HYDROGEN-BONDING .29. CHARACTERIZATION OF 14 SORBENT COATINGS FOR CHEMICAL MICROSENSORS USING A NEW SOLVATION EQUATION

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 + rR(2) + s pi(2)(H) + a Sigma alpha(2)(H) + b Sigma beta(2)(H) + IlogL(16) where log K relates to a series of solutes on the same phase. The explanatory variables are solute parameters, R(2) an excess molar refraction, pi(2)(H) the solute dipolarity-polarizability, Sigma alpha(2)(H) and Sigma beta(2)(H) the solute hydrogen bond acidity and basicity and log L(16) where L(16) 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 term-by-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.