A method to differentiate total organic chlorine (TOCl), total organic bromine (TOBr)
and total organic iodine (TOI), which involves carbon adsorption, pyrolysis and ion
chromatographic detection, has been developed by previous researchers and applied to
the analysis of water samples. However, incomplete recoveries from model compounds
and interference from auxiliary gas (CO<sub>2</sub>) were reported. The objective of this research
was to determine the best TOX protocol for use with IC analysis. Two commercial
analyzers (one using a pure O<sub>2</sub> carrier and one using O<sub>2</sub>/CO<sub>2</sub> mixture) and three
commercially available activated carbons (two coconut based and one bituminous coal
based) were selected for this research. Chlorine, bromine and iodine containing model
compounds and chlorinated water samples with varying levels of bromide and iodide
were tested on both analyzers and three activated carbons. Results showed that the
pyrolytic analyzer using pure O<sub>2</sub> and off-line IC combined with a standard TOX carbon
(coconut based) achieved the most complete recovery of TOCl, TOBr and TOI for both
model compounds and real samples. There was no obvious difference between the two
analyzers when used in microcoulometric detection mode. The O<sub>2</sub>/CO<sub>2</sub> pyrolytic system
and off-line IC method showed incomplete recovery for some samples due to the
condensation of halide ions and incomplete transfer line flushing. The use of CO<sub>2</sub> as an
auxiliary gas resulted in interference in IC analysis, which made it necessary to purge
dissolved CO<sub>2</sub> before IC analysis. The TOX method is moderately sensitive to nitrate
rinse volume. The monohaloacetic acids were partly washed out during sample
preparation. This problem was solved by modifying the nitrate rinsing solution. Complete
recovery was achieved for all the selected compounds by this modified TOX protocol. Includes 13 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 11/15/2004 |
