Salifert test disagrees with Hannah and trident now

c0kefree · Nov 14, 2022

Sorry if this is a bit rambly, just had 2 glasses of wine at dinner.

So i recently recalibrated my trident to my salifert test when i changed the reagents.

i used salifert kits and Hannah checkers for quite awhile, got a trident 2 months ago.
My salifert test has always read about 1dkh too high compared to my trident. My hannah normally agreed with my trident.

So this past Saturday i changed reagents, recalibrated the trident and went about my merry way.
The following day i dosed my normal 6ml of alk (it was reading 1dkh higher than normal on the trident, as expected by the calibration to my salifert kit)

——-

This brings me to my current situation:

The trident is reading what i would expect and my hannah checker is reading what i would expect (and agrees with trident) but my salifert test is now reading a full dkh too high. Huh?

The ONLY thing i can think that might be causing this result (pending my chemistry ignorance) is i accidentally used my calcium syringe to suck up the alk reagent. And might have deposited some into the remaining reagent.

So to the question: did i compromise the accuracy of my salifert test kit? Should i just ignore my salifert test since my hannah and trident now agree? Or wait for the alk to drop according to the salifert to dose again?

it’s only a 1dkh jump, so it’s not like its a problem… i’m just trying to figure out what happened and what i should do further.

thanks in advance, and apologies again if this is as incoherent as i think lol

AKG · Nov 14, 2022

If your Hanna and Trident still agree but you didn't calibrate the Hanna wouldn't that mean the Trident didn't actually save the calibration?

If Hanna+Trident = 2,
But Salifert = 3

Calibrate Trident to Salifert
Trident = 3
Salifert = 3
Hanna = 2

Calibrate Hanna
Trident = 3
Salifert = 3
Hanna= 3

Dose:
Trident=3
Hanna=3
Salifert=4

I'm going to say it's a vision or precision related issue rather than the Salifert you initially calibrated to.

This said, the key issue here is you used a agent and a reagent in the same syringe which fudged your numbers because the reagent works by having (I imagine) like I can describe below. For the calcium colorimeter reagents with Hanna, they basically use a zincon indicator, a zinc complex, and sodium hydroxide. Calcium displaces the zinc, zinc reacts with the indicator, and the sodium hydroxide is purely to have proper pH for this to happen. So I imagine depending on what you mean by calcium syringe, if it's the calcium reagent then yes, I would hazard a guess the other reagent is now cross contaminated.

If you mean just calcium additive, then also yes, likely contaminated.

These methods use acid base titrations at their core so mixing things is a good way to get wrong measurements, but 1 DKh is a lot to ask for imo. Then again, it's just within the syringe and or containers used.

Tl,Dr;

My two cents: calibrate the Hanna and consider your Salifert kit toast until you can replace your it.

c0kefree · Nov 14, 2022

I

AKG said:
If your Hanna and Trident still agree but you didn't calibrate the Hanna wouldn't that mean the Trident didn't actually save the calibration?

If Hanna+Trident = 2,
But Salifert = 3

Calibrate Trident to Salifert
Trident = 3
Salifert = 3
Hanna = 2

Calibrate Hanna
Trident = 3
Salifert = 3
Hanna= 3

Dose:
Trident=3
Hanna=3
Salifert=4

I'm going to say it's a vision or precision related issue rather than the Salifert you initially calibrated to.

This said, the key issue here is you used a agent and a reagent in the same syringe which fudged your numbers because the reagent works by having (I imagine) like I can describe below. For the calcium colorimeter reagents with Hanna, they basically use a zincon indicator, a zinc complex, and sodium hydroxide. Calcium displaces the zinc, zinc reacts with the indicator, and the sodium hydroxide is purely to have proper pH for this to happen. So I imagine depending on what you mean by calcium syringe, if it's the calcium reagent then yes, I would hazard a guess the other reagent is now cross contaminated.

If you mean just calcium additive, then also yes, likely contaminated.

These methods use acid base titrations at their core so mixing things is a good way to get wrong measurements, but 1 DKh is a lot to ask for imo. Then again, it's just within the syringe and or containers used.

Tl,Dr;

My two cents: calibrate the Hanna and consider your Salifert kit toast until you can replace your it.

Whoa crap… you solved it. Thanks a lot!! I cannot believe i couldn’t see it! I was racking my mind trying to figure it out.

I can see now in my graphs, my trident doesn't appear to have taken the calibration. I didn’t even notice it.
My magnesium was trending up twords the end, so when i saw the drop in the graph, my mind said “calibrated”

So i essentially just jacked my alk up 2 dkh in like 2 days… oops.

AKG · Nov 14, 2022

c0kefree said:
I

Whoa crap… you solved it. Thanks a lot!! I cannot believe i couldn’t see it! I was racking my mind trying to figure it out.

I can see now in my graphs, my trident doesn't appear to have taken the calibration. I didn’t even notice it.
My magnesium was trending up twords the end, so when i saw the drop in the graph, my mind said “calibrated”

So i essentially just jacked my alk up 2 dkh in like 2 days… oops.

Glad my first idea was the right idea.

Best of luck with your tank!