Manganese interference in the determination of free chlorine using DPD indicator is an
on-going problem for analysts in the drinking water industry. This problem will increase
as additional source water supplies are required to comply with the Ground Water Rule.
The positive interference caused by manganese often leads to the question, "Is the pink
color in my sample really coming from chlorine?" The interference from manganese is
not readily obvious to the analyst because the color forms immediately with the DPD
indicator in the same manner as free chlorine. The level of interference can vary from
sample to sample depending upon the relative concentration and reactivity of the
manganese present. The impact of the manganese interference is that it will cause an
over-estimation of the disinfectant level and microbial protection actually present in the
waters tested. Utilities that are required to monitor free chlorine may not be maintaining
a true detectable level throughout all points in their distribution systems. Work has been completed on the evaluation of a new method for determining free
chlorine concentrations in the presence of manganese. No pretreatment steps are
required and the reagents used are not regulated for disposal. The key to the
development of the method was to design a reaction mechanism for free chlorine that
does not require the oxidation of an indicator such as DPD. This automatically
eliminates the oxidant effects of any manganese present in the samples. Analysts do
not have to predetermine if manganese is present nor do they need to apply a correction
factor to compensate for the manganese interference.
Results from three utilities comparing the results of this work versus DPD are presented. Includes 3 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 960 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/01/2009 |
