Prototype of electrochemical sensor for measurements of volatile organic compounds in gases

The paper presents a laboratory prototype of an electrochemical sensor for measurements of volatile organic compounds (VOCs) in gases, utilizing ionic liquids and commercial screen printed electrodes by DropSens. The following ionic liquids have been tested as the electrolyte and redox reaction environment: 1-butyl, 3-methylimidazolium dicyanoamide ([BMIM][N(CN)2]), 1-octyl, 3-methylimidazolium tetrafluoroborate ([OMIM][BF4]), 1-butyl, 3-methylimidazolium bis (trifluoromethanesulfonyl)imide ([BMIM][Tf2N]). VOCs investigated in the studies were: benzaldehyde, methyl benzoate, acetophenone. Gaseous reference mixtures have been prepared using permeation technique. Two metrological parameters of the sensor have been subjected to validation: limit of detection and sensitivity. The most advantageous parameters have been exhibited by the sensor for measurement of benzaldehyde in argon environment, where [OMIM][BF4] has been the ionic liquid employed. The limit of detection was at a level of 1 ppm by volume, whereas sensitivity amounted to 200 nA/ppm. The limit of detection has been evaluated in three ways: (a) based on the residual standard deviation of the calibration curve, (b) using standard deviation of the intercept of the calibration curve, and (c) utilizing standard deviation of the series of the results obtained for blank sample.