Correlation between Relative Sensitivities for Electron Capture Detector and Chemical Structure of Aromatic Halogeno and Nitro Compounds

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Abstract
Relative sensitivities of an electron capture detector (ECD, 63Ni) for aromatic halogeno and nitro compounds were measured at detector temperatures of 230, 290, and 320 °C. The effects of various substituents on the sensitivity of ECD were determined. A good correlation was recognized between the relative sensitivities of ECD and the positions of substituents for aromatic chloro, bromo, and nitro compounds. The plotted logarithm values of ECD sensitivities for aromatic chloro and bromo compounds vs. Hammett’s σ values of various substituents are not linear, but the plots for aromatic nitro compounds follow a straight line. Modified σ values (σH) were determined on the basis of the relative sensitivities of aromatic chloro compounds. Plots of aromatic chloro, bromo, and nitro compounds vs. σH values gave straight lines. The temperature dependence of electron capture coefficients for these compounds was determined using D.C. mode. The electron capture spectra obtained are similar to those using pulsed mode.