Use of an electrochemical room temperature ionic liquid-based microprobe for measurements in gaseous atmospheres

A simple electrochemical microprobe (EMP) is proposed for the detection of analytes in gaseous atmospheres. The EMP consists of two platinum fibres of 25 and 300 μm in diameter encased into a theta glass pipette to form an electrochemical cell in a two-electrode configuration. Ion conductivity between the two electrodes is ensured by a thin film of the room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, which is applied onto the EMP tip surface by a simple dip-coating procedure. The ionic liquid-coated microprobe (RTIL-EMP) was preliminarily investigated by using ferrocene as an electroactive species to ascertain the mass transport properties of the analytes that influence the voltammetric responses as well as the stability and reproducibility of the RTIL-EMP in the gas phase. The performance of the RTIL-EMP to gas analysis was afterward evaluated by using oxygen as electroactive species. The RTIL-EMP was exposed to different synthetic O2/N2 (v/v) mixtures and current responses were recorded as a function of O2 concentration, using either cyclic voltammetry (CV) or chronoamperometry (CA). Regression analysis of the experimental current against % O2 was linear over the range 0–100% with correlation coefficient and sensitivity of, respectively, 0.996 and 0.29 nA/(v/v) % O2 in CV and 0.998 and 0.27 nA/(v/v) % O2 in CA measurements. Long term stability, reproducibility of the RTIL-EMP recovery of the RTIL film layers to the initial conditions and effects of humidity on the current responses were investigated in detail.