Fast-responding thermionic chlorine analyzer for respiratory applications

To noninvasively determine the distribution of inhaled air pollutants in the intact human respiratory tract, a gas analyzer with a fast dynamic performance, small sampling flow, and high sensitivity is required. Such an analyzer was developed for chlorine (Cl-2) by utilizing a commercially available transducer consisting of a thermionic catalytic source and a metallic collector. Operation of the transducer at 600-800 degrees C, an absolute pressure of 120 Torr, and a sampling flow rate of 0.6 l /min resulted in a sensitivity of 3-5 pA/ppm Cl-2, a minimum detection limit of 0.04 ppm, a response time of less than 100 ms, and signal-to-noise ratios of approximately 10 and 40 at Cl-2 mole fractions of 0.1 and 1.0 ppm, respectively. The calibration was linear in the range of 0.3 to 4.0 ppm Cl-2 and insensitive to variations in temperature, CO2 content, and humidity which exist in respired air during a breathing cycle. (C) 1998 American Institute of Physics. [S0034-6748(98)01711-0]