Conditional Equilibrium Constants Reviewed.

A free energy-based conceptual theoretical framework from which the conditional equilibrium constant can be comprehensibly understood is presented. This constant is found to be a weighted geometric mean of the equilibrium constants of the reactions of all forms of the conditioned species under buffering conditions, where the weight is given by a function of their predominance in terms of their mole fractions. Once it is shown that this type of equilibrium constant can be easily deduced form free energy functions, it is shown how corrections for activity coefficient can be incorporated as well.

Comparative study of As (V) uptake in aqueous medium by a polymer inclusion membrane-based passive sampling device and two filamentous fungi (Aspergillus niger and Rhizopus sp.).

In this work a polymer inclusion membrane (PIM) is proposed as passive sampler material and compared with two filamentous fungi for As (V) uptake to evaluate its ability as chemical surrogate material for the monitoring of this metalloid in aquatic environments. Results show excellent passive sampling characteristics of the device since a linear uptake profile as a function of time was observed. The correlation coefficients between the PIM passive sampler with Aspergillus niger (r = 0.

Determination of Cadmium (II) in Aqueous Solutions by In Situ MID-FTIR-PLS Analysis Using a Polymer Inclusion Membrane-Based Sensor: First Considerations.

Environmental monitoring is one of the most dynamically developing branches of chemical analysis. In this area, the use of multidimensional techniques and methods is encouraged to allow reliable determinations of metal ions with portable equipment for in-field applications. In this regard, this study presents, for the first time, the capabilities of a polymer inclusion membrane (PIM) sensor to perform cadmium (II) determination in aqueous solutions by in situ visible (VIS) and Mid- Fourier transform infrared spectroscopy (MID-FTIR) analyses of the polymeric films, using a partial least squares (PLS) chemometric approach.

Influence of some physicochemical parameters on the passive sampling of copper (II) from aqueous medium using a polymer inclusion membrane device.

Recently polymer inclusion membranes (PIMs) have been proposed as materials for passive sampling, nonetheless a theoretical base to describe the mass transfer process through those materials, under such conditions of monitoring, has not been elucidated. Under the assumption that: (i) the transport of the metal ion occurs at steady state conditions, (ii) the concentration gradients are linear, and (iii) the kinetics of the chemical reactions in the extraction process on the membrane are elemental; an equation for the passive sampling of copper (II) using a PIM system containing Kelex-100 as carrier is derived. The prediction capacity of this sampler under different conditions of temperature, metal concentration, flow velocity, ionic strength and pH is analyzed as well.