糖类研究(ⅩⅩⅪ)带连接臂的乳糖衍生物及二聚体的合成

八乙酰乳糖与一缩二乙二醇或二缩三乙二醇在 BF3.Et2 O催化下反应生成相应的 β-糖苷 ,后者在同样的催化剂存在下再与八乙酰乳糖反应生成对称的 β-构型二聚体 .糖苷与二聚体在甲醇钠 /甲醇溶液中脱去乙酰基生成目标化合物用于抗癌转移活性研究 .     

糖类研究(ⅩⅩⅩⅠ)--带连接臂的乳糖衍生物及二聚体的合成

八乙酰乳糖与一缩二乙二醇或二缩三乙二醇在BF3.Et2O催化下反应生成相应的β-糖苷,后者在同样的催化剂存在下再与八乙酰乳糖反应生成对称的β-构型二聚体.糖苷与二聚体在甲醇钠/甲醇溶液中脱去乙酰基生成目标化合物用于抗癌转移活性研究.     

糖类研究（XXXI）：带连接臂的乳糖衍生物及二聚体的合成

八乙酰乳糖与一缩二乙二醇或二缩三乙二醉承ＢＦ３．Ｅt２Ｏ催化下反应生成相应的β－ 糖苷,后者在同样的催化剂存在下再与八乙酰乳糖反应生成对称的β－构型二聚体。糖苷与二聚体在甲醇钠／甲醇溶液中脱去乙酰基生成目标化合物用于抗癌转移活性研究。     

分光光度法测定固相表面酰肼活化基团

建立了一种测定固相表面酰肼基团含量的方法.运用Fe(Ⅲ)-邻二氮菲显色体系,通过固相表面具有较强还原性的酰肼基团将Fe(Ⅲ)还原为Fe(Ⅱ),生成的Fe(Ⅱ)可与邻二氮菲生成稳定的桔红色络合物,从而利用分光光度法测定溶液体系吸光度来表征固相表面酰肼基团的含量.该方法在0～0.02 μmol/mL范围内呈良好线性关系,线...     

光度法快速测定长链二元酸的含量

长链二元酸与硫酸铜甲醇溶液反应生成沉淀,离心去除沉淀后,于波长820 nm处测定上清液吸光度,提出了光度法间接测定长链二元酸含量的方法。长链二元酸的质量浓度在5～40 g·L^-1范围内与吸光度呈线性关系,方法检出限（3s/k）为0.011 g·L^-1。方法的回收率在104%～105%之间,测定值的相对标准偏差（n=5）小于0.6%。     

二碘荧光素测定微量蛋白质研究

研究了试剂2,7-二碘荧光素与蛋白质的显色反应,建立了一种测定蛋白质的新方法。在pH=7．00的缓冲溶液中,2,7-二碘荧光素与蛋白质发生灵敏的显色反应,生成1：1的复合物。最大吸收波长为505nm,且吸光度在4h内稳定,蛋白质在15～200mg／L范围内符合比耳定律,回收率在95％～104％之间,探讨了氨基酸及金属离子对测定的影响。用本法测定了果汁中蛋白质的含量,结果满意。     

三氯乙酸法测定烟叶中蛋白质含量

烟叶中蛋白质的含量与烟草的品质息息相关.如何快速、准确地测定烟叶中蛋白质含量则显得尤为重要.本实验通过对烟叶蛋白质抽提液的最佳浓度、蛋白质沉淀剂的最佳浓度及加入量进行确定,探索出了一种适合于测定烟叶中蛋白质含量的方法:室温条件下,用浓度为8 mol·L-1的尿素溶液充分抽提烟叶中的蛋白质(抽提时间大于6 h),12 000 r/min离心20 min后仅留上清液,将所得上清液稀释4倍后加入3%三氯乙酸,静置10 min,充分沉淀上清液中的蛋白质,之后再次12 000 r/min离心20 min后弃上清,留沉淀,将沉淀加入丙酮清洗后烘干至恒重,达到恒重的沉淀质量即为该烟叶中蛋白质的质量.     

新树型配体 TBOAA 与钴配合物的研究

研究了新配体N，N’，N”－（三苯甲酰）－三乙氨基胺（TOBAA）与二价钴离子生成配合物的光度特征和电化学特征。在较宽的pH范围内，新试剂和钴离子形成2：1的配合物，并且在一定范围内其吸光度与浓度具有良好的线性关系。     

萃取光度法测定矿石中微量铀

用二苯甲酰甲烷(简称DBM)测定矿物中微量铀的经典方法烦冗费事。近年虽多用磷酸三丁酯-DBM法萃取光度测定铀,但其灵敏度较差。 Baltisbergr用三正辛基氧化膦(简称TOPO)的环己烷溶液从2N硝酸溶液萃取铀,继以1-(2-吡啶偶氮)-2-萘酚(简称PAN)在有机相分光光度测定大量钚中之微量铀。2-(2’-噻唑偶氮)-5-二乙氨基苯酚(简称TAE) 曾用于微量铀的分光光度测定,其性质与PAN相似,且较之灵敏。本文借氟化铵作隐蔽剂,用     

碳酸钠溶液光度滴定法快速评定阻垢剂的性能

基于向含钙离子的溶液中逐滴加入碳酸钠溶液导致最终生成碳酸钙沉淀的反应过程,提出了一种新的评价用于循环冷却水系统的阻垢剂性效的快速光度滴定方法.设计并制造了光度滴定的试验装置,用单易的分光光度作为终点检测器,1.4 g·L-1氯化钙溶液作为试验用的模拟硬水.分取一定量的模拟硬水置于滴定装置的吸收池中,同时加入一定量的需测试、评定的阻垢剂.随着滴定的进行,当加入的1.4 g·L-1碳酸钠溶液的浓度足够时,即生成碳酸钙沉淀,随即引起溶液的透光率的突然下降(即到达滴定终点).根据碳酸钠溶液在滴定中的消耗量(毫升数)的多少,对阻垢剂的性效作出评定.滴定剂的消耗量越多,说明阻垢剂的性效越好.     

超快速液相–质谱法同时测定液体奶和奶粉中磺胺和喹诺酮类药物残留

建立超快速液相–质谱联用法测定乳制品中磺胺和喹诺酮类药物残留的方法。试样加入乙腈沉淀蛋白,用0.22μm滤膜过滤,经EndeavorsilTMC18柱分离,选用乙腈–0.1%甲酸为流动相。在0.05~100.00μg/L范围内,17种兽药的质量浓度均与色谱峰面积均呈良好的线性,相关系数(r2)为0.990 6~0.999 8,方法检出限为0.05~0.10μg/kg,加标回收率为75.88%~116.00%,测定结果的相对标准偏差为1.5%~13%(n=5)。该方法快速、灵敏,可以满足对乳制品中多种兽药残留的快速检测要求。     

高效液相色谱串联质谱法测定牛奶中的高氯酸盐

建立了高效液相色谱-串联质谱测定牛奶中高氯酸盐的方法.样品经1%乙酸-乙腈(体积比1:4)混合溶液提取,于6 000 r/min离心20 min后,经0.2μ m的尼龙滤膜、On-GuardⅡRP柱、On-GuardⅡAg柱和On-GuardⅡBa柱净化,最大反相性能色谱柱C12(Synergi 4u MAX-RP 8...     

奶粉中唾液酸的测定方法

利用酸水解把奶粉中的唾液酸释放出来，通过聚丙烯酰胺凝胶除去奶粉中大量乳糖的干扰。利用Cu^2＋和Cr^3＋协同催化唾液酸与间苯二酚的显色，用乙酸丁酯-正丁醇萃取有色物质，在610nm处测定牛奶中唾液酸含量。方法的线性范围0～55．90mg／L，回收率为94％～96％。     

Infrared spectroscopy in hemodialysis: reagent-free monitoring of patient detoxification by infrared spectroscopy

A method for monitoring hemodialysis based on quantitative infrared spectroscopic determination of the molecules dialyzed from patient blood is reported. The measurements are reagent-free and aim at real-time and in-line monitoring of the hemodialysis patient. A flow cell using attenuated total reflection infrared spectroscopy is coupled downstream of the dialysis filter unit. A calibration model has been developed from real hemodialysis samples analyzed by chemical reference analysis and from artificially mixed dialysis samples. The infrared monitoring of hemodialysis includes quantitative determination of urea as the lead substance, as well as glucose, lactate, and creatinine, all at a precision only limited by the chemical reference analysis. The flow cell can be fitted to all standard hemodialysis systems. Preliminary tests with hemodialysis patients have demonstrated that detoxification can be clearly monitored. Furthermore, these experiments demonstrate that a wide, real-time control of the patient’s physiological parameters is possible with this method, which could lead to increased patient safety.     

Isolation of Lipophilic Persistent Organic Pollutants From Human Breast Milk

Background: Lipid removal from biological samples can be achieved by addition of concentrated sulfuric acid. However, certain persistent organic pollutants (POPs) such as chlorophenols are decomposed by sulfuric acid treatment and, thus, a more gentle lipid reduction method is needed for extraction of many environmental contaminants from biological samples. Membrane dialysis extraction (MDE) is a non-disruptive method to extract POPs from biological matrices.

Methods: Human breast milk samples were spiked with radiolabelled p,p′-dichlorodiphenyl trichloroethane ([C-14]-DDT) as a POP proxy and extracted using solid phase extraction (SPE). The extracts obtained were dialyzed by MDE in low-density polyethylene tubings containing a mixture of n-hexane and dichloromethane for 24 h, 48 h, or 72 h.

Results: The lipid content was reduced by 86.2% after one dialysis cycle of 24 h using MDE, and 87.1% recovery of the [C-14]-DDT standard was obtained. The DDT recovery could be further increased up to 96.3% and 98.1% by repeating the dialyses for one or two more cycles, respectively. However, the increased [C-14]-DDT recovery includes a concomitant increase in lipid carryover from 13.8% with one dialysis cycle to 22.1% with three cycles.

Conclusion: An SPE procedure for extracting POPs from breast milk and dialytic conditions for isolation of the extracted POP with minimal lipid carryover was established. The method is nondestructive and acceptable recoveries can be obtained within a single solvent shift as demonstrated by spiking standards. The lipid carryover was minimized, and the method may be considered for lipid removal before HPLC or GC analysis of environmental contaminants.     

Determination of Urea in Milk by Liquid Chromatography-Isotope Dilution Mass Spectrometry

A definitive method based on liquid chromatography isotope dilution mass spectrometry (LC-IDMS) has been developed for the determination of milk urea, an indicator of nutrition status for the lactating animals. The milk samples were treated twice by sequentially adding acetonitrile and chloroform to precipitate proteins and then were directly separated using normal phase liquid chromatography without chemical derivatization. After the matrix separation, exact matching IDMS was used for the determination of milk urea, with high accuracy, high precision, good linearity and low uncertainty. The recoveries obtained for the four spiked milk samples were 100.6–102.2%. The linear range of signal responses was 10–2000 mg · kg^?1 with a linearity coefficient of 0.9995. The intraday and interday precisions in terms with relative standard deviations (RSDs) were 0.17–0.38% and 0.28–0.40%, respectively. The uncertainties of the whole sample analysis process were estimated to be 0.83%, 0.60%, and 0.64% for three samples with concentrations of 151.28, 184.36, and 266.66 mg · kg^?1.     

傅里叶变换红外光谱法分析乳制品的成分

利用甲醇沉淀进口奶粉、国产奶粉和奶茶粉水溶液中的蛋白质,所得上清液用二氯甲烷萃取,再经傅里叶变换红外光谱法(FT-IR)分析沉淀物和各相中物质的成分.试验结果表明:3种样品沉淀物中均含有蛋白质和脂肪酸甘油三酯,在萃取时均有乳糖析出.三者上层(水+甲醇)均含有糊精;而下层(二氯甲烷-甲醇)进口奶粉中含有磷脂酰胆碱,国产奶粉中含有磷脂酰胆碱和长碳链伯酰胺,奶茶粉中含有咖啡因.     

Amperometric Determination of Lactic Acid. Applications on Milk Samples

Abstract

A hydrogen peroxide electrochemical sensor, coupled with immobilized lactate oxidase and covered with a cellulose acetate dialysis membrane has been applied in flow analysis of lactate in milk samples. The hydrogen peroxide produced by the enzymatic reaction is measured with a platinum electrode polarized at +650 mV versus Ag/AgCl. Milk samples were analyzed and compared with a spectophotometric reference method. The developed procedure is very simple and the short response time allows its use in assaying milk samples on dairy farms.     

Determination of aflatoxin M1 using a dialysis-based immunoaffinity sample pretreatment system coupled on-line to liquid chromatography. Reusable immunoaffinity columns.

A liquid chromatographic column-switching system containing a dialysis unit and an anti-aflatoxin immunoaffinity precolumn (immuno precolumn) is described for the automated determination of aflatoxin M1 in milk samples. Both a flat membrane dialysis unit working according to the flowing donor-flowing acceptor principle and a laboratory made hollow-fibre dialysis unit working according to the stagnant donor-flowing acceptor principle were evaluated. The hollow-fibre unit is superior with respect to repeatability (3% relative standard deviation) and detection limit (10 ng/l for aflatoxin M1 in milk), in spite of the fact that the overall recovery is only 6%. Interfering compounds, which would destroy the activity of the immuno precolumn, are efficiently removed from the system by the dialysis step; a single immuno precolumn can then be used for over 70 milk analyses. No decrease in the performance of either the immuno precolumn or the hollow-fibre dialysis unit is observed.     

Dynamic continuous-flow dialysis method to simulate intestinal digestion for in vitro estimation of mineral bioavailability of food

A system for dynamic continuous-flow dialysis during intestinal digestion for an in vitro simulation of gastrointestinal digestion is presented as an alternative to human and animal in vivo methods for estimation of the bioavailability of minerals. The method is based on the in vitro batch dialysis method described by Miller, which was developed into a continuous-flow system of a simple design to perform dynamic dialysis in the intestinal digestion stage. A flow dialysis system has the advantages of simulation being close to in vivo physiological conditions because pH change during dialysis is gradual and dialyzed components are continuously removed. The proposed new design performed dialysis during a continuous flow of dialyzing solution (NaHCO₃) around a dialysis bag containing peptic digest, which is placed inside a glass dialysis chamber. Gradual change of dialysis pH, similar to that occurring in the gastrointestinal tract, was obtained by optimization of flow rate and concentration of NaHCO₃. The dialysate collected in fractions was analyzed to determine dialyzed minerals and pH change in the course of dialysis. The method was tested by determination of calcium bioavailability of powder milk and calcium carbonate tablets.