Hi,
Hmm.....maybe its the technique
I don't know...but my Hagen kits agrees with my LaMotte kit. Did you shake the test tube or just swirl it ?
Oh...and do not add too much reagent (i.e. 1 to 2 drops should do the trick). It makes it hard read. But, LaMotte is pretty good....it actually has a chart with 0.1 accuracy.
- Victor.