Analyzing Hanna Ammonia checker Hi784, chemistry and performance

[Malcontent]

Which Hach version you thinking of?
You only need two if it's freshwater.
One version, Hach hides some reagents in the cap.

What does seawater need? Citrate?

Hach ammonia salicylate
sodium salicylate	54-21-7	40-50%
sodium nitroferricynade	14402-89-2	<1%
m-nitrophenol	554-84-7	<0.5%
sodium citrate	68-04-2	40-50%
sodium tartrate	868-18-8	10-20%
Hach ammonia cyanurate
lithium hydroxide, anhydrous	1310-65-2	1-5%
sodium dichloroisocyanurate	2893-78-9	1-3%
sodium citrate	68-04-2	80-90%
sodium tartrate	868-18-8	5-15%

Hanna HI784:

"A" (liquid)
sodium hydroxide	1310-73-2	2-5%
"B" (powder)
not disclosed
"C" (powder)
sodium salicylate	54-21-7	50-100%
triclosene sodium dihydrate	51580-86-0	1-2.5%
sodium nitroprusside dihydrate	13755-38-9	1-3.5%

 

[taricha]

What does seawater need? Citrate?

right. citrate or other chelator to suppress the precipitation. The hanna B packet is that chelator.
There's also a chlorine / hypochlorite in there somewhere as the salycilate reaction needs it. Don't know if it's a tiny undeclared amount, or if one of the hach chemicals produces it during the reaction.
The chlorine/hypochlorite often goes in along with the high pH additive in several kits - Red Sea, API etc.