微波预处理提取蛇足石杉中总生物碱的工艺优化

蛇足石杉为厥类植物,属石松类石杉科(Huperziacease)石杉属(Huperzia),又名千层塔、蛇足草.从蛇足石杉中提取分离得到的石杉碱甲(Hup A),是一种强效的可逆性胆碱酯酶抑制剂,在临床上主要用于治疗重症肌无力、改善老年性记忆功能减退 [1-2].     

常压热解离化学电离源的研制及表征

自行研制了常压热解离化学电离源(TDCI),与商品化LTQ XL质谱仪成功联用,进一步考察了TDCI的性能,并对其应用领域进行了初步探索.TDCI-MS/MS谱图表明,离子液体可在现有实验条件下产生特征离子碎片;升高TDCI源偏置电压和温度,可以提高离子液体的信号强度.基于优化后的实验参数,常压热解离化学电离质谱方法(...     

气相色谱法测定有机锡化合物的样品前处理技术

用气相色谱分析有机锡化合物，前处理技术是降低检出限、提高灵敏度的前提和重要途径，也是研究的重点和难点。本文就气相色谱分析有机锡化合物时样品的制备与储存，样品的萃取、衍生、净化等前处理技术作了较为系统的介绍。     

Nafion修饰电化学活化碳纤维微电极测定去甲肾上腺素

本用自制的碳纤维微电极，经过适当的电化学预处理以后，测定神经递质去甲肾上腺素时，表现出较高的灵敏度，用Ｎａｆｉｏｎ修饰后，能有效地消除脑中去甲肾上腺素的主要干扰物抗坏血酸的干扰，线性范围５×１０＾－５－２×１０＾－４ｍｏｌ／Ｌ，检出下为２×１０＾－８ｍｏｌ／Ｌ，用这种微电极对注射液中的去甲肾上腺素进行测定，回收率在９７．２％－１０２．８５之间，可用于活体分析。     

氢键在煤大分子溶胀行为中的作用

选择对氟苯酚（ＰＦＰ）做为煤中羟基的模型化合物，考察了煤与溶剂间氢键强度对煤大分子溶胀行为的影响。发现煤在溶剂中的溶胀率随着ＰＦＰ与溶剂间氢键生成热的增大而增加；煤的溶胀率随煤化程度的提高而降低以及煤经碱、酸处理后溶胀率增加。这些结果表明，煤中羟基与溶剂间的氢键力是决定煤大分子溶胀行为的关键因素。     

Rapid Pretreatment of a Solid Silver Electrode for Routine Analytical Practice

A very fast electrochemical method for renovation of solid electrodes and storage of the electrodes in a ready for use state, as well as necessary original hardware, is presented in this work. The device has the shape of a cylindrical container with a volume of about 3–5 mL filled with an electrolyte solution in which auxiliary and reference electrodes are placed. It may be fastened in a typical electrochemical cell. The method relies on suitable electrode polarization in the device. During the renovation process, the electrode is inside the device and immediately after the activation, it is moved into the tested solution where the measurement is realized.     

A simple method for automated pretreatment of usable chromatographic profiles in pattern-recognition procedures: application to HPAEC-PAD chromatograms of honeys

In this article a simple method for automated pretreatment of chromatograms is presented. The resulting data matrix can be used as input for multivariate statistical analysis. Application of this method to high-performance anion-exchange chromatography-pulsed amperometric detection (HPAEC-PAD) chromatograms of honeys before canonical discriminant analysis results in very good performance in the data reduction with regard to the preservation of the original information content of the data. This pretreatment of the chromatogram allows for the use of all the peaks corresponding to the sugars present in the sample. This results in a high-quality discrimination between honeys of various types. A versatile program has been developed to apply this method. This serves as a starting point for software suited for food characterization and adulteration detection by semi-automatic pattern recognition applied to chromatographic analysis.     

Conversion of distiller's grain into fuel alcohol and a higher-value animal feed by dilute-acid pretreatment

Over the past three decades ethanol production in the United States has increased more than 10-fold, to approx 2.9 billion gal/yr (mid-2003), with ethanol production expected to reach 5 billion gal/yr by 2005. The simultaneous coproduction of 7 million t/yr of distiller's grain (DG) may potentially drive down the price of DG as a cattle feed supplement. The sale of residual DG for animal feed is an important part of corn dry-grind ethanol production economics; therefore, dry-grind ethanol producers are seeking ways to improve the quality of DG to increase market penetration and help stabilize prices. One possible improvement is to increase the protein content of DG by converting the residual starch and fiber into ethanol. We have developed methods for steam explosion, SO₂, and dilute-sulfuric acid pretreatment of DG for evaluation as a feedstock for ethanol production. The highest soluble sugar yields (∼77% of available carbohydrate) were obtained by pretreatment of DG at 140°C for 20 min with 3.27 wt% H₂SO₄. Fermentation protocols for pretreated DG were developed at the bench scale and scaled to a working volume of 809 L for production of hydrolyzed distiller's grain (HDG) for feeding trials. The pretreated DG was fermented with Saccharomyces cerevisiae D₅A, with ethanol yields of 73% of theoretical from available glucans. The HDG was air-dried and used for turkey-feeding trials. The inclusion of HDG into turkey poult (as a model non-ruminant animal) diets at 5 and 10% levels, replacing corn and soybean meal, showed weight gains in the birds similar to controls, whereas 15 and 20% inclusion levels showed slight decreases (−6%) in weight gain. At the conclusion of the trial, no negative effects on internal organs or morphology, and no mortality among the poults, was found. The high protein levels (58–61%) available in HDG show promising economics for incorporation of this process into corn dry-grind ethanol plants.     

Steam pretreatment of acid-sprayed and acid-soaked barley straw for production of ethanol

Barley is an abundant crop in Europe, which makes its straw residues an interesting cellulose source for ethanol production. Steam pretreatment of the straw followed by enzymatic hydrolysis converts the cellulose to fermentable sugars. Prior to pretreatment the material is impregnated with a catalyst, for example, H₂SO₄, to enhance enzymatic digestibility of the pretreated straw. Different impregnation techniques can be applied. In this study, soaking and spraying were investigated and compared at the same pretreatment condition in terms of overall yield of glucose and xylose. The overall yield includes the soluble sugars in the liquid from pretreatment, including soluble oligomers, and monomer sugars obtained in the enzymatic hydrolysis. The yields obtained differed for the impregnation techniques. Acid-soaked barley straw gave the highest overall yield of glucose, regardless of impregnation time (10 or 30 min) or acid concentration (0.2 or 1.0 wt%). For xylose, soaking gave the highest overall yield at 0.2 wt% H₂SO₄. An increase in acid concentration resulted in a decrease in xylose yield for both acid-soaked and acid-sprayed barley straw. Optimization of the pretreatment conditions for acid-sprayed barley straw was performed to obtain yields using spraying that were as high as those with soaking. For acid-sprayed barley straw the optimum pretreatment condition for glucose, 1.0 wt% H₂SO₄ and 220°C for 5 min, gave an overall glucose yield of 92% of theoretical based on the composition of the raw material. Pretreatment with 0.2wt% H₂SO₄ at 190°C for 5 min resulted in the highest overall xylose yield, 67% of theoretical based on the composition of the raw material.     

TS—1催化合成环氧丙烷

研究了ＴＳ－１催化下的丙烯与Ｈ２Ｏ２的环氧化过程，考察了操作条件对反应的影响，发现较低的温度（３０～５０℃），压力（０．４～０．６ＭＰａ）以及Ｈ２Ｏ２浓度（１．０ｍｏｌ／ｋｇ）对反应有利，产物环氧丙烷与溶剂甲醇在沸石表面酸性中心的催化下反应生成丙二醇单甲醚是主要的副反应，副产物丙二醇单用甲醚堵塞了沸石孔道引起催化剂失活，失活后的催化剂可以通过灼烧或用溶剂洗涤恢复活性，用盐类对催化剂进行预处理后催化