Continuous monitoring of gas-phase species at trace levels with electrochemical detectors Part 2. Detection of chlorine and hydrogen chloride

A detection system suitable for the contmuous and simultaneous measurement of gas-phase chlonne and hydrogen chlonde m the low parts per b&on (10’) by volume (ppbv) range 1s described Both gases are trapped through the walls of a microporous polypropylene tube mto an appropriate flowmg recipient buffer. The buffer then flows through two electrochenncal detectors placed m series downstream from the sampling tube. Chlonde ions from gas-phase hydrogen chlonde are detected potentlometncally with an Ag/AgCI working electrode Chlonne IS detected biarnperometncally (at 0 1 V) via its oxidation of added lo&de tons to form ttiodide. In a contmuous-flow measurement mode, detection of chlonne and hydrogen chloride at levels as low as 0.75 and 2.1 ppbv, respectively, 1s possible. Use of a 2-mm stopped-flow/flow-mjectlon arrangement results m a three-fold improvement m detectIon linnts The selectlvlty of each detector wth respect to carbon &oxlde, sulfur &oxlde, rutrogen dioxide and hydrogen sulfide 1s also exammed