Conductometric Sensor Based on Electropolymerized Pyrrole-Tailed Ionic Liquids for Acetone Detection

In the chemical industry and research institutes, acetone serves routinely as a solvent, a reactant, and an extractant. However, due to its high volatility and toxicity, monitoring its vapor concentration is of great necessity for health and industrial safety. Besides this, simple and easy-to-use portable sensors are still lacking. In this work, a conductometric transducer was developed for the detection of acetone vapor. For this, interdigitated electrodes were functionalized by electropolymerization of a series of N-(1-methyl-3-octylimidazolium)pyrrole [PyC(8)MIm]X monomers that contain different counteranions X-, namely, hexafluorophosphate (PF6-), tetrafluoroborate (BF4-), and bis(trifluoromethylsulfonyl)imide (TFSI-). The functionalized interdigitated electrodes were widely characterized. The analytical performances of the microsensors were determined in the presence of gaseous acetone, chloroform, ethanol, methanol, and toluene, collected from the headspace of the above aqueous solutions of known concentrations. The gas-sensing responses of the films were measured at room temperature through differential conductometric measurements conducted at 10 kHz. Among the different sensors, the one bearing BF4- anions presented the best analytical performances and was able to selectively detect acetone vapors. The sensor's response time (t(res)) varied from 6 to 13 s from lower to higher concentrations. The detection limit was 0.76 v/v % (7600 ppm) in the gas phase. The relative standard deviation was 6% for lower concentrations and 2% for higher concentrations. The acetone sensor presented 2 times lower sensitivity for ethanol and 4 times lower sensitivity for methanol. Detection of acetone in the headspace of a nail varnish remover sample led to an acetone content that was in compliance with the value given by the producer.