Why does my DPD powder disagree with DPD tablets?

[tomfrh]

I have clearchoice DPD powder and also DPD tablets (palintest dpd1)

They give different titration readings. The powder takes 14 drops to go clear, the tablets 10 drops. Makes no difference if i add multiple tablets.

Can anyone explain why?

what exactly does DPD do? And what do the titration drops do?

 

[JamesW]

Dpd is a chemical that turns pink when it is oxidized by chlorine, bromine or iodine (halogen).

The more halogen, the more colored product is created.

The FAS reagent is a reducing agent, which is the opposite of an oxidizing agent.

The FAS reduces or unoxidizes the dpd to change it from pink back to colorless.

The more halogen there is in the water, the more dpd is oxidized into a pink product.

Every drop of fas reagent reduces a specific amount of colored dpd product.

So, by counting the number of drops that it takes to convert the colored dpd to colorless dpd, one can determine the amount of halogen that was in the sample.

 

[tomfrh]

Thanks.

Do you have any idea why the powder and tablet DPD give different results?