Methanol selective gas sensor based on nano-structured conducting polypyrrole prepared by electrochemically on interdigital electrodes for biodiesel analysis

Nano-structured conductive polypyrrole (NCP) has been prepared by constant current electrodeposition on interdigital electrodes (IDEs) in the presence of an anionic dopant (PPy-X) and has been investigated as a gas sensor. The effects of the electrochemical conditions and dopant type (perchlorate and para toluene sulfonate) on sensing behavior of the PPy-X gas sensor toward the aliphatic alcohols vapor have been studied. The PPy-ClO4 has been demonstrated to have fast response time (<1 s), high calibration sensitivity, high selectivity, and good reproducibility to the methanol in ambient temperature. The calibration sensitivity order of the PPy-ClO4 for aliphatic alcohol vapors has been revealed as: methanol ≫ ethanol > 1-propanol > 2-propanol. Therefore, the PPy-ClO4 can be successfully utilized as a selective sensor for detection of methanol (DL = 0.03%, mass/mass). It has been found in all of cases that the normalized electrical resistance directly correlates with the concentration of aliphatic alcohols in gas phase. Based on the obtained calibration curve linear range of about 0.15–2.01% (mass/mass) and 0.61–17.62% (mass/mass) was obtained for methanol at 30 °C and 120 °C sensing temperatures, respectively. The PPy-ClO4 gas sensor has been applied for determination of residual methanol content in the biodiesel samples. The results are in good agreement with values obtained by GC/MS method.