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+sπ₂^H+aΣα^H₂+bΣβ^H₂+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, π^H₂ the solute dipolarity–polarizability, Σα^H₂ and Σβ^H₂ 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.