Will bromine, iodine, ozone, oxidized manganese, and chromium interfere with a chlorine amperometric titration test?

Document ID

Document ID TE4969

Published Date

Published Date 27/05/2017
Question
Will bromine, iodine, ozone, oxidized manganese, and chromium interfere with a chlorine amperometric titration test?
Summary
Interferences with chlorine amperometric tests
Answer
Bromine, iodine, ozone, oxidized manganese, and chromium in the sample my react and interfere with the normal chlorine titration. To compensate for the effects of oxidized manganese and chromium, the sample can be “dechlorinated” and then titrated. The results of such a titration (expressed in terms of mg/L or ug/L chlorine) can then be subtracted from subsequent chlorine determinations to correct the chlorine concentrations for such sample interferences.

Sample Dechlorination

1) Collect 200 mL of sample in a 250 mL beaker
2) Adjust the pH to between 6 and 7 by adding 1 mL of Buffer Solution, pH 7.00 (NIST; Catalog Number/Order Code 1222249)
3) Add one powder pillow of Potassium Iodide (Catalog Number/Order Code 107799)
4) Mix and wait one minute
5) Add 1 mL of Sodium Arsenite Solution. 5.0 g/L (Catalog Number/Order Code 104732)
6) Titrate to a normal amperometric end point with Phenylarsine Oxide (PAO) titrant, 0.00564N (Catalog Number/Order Code 2700349)

The titration results (expressed in terms of equivalent concentration of chlorine) should be subtracted from subsequent sample titrations to correct the titration results for the sample interferences.

*Adapted for 200-mL sample from Hach “Water Analysis Handbook” 3rd Ed., p. 384