A humid electronic nose based on pulse voltammetry: A proof-of-concept design

We report herein the design, manufacture and use of a “humid electronic nose” prototype based on voltammetric techniques. It consists of an array of four working electrodes (i.e., Au, Pt, Ir and Rh) housed inside a homemade stainless steel cylinder, in contact with a fabric mesh made of nylon damped with a NaCl aqueous solution, used as the supporting humid membrane. The “humid electronic nose” was tested for the discrimination of different samples displaying different volatile compounds. The samples chosen involve aqueous solutions of different simple volatile products (i.e., ammonia, acetone, acetic acid and 6-amino-1-hexanol) and different food samples (i.e., onion, coffee and Roquefort cheese). Under working conditions, the volatile compounds from the corresponding sample were generated in the measurement chamber and were partially dissolved in the damped nylon fabric, which was in contact with the set of electrodes. It was envisioned that provided different samples offer different vapours, the application of a suitable set of pulses to the electrodes will differentiate the samples. This proof-of-concept study employed a Large Amplitude Pulse Voltammetry (LAPV) waveform. The increment for the potential steps was of 200 mV and potentials ranged from +1 to −1 V with each pulse applied for 50 ms. PCA studies from the response obtained by the “humid electronic nose” discriminated the different samples studied. The neural network Self Organized Map (SOM) was also used to analyze the electrochemical data obtained from the “humid electronic nose”.