Increased sensor sensitivities obtained by polymer-coated quartz microbalances

Polymer-coated quartz microbalances were produced and studied. They exhibit ed high sensitivities for heavy noncyclical hydrocarbons and CO2 concentrat ion measurements. Detection limit of 1 ppm CO2 and 10 ppm Shellsol (Shell s olvent containing: 28.7% C10H22; 66.4% C11H24; 5% C12H26) are obtained and reported. The time constants of the absorption and desorption processes wer e investigated also. A diffusion-free behaviour was observed and related to the porosity of the layer. Collateral AFM (atomic force microscopy) analys is of the polymer structure was performed. We explain big values of the abs orption-desorption time constant for CO2 and small values for CnH2n+2 mixtu res in connection with the peculiarities of the chemical reaction involved by the sensing mechanisms. (C) 1999 Elsevier Science S.A. All rights reserv ed.