固相络合反应法提取茶叶中茶多酚

提出以CaCO_3作为络合剂,采用固相络合反应法提取茶叶中茶多酚的新工艺。在固相状态中通过机械力的作用使络合剂与茶叶中多酚物质进行络合反应,并用水作为溶剂在常温下洗去反应后的可溶性部分,获得混合沉淀,利用酸液对混合沉淀转溶,最终将转溶液进行萃取提取茶多酚。通过XRD衍射图定性判定了固相络合反应的发生,探究了固相络合剂用量与反应后颗粒粒径对茶多酚提取率的交互影响,得出最佳工艺条件为络合剂CaCO_3质量分数为25%,固相物料粒度D_(95)为50～55μm,浸取过程中水与固相物料的质量比120:1,浸取时间20min,茶多酚综合提取率可达15.4～15.8%,茶多酚纯度为96.8～97.1%,产物红外光谱图证实了茶多酚结构。固相络合反应法实现了常温下提取茶多酚工艺,有效避免了茶多酚因热而氧化,是一种绿色提取工艺。     

络合条件对漂白黑色人发纤维性能的影响

分别运用草酸、柠檬酸、水杨酸、酒石酸4种络合剂对经硫酸亚铁预处理过的黑色人发进行络合处理,而后进行漂白加工,考察络合剂种类、络合温度、络合时间对黑色人发漂白效果的影响。结果表明:4种络合剂中,经草酸络合处理的漂白人发白度和强力最好。当草酸作为硫酸亚铁预处理黑色人发的络合剂,草酸用量为25 g/L、络合温度为80℃、络合时间为80 min时,经漂白处理所得漂白黑色人发白度为34.9%,强力为85.2 cN。     

食盐中柠檬酸铁铵的高效液相色谱检测方法

对食用盐中柠檬酸铁铵的检测方法进行了研究。通过考察EDTA和氨三乙酸等络合剂对色谱分离的影响发现,采用络合剂将试样中的铁络合后可对柠檬酸色谱峰产生显著影响,从而建立了针对食盐中柠檬酸铁铵的高效液相色谱(HPLC)检测方法。将试样溶解后加入EDTA溶液,加热使其与铁离子充分络合,然后以磷酸二氢钾水溶液/甲醇(V/V)99.0∶1.0为流动相,在pH 2.6条件下进行色谱分离,可实现柠檬酸铁铵的检测。该方法平均回收率大于92%,并可避免其他铁盐类抗结块剂和铁离子的干扰。     

金属络合法纯化火炭母黄酮工艺研究

目的:研究金属络合法纯化火炭母黄酮的工艺。方法:对4种不同金属盐与火炭母黄酮的络合效果进行了比较,并通过单因素实验优化金属络合法纯化火炭母黄酮的最佳工艺。结果:筛选出最佳络合金属盐为氯化钙,得到金属络合法纯化火炭母黄酮的最佳工艺条件为:反应液的p H为8.0、氯化钙溶液浓度为6.0mmol/L、黄酮浓度为0.2mg/m L,解络剂EDTA与络合剂Ca Cl2的摩尔比为1.5∶1。在此纯化条件下,黄酮含量由粗提物的20.5%增加到56.5%,提高了2.8倍。结论:采用金属络合法纯化火炭母总黄酮是一种简单、有效的纯化方法。     

4-磺酸苯基卟啉与铅显色反应测定食品中的痕量铅

采取分光光度法研究了铅与TPPS4的显色反应条件,结果表明,用盐酸羟胺作辅助络合剂,以邻二氮菲、硫氰酸铵、酒石酸钾钠作联合掩蔽剂,在室温及碱性介质(pH12)条件下,TPPS4与铅只需12min即可完全生成淡紫色络合物,该络合物的最大吸收波长为465nm,络合比为1:1,当铅含量在0μg/mL～0.2μg/mL时,萃取曲线呈线性关系。通过APDC/MIBK体系萃取分离并富集样品中的铅离子,将TPPS4络合显色方法用于部分食品中痕量铅的测定,结果令人满意。     

从鱼油中提取分离高纯度二十二碳六烯酸的试验研究

研究了用超临界ＣＯ２萃取技术与硝酸银络合相结合的方法，从鱼油中提取分离高纯度二十二碳六烯酸的试验工艺。结果表明：单独用超临界ＣＯ２只能将ＤＨＡ浓缩到７５％左右，而用两步法则可获得纯度为９５％以上的ＤＨＡ。     

铅与meso-四(4-磺酸苯基)卟啉的显色系统研究及其在食品中铅的检测应用

本文采用吸光光度法,研究并优化了了铅与水溶性络合剂meso-四(4-磺酸苯基)卟啉(TPPS4)的显色条件,实验表明,在碱性条件(pH12)下,用邻二氮菲、硫氰酸铵、酒石酸钾钠作联合掩蔽剂,盐酸羟胺作辅助络合剂,铅与TPPS4需12min即可生成淡紫色络合物,该络合物的吸收峰为465nm,络合比为1:1。当铅含量在0～0.2μg/ml范围内时,萃取曲线符合比尔定律,用APDC/MIBK体系萃取样品中的铅离子,与TPPS4络合后比色测定几种食品中的铅,结果可行。     

络合萃取降低三七中的重金属及其萃取前后形态分析

研究了不同溶剂与不同络合剂对三七中重金属的降低作用,对筛选出的结果进行进一步优化,并探讨三七中Pb2+、Cd2+离子吸附与有效成分的变化情况,进而以重金属降低前后的三七为对象进行形态分析。结果表明,混合溶剂a、b与配合剂c体系对三七中Pb2+、Cd2+重金属离子有良好的萃取效果,重金属降低率主要取决于溶剂比例和络合剂添加量,而反应时间与反应温度影响较小,萃取后三七中有效成分存留率高;络合萃取降低三七中的重金属Pb2+主要以NaCl提取态与盐酸提取态形式存在,Cd2+主要以NaCl提取态与醋酸提取态形式存在。     

新型金属络合剂：涤／棉混纺织物一浴一步法染色助剂

述评了涤/棉混纺织物一治一步法染色时,解决铜离子对分散染料破坏作用的最有效的方法是采用铜离子络合剂;介绍了铜离子络合剂的种类、应用工艺、性能;推荐了自行合成的新型铜络合剂CI—1.     

脱矿质的新进展

在连续和间歇的加工过程中,天然纤维的脱矿质已成为预处理工艺中一个常规的组成部分。新型络合剂能满足技术要求和减轻环境负担,因此,络合剂领域中的新发展将更进一步强化这一加工步骤。     

不同配体硅胶弱阳离子交换剂的再生与应用

将不同配体的硅胶填料回收酸洗后,以亚氨基二乙酸(IDA)为新配体,分别用直接法和间接法合成IDA-回收硅胶,研究合成填料的色谱性能,并与制备的IDA- 新硅胶色谱柱进行比较。结果表明,尽管IDA- 回收硅胶柱的各项性能均略低于新硅胶色谱柱,但也能有效分离蛋白。用直接法合成得到的IDA- 回收硅胶柱的性能要比用间接法合成得到的IDA- 回收硅胶柱的性能好,并且成功的提取和纯化了蛋清中的溶菌酶(Lys)和猪心中的细胞色素-C(Cyt-C)。研究证明了硅胶回收再利用的可行性。     

Adsorption of Cu, Cd, and Ni on goethite in the presence of natural groundwater ligands

The adsorption of copper, cadmium, and nickel on goethite was examined in natural groundwater samples from an infiltration site of the river Glatt at Glattfelden (Switzerland). Unfractionated dissolved organic matter was used at its natural concentrations. Metal concentrations were close to environmental conditions. Cu, Cd, and Ni presented the typical pH adsorption edge of cations. The major influence on metal adsorption was due to a strong organic ligand L(I), which inhibited adsorption of Cu, Cd, and Ni in the alkaline pH region. Complexation of Cu, Cd, and Ni by the natural organic ligands was described with a model defining a minimum number of discrete ligands: a strong ligand L(I) at low concentration and additional weaker ligands with higher concentrations. The adsorption of Cu, Cd, and Ni on the goethite surface in the presence of the natural organic ligands was adequately described by considering only surface complexation and complexation in solution by organic ligands. No ternary complexes had to be invoked in the model. The major effect was complexation by the strongest ligand, whereas interactions with other cations and anions had only a minor influence. Competition reactions between Cu and Ni for complexation with the same strong ligand L(I) were observed.     

双元配体转光剂的合成及其在防紫外线织物中的应用

本文讨论了使用固相和液相两种合成方法,合成稀土金属有机配合物防紫外转光剂材料。通过对比固相和液相合成转光剂的红外谱图、水溶液中的分散性能、对织物的防紫外效果,发现液相合成方法中稀土金属铕离子与有机配体分子结合更充分,液相合成的转光剂材料在水溶液中更易于分散均匀,其提升织物防紫外效果更加显著。     

亲和-膜过滤技术及其在生物工程中的应用

论述了亲和 膜过滤技术的原理、影响因素 (包括配体、载体以及合适孔径的超滤膜的选择 )以及发展方向 ,进一步综述了其在生物工程中用于分离纯化酶、蛋白质和其它生物活性物质等方面的应用 .     

Strong copper-binding behavior of terrestrial humic substances in seawater

In coastal areas, strong complexation of copper generally reduces its toxicity; our ability to monitor and regulate copper as a toxin therefore depends on our understanding of the sources and sinks of the copper-binding ligands. Terrestrial humic substances (HS) are well-recognized contributors to weak ligand concentrations in aquatic systems. In this work, we show that HS are likely contributors to both stronger and weaker ligand classes controlling copper speciation in coastal areas receiving typical inputs of terrestrial organic matter. We used competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-ACSV), with the added ligands benzoylacetone and salicylaldoxime, to examine copper binding by terrestrial HS in a seawater matrix, at HS and copper concentrations typical of coastal waters. Copper titration data of 1 mg/L Suwannee River humic acid (SRHA) in seawater could be modeled using conditional stability constants of 10(12.0) and 10(10.0) and total ligand concentrations of 10.4 and 199 nM for a stronger and weaker ligand, respectively. Similar results were obtained for Suwannee River fulvic acid (SRFA). Strong copper binding by SRFA in seawater was weaker than previously reported for a freshwater at similar pH, possibly indicating effects of Ca and Mg competition or ionic strength. Nevertheless,the concentrations and binding strengths of copper ligands we observed are comparable to the range reported in previous coastal speciation studies. In addition, we show that the weaker copper ligands cause internal calibration techniques to significantly underestimate the sensitivity of ACSV in the presence of HS concentrations typical of coastal waters. To address this issue, we demonstrate the use of "overload titrations", using a high enough concentration of added ligand to outcompete all natural ligands as an alternative calibration technique for analysis of coastal samples.     

Lutetium speciation and toxicity in a microbial bioassay: testing the free-ion model for lanthanides

The validity of the free-ion model (FIM) for the element lutetium (Lu), a member of the lanthanides, was assessed in experiments with the bacterium Vibrio fischeri. The FIM is mainly based on divalent metals and synthetic ligands and has not yet been validated for the trivalent lanthanides. The bioluminescence response of V. fischeri was studied at different Lu concentrations in the presence and absence of natural and synthetic organic ligands [citrate, malate, oxalate, acetate, ethylenediaminetetraacetate (EDTA), and nitrilotriacetate (NTA)]. All ligands were tested separately to ensure that their concentrations would not cause adverse effects themselves. Free Lu3+ concentrations were calculated with a speciation program, after extension of its database with the relevant Lu equilibria. The results confirmed the FIM for Lu: that is, in contrast to total dissolved Lu concentrations, free Lu3+ concentrations had an apparent relationship with the response of V. fischeri. However, a contribution of minor inorganic Lu complexes cannot be ruled out. In the presence of malate and oxalate, the EC50 for Lu3+ decreased faster in time than for the other ligands, indicating lower elimination rates. With an EC50 of 1.57 microM, Lu3+ is more toxic than La3+, Cd2+, or Zn2+ and approximately equally as toxic as Cu2+. Although the pH increased slightly during the experiments, it was shown that the influence of pH on Lu speciation was limited.     

Superoxide mediated reduction of organically complexed iron(III): comparison of non-dissociative and dissociative reduction pathways

We have investigated the mechanism of reduction of organically complexed iron(III) in the presence of superoxide, the one-electron reduced form of dioxygen that is produced in natural waters by thermal, photochemical, and biological pathways. Experimental results show that reduction of organically complexed iron(III) by superoxide may occur by either (or, in some instances, both) reaction of superoxide with inorganic iron(III) after its dissociation from the complex (dissociative reduction) or by direct reaction of superoxide with the complex (non-dissociative reduction). In the presence of low concentrations of ligands such as citrate and sulfosalicylate that bind iron(III) relatively weakly and result in complexes with high dissociation rate constants (kd > 1 x 10(-4) s(-1)), a dissociative reduction pathway dominates. However, in the presence of strong ligands or high concentrations of weak ligands, only non-dissociative reduction of complexed iron(III) occurs. The relative contribution of each pathway has major implications for the lability and hence potential bioavailablity of iron in natural waters. The simple kinetic model developed here can be used to correctly predict the superoxide-mediated formation rates of iron(II) in natural systems.     

Dissolution of uranium-bearing minerals and mobilization of uranium by organic ligands in a biologically reduced sediment

The stability and mobility of uranium (U) is a concern following its reductive precipitation or immobilization by techniques such as bioremediation at contaminated sites. In this study, the influences of complexing organic ligands such as citrate and ethylenediaminetetraacetate (EDTA) on the mobilization of U were investigated in both batch and column flow systems using a contaminated and bioreduced sediment. Results indicate that both reduced U(IV) and oxidized U(VI) in the sediment can be effectively mobilized with the addition of EDTA or citrate under anaerobic conditions. The dissolution and mobilization of U appear to be correlated to the dissolution of iron (Fe)- or aluminum (Al)-bearing minerals, with EDTA being more effective (with R2≥0.89) than citrate (R2<0.60) in dissolving these minerals. The column flow experiments confirm that U, Fe, and Al can be mobilized by these ligands under anoxic conditions, although the cumulative amounts of U removal constituted ～0.1% of total U present in this sediment following a limited period of leaching. This study concludes that the presence of complexing organic ligands may pose a long-term concern by slowly dissolving U-bearing minerals and mobilizing U even under a strict anaerobic environment.     

高效液相色谱天然产物成分键合硅胶固定相研究进展

近年来,高效液相色谱(high performance liquid chromatography,HPLC)因其高效、快速、灵敏等特征,广泛应用于生命科学、食品药品分析等领域。但目前色谱配体主要来源于化学合成,结构复杂且常伴有高度毒性,难以满足绿色产品纯化需求。天然产物成分作为绿色低毒、来源广泛的色谱配体显现出其独特优势。本文对近年来高效液相色谱天然产物成分键合硅胶固定相的研究进展进行了综述,主要介绍了中草药药用成分、糖类、氨基酸类、大环抗生素类、环糊精类等天然产物成分键合硅胶固定相的制备、色谱性能和保留机制。以C18(octadecylsilyl-bonded silica,ODS)色谱柱为参照,探讨了新型固定相在分离富集天然产物和实际复杂样品中的优良选择性和应用价值,并对我国的天然产物成分键合硅胶固定相的研究和应用前景进行了展望。     

Opportunities for plant-derived enhancers for iron,zinc, and calcium bioavailability: A review

Understanding of the mechanism of interactions between dietary elements, their salts, and complexing/binding ligands is vital to manage both deficiency and toxicity associated with essential element bioavailability. Numerous mineral ligands are found in both animal and plant foods and are known to exert bioactivity via element chelation resulting in modulation of antioxidant capacity or micobiome metabolism among other physiological outcomes. However, little is explored in the context of dietary mineral ligands and element bioavailability enhancement, particularly with respect to ligands from plant-derived food sources. This review highlights a novel perspective to consider various plant macro/micronutrients as prospective bioavailability enhancing ligands of three essential elements (Fe, Zn, and Ca). We also delineate the molecular mechanisms of the ligand-binding interactions underlying mineral bioaccessibility at the luminal level. We conclude that despite current understandings of some of the structure–activity relationships associated with strong mineral–ligand binding, the physiological links between ligands as element carriers and uptake at targeted sites throughout the gastrointestinal (GI) tract still require more research. The binding behavior of potential ligands in the human diet should be further elucidated and validated using pharmacokinetic approaches and GI models.