An Investigation of the Concentration Dependence and Response to Analyte Mixtures of Carbon Black/Insulating Organic Polymer Composite Vapor Detectors

The responses relative to an air background of carbon black/polymer composite vapor detectors have been determined as a function of the concentration of a homologous series of alcohols (n-C_nH_(2n+1)OH, 1 ≤ n ≤ 8), a homologous series of alkanes (n-C_nH_(2n+2), 5 ≤ n ≤ 10 and n = 12, 14), and a set of diverse solvent vapors. In all cases, the steady-state relative differential resistance responses, ΔR/R_b, of the carbon black/polymer composite vapor detectors were well-described by a linear relationship with respect to the analyte partial pressure, at least over the tested concentration range (P/P° = 0.005−0.03, where P° is the vapor pressure of the analyte). When two vapors in air were simultaneously presented to the detectors, the ΔR/R_b response, relative to an air background, was the sum of the ΔR/R_b values obtained when each analyte was exposed separately to the carbon black/polymer composite detectors under study. Similarly, when an analyte was exposed to the detectors on top of a background level of another analyte, the ΔR/R_b values of the array of detectors were very close to those obtained when the test analyte was exposed to the detectors only in the presence of background air. The initial training requirements from the array response output data of such detectors are minimized because the ΔR/R_b response pattern produced by the analyte of concern can be associated uniquely with that odor, under the conditions explored in this work