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1.
The influence of inorganic salts on the formation of lyotropic liquid crystals of hydroxyethyl cellulose acetate (HECA) in N,N′dimethylformamide (DMF) was studied. In the presence of CaCl2, an inorganic salt of a principal group metal, the solution of HECA/DMF/CaCl2 was a biphasic system. The temperature of the transformation from the liquid crystalline phase to the isotropic one increased with adding CaCl2 because local HECA concentration increases in the HECA/DMF phase. When CuCl2 or CoCl2, inorganic salts of transitional metals, was added, the solutions were monophasic systems and the complexes of HECA with Cu2+ or Co2+ were formed in solutions, which results in the increase of the temperature of the transfomation from the liquid crystalline phase to the isotropic one.  相似文献   

2.
N,N′-Dicaproyl (–)1,2-diaminopropane (I) was used as a convenient model for the study of the optical activity of a nylon type polyamide: polysebacamide (–)1,2-diaminopropane (II). ORD of I was measured in different solvents. A peculiar behavior is observed in methanol in the presence of mineral salts. The influence of 0.1M potassium salts (Cl?, Br?, SCN?, NO3?, SO4?2) and 0.1M alkaline chlorides and alkaline earth chloride hexahydrates on the optical activity of I in methanol are described. Alkaline salts and MgCl2 give approximately the same effect: there is a decrease of the rotations without change of sign. SrCl2 and CaCl2 shift ORD curves towards the negative rotations, the last one giving complete inversion. This inversion is directly related to the CaCl2 concentration and is attributed to adduct formation between amide groups and salt. Assuming that the different species are at equilibrium, an apparent equilibrium constant is obtained from the optical rotations for a complex of one mole of CaCl2 with one mole of I. Results are used to discuss the complex ORD of poly(?) 1,2-diaminopropane sebacamide in methanol saturated with CaCl2.  相似文献   

3.
 A new and simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions is described. In particular, starting from water/sodium bis(2-ethylhexyl)sulfosuccinate/n-heptane microemulsions carrying inside the aqueous core of the reversed micelles some water-soluble salts [CaCl2, Na2HPO4, Cu(NO3)2], after evaporation of the volatile components (water and apolar organic solvent), the resulting inorganic salt/surfactant composites were found to be totally dispersible in pure n-heptane. The presence of nanoparticles in these resuspended composites was ascertained by transmission electron microscopy observation of samples obtained by gentle evaporation of the organic solvent. Received: 8 July 1999/Accepted in revised form: 5 October 1999  相似文献   

4.
Summary The retention and selectivity of flavonoids (baicalin, baicalein, wogonin, oroxylin A) inScutellariae radix have been studies by high-performance thin-layer chromatography on phenyldimethylethoxysilane-treated silica plates. The silica plates treated with phenyl groups were used for physical and chemical analysis. From elemental carbon analysis, the maximum number of bonded phenyl surface groups per gram was calculated to be 0.467×1021 (Oginal silica plate: Merck Art. 15109, Silica gel 100 F254). With methanol-1/15 M phosphate buffer (pH 6.2) mixtures as mobile phase, baicalin, baicalein, wogonin, and oroxylin A inScutellariae radix were separated. It has been shown that phenyl-treated plates are more suitable for selective separation of baicalin, baicalein, wogonin, and oroxylin A than octadecyl-treated plates.  相似文献   

5.
The influence of various salts on the atomization signal of lead has been examined by using a transverse heated atomic absorption spectrometer. To get more information about interference mechanisms, volatilization of salts has been studied by ion chromatographic analysis of the residue left on the furnace after drying or charring. The use of a Pd/Mg chemical modifier in these model solutions has also been examined. In 0.1 M chloride medium, NaCl, MgCl2 and CaCl2 do not interfere significantly. However, their different behaviour in the furnace, and particularly hydrolysis of MgCl2 influence greatly the charring curves of Pb. The use of a Pd/Mg modifier appears interesting only in the case of NaCl. Indeed, Pd stabilizes Pb sufficiently to permit the removal of NaCl by charring. In the case of MgCl2, Pb is not sufficiently stabilized to remove chloride through hydrolysis of MgCl2 or volatilization of MgCl2. In the presence of CaCl2, the Pb signal is delayed and coincides with the background absorption signal of CaCl2; the stabilization effect is not sufficient to eliminate CaCl2 by charring before atomization. At 0.1 M nitrate concentration, the presence of NaNO3, Mg(NO3)2, and particularly Ca(NO3)2, greatly modifies the atomization signal shape of Pb. Pb is more stabilized in nitrate medium, but losses are observed at the decomposition step of nitrate salts. In this medium, the stabilization effect of Pd leads to a single peak signal and permits elimination of nitrate decomposition products before atomization. Interference effects are more important in the presence of 0.1 M sulphate salts and increase with the acidity of the medium. Na2SO4, which is reduced to Na2S on the graphite, does not interfere significantly. However, the decomposition products of MgSO4 and CaSO4 induce an important interference effect on the determination of Pb which is stabilized in the furnace. In the case of Na2SO4, the use of the Pd/Mg modifier delays the atomization signal which coincides with the background absorption signal, leading to an important interference effect which cannot be eliminated by charring. In the presence of MgSO4 and CaSO4, the stabilizing effect of Pd permits the elimination of decomposition products of sulphate salts before atomization and suppresses the chemical interference effect.  相似文献   

6.
A hybrid monolithic column with sulfonate functionality was successfully prepared for the simultaneous separation of common inorganic cations in ion‐exchange chromatographic mode through a simple and easy single‐step preparation method. The strong cation‐exchange moieties were provided directly from allylsulfonate, which worked as an organic monomer in the single‐step reaction. Inorganic cations (Li+, Na+, K+, NH4+, Cs+, Rb+, Mg2+, Ca2+, and Sr2+) were separated satisfactorily by using CuSO4 as the eluent with indirect UV detection. The allysulfonate hybrid monolith showed a better performance in terms of speed and pressure drop than the capillary packed column. The number of theoretical plates achieved was 19 017 plates/m (in the case of NH4+ as the analyte). The relative standard deviations (n = 6) of both retention time and peak height were less than 1.96% for all the analyte cations. The allysulfonate hybrid monolithic column was successfully applied for the rapid and simultaneous separation of inorganic cations in groundwater and the effluent of onsite domestic wastewater treatment system.  相似文献   

7.
The non-specific absorption from inorganic and organic molecules between 190 and 400 nm are measured using a graphite furnace and an atomic absorption spectrometer with a deuterium source.The molecular absorption spectra of NaCl, KCl, RbCl and CsCl are very similar, with two maxima at ca. 200 and 250 nm. That of LiCl is very weak, as is that of NaF. The spectra of NaBr, NaI, KBr, KI, CaCl2, MgCl2, SrCl2, FeCl3, LaCl3 are also reported.The non-specific absorption spectrum arising from albumin decreases fro 190 to 400 nm, and that for plasma is similar to albumin, although a contribution from inorganic salts can also be seen. To decrease the non-specific absorption from metal chlorides or biological samples of mainly inorganic composition such as urine, addition of HNO3 is satisfactory. Oxygen introduction during low temperature charring is better for removing contribution from organic molecules.  相似文献   

8.
This study was designed to evaluate the emulsifying and rheological properties of acorn protein isolate (API) in different pH mediums (pH 3, 7 and 9) and in the presence of ionic salts (1 M NaCl and 1 M CaCl2). API shows higher solubility in distilled water at pH 7, while at the same pH, a decrease in solubility was observed for API in the presence of CaCl2 (61.30%). A lower emulsifying activity index (EAI), lower stability index (ESI), larger droplet sizes and slight flocculation were observed for API in the presence of salts at different pHs. Importantly, CaCl2 treated samples showed relevantly higher EAI (252.67 m2/g) and ESI (152.67 min) values at all pH as compared to NaCl (221.76 m2/g), (111.82 min), respectively. A significant increase in interfacial protein concentration (4.61 mg/m2) was observed for emulsion at pH 9 with CaCl2, while the major fractions of API were observed in an interfacial layer after SDS-PAGE analysis. All of the emulsion shows shear thinning behavior (τc > 0 and n < 1), while the highest viscosity was observed for emulsion prepared with CaCl2 at pH 3 (11.03 ± 1.62). In conclusion, API, in the presence of ionic salts at acidic, neutral and basic pH, can produce natural emulsions, which could be substitutes for synthetic surfactants for such formulations.  相似文献   

9.
Unlike linear extracting agents, in the extraction of metal salts from aqueous solutions of inorganic acids with crown ethers, the inclusion compounds, whose composition depends on several external and internal factors, go to the organic phase. The study of the molecular structure of the formed complexes by X-ray diffraction analysis showed that adducts of crown ethers with inorganic acids are host–guest complexes in which the hydroxonium ion is in the polyether macrocycle cavity. When the aqueous phase contains metal ions capable of displacing the hydroxonium ions from the macrocycle (K+, Pb2+, Hg2+, Sr2+, NH4 +), complexes containing metal cations as the guest in the macrocycle cavity, according to X-ray diffraction data, go to the organic phase. In addition, metals forming ionic associates (AuCl4 -, FeCl4 -, GaCl4 -) in an aqueous solution are extracted with crown ethers in accordance with the anion-exchange mechanism. A system in which traces of metals in the 2 M HNO3 +5 M HCl mixture serve as the aqueous phase was proposed for estimation of the general extraction ability of crown ethers. Such a system can be used for metal extraction via any possible mechanism. The stereochemical peculiarities of the extraction ability of crown ethers (compared to linear molecules) can be used for selective extraction and separation of metals.  相似文献   

10.
The effect of inorganic salts (CaCl2, MgCl2, NaCl, NaI and NaSCN) on the aggregation behavior of a synthesized polyether with seven poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) (PEO-PPO-PEO) arms attached to a tetraethylenepentamine core (simplified AE73) at air/water and n-heptane/water interfaces has been investigated by interfacial tension and oscillating bubble methods. The additions of NaCl, CaCl2, and MgCl2 may facilitate the micellization of AE73 and increase its maximum interfacial excess concentration (Γmax) due to the “salting out” effect, while NaSCN induces opposite effect and NaI exerts little influence. The adsorption kinetics of AE73 is controlled not only by the diffusion between the bulk solution and the interfacial layer but also by the energetic and steric barriers generated by the already adsorbed molecules. The adsorption relaxation time of AE73 is reduced with the addition of salts and this phenomenon is more prominent at the n-heptane/water interface. The “salting in” ions decrease the dilational modulus of AE73 while the “salting out” ions induce an opposite effect. The mechanisms of the interaction between inorganic ions and the polyether were discussed; the difference in aggregation behavior between linear and branched block polyethers were also compared.  相似文献   

11.
Extraction and separation of no-carrier-added (nca) 99mTcO4 ? from 99Mo–99mTc equilibrium mixture was carried out by environmentally benign polyethylene glycol based liquid–liquid aqueous biphasic systems (ABS) consisting various inorganic salts. Among the various inorganic salt trisodium citrate and potassium sodium tartrate showed the suitable salt rich phase for the best separation in this report. The concentration variation of salt rich phase, temperature and PEG phase also exhaustively studied in paper for the achievement of high separation factor. At 40 °C temperature in 50 % (w/v) PEG-4000-2M Na3citrate showed the highest separation factor (S Tc/Mo) 1.2 × 107.  相似文献   

12.
The solubility in the NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems were determined at 75°C and the phase diagrams and the diagram of physicochemical property vs composition were plotted. One invariant point, two univariant curves, and two crystallization zones, corresponding to potassium chloride, dihydrate (CaCl2 · 2H2O) showed up in the phase diagrams of the ternary systems. The mixing parameters θM, Ca and ΨM, Ca, Cl (M = Na or K) and equilibrium constant K sp were evaluated in NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl, KCl, and CaCl2 β(0), β(1), β(2), and C Φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.  相似文献   

13.
The influence of the inorganic salt-silica gel surface interaction on the chemical and phase compositions and sorption properties of composites of the salt in silica gel pores type is studied. Two possible interaction mechanisms are considered: (1) the ion-exchange adsorption of metal cations on the silica gel surface from a solution of a salt (CaCl2, CuSO4, MgSO4, Na2SO4, and LiBr) and (2) the solid-phase spreading of a salt (CaCl2) over the silica gel surface. The adsorption of metal cations on the silica gel surface in the impregnation step affords ≡Si-OM n+1 surface complexes in the composites. As a result, two salt phases are formed in silica gel pores at the composite drying stage, namely, an amorphous phase on the surface and a crystalline phase in the bulk. The sorption equilibrium between the CaCl2/SiO2 system and water vapor depends on the ratio of the crystalline phase to the amorphous phase in the composite.  相似文献   

14.
In its using or eliminating processes, surfactant solutions usually exhibit different behaviors because of the different species or concentrations of the encountered metal ions. Interactions between anionic surfactant (SDS) micellar solutions and several familiar metal salt solutions (Al2(SO4)3, FeCl3, CaCl2 and MgCl2) were investigated. Precipitates were formed in all systems except SDS‐MgCl2 visually. Stoichiometric analysis reveals that, in SDS‐Al2(SO4)3 system, the precipitation phenomenon is mainly owing to the effect of adsorption‐charge neutralization between Al3+ ions and SDS micelles; in SDS‐FeCl3 system, bridge connection effect of Fe(OH)2+ ions among SDS micelles becomes the dominant mechanism; while in SDS‐CaCl2 system, all SDS micelles are decomposed and solubility product of Ca(DS)2 crystal results in the precipitation. SEM photographs of the precipitates can serve as additional vivid proofs of the above conclusion.  相似文献   

15.
Summary The lipophilicity of aniline and 36 ring-substituted aniline derivatives was determined by reversed-phase thin-layer chromatography using NaCl, KCl, MgCl2, CaCl2, AlCl3 and tetramethyl-ammoniumhydroxide, either adsorbed on the silica surface before impregnation or added to the eluent. In most cases the salts decreased the retention power of silica resulting in enhanced mobility of the aniline derivatives. The monovalent cations had the lowest, while AlCl3 and tetramethylammoniumhydroxide had the highest impact on selectivity. This phenomenon can be explained by the different ion charges. The correlation between the RM values and the partition coefficient between n-octanol: water were in all cases inferior to those obtained in salt-free systems this means that the presence of salts modifies differently the lipophilicity of aniline derivatives.  相似文献   

16.
Retention indices for some precursors of peraza crown ethers were determined by reversed phase high-performance thin layer chromatography on RP-18 plates with methanol-water in different volume proportions as mobile phase. The Log P values for the same compounds were calculated using different computer programs: SciQSAR, SciLogP, Chem3D Ultra 8.0, XLOGP (based on atom contributions), Chemaxon and KOWWIN (based on atom/fragment contributions), cLogP (based on fragmental contributions), ALOGPS and IAlogP (based on atom-type electrotopological-state indices and neural network modeling). A comparative study concerning lipophilic parameters (RM0, b and ϕ0) and computed partition coefficients has been developed. Taking into account the correlation coefficients between determined and calculated Log P values, it seems that RM0 and b are less suitable than ϕ0 for estimating lipophilicity of the compounds investigated, and cLogP and ALOGPS provide the best correlations with experimental values.  相似文献   

17.
It is shown that aqueous solutions of polyethylaminophosphazene hydrochloride undergo phase separation during heating. This phenomenon is studied in detail at pH 3.5 (0.1 M citrate buffer) in relation to the composition of the system with the use of nephelometry and high-sensitivity DSC. The cloud points and the enthalpy of phase separation of the system are determined, and its phase diagram is constructed. The system features a lower critical solution temperature: w 2,cr = 7.3 × 10−4 and T cr = 34.3°C. The enthalpy of phase separation is 12.8 ± 0.6 J/g of the polymer, regardless of the system composition. A new approach to the analysis of DSC data on the phase separation of aqueous solutions of polymers during heating is advanced on the basis of calorimetric parameters coupled with the data on the composition of coexisting phases. Through this approach, the main contribution to the heat effect of phase separation of the system under study is related to a change in the energy state of a polyethylaminophosphazene hydrochloride molecule as a result of its dehydration.  相似文献   

18.
The first solid‐state structures of ortho‐sulfonated monoazo dyestuffs are reported and compared to those of their para‐ and meta‐sulfonated analogues. The structures of the 16 Na, K, Cs, Mg, Ca, Sr, and Ba ortho‐sulfonated salts are found to have fewer M? O3S bonds than their isomeric equivalents and this in turn means that the metal type is no longer the prime indicator of which structural type will be adopted. M? O3S bonds are replaced by M? OH2, M? HOR and M–π interactions, apparently for steric reasons. As well as new bonding motifs, the changed dye shape also leads to new packing motifs. The simple organic/inorganic layering ubiquitous to the para‐ and meta‐sulfonated dye salt structures is replaced by variations (organic bilayers, inorganic channels), each of which correlates with a different degree of molecular planarity in the sulfonated azo dye anion.  相似文献   

19.
The course of solid-phase peptide-coupling reactions as well as the swelling properties of a peptide-resin are influenced by the addition of inorganic salts (LiCl, LiBr, LiClO4, KSCN). Used as additives, these salts can (i) improve coupling yields (e.g., for Fmoc-(Ala)5-Phe-resin → Fmoc-(AIa)6-Phe-resin in DMF/CH2Cl2 1:1 from 89.4 to 97.1% (for polyethylene oxide) on polystyrene (? PEO-PS) resin) or from 77.5 to 93.8% (for poly-(N,N′-dimethylacrylamide) on ‘Kieselgur’ (?PDMAA-KG) resin) without and with 0.4M LiCl, respectively), (ii) increase resin swelling (e.g. for Fmoc-(Ala)5-Phe-(polystyrene resin) from 2.42- to 5.73-fold in 1-methylpyrrolidin-2-one (?NMP) without and with LiCl, (respectively), and (iii) change coupling rates. Example;; of coupling reactions and swelling behaviour (degree and rate) in different solvents (DMF, DMF/CH2Cl2 1:1, THF, NMP, N,N-dimethylpropyleneurea (? DMPU) with and without salts) using different resins (polystyrene (PS); PEO–PS, and PDMAA-KG) and an improved analysis of alanine oligomers up to Ala12-Phe by HPLC and FAB-MS are reported.  相似文献   

20.
Thermoresponsive colloidal microgels were prepared by polymerization of N‐isopropylacrylamide (NIPAM) in the presence of a crosslinking monomer, N,N‐methylenebisacrylamide, in water with varying concentrations (<CMC) of an anionic surfactant, sodium dodecylsulphate (SDS). Volume phase transitions of the prepared microgels were studied in D2O by 1H NMR spectroscopy including the measurements of spin–lattice (T1) and spin–spin (T2) relaxation times for the protons of poly(N‐isopropylacrylamide) (PNIPAM) at temperature range 22–50 °C. In addition, microcalorimetry, turbidometry, dynamic light scattering, and electrophoretic mobility measurements were used to characterize the aqueous microgels. As expected, increasing SDS concentration in the polymerization batch decreased the hydrodynamic size of an aqueous microgel. Structures with high mobilities at temperatures above the LCST of PNIPAM were observed in the microgels prepared with small amount of SDS, as indicated by the relaxation times of different PNIPAM protons. It was concluded that the high mobility at high temperatures is in connection to a mobile surface layer with polyelectrolyte nature and with high local LCST. High SDS concentration in the synthesis was observed to prevent the formation of permanent, solid PNIPAM particles. The results from different characterization methods indicated that PNIPAM microgels prepared in high SDS concentrations appear to be more homogeneously structured than their correspondences prepared in low SDS concentration. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3305–3314, 2006  相似文献   

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