DPD test, Is it Desolved?

[moodmiester]

I've been using the K-2006 kit for a couple years now. During my DPD test I've let the sample sit a few minutes, and notice the pink tint returns. Is this due to the FAS-DPD evaporating or the powder is not fully desolved?

 

[Divin Dave]

I cannot technically tell you why this happens, but it does. Has nothing to do with having enough powder or being fully desolved.

When you do the test and let the sample sit, it will turn pink again. This is why you need to do the CC test immediately after the FC test.
You get a false CC test result if you wait too long.

 

[tim5055]

I cannot technically tell you why this happens, but it does. Has nothing to do with having enough powder or being fully desolved. .

When in doubt I always look to Richard's (Chem Geek) posts....

Taylor website, they have some interesting Q&As such as the following:

In the FAS-DPD test if you wait too long after the sample turns clear, it may turn light pink again. This can be caused by oxygen in the air oxidizing the DPD dye.