sodium-perchlorate and sodium-bromide

Some of the most important processes in nature involve interfacial water. It has long been conjectured that specific ion effects therein are associated with the unique properties of interfacial water. Here we reveal the mechanism of such association by showing that the strength of ion-specific long-range correlations tracks the amplification of fluctuations on the surface of water-alcohol mixtures at the percolation thresholds of their hydrogen-bonded water networks. We used in situ online electrospray mass spectrometry to determine χ = [I(-)]/[Br(-)] ratios in microfilms of (NaI + NaBr) solutions in water-methanol (ME) and water-isopropanol (IP) mixtures as functions of x(ME) and x(IP) molar fractions, and the addition of NaClO4. We found that, beginning at 0.1 μM, ClO4(-) has detectable effects on χ that peak at x(ME) ~ 0.40, x(IP) ~ 0.15, i.e., at water percolation thresholds where fluctuations maximize mean water cluster sizes and, hence, interionic connections. The stronger correlations between ions of similar surface propensities suggest that correlations propagate preferentially along 2-D interfacial layers.

Topics: 2-Propanol; Alcohols; Bromides; Hydrogen Bonding; Ions; Mass Spectrometry; Methanol; Perchlorates; Sodium Compounds; Sodium Iodide; Surface Properties; Water

Aqueous two-phase systems composed of ethylene oxide/propylene oxide random co-polymers, EO30/PO70 or Ucon (EO50/PO50), in the top phase and dextran T500 in the bottom phase, have been studied. The cloud point diagram for EO30/PO70 in water solution was determined. EO30/PO70 has a cloud point of 32 degrees C at a concentration of 10% (w/w). The phase diagram for the system EO30/PO70-dextran T500-water was determined. Salt effects have been studied on the partitioning of two model proteins, bovine serum albumin and hen egg white lysozyme, in EO30/PO70-dextran and Ucon-dextran systems. Ions with different hydrophobicity, i.e., with different position in the Hofmeister or lyotropic series, were investigated with reference to their effect on protein partition. The counterion hydrophobicity was shown to have a strong influence on the partitioning of BSA and lysozyme. Most extreme partitioning was obtained with hydrophobic (chaotropic) ions like CIO4- and I-. A comparison of protein partitioning between PEG-dextran and EO30/PO70-dextran has been done. A more extreme protein partitioning was obtained in the EO30/PO70-dextran containing system. Temperature-induced phase separation was studied with EO30/PO70 at 45 degrees C. Both BSA and lysozyme were completely partitioned to the water phase formed above the cloud point of EO30/PO70. Model calculations, based on Flory-Huggins theory of polymer solutions, have been done which could reproduce the salt effect on the protein partitioning in aqueous-two phase system.

Topics: Bromides; Chemical Phenomena; Chemistry, Physical; Glycine; Ions; Models, Chemical; Muramidase; Perchlorates; Polyethylenes; Polypropylenes; Serum Albumin, Bovine; Sodium Chloride; Sodium Compounds; Sodium Iodide; Water