Journal
TALANTA
Volume 74, Issue 4, Pages 958-964Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.talanta.2007.08.002
Keywords
ozone; bleaching; colorimetry; ambient air
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The bleaching action of ozone on indigo and related compounds is well known. We describe sensitive automated instrumentation for measuring ambient ozone. Air is sampled around a porous polypropylene tube filled with a solution of indigotrisulfonate. Light transmission through the tube is measured. Light transmission increases as O-3 diffuses through the membrane and bleaches the indigo. Evaporation of the solution, a function of the RH and the air temperature, can, however cause major errors. We solve this problem by adding an O-3-inert dye that absorbs at a different wavelength. Here we provide a new algorithm for this correction and show that this very inexpensive instrument package (controlled by a BASIC Stamp Microcontroller with an on-board data logger, total parts cost US$ 300) provides data highly comparable to commercial ozone monitors over an extended period. The instrument displays an LOD of 1.2 ppbv and a linear span up to 300 ppbv for a sampling time of 1 min. For a sampling time of 5 min, the respective values are 0.24 ppbv and 100 ppbv O-3. (C) 2007 Elsevier B.V. All rights reserved.
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