I have read and read and read some more that the amount of DPD powder you add to the sample doesn't matter and WILL NOT affect the results, so long as it turns pink and stays pink.
OK, so 2 questions and then a semi brief elaboration.
1. If it turns pink, but it's only a light pink, not vibrant neon pink. Does that count?
2. What happens if you add too much? Say a really heaping scoop that makes it super dark, compared to a less heaping scoop. Will this throw of the test for the former by requiring more drops to reach endpoint?
I ask the 1st question because I have noticed that if I use a full heaping scoop when shocking, at my CYA it's 12ppm+, then I get a nice dark pink. But if I use a level scoop, I still get pink, but it's much lighter.
Also, granule size, there are big huge granules, in relation to the others that is and there are sizes ranging down from there, all the way to a fine dust.
So I have also seen when adding a heaping scoop of just the big granules, that the water doesn't turn pink at all!! Recently I had to add almost 2.5 scoops to get it to go pink and FC was only at about 12/13ppm.
I did let the SS run for a full cycle after each addition.
On question #2. Wouldn't more powder, thus making a darker sample color, take more titrating reagent to neutralize the dye?