CaO和NaCl焙烧混合稀土精矿过程中的分解反应

用XRD和TG-DTA热分析技术, 研究了含独居石和氟碳铈镧矿的混合稀土精矿在100～1000 ℃焙烧过程中, 添加CaO, NaCl时, REPO4和REFCO3的分解反应. 研究结果表明: 不添加CaO和NaCl时, 仅在377～450 ℃范围内存在REFCO3的分解反应, 其产物是REOF, RE2O3, 以及Ce2O3进一步的氧化产物CeO2, 而REPO4不分解; 添加CaO后在660～750 ℃之间, CaO有3种分解作用: (1) CaO分解REPO4, 其产物是RE2O3和Ca3(PO4)2. (2) CaO分解REOF, 其产物是RE2O3和CaF2. (3) CaO和REOF的分解产物CaF2共同作用分解REPO4, 其分解产物为RE2O3, Ca5F(PO4)3; 添加CaO, NaCl后, 混合精矿的分解率明显提高, NaCl的作用是为反应体系提供了液相, 促进了固相反应物间的传质过程, 加快了反应速度. 与此同时NaCl还可能参加了CaO分解REPO4的反应.     

Selenium and mercury bioaccessibility in fish samples: an in vitro digestion method

The assessment of hazard from selenium (Se) and mercury (Hg) contaminants in the food chain based on their potential bioaccessibility and on estimate of their actual content in fish is reported under an in vitro model. Atomic fluorescence spectroscopy (AFS) was applied for total selenium and mercury quantification. Selenium and mercury bioaccessibility varied depending on the type of fish analyzed. Se solubility in the gastrointestinal supernatants was higher in swordfish and sardine (76 and 83%, respectively) than in tuna (50%). A low Hg bioaccessibility (9-17%) was found for all the samples.Simulated human gastric and intestinal digestion led to the identification of selenomethionine (SeMet) and organic mercury in the three digested fish. Furthermore, these species were not modified during the digestion. Speciation of selenium compounds was done by liquid chromatography in conjunction with inductively coupled plasma mass spectrometry (LC-ICP-MS).Sardine had the most favorable Se:Hg, [Se:Hg]_{bioaccessible} and [SeMet:Hg]_{bioaccessible} molar ratios, making it preferable to tuna and swordfish.The effect of cooking was also evaluated.     

Topographical properties of polymer films deposited in capillaries for electrophoretic separations of large organic molecules

Topography and thickness of hydrophilic polymer coatings of fused-silica capillaries for capillary electrophoresis (CE) were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and profilometry. Three hydrogels, poly(2-hydroxyethyl methacrylate) [poly(HEMA)], poly(diethylene glycol monomethacrylate) [poly(DEGMA)], and poly(triethylene glycol monomethacrylate) [poly(TEGMA)], were deposited using two procedures, either by simple physical sorption of the polymers, or by derivatization of the capillary wall surface with glycidyl methacrylate (EPMA) followed by polymerization of the appropriate monomers. The performance of the modified capillaries was tested under CE conditions (decrease in the electroosmotic flow, EOF dependence on pH, separation of milk and standard proteins). It has been found that the most important property of the polymer coating is its thickness, whereas its topography and the degree of its hydrophobicity are less significant. Film deposition by physical adsorption is preferable to polymerization on the derivatized surface.     

The impact of LIMS design and functionality on laboratory quality achievements

 A laboratory information management system (LIMS) can make a major contribution to the quality and therefore to the efficiency and competitiveness of a laboratory. Since it can impact all aspects of a laboratory's organization it must be the key if not the principal player of the laboratory's quality system. It should support the laboratory in establishing, maintaining and applying quality procedures thereby enabling the laboratory to achieve its quality goals. As a tool, LIMS permits the laboratory to input and use its own know-how and experience to optimize the total organization (internal and external) and workflow of generated information. However, perceived "quality" in the context of an LIMS, can be viewed as being made up of different facets such as the security, reliability and accessibility of information as well as its turn around time and production cost. This paper reviews the role of a LIMS in the laboratory and the contribution that both system design and functionality can have on "building quality ". Received: 5 October 1998 · Accepted: 20 October 1998     

Determination of diethanolamine or <Emphasis Type="Italic">N</Emphasis>-methyldiethanolamine in high ammonium concentration matrices by capillary electrophoresis with indirect UV detection: application to the analysis of refinery process waters

Alkanolamines such as diethanolamine (DEA) and N-methyldiethanolamine (MDEA) are used in desulfurization processes in crude oil refineries. These compounds may be found in process waters following an accidental contamination. The analysis of alkanolamines in refinery process waters is very difficult due to the high ammonium concentration of the samples. This paper describes a method for the determination of DEA in high ammonium concentration refinery process waters by using capillary electrophoresis (CE) with indirect UV detection. The same method can be used for the determination of MDEA. Best results were achieved with a background electrolyte (BGE) comprising 10 mM histidine adjusted to pH 5.0 with acetic acid. The development of this electrolyte and the analytical performances are discussed. The quantification was performed by using internal standardization, by which triethanolamine (TEA) was used as internal standard. A matrix effect due to the high ammonium content has been highlighted and standard addition was therefore used. The developed method was characterized in terms of repeatability of migration times and corrected peak areas, linearity, and accuracy. Limits of detection (LODs) and quantification (LOQs) obtained were 0.2 and 0.7 ppm, respectively. The CE method was applied to the determination of DEA or MDEA in refinery process waters spiked with known amounts of analytes and it gave excellent results, since uncertainties obtained were 8 and 5%, respectively.     

金橙G螯合形成树脂分离富集地质样品中的微量贵金属

主要研究了金橙Ｇ螯合形成树脂分离富集地质样品中金、铂、钯的最佳实验条件。在柱高大于１６ｃｍ，０．１ｍｏｌ／Ｌ ＨＣｌ介质的样品溶液以小于或等于０．５ｍＬ／ｍｉｎ流速过柱，用０．１ｍｏｌ／Ｌ ＨＣｌ的３％硫脲溶液以小于或等于０．５ｍＬ／ｍｉｎ流速洗脱金、铂、钯（和铑），都能同时定量富集。用火焰原子吸收光谱法测定，回收率均在９５％￣１１０％之间。经地质样品加标准回收实验，结果令人满意。证明这种以磺酸基     

Effect of N2O pretreatment on fresh and regenerated Pd-Ag/α-Al2O3 catalysts during selective hydrogenation of acetylene

N₂O pretreatment has shown to result in enhancement of the performance of fresh commercial Pd-Ag/α-Al₂O₃ catalyst during selective acetylene hydrogenation. However, it showed no effect for the used and regenerated catalysts probably due to changes int he metal arrangement on the catalyst surface after regeneration.     

全自动QuEChERS样品制备系统结合高效液相色谱-串联质谱法检测植物源性食品中34种农药残留

建立了全自动QuEChERS样品制备系统结合高效液相色谱-串联质谱（HPLC-MS/MS）同时检测植物源性食品中34种农药残留的分析方法。方法利用全自动QuEChERS样品制备系统涡旋振动和离心功能，将手动QuEChERS方法中样品提取和分散固相萃取相结合；优化了操作参数及前处理步骤，在多反应监测（MRM）模式下检测，基质匹配外标法定量。从方法学验证角度对全自动QuEChERS法与手动QuEChERS法进行了比较。结果表明：该方法中大多数农药在一定范围内呈现良好的线性关系，相关系数（R²）均大于0.99，检出限为0.76~3.60 μg/kg，定量限为2.28~10.80 μg/kg，加标回收率为53.0%~125.2%，相对标准偏差（RSD）<15.9%（n=5）。该方法与手动QuEChERS法的方法验证比对结果显示差异不明显，用于植物源性食品中多农药残留检测可有效降低劳动强度和出错概率。     

Continuous pH monitoring during pretreatment of yellow poplar wood sawdust by pressure cooking in water

Yellow poplar wood sawdust consists of 41% cellulose and 19% hemicellulose. The goal of pressure cooking this material in water is to hydrate the more chemically resistive regions of cellulose in order to enhance enzymatic conversion to glucose. Pretreatment can generate organic acids through acid-catalyzed degradation of monosaccharides formed because of acids released from the biomass material or the inherent acidity of the water at temperatures above 160°C. The resulting acids will further promote the acid-catalyzed degradation of monomers that cause both a reduction in the yield and the formation of fermentation inhibitors such as hydroxymethyl furfural and furfural. A continuous pH-monitoring system was developed to help characterize the trends in pH during pretreatment and to assist in the development of a base (2.0 M KOH) addition profile to help keep the pH within a specified range in order to reduce any catalytic degradation and the formation of any monosac-charide degradation products during pretreatment. The results of this work are discussed.     

The role of ester groups in resistance of plant cell wall polysaccharides to enzymatic hydrolysis

Xylan backbones in native plant cell walls are extensively acety-lated. Previously, no direct investigations as to their role in cellulolytic enzyme resistance have been done, though indirect results point to their importance. An in vitro deesterification of aspen wood and wheat straw has been completed using hydroxylamine solutions. Yields of 90% acetyl ester removal for both materials have been accomplished, with little disruption of other fractions (i.e., lignin). Apparently, as the xylan becomes increasingly deacetylated, it becomes 5–7 times more digestible. This renders the cellulose fraction more accessible, and 2–3 times more digestible. This effect levels off near an acetyl removal of 75%, where other resistances become limiting.