Extraction of Nitric Acid and Np(IV) by some aliphatic ketones and alcohols

The extraction behaviour of HNO₃ and Np(IV) from aqueous nitrate solutions with some aliphatic alcohols and ketones using hexane, carbon tetrachloride, benzene and chloroform as diluents was studied. The acid concentration in the aqueous phase varied from 0.25 to 10 M and that of the extractant in the organic phase varied from 0.5 M to the undiluted fraction. In the alcohol systems, solutions of the same alcohol in the diluents CCl₄ and CHCl₃ showed similar capacity for acid extraction, and also in the same diluents, solutions of diisopropyl and diisobutyl alcohol showed similar capacity for extraction. Extraction of Np(IV) with the different ketones and alcohols used follow the same pattern as HNO₃.     

On the nature of phase separation of polymer solutions at high extension rates

Experiments with stretching moderately concentrated polymer solutions have been carried out. Model experiments were carried out for poly(acrylonitrile) solutions in dimethyl siloxane. Just the choice of concentrated solutions allowed for a clear demonstration of a demixing effect with the formation of two separate phases—an oriented polymer fiber and solvent drops sitting on its surface. An original experimental device for following all subsequent stages in the demixing process was built. It combined two light beams, one transverse to the fiber and a second directed along (inside) the fiber, the latter played the role of an optical line. This gives a unique opportunity to observe processes occurring inside a fiber. The process of demixing starts from the volume phase separation across the whole cross section of a fiber at some critical deformation and the propagation of the front of demixing along the fiber. Then a solvent cylindrical skin appears which transforms into a system of separate droplets. New experimental data are discussed based on a comparison of the current different points of view on the phenomenon of deformation‐induced phase separation: thermodynamic shift of the equilibrium phase transition temperature, growth of stress‐induced concentration fluctuations in two‐component fluids, and mechanically pressing a solvent out from a polymer network. The general belief is that a rather specific (so‐called “beads‐on‐a‐string”) structure of a filament is realized in stretching dilute solutions: beads of a polymer solution connected by oriented polymer bridges forming a single object. The situation in stretching moderately concentrated solutions appears quite different: real phase separation was observed. So, the alternative phenomenon to the formation of the “beads‐on‐a‐string” structure has been experimentally proven. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 559–565     

Effect of the polarity of additional solvent on membrane formation in polysulfone/N-methyl-2-pyrrolidone/water ternary system

Asymmetric polysulfone membranes were prepared by wet phase inversion method with different demixing rate of casting solutions. The influent factor of demixing rate was focused on the polarity of additive in the polysulfone/N-methyl-2-pyrrolidone/water ternary system. With increasing the polarity of alcohols in the casting solution, the decrease in skin layer thickness was observed and then a poor separation performance of membranes can be obtained. It was found that the polar additive caused the rapidly demixing of casting solution in coagulation bath and formed porous asymmetric membranes with defective skin layer. In the other case, chloroform was used as the non-polar additive in casting solution. With increasing the mount of chloroform in the casting solution, the increase in skin layer thickness was observed and then lead to a good separation performance of these membranes. It was found that of the non-polar additive delays the demixing rate of casting solution in this ternary system. The separation performance of these asymmetric membranes were characterized by the measurement of dehydration of ethanol/water mixture by pervaporation and observed the morphology by scanning electron microscopy. It was found that the separation performance of asymmetric polysulfone membrane strongly depends on the polarity of adding solvent in polysulfone/N-methyl-2-pyrrolidone/water ternary system.     

Thin-layer chromatography of inorganic ions. IV — Distribution of solvent on the layer

Summary A techniue for evaluating qualitatively and quantitatively the solvent adsorbent at different heights on the thin layer froml the immersion line to the liquid front is described. These measurements permit a study of the eluent demixing phenomenon. The results of standard experiments are shown. When the solvent is a mixture of volatile compounds, the percentage compostion of eluent changes continously. When the solventt is a mixture of in volatile compounds, a sharper eluent demixing is found with consequent formation of pure solvent zones. This work has been in part supported by the C.N.R. of Italy     

Effect of liquid-liquid demixing on the membrane morphology,gas permeation,thermal and mechanical properties of cellulose acetate hollow fibers

The polymer/solvent/nonsolvent systems with different L-L demixing rates were prepared by employing a binary solvent mixture consisting of two solvents - one exhibits an instantaneous liquid-liquid (L-L) demixing process, while the other exhibits a delayed L-L demixing process. It was found that an increase in the delay time of L-L demixing results in a denser membrane structure, an increase in fiber mechanical strength, a delay desorption of moisture in membrane, and a decrease in gas permeance, for a hollow fiber fabrication system consisting of cellulose acetate (CA) (polymer), N-methyl-pyrrolidone (NMP) (solvent having an instantaneous L-L demixing property), tetrahydrofuran (THF) (solvent having a delayed L-L demixing property) and water (nonsolvent). Hollow fibers prepared under an instantaneous L-L demixing process tends to have more mechanically weak points (flaws) than those prepared under a delayed L-L demixing process. Surprisingly, SEM observation suggests that membranes wet-spun from solutions containing both THF and NMP tend to have a rough outer skin morphology. Inconsistent demixing and the collapse of the outer nascent skin may be the main causes. In addition, the effect of bore fluid chemistry on fiber performance is much more pronounced for systems having a delayed L-L demixing mechanism than that having an instantaneous L-L demixing.     

Demixing effects in thin-layer chromatography with NH2-modified silica gel precoated plates

Summary Demixing effects in thin-layer chromatography have been investigated with NH₂-modified silica gel precoated plates and for frequently used hydroorganic binary solvents of various compositions with salt addition.The position of the solvent demixing front depends on: (1) solvent composition, (2) nature of the organic modifier and (3) salt concentration. Whatever the organic modifier, for a given water percentage in the developing solvent, solvent demixing is found to occur at the same concentration of NaCl.     

溶剂对PVDF铸膜液相转化和微孔膜皮-亚两层结构的不同影响

采用皮-亚分步凝固成膜机理分析了3种不同溶剂对聚偏氟乙烯(PVDF)铸膜液相转化和膜结构的影响,采用浊度法测定铸膜液体系的热力学性质,沉淀速度采用光透射仪测定.结果显示,3种膜的皮层分相主要由热力学性质控制,均发生延时液固分相,生成了相互融合的球粒组成的致密皮层.3体系的亚层分相行为由动力学扩散过程控制;对于二甲基亚砜(DMSO)、N,N-二甲基乙酰胺(DMAc)体系亚层发生瞬时液液分相,结晶化对动力学过程影响小,表现为光透射曲线上分相时间t2短,生成了大孔结构为主的亚层,膜厚度、孔隙率和气通量均高、结晶度低;N,N-二甲基甲酰胺(DMF)体系亚层发生延时液液分相,结晶化对动力学过程影响大,t2长,生成蜂窝状孔结构亚层,其膜厚度、孔隙率和气通量较低,但膜的结晶度高.     

Thermodynamics of solvent extraction of thorium by solutions of HHTA and mixtures of HHTA and TBP

The changes in free energy, enthalpy and entropy for the extraction of thorium by solutions of thenoyltrifluoroacetone (HTTA) and mixtures of solutions of HTTA and tri-n-butylphosphate (TBP), in three diluents, viz. cyclohexane, benzene and chloroform, were determined using the solvent extraction data obtained at different temperatures. From these data the thermodynamic parameters associated with the formation of Th(TTA)₄ · TBP in the respective organic diluents were evaluated. Trends in the enthalpy changes were attributed to different degrees of association of the diluents with themselves and with the solutes present in them.     

Large Volume Injection of Biological Samples Dissolved in a Non-Eluting Solvent: A Way to Increase Sensitivity and a Means of Automating Drug Determination Using Hplc

Abstract

The injected volume of a sample dissolved in the mobile phase of an HPLC system must be maintained as small as possible so as to minimize the loss in efficiency. Generally this requirement limits the sensitivity of HPLC methods devoted to trace quantity determinations of drugs in biological fluids. In order to avoid this limitation and to increase the effective sensitivity of HPLC methods for determination of drugs such as antrafenine, nifuroxazide and cipropride, the samples were dissolved in a non-eluting solvent and a large volume (> 100 μl) was injected on to the chromatographic column.

The above-mentioned compounds and their internal standards were dissolved in a series of eluting and non-eluting solvents and increasing volumes (5 to 1000 μl) were injected. Peaks corresponding to injections made in an eluting solvent showed retention times independent of the injection volume but their variances increased with the volume injected. In contrast, peaks corresponding to injections made in a non-eluting solvent, similar to the mobile phase, had a variance independent of the injection volume but their retention times increased linearly with the injection volume. The repeated injection of such non-eluting solvents had no influence on chromatographic behaviour. Peaks corresponding to compounds injected in a non-eluting solvent made with components different from those of the mobile phase had a variance independent of the injection volume but their retention times varied both with the injection volume and with the interval between injection.

The application of non-eluting solvents has been defined theoretically and it has been demonstrated that solutions composed of 25% of the mobile phase diluted with the least eluting of its components act as non-eluting solvents and can be injected in large volume without loss in efficiency. This feature could be used to inject all the samples volume or only part of it, manually or automatically, since any automatic injector can be used with large volumes.

Thus, using the relatively simple procedure of making injections with a non-eluting solvent it is possible to increase both sensitivity and the rate of sample analysis.     

Adsorption Effects Observed in Gel Permeation Chromatography of Thiouracil

Abstract

In gel permeation chromatography (GPC), several compounds deviate from the molecular volume/elution count relationship which is prepared using satured hydrocarbons. In this paper, this problem is investigated in detail using thiouracil in aqueous solution as a model chromatographic adsorbate. The concentration dependences of elution counts and peak heights prove the adsorption of thiouracil on Sephadex G-25 when water is the solvent. Thus to investigate further the mechanisms of adsorption responsable for the chromatographic behaviour, thiouracil-Sephadex interac—tions were investigated by studying equilibrium adsorption. Isotherms of type IV of BDDT classification were found which are typically associated with a weak adsorption such as physisorption, on a porous solid. The effect of water structure perturbants, ionic strength and pH on this adsorption was consistent with the-hypothesis that with water as a solvent both aromatic adsorption and electrostatic interaction are the determinants of the affinity of this gel for a thiouracil compound. This may be particularly useful since results of equilibrium adsorption isotherms are frequently used to develop liquid chromatographic theories.     

Magnetic solid-phase extraction of rose bengal using iron oxide nanoparticles modified with cetyltrimethylammonium bromide

Magnetic solid phase extraction (MSPE) based on cetyltrimethylammonium bromide (CTAB)-coated magnetic iron oxide nanoparticles (C-MIONPs) was investigated for the separation, preconcentration and determination of Rose Bengal (RB) in aqueous solutions. The influences of different analytical parameters such as pH, temperature, ionic strength, volume of desorbent solvent, amount of adsorbent and interfering ions in the adsorption of RB on C-MIONPs were investigated. The RB adsorption on C-MIONPs follows Langmuir isotherm. The sizes of C-MIONPs were in the range of 20–80 nm. The method was capable of determining RB concentration in the range of 0.01–1.20 μg ml^?1. The limit of detection (LOD) of RB based on three times the standard deviation of the blank (3Sb) was found to be 5.91 × 10–3 μg ml^?1 (n = 8). The relative standard deviation (RSD) for 0.3 μg ml^?1 and 0.8 μg ml^?1 of RB were 4.1% and 1.1%, respectively. The proposed method was applied to the determination of RB in Brucella Antigen solution and water samples from the Karoon River.     

Solvent effects in the preparation of molecularly imprinted polymers for melatonin using N-propionyl-5-methoxytryptamine as the pseudo template

To clarify the role of diluents in the preparation of molecularly imprinted polymers utilizing only hydrogen bonding, we investigated the effects of diluents by using different solvents. Melatonin (N-acetyl-5-methoxytryptamine), an amide bond and indole ring-containing hormone was chosen as the target molecule. N-Propionyl-5-methoxytryptamine was used as the pseudo template, methacrylic acid as the functional monomer, and solvents were used as diluents. Interactions between the template, the functional monomer, melatonin, and the solvents, were observed by ¹H NMR spectroscopy. The polymers were evaluated by high-performance liquid chromatography. The results suggest the hydrogen bonding-acceptor capacity of the solvent is the most important factor in the preparation of molecularly imprinted polymers for hydrogen bonding-donating molecules. Hydrogen bonding between the template, the functional monomer, and solvent can be estimated from the chemical shifts in ¹H NMR spectra of those molecules in the solvent.     

Demixing and gelation behavior of ternary cellulose acetate solutions

The demixing behavior on cooling of ternary systems of cellulose acetate/solvent/water has been examined for CA concentrations up to 40 wt% CA in several solvents. Cloud points have been measured as a function of cooling rate. The rapid process of liquid—liquid demixing can be discriminated from the slow process of aggregate formation by examining the dependence of the cloud point on the cooling rate and by structure analysis of quenched solutions with scanning electron microscopy. The appearance of aggregate formation depends strongly on the type of solvent. Slow cooling of ternary solutions in which acetone is the solvent leads to aggregate formation long before liquid—liquid demixing occurs. In addition, isothermal sol—gel transitions have been measured for quenched solutions at varying gelation times. It is concluded that gelation is not always preceded by aggregate formation.     

Adsorption of alkanes on a bismuth electrode from an alcoholic medium

The adsorption of higher alkanes (from C₁₀H₂₂ to C₂₁H₄₄) on a polarized bismuth electrode was studied from methanolic, ethanolic and n-butanolic solutions of LiClO₄ by differential capacity measurements. Alkane molecules, which do not contain either polar groups or double bonds, are compounds of low chemical activity. The adsorption of this group of compounds is purely physical. Nevertheless, a considerable difference in their adsorption activity on the various areas of the electrode surface caused by the two types of bond (metallic and covalent) between the atoms in the bismuth crystal lattice was discovered. Such a large difference indicates the different wettabilities of the separate single-crystal faces by alkanes. A weak dependence of the interaction parameter in the Frumkin isotherm on the length of the alkane molecule as well as on the length of the hydrocarbon chain of the solvent molecule was established. Various adsorption effects at high bulk concentrations of adsorbate (desolvation of the cations of the supporting electrolyte, thickening of the adsorption layer, maximum in the isotherm) were analysed.     

Effect of Different Salt Leachates on the movement of some Carbamoyl Groups Containing Pesticides in Soils using Thin-Layer Chromatography

Abstract

The influence of pH, leachates of alkaline and saline salts, inorganic fertilizers and surfactants on the mobility of five carbamoyl group containing pesticides, viz. aldicarb, bavistin, carbofuran, dimecron and oxamyl has been studied using soil thin layer chromatographic technique. The variation in the movement of pesticides under different solvent amendments expressed in terms of Rf, RB and RM values and explained on the basis of adsorption and leachability.     

二氧化硅与液体介质的亲和性表征

利用动态核磁脉冲(Dynamic NMR)技术对高浓度的二氧化硅浆料的亲和性进行研究,并建立表征束缚层厚度与亲和性的定量模型。结果表明,在纯丁酮溶剂中,二氧化硅的含量越高,分散时间越长,填料表面束缚层厚度越大;而在树脂溶液体系中,在30%二氧化硅含量附近,填料表面束缚层厚度最大。当处理剂用量约为0.5%(w/w)时,颗粒表面与介质的吸附作用最强。使用不同处理剂制备的二氧化硅浆料,其表面吸附效应也有所不同,并且当浆料静置16 h后,其厚度层发生不同的变化,在丁酮体系中,束缚层厚度部分增加,而甲苯体系中,束缚层厚度减小。     

Improved Liquid Chromatographic Method for Acyclovir Determination in Plasma

Abstract

A simple and reproducible method for determining acyclovir (ACV) in plasma is presented. The method involved the use of acetaminophen as internal standard. A single extraction step was performed using trichloroacetic acid for protein separation. After pH adjustment, samples from the supernatent layer were directly injected into a high pressure liquid chromatograph. Components separation was perfected through manipulation of solvent combinations and pH. The acyclovir and the internal standard retention times were 8.5 and 11 min. respectively. High correlation was obtained between AUC and the drug concentration (r>0.99). Statistical analysis showed that the method is highly reproducible for ACV determination in aqueous solutions or in plasma. The mean drug recovery was better than 88%. The sensitivity obtained should enable the use of the method in future bioavailability and/or pharmacokinetic studies.     

Adsorption of compounds with the skeleton molecular structure from dimethylsulfoxide solutions on mercury electrode

The adsorption of adamantane (Ad), adamantanol (AdOH), thiocamphor (TC), and a supramolecular complex (cryptate) of sodium ion [Na⁺ ⊂ 2.2.2.] from DMSO solutions on the mercury electrode is studied by the differential capacitance method. In the considered systems, the surfactants exhibit the high surface activity, which manifests itself in different ways depending on the potential scan direction. For AdOH, TC, and [Na⁺ ⊂ 2.2.2.] that have either a dipole moment or an electrostatic charge, it is assumed that the important role is played by the adsorbate-solvent interaction at the interface, which can be the key factor determining the formation of a new adsorption layer structure in the positive potential range. The adsorption behavior of the mentioned group of surfactants radically differs from that of Ad hydrocarbon, namely, the adsorption of the latter is not accompanied by the formation of a new adsorption layer structure. The obtained results suggest that for the adsorption of surfactants from nonaqueous solvents (in contrast to aqueous solutions), the interaction between the adsorbate and the solvent molecules, which under certain condition results in the formation of two-dimensional supramolecular structures at the electrode/solution interface, acquires substantial importance.     

Isclation of Lecithin and Sphingomyelin from Lipid Mixtures for Quantitation by Infrared Spectroscopy

Abstract

A new procedure for the determination of lecithin and sphingomyelin in amniotic fluid is described. rapid column chromatography in the sample preparation steps with computer-assisted infrared spectroscopy in the final determination. Lipids are extracted from amniotic fluid with a chloroform/methanol solvent. The organic layer is separated and evaporated to dryness. The residue is The new method couples the use of simple, redissolved i n chloroforn and Fassed through a hydroxyapatite column to remove interfering constituents. The complete isolation cflecithin and sphingomyelin fror other li Fidsis confimec by both infrared spectroscopy and thin layer chronatcgrayhy.     

REDUCTION OF CARBONYL COMPOUNDS TO THE CORRESPONDING ALCOHOLS WITH ISOPROPANOL ON DEHYDRATED ALUMINA UNDER MICROWAVE IRRADIATION

ABSTRACT

The reduction of different types of aldehydes and ketones were performed in the presence of isopropylalcohol (as solvent and hydride source) under microwave irradiation. It is proved that dehydrated Woelm chromatographic alumina supported KOH catalyses these transformations. Regioselectivity was observed in the reduction of cinnamaldehyde and chemoselectivity was observed in the reduction of carbonyl in the presence of nitro group.