December 2008
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UV degradation of carboxylic acids involves complex chemical reactions and the formation of many conductive intermediates along the pathway to complete mineralization. However, resistivity and TOC analyzers are sensitive to low-ppb levels of dissociated carboxylic acids and should be useful instruments for on-line detection of organic acid excursions in semiconductor high-purity water systems. Complete oxidation of organic acids at concentrations < 50 ppb have been demonstrated under high-DO conditions, but similar results should occur at low-DO conditions with similar acid concentrations. Complete oxidation is confirmed by full recovery of TOC after carboxylic acid injections. The ability to employ a TOC analyzer to detect trace level organic acid excursions using standard injections on a high-purity water loop creates new opportunities to use TOC analyzers for rudimentary speciation. When an analytical instrument reacts in a unique way to a specific type of contaminant, then this implies the ability to provide some level of speciation for that contaminant. This research has demonstrated a unique method of detecting a specific class of organic compounds, carboxylic acids, in high-purity water using an algorithm-modified TOC analyzer.