Vapor–liquid equilibria of binary tri-potassium citrate + water and ternary polypropylene oxide 400 + tri-potassium citrate + water systems from isopiestic measurements over a range of temperatures

Water activity measurements have been carried out on the aqueous solutions of both tri-potassium citrate (K₃Cit) and polypropylene oxide (PPO) 400 + K₃Cit over a range of temperatures at atmospheric pressure. The data obtained is used to calculate the vapor pressure as a function of temperature and concentration. The effect of temperature on the constant water activity lines of aqueous PPO + K₃Cit systems has been studied and it was found that, at higher temperatures the higher concentration of polymer is in equilibrium with a certain concentration of the salt. Also it was found that the vapor pressure depression for an aqueous PPO + K₃Cit system is more than the sum of those for the corresponding binary solutions. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. The agreement between the correlation and the experimental data is good.     

Thermodynamic Properties of Aqueous Glucose–Urea–Salt Systems

In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl₂), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum solutions, the osmotic coefficients were found to be in the range of 0.90–0.93. In a second step, the state of water in different glucose/salt/water and urea/salt/water systems was investigated. Depending on the kind of salt, the chemical potential of water in urea/salt/water is either higher or lower than in glucose/salt/water systems at equal nonelectrolyte concentrations. This result was found to be independent of the salt molality. Finally, the investigated systems were modeled with the Pitzer model and the ePC-SAFT equation of state, which allowed predicting of the properties of these multi-solute aqueous solutions.     

Comparative study of honeycomb optimization using Kriging and radial basis function

Structural optimization for crashworthiness criteria is of particular significance especially at early stage of design. The comparative study of Kriging and radial basis function network (RBFN) was performed in order to improve the crashworthiness effects of honeycomb. Improving the crashworthiness characteristic of honeycomb was achieved using LS-OPT® and domain reduction strategy. This optimization is performed on the basis of validated numerical simulation to establish the approximated model to illustrate the relationship between the responses and design variables. The results showed that Kriging meta-model is excelled in accuracy, robustness and efficiency compared to radial basis function (RBF) and crashworthiness characteristic of honeycomb is improved by 4%.     

Combining gold nanoparticle-based headspace single-drop microextraction and a paper-based colorimetric assay for selenium determination

Analytical and Bioanalytical Chemistry - A novel method combining headspace single-drop microextraction with a paper-based colorimetric assay was developed. Headspace single-drop microextraction...     

A high selective ion‐imprinted polymer grafted on a novel nanoporous material for efficient gold extraction

In this work, for the first time, an ion‐imprinted polymer was developed for selective extraction and determination of gold ions. To increase the sorbent efficiency, this polymer was coated on a novel nanoporous carbon‐based material, carbohydrate‐derived Max‐Planck Gesellschaft 1, which is also the first example of grafting imprinted polymer on nanoporous‐carbon material. These particles were applied successfully for preconcentration of ultratrace amount of gold ions, following determination by flame atomic absorption spectrometry. Some effective factors on the efficiency of gold ions extraction, such as concentration and volume of eluent, sample and eluent flow rates, and also effect of interfering ions especially palladium and platinum ions, were investigated. The LOD was determined to be 0.27 ng/mL. Furthermore, the precision of the method was calculated to be 2.14% under optimal conditions with recovery more than 97.3%. The technique was also used to determine the concentration of gold ions in mine stone samples with satisfactory results. The accuracy of this method was investigated by determination of gold ions concentrations in several reference materials with certified gold content.