Chemiluminometric Measurement of Atmospheric Ozone with Photoactivated Chromotropic Acid

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• 作者：Toshio Takayanagi ; Xiao-Li Su ; Purnendu K. Dasgupta ; Kalyani Martinelango ; Guigen Li ; Rida S. Al-Horr ; and Robert W. Shaw
• 刊名：Analytical Chemistry
• 出版年：2003
• 出版时间：November 1, 2003
• 年：2003
• 卷：75
• 期：21
• 页码：5916 - 5925
• 全文大小：207K
• 年卷期：v.75,no.21(November 1, 2003)
• ISSN：1520-6882

文摘

A highly sensitive, robust, fast, affordable measurementsystem based on interfacial gas-liquid chemiluminescence (CL) on a wetted transparent screen directly on topof a miniature photomultiplier tube provides the basis ofan attractive method for ozone (O₃). Alkaline chromotropic acid (CA, 4,5-dihydroxynaphthalene-2,7-disulfonicacid) chemiluminesces upon exposure to ozone. No lightemission is observed from exposure of alkaline CA to NO₂or H₂O₂. However, response to ozone is highly dependenton the age and storage condition of the CA solution. Assuch, quantitative analysis will require frequent calibration, and the method will not be attractive. We havediscovered that photoactivation plays the key role inproducing (a) compound(s) from chromotropic acid thatappear(s) to be the primary agent(s) responsible for theCL reaction with O₃. We thus devised a method whereina flowing solution of CA (that is stable in neutral/acidicsolutions) is rendered alkaline and then exposed for a fewseconds on-line to UV radiation. The solution then reactswith ozone on a screen consisting of an "invisible" nylonstocking that provides for low liquid residence time andhigh light throughput and results in an LOD of 40 pptv,a determination range at least up to 230 ppbv, and 10-90% and 90-10% response times of 130 and 80 ms,respectively. Intra- and interday repeatabilities at the sameconcentration were 0.32 and 3.8% in relative standarddeviation. On the basis of aging, CL, chromatography, andchromatography-mass spectrometry studies, we suggestthat the primary CL-active species are likely dimericsemiquinone species derived from CA by a series ofradical reactions.