[jcjlf]

I read somewhere that peroxide cleaners convert chloride ions to hypochlorite ions or hypochlorous acid.
This is interesting because some environmentalists claim that oxygen cleaners/bleaching agents are better than the (to be banned) chlorine compounds. I want to present this research question to a group of my college students.

I'm trying to find out if there is a (wet) analysis method to determine the presence of hypochlorite/hypochlorous acid by titration or spectrophotometric analysis in the presence of hydrogen peroxide or other peroxide compounds.

Does anyone know a method?

[marquis]

The standard method for hypochlorite determination is to react the HOCl with KI.  The solution is acidified.  The solution is titrated with sodium thiosulfate.  When the amber color starts to dissappear, starch is added as an indicator.  Endpoint is when the purple starch color dissappears.

You should be able to find the method listed in any environmental methods book.  It is often used for chlorination (Cl2 added to water generates HCl and HOCl). Bleach vendors use the same base method, but with higher concentrations of reagents and a diluted bleach sample.

Don't know how peroxide will interfere.  Wouldn't be surprised if it did.

[jcjlf]

The standard method for hypochlorite determination is to react the HOCl with KI.  The solution is acidified.  The solution is titrated with sodium thiosulfate.  When the amber color starts to dissappear, starch is added as an indicator.  Endpoint is when the purple starch color dissappears.

You should be able to find the method listed in any environmental methods book.  It is often used for chlorination (Cl2 added to water generates HCl and HOCl). Bleach vendors use the same base method, but with higher concentrations of reagents and a diluted bleach sample.

Don't know how peroxide will interfere.  Wouldn't be surprised if it did.

Peroxide will certainly interfere because it reacts in the same way with KI (to iodine). So you could add excess chloride to a peroxide solution, maybe it reacts, but with this titration you don't prove the conversion to hypochlorite...
Maybe a complexometric titration? This is just a wild guess.

[marquis]

I guess I would try ion specific electrodes.  I have seen some of those for water treatment stations.  They are calibrated for Cl2, but that means a hypochlorite and chloride mixture.

Its a guess, but better than nothing.

[408]

Why not just kill the peroxide after with some catalytic MnO2 which can be filtered out before the analysis.
Same goes with Ag powder.

[jcjlf]

Tnx for your ideas, I let my students find out if the MnO₂ works. Could imagine though that Ag or MnO₂ also reacts with hypochlorite/hypochlorous acid. I will do some library work/googling on that  .