum of 71.6% of the content in raw material at 483.15 K and 0.010 kmol/m³ of acid concentration. The conversion of hemicellulose into monosaccharides and oligosaccharides also was analyzed. After the wash and filtration of solids, a significant quantity of d-glucose was obtained in the liquid fraction. For ethanol generation, the bio-fuel yield (maximum of 9.6 kg from 100 kg olive-pruning debris), and volumetric ethanol productivity (maximum of 0.27 kg/(m³ h)), strongly depended on pre-treatments conditions. According to statistical optimization, the highest ethanol yield (9.9 kg ethanol from 100 kg olive-pruning debris) is achieved at 480.15 K using a catalyst concentration of 0.016 kmol/m³. A maximum overall process yield of 15.3 kg ethanol/100 kg olive-pruning debris may result when taking into account ethanol from SSF and d-glucose present in the pre-hydrolysate, assuming its theoretical conversion (22.8 kg ethanol/100 kg raw material, also considering the total conversion of d-xylose in the filtrate).     

Diurnal variation of plasma methyl sterols and cholesterol in the rat: Relation to hepatic cholesterol synthesis

Free cholesterol of plasma low density lipoproteins (LDL) and high density lipoproteins (HDL) of the rat was high and that of plasma very low density lipoproteins (VLDL) was low during the dark period of the diurnal cycle. Variations in the esterified plasma sterols were inconsistent. Free methyl sterols were high in all lipoproteins during the dark phase. Simultaneously, the incorporation of¹⁴C-acetate into nonsaponifiable sterols and the concentrations of free methyl sterols and cholesterol in the liver were elevated.     

2-氨基乙醇硫酸酯溶解度的测定与关联

用带激光监视系统的可控升温速率的溶解度测定装置,常压下测定温度范围为288.66-335.46 K用乙醇胺和硫酸作原料合成牛磺酸过程中的中间产物2-氨基乙醇硫酸酯在水、水+乙醇混合溶剂(体积分数为0.1,0.2,0.3,0.4,0.5)中的固液相平衡数据.并用简单模型、Apelblat模型、λh方程模型对实验数据进行关...     

Determination of the optimum conditions for the cementation of cadmium with zinc powder in sulfate medium

The orthogonal array design has been used to determine the optimum conditions for the cementation of cadmium from a synthetic zinc sulfate solution and hence to achieve the highest cementation efficiency and the best robustness of the quantitation from the least number of trials in a laboratory scale. Cementation was performed using zinc powder. The orthogonal array L₉ (3⁴) that comprises four parameters at three levels was chosen. The parameters and their levels were as: zinc powder quantity (Z): 1, 1.2 and 1.5 times of stoichiometric quantity of cadmium; time (t): 4, 8 and 12 min; temperature (T): 25, 35 and 45 °C and zinc powder particle size distribution (R): nos. 1–3. The ultimate optimum cementation conditions were found to be Z₁ (equal to stoichiometric quantity of cadmium), T₁ (25 °C), R₃ (no. 3) and t₁ (4 min). Under these conditions, cementation percentages for cadmium and nickel were 95.83% and 6.63%, respectively.     

硫酸镁亚型含钾卤水制取硫酸钾工艺系统温度的分析与控制

系统分析探讨了在利用罗布泊盐湖卤水制取硫酸钾的过程中,温度对各工序产品质量和钾收率的影响,并提出了相应的控制措施,对改进硫酸钾工艺生产、提高钾收率具有一定指导意义.     

Macromolecular complexes consisting of poly(aluminum chloride), [2-(diethylamino)ethyl]dextran hydrochloride,and potassium poly(vinyl sulfate)

The mixture of poly(aluminum chloride) (PAC) and [2-(diethylamino)ethyl]dextran hydrochloride (EA) were allowed to react with potassium poly(vinyl sulfate) (PVSK) to form many different water-insoluble macromolecular complexes (MCs) in aqueous solution at various hydrogen ion concentrations. According to elemental analyses, IR spectroscopy, and solubilities of MCs, molecular structures of each MC depend on [H⁺]. It is suggested that the MCs obtained at pH 1.0 are products consisting of EA, PVSK, and aluminum aquo-complex having coordination water whereas the MCs at pH 4.0 are higher molecular products consisting of EA, PVSK, and basic aluminum maltidentate complex. This result is attributable to change with [H⁺] in the degree of dissociation and conformation of EA, PVSK, and the dissociation of hydrated coordination of PAC. MC membranes were made by casting solutions of all kinds of MCs, and active, selective transport phenomena through a membrane of the MC prepared in a solution of pH 1.0 HCl were investigated under various conditions. Transport ratio of Na⁺ and the electric potential difference between the left and right sides of the membrane were measured, with a result that the higher value the membrane potential difference was long allowed to maintain, the higher the transport ratio became. According to this result, the driving force of transport is dependent on the membrane potential, Donnan potential, and diffusion potential, between both sides of the membrane. The Cl^? exclusion (Donnan exclusion), however, is small due to the small cation-exchange capacity, so that the membrane potential difference is caused to decrease rather rapidly by Cl^? permeation. It was also suggested that the affinity of the carrier and both the chemical and physical properties of the MC membrane controlled the selective transport through the membrane.     

Determination of conditions for depositing crystalline calcium chloride hydrate on the heat and moisture exchanging layer of breathing filters

The moisture content and hygroscopicity of viscose fiber and filter material of the heat-exchanging layer of a breathing filter were determined as a function of the mass fraction of calcium chloride, drying temperature, and the calcium chloride soaking method in order to define these parameters.     

Absorption and reaction of isobutene in sulfuric acid—II: Determination of parameters and optimal conditions in bubble columns

The sulfuric acid catalysed absorption and reaction of isobutene was studied in a bubble column (10.2 cm diameter, 256 cm height) covering a wide range of liquid phase compositions. At acid concentrations of 40–48% wt and tert-butanol concentrations of 3.2–4.3 moles/l. the absorption rate has a maximum value. From measurements in the slow reaction or diffusional regime of mass transfer it was possible to obtain a value of liquid side mass transfer coefficient k_L. As interfacial areas and solubilities of isobutene were determined by independent means the rate constants of the hydration could be evaluated from this and other studies in bubble column reactors. The reaction rate constant follows a simple correlation which considers the effect of the acid and the generated butanol. Thus, all relevant data of the absorption-reaction system are available. The significance of these data was checked by a dynamic study in a smaller bubble column.     

电感耦合等离子体原子发射光谱法测定铬矿中铁、铝、硅、镁、钙

提出了使用电感耦合等离子体发射光谱法测定铬矿中铁、铝、硅、镁、钙的分析方法。通过试验确定了熔样方法,仪器的最佳工作参数,分析谱线等。为了防止产生胶体,在测定时选用硝酸作为介质。使用铬矿国家标准样品(BGBW07201、GSBD33001.3)与待测样品同时操作后制作标准曲线。方法的回收率在99.1%~101.5%之间。用本法分析了铬矿标样(GSBD33001.2、Cr-2、72-Cr-01)。测定值与证书值基本一致,相对标准偏差(n=6)小于1%。     

Initial cholesterol uptake by everted sacs of rat small intestine: Kinetic and thermodynamic aspects

The kinetics of initial cholesterol uptake by everted rat proximal and distal small intestinal sacs were evaluated in vitro. The mucosal incubation solution consisted of 0.05 mM cholesterol solubilized in 4.8 mM sodium taurocholate micellar solution at pH 7.4. Experiments were performed at temperatures from 26 to 38 C. The rate of cholesterol uptake followed a linear relationship when plotted against time indicating an apparent zero-order kinetics mechanism for initial uptake. An Arrhenius plot of the results of uptake versus temperature remained linear over the entire range of temperatures studied. The large free energy of activation (20 kcal/mole) suggests that an energy barrier for cholesterol uptake exists at the enterocyte luminal cell membrane and may be an important limiting step in cholesterol uptake. It is proposed that a transient association between cholesterol and a component of the enterocyte luminal cell membrane is formed during initial uptake of cholesterol. The transient association may be an activated complex formed with proteins present at or within the luminal enterocyte cell membrane.     

Autoxidation of cholesterol in tallows heated under deep frying conditions: Evaluation of oxysterols by GLC and TLC-FID

The products of cholesterol autoxidation (oxysterols) in heated animal food fat were determined qualitatively and quantitatively to evaluate their toxicity and those of the foods in which they occur. Samples of beef tallow were taken from deep-fat fryers while they were in use. The oxysterols were identified and assayed by gas liquid chromatography and thin layer chromatography on Chromarods with flame ionization detection (TLC-FID). The two methods were compared and the TLC-FID method was found more convenient for a rapid estimation of autoxidation. Of the original cholesterol, 25% was destroyed during cooking and partly transformed into 3β-5-6β-trihydroxy-5α-cholestane, 7α-hydroxy-, 7β-hydroxy-, 7-oxo-cholesterol, 7-oxo-cholesta-3-5-diene and cholesterol epoxides. Certain other oxysterols were present in smaller quantities.     

Preparation and characterization of oxide films containing crystalline TiO2 on magnesium alloy by plasma electrolytic oxidation

Oxide films have been produced on AM60B magnesium alloy using plasma electrolytic oxidation process in an alkaline phosphate electrolyte with and without addition of titania sol. The microstructure and composition of the oxide films were analyzed by Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscope (XPS) and X-ray Diffraction (XRD). The corrosion resistances of the oxide films were evaluated using potentiodynamic polarization measurements in 3.5 wt% NaCl solution. It is found that the oxide film containing crystalline rutile and anatase TiO₂ compounds are produced in an alkaline phosphate electrolyte with addition of titania sol. The oxide film formed in electrolyte with addition of titania sol has more uniform morphology with less structural imperfections than that formed in electrolyte without addition of titania sol. The results of potentiodynamic polarization analysis show that the oxide film formed in the present modified electrolyte is successful in providing superior corrosion resistance for magnesium alloy.     

Characteristics of the radiation emitted by and the conditions for nucleation of submicron oxide particles during combustion of magnesium

The radiative characteristics of the zone of combustion of MgO particles were investigated in the pressure range p=10⁴–10⁵ Pa. The absorption efficiency factors O_a of MgO particles were determined for different wavelengths and temperatures. The depth of the levels in the forbidden band which are responsible for the high values of u_a were determined: E_g=3.3±0.4 eV. The composition of the reaction zone, determining the appearance of defects of the MgO crystal lattice and influencing the condensation regime, was investigated. Odessa. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 17–22, September–October, 1993.     

Transparent LiOH-doped magnesium aluminate spinel produced by spark plasma sintering: Effects of heating rate and dopant concentration

The effects of LiOH doping of magnesium aluminate spinel powders and various Spark Plasma Sintering (SPS) schedules on densification behavior and final transparency of polycrystalline magnesium aluminate spinel were studied. Two commercial magnesium aluminate spinel powders, with different specific surface areas, were doped with up to 0.6 wt% of LiOH and consolidated using SPS with slow (2.75 °C/min) and fast (100 °C/min) heating rates. The slow heating rate was optimal for undoped magnesium aluminate spinel (LiOH-free) with the best real in-line transmittance (RIT) of 84.8% (measured at 633 nm on a disc 0.8 mm thick). For the magnesium aluminate spinel doped with 0.3 wt% of LiOH, the fast heating rate was beneficial, and an RIT of 76.5% was achieved. μ-Raman analysis confirmed that the addition of LiOH suppressed carbon contamination.     

Effect of process parameters on the synthesis of nanocrystalline magnesium oxide with high surface area and plate-like shape by surfactant assisted precipitation method

A surfactant assisted precipitation method was employed for the preparation of nanocrystalline magnesium oxide with high specific surface area and plate-like shape. Ammonium hydroxide and polyvinyl alcohol (PVA) were used as precipitant and polymeric surfactant, respectively. The effects of several process parameters such as refluxing time, refluxing temperature and magnesium oxide to PVA monomer unit mole ratio (MgO/PVA) were investigated on the structural properties of the powders. The obtained results showed that the increase in refluxing time and temperature increased the specific surface area and decreased the crystallite size. The results revealed that the polymeric surfactant (PVA) has a significant effect on the synthesis of MgO nanocrystals and led to obtain a powder with higher surface area and plate-like shape.     

非均相催化一步合成碳酸二苯酯及溶胶凝胶法制备催化剂载体合成条件的优化

The support of catalyst for the direct synthesis of diphenyl carbonate （DPC） by heterogeneous catalytic reaction was prepared by the sol-gel method. Compared with activated charcoal, molecular sieve, porous ceramics, hopcalite, the support prepared by the sol-gel method has higher activity. The characterization of the support by X-ray diffraction （XRD） and transmission electron microscope （TEM） show that the mare crystal phase is Co2MnO4 and the average particle diameter is about 40 nm. The optimum conditions for synthesis of the support were determined by orthogonal experiments, which indicate that the proportion of Cu, Mn, and Co is the first important factor influencing the yield and selectivity of DPC. Temperature of calcination is the second one. The optimum conditions are： molar proportion of Cu, Mn, and Co being 1 ： 1 ： 1, temperature of calcination 700℃, drying at 100~C, temperature of water bath 85~C. The yield and selectivity of DPC in the process can reach 38% and 99% in the batch operation, respectively. The copper cobalt manganese mixed oxides chosen as the support contribute more to the high catalytic activity than the sol-gel method.