N,N-二仲辛基乙酰胺反相纸层析分离Ru-Os、Rh-Ir、Pd-Pt等金属离子及其R_f图谱

N,N-二仲辛基乙酰胺(DOAA),又名N-503,它对金属离子有一定的萃取能力。例如:N-取代酰胺曾用来萃取铀、锕系元素等,李树森等用DOAA萃取分离铌、钽,取得很好的效果,目前DOAA是一种广泛使用的废水脱酚剂。根据我们以前的工作认为反相纸层析对金属离子的滞留机理为分配机理。反相纸层析与萃取是在相同的机理下的两种不同操作技术。关于纸层析所得的比移值(R_f)与分配系数(D)可建立起如下     

DEHSO反相纸层析分离Ru-Os、Rh-Ir、Pd-Pt等金属离子及其Rf图谱

本文合成了易溶于脂肪烃类溶剂的萃取剂二(2-乙基己基)亚砜。用它的十二烷基苯溶液作为固定相,在盐酸和硝酸体系中对四十多种金属离子进行了反相纸层析,并绘制了R_f图谱。同时成功地用反相纸层析分离了Ru-Os、Rh-Ir、Pd-Pt等组金属离子。     

用反相纸层析研究二(2-乙基己基)磷酸萃取稀土、铀(Ⅵ)、铜、钙、锌等离子的萃取机理

在前文中曾用反相纸层析研究了中性萃取剂磷酸三丁酯萃取铀酰离子的机理,并指出在纸上存在高沸点溶剂时可以测得准确的结果.现用酸性萃取剂二(2-乙基己基)磷酸(HDEHP)作为固定相进行反相纸层析.     

α-正十二烷硫基乙酸乙酯的反相纸层析R_f图谱及其对钯的萃取

本文研究了α-正十二烷硫基乙酸乙酯在盐酸和硝酸体系中的R_f图谱,对四十多种金属离子进行反相纸层析,初步确定对钯具有优异的萃取性能,并用液-液萃取法研究了稀释剂和酸度对萃取钯的影响,测定了萃取络合物的组成为PdCl_2·2ELTA,探讨了萃取机理。     

分散液液微萃取技术的研究进展

分散液液微萃取是一种基于传统液液萃取的新型样品前处理技术。该文以分散液液微萃取技术中萃取剂的筛选为出发点,综述了低密度萃取剂、辅助萃取剂、反萃取剂和离子液体等低毒性萃取剂在该技术中的应用,以及应用自制装置、溶剂去乳化、悬浮萃取剂固化,辅助萃取,反萃取和离子液体-分散液液微萃取等萃取模式;并简要评述了该技术与液液萃取、固相萃取、固相微萃取、分散固相萃取、基质固相分散萃取、超临界流体萃取、超声辅助萃取等其他样品前处理技术的联用特性。     

表面活性剂从碱性氰化液中萃取金

溶剂萃取法从碱性氰化液中提取金的工艺相对于传统锌置换法和活性炭吸附法具有潜在的优势,因而备受青睐。本文综述了近几年来从碱性氰化液中溶剂萃取金的研究进展。文中对表面活性剂/改性剂萃取Au(Ⅰ)的机理、萃取及反萃取行为进行了总结,报道了表面活性剂种类、改性剂种类、稀释剂以及盐析剂等各种因素对萃取过程的影响。同时,在萃取机理方面,提出一种基于氢键的超分子萃合物模型,在反萃取方面,介绍了阴离子交换法、转化还原法及直接电解有机相3种方法。     

纸上反相分配层析与液液萃取分离2-乙基己基膦酸单(2-乙基已基)酯对镧系元素反相分配层析研究

Cerrai^[1,2]等曾研究了二(2-乙基己基)磷酸(HDEHP)对稀土元素的反相层析,并用斜率法测定了萃合物组成.Cvjelicanin^[3]用反相层析研究了二丁基磷酸对铍、镧及铈的萃取机理和平衡常数.我们以往的研究结果说明,配位体结构的极性效应和空间效应对分离金属离子的反相层析行为与液液萃取极相似^[4,5].     

基于冷冻熔炼的液-液萃取样品富集技术研究

本文通过对区域熔炼原理及液-液萃取技术的探讨,发展了一种简单高效的基于冷冻熔炼的液-液萃取样品富集新技术.通过理论分析,探讨了冷冻熔炼、常温液-液萃取以及冷冻熔炼液-液萃取中溶质浓度的分布特征,通过富集效率的探讨证明冷冻熔炼液-液萃取技术是液-液萃取与区域熔炼技术的结合.通过葡萄汁样品的分析,对该技术进行了评价.理论计算求得冷冻熔炼液-液萃取中相应组分的富集效率为4.5,而试验测得富集效率为4.8,两者结果一致,说明冷冻熔炼液-液萃取是一种简单高效的样品富集技术.     

中空纤维分散液膜富集稀土元素

采用2-乙基己基膦酸单-2-乙基己基酯(HEHEHP)-正庚烷为萃取剂,盐酸为反萃取剂,中空纤维膜作支撑膜,研究中空纤维分散液膜技术富集稀土镱(Yb~(3+))离子。考察了体系物性:反萃分散相中反萃剂浓度、萃取剂浓度、萃取剂与反萃剂体积比、料液相p H值、稀土离子浓度;流体流动状态:反萃分散相与料液相流速变化等因素对富集稀土离子的影响。中空纤维分散液膜富集Yb~(3+)的最佳条件为:萃取剂浓度为0.25 mol/L,反萃取剂HCl浓度为4.00 mol/L,萃取剂与反萃剂体积比为10∶40,料液相p H=2.80,稀土离子浓度为0.025 mol/L。反萃分散相体积流量和料液相体积流量较小时,萃取率随流量的增加呈现逐渐增大的趋势。若两相体积流量过大,反萃过程进行不完全,萃取率反而下降。研究结果表明,中空纤维分散液膜技术可实现稀土离子的有效富集。     

液-液萃取效率的讨论

本文讨论了液液萃取中分配系数Ｋ对萃取效率的影响与关系。     

Distribution ratio, distribution constant and partition coefficient. Countercurrent chromatography retention of benzoic acid

There is some confusion in chromatography between terms such as solute distribution ratio, distribution constant and partition coefficient. These terms are very precisely defined in the field of liquid-liquid systems and liquid-liquid extraction as well as in the field of chromatography with sometimes conflicting definitions. Countercurrent chromatography (CCC) is a chromatographic technique in which the stationary phase is a support-free liquid. Since the mobile phase is also liquid, biphasic liquid systems are used. This work focuses on the exact meaning of the terms since there are consequences on experimental results. The retention volumes of solutes in CCC are linearly related to their distribution ratios. The partition coefficient that should be termed (IUPAC recommendation) distribution constant is linked to a single definite species. Using benzoic acid that can dimerize in heptane and ionize in aqueous phase and an 18 mL hydrodynamic CCC column, the role and relationships between parameters and the consequences on experimental peak position and shape are discussed. If the heptane/water distribution constant (marginally accepted to be called partition coefficient) of benzoic acid is 0.2 at 20 °C and can be tabulated in books, its CCC measured distribution ratio or distribution coefficient can change between zero (basic aqueous mobile phase) and more than 25 (acidic aqueous mobile phase and elevated concentration). Benzoic acid distribution ratio and partition coefficient coincide only when both dimerization and ionization are quenched, i.e. at very low concentration and pH 2. It is possible to quench dimerization adding butanol in the heptane/water system. However, butanol additions also affect the partition coefficient of benzoic acid greatly by increasing it.     

Determination of liquid-liquid partition coefficients by separation methods

By essence, all kinds of chromatographic methods use the partitioning of solutes between a stationary and a mobile phase to separate them. Not surprisingly, separation methods are useful to determine accurately the liquid-liquid distribution constants, commonly called partition coefficient. After briefly recalling the thermodynamics of the partitioning of solutes between two liquid phases, the review lists the different methods of measurement in which chromatography is involved. The shake-flask method is described. The ease of the HPLC method is pointed out with its drawback: the correlation is very sensitive to congeneric effect. Microemulsion electrokinetic capillary electrophoresis has become a fast and reliable method commonly used in industry. Counter-current chromatography (CCC) is a liquid chromatography method that uses a liquid stationary phase. Since the CCC solute retention volumes are only depending on their partition coefficients, it is the method of choice for partition coefficient determination with any liquid system. It is shown that Ko/w, the octanol-water partition coefficients, are obtained by CCC within the -1 < log Ko/w < 4 range, without any correlation or standardization using octanol as the stationary phase. Examples of applications of the knowledge of liquid-liquid partition coefficient in the vast world of solvent extraction and hydrophobicity estimation are presented.     

Solvent generated liquid-liquid chromatography with nonaqueous ternary systems

Summary It is demonstrated that highly stable and reproducible LLC-columns can be prepared by generating the stationary phase dynamically by the mobile phase. It is shown that such a solvent generated liquid-liquid chromatography can be realized if two conditions are fulfilled: one phase of a liquid-liquid system must be used as mobile phase and the solid support must be better wetted by the other phase of the system. This general principle of solvent generated LLC was investigated for nonaqueous ternary liquid-liquid systems. The liquid-liquid retention mechanism was verified by correlation of chromatographic and partition data. It is shown that significant changes in the retention characteristics occur when going from the liquid-solid to the liquid-liquid retention mode for systems having the same qualitative composition.Presented at the 14th International Symposium on Chromatography London, September, 13–17, 1982.     

Behavior of lanthanides in countercurrent chromatography using dihexyl-N,N-diethylcarbamoyl methylene phosphonate as stationary phase

Counter-current chromatography is a real liquid-liquid chromatography. The retention volume of the solute can be calculated from the batch distribution ratio in organic separations. In the separations of metal ion, there are several complex and dissociation reactions involved in the two phases, and the retention volume cannot be always predicted from the batch distribution ratio. A mass transfer model is proposed in this paper and an expression of V(R) is derived. The retention volume of metal ion is determined not only by the batch distribution ratio but also by the mechanism of the extraction reaction. When 25% dihexyl-N,N-diethylcarbamoyl methylenephosphonate in cyclohexane is used as stationary phase and 2.91 mol/l HNO3 as mobile phase, the dynamic distribution ratios obtained from the chromatogram are not equal to but proportional to the batch distribution coefficients. These results are in agreement with the theoretical expression.     

Separation of Antibodies by Liquid-Liquid Aqueous Partition and by Liquid-Liquid Partition Chromatography

In this review, we describe the use of liquid-liquid aqueous partition as a method for the separation of antibodies. Water-based two-phase systems made up of polyethylene glycol and dextran have, by far, been the most frequently used systems. The distribution of a molecule in these systems depends on its exposed surface properties and is described by its partition coefficient. The separation may be performed in a single step in a batch experiment or in several steps using various forms of automated counter-current extraction methods, referred to in this review as liquid-liquid partition (LLP). The sensitivity and selectivity of the two-phase technique can be considerably improved by employing a column chromatographic approach, liquid-liquid partition chromatography (LLPC). In LLPC, the bottom-phase of the two-phase system is adsorbed onto a support and packed into a column which is eluted with the corresponding top-phase. In the first part of this review, the methodology behind UP and UPC is described and outlined in broader terms, before the properties and prestanda of the two approaches are compared. In the second part, the results obtained by LLP and LLPC on antibodies are described in more detail. This review shows, that liquid-liquid aqueous partition is a powerful tool for antibody analysis, that is for purification and fractionation, detection and separation of conformational isomeric forms, examination of surface properties related to antigen specificities and for providing new interesting information about the events upon antigen-antibody complexation and about possible ligand-induced conformational changes.     

Solvent-generated liquid-liquid chromatography with aqueous ternary systems

Summary It is shown that solvent-generated liquid-liquid chromatography can also be realized with aqueous ternary systems. One phase of such a liquid-liquid system is used as eluent and the column is packed with a porous solid support whose surface is better wetted by the other phase which is then generated dynamically on it by the mobile phase. The partition mode of retention was verified by linear regression of the chromatographic retention data and the partition coefficients measured at equilibrium. A further confirmation was obtained by the sharp change observed in the retention characteristics when approaching a composition of the mobile phase corresponding to the liquid-liquid equilibrium. The stationary phase is generated rather quickly needing between 10 and 100 times the column volume of mobile phase for equilibration depending on the magnitude of the change of composition of the mobile phase and the specific surface area of the solid support. The stability of solvent-generated LLC columns is very high allowing long term reproducibility of the selectivity coefficient of about 1 %. It is demonstrated that solvent-generated LLC offers a powerful means to optimize the separation of a mixture by chromatography. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984; including results already presented at the 5th International Symposium on Column Liquid Chromatography, Avignon, May 11–15, 1981.     

The use of solid sorbents for direct accumulation of organic compounds from water matrices–a review of solid-phase extraction techniques

The main principles of solid-phase extraction techniques are reviewed in this paper. Various solid sorbents can be used as a suitable trap for direct accumulation of organic compounds from aqueous solutions. The trapped analytes can be desorbed by elution with suitably chosen liquid phases. These preconcentration procedures can be considered as low performance liquid chromatography and the efficiency of the procedure can thus be related to the retention characteristics of the preconcentration column. The main sorbents used for trace enrichment purposes are also reviewed. Besides, the concise methodology, sample storage, and automation are discussed. The advantages of solid phase extraction as compared to liquid-liquid extraction are given as well as some drawbacks of this method.     

Mutual Separation of Lanthanoid Elements by Centrifugal Partition Chromatography

Abstract

Multistage separation based on liquid-liquid extraction has been investigated by means of centrifugal partition chromatography (CPC). A kerosene solution of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (EHPA) was employed as a stationary phase without any solid support. Metal ions eluted by the aqueous mobile phase were detected by the post-column reaction with Arsenazo III. The retention volumes are approximately linear with the distribution ratios of metals. The mutual separation of adjacent lanthanoids was accomplished by CPC.     

分散液-液微萃取-气相色谱/质谱联用法测定机械加工水基切削液及其废水中的三氯苯

建立了以丙酮为分散剂、氯苯为萃取剂,采用分散液-液微萃取、气相色谱/选择离子质谱联用测定机械加工水基切削液及其废水中三氯苯的方法。该方法与顶空萃取、液-液萃取和固相萃取结合气相色谱/电子捕获检测法相比,具有线性范围广、富集倍数高、重现性好、操作简便、干扰小等优点。样品中三氯苯的加标回收率为94.7％~104.3％,相对标准偏差为2.3％～7.8％。三氯苯的3种同分异构体1,3,5-,1,2,4-和1,2,3-三氯苯的检出限分别为2.0,6.0和3.0 μg/L。重点探讨了萃取剂和分散剂的种类、体积、萃取时间和盐效应等对三氯苯萃取效率的影响,优化了萃取条件。考察了机械加工水基切削液中常用的添加剂对检测结果的影响,结果表明1.0％的亚硝酸钠和聚乙二醇对三氯苯的检测基本无影响。采用该方法对4种实际样品中的三氯苯进行了测定,其中两个样品中含有三氯苯,质量浓度范围为0.15～1.67 mg/L。