Hydrogen bonding. Part 29. Characterization of 14 sorbent coatings for chemical microsensors using a new solvation equation
Abstract
Gas-liquid partition coefficients, K, have been obtained for 20–70 solute analytes on 14 candidate phases for chemical microsensors at 298 K and on three of the phases at higher temperatures. The phases can then be characterized through the equation log K=c+rR2+sπ2H+aΣαH2+bΣβH2+llog L16 where log K relates to a series of solutes on the same phase. The explanatory variables are solute parameters, R2 an excess molar refraction, πH2 the solute dipolarity–polarizability, ΣαH2 and ΣβH2 the solute hydrogen bond acidity and basicity and L16 where L16 is the K-value on hexadecane. The coefficients in the above equation then characterize the particular phase, the most important being s the phase dipolarity–polarizability, a the phase basicity, b the phase acidity and I a constant that reflects a combination of cavity effects and general dispersion interactions and is related to the ability of the phase to distinguish between homologues. Derivation of the constants for the various phases provides a quantitative method for the analysis of the selectivity of phases for particular solute analytes and a termby-term investigation of log K values shows exactly the solubility interactions that lead to sorption of a solute by a phase and hence to the analytical determination of the solute through chemical microsensors.