Polymer-coated QCR sensors for the detection of organic solvents in water

Poly(ethyl acrylate) (PEA), poly(epichlorohydrin) (PECH) and a silicon-based copolymer of trimethoxypropylsilane/octadecyltrimethoxysilane (TMPS/ODTMS) were used as sensitive materials for the detection of organic solvent molecules in water. Quartz crystal resonators (QCR) with modified electrode configurations are used to monitor the changes in mass and in electrical properties by measuring the shifts in series resonance frequency (f(s)), parallel resonance frequency (f(p)), and frequency of maximum admittance (f(m)), respectively. The result is a multi-information chemical sensor. The sensor signals are completely reversible at room temperature with the response and recovery time in the order of minutes under our measurement conditions. The sensitivities obtained from the measurements of f(m) for all organic solvents investigated are generally larger than those obtained from f(s) and f(p). It is also found that there is no correlation between the measured sensitivities of the series resonance frequency and the boiling point temperatures of the organic solvents investigated in the liquid phase under our experimental conditions, as is generally obtained in the gas phase.