Hanna cuvettes are off!!

[SMSREEF]

Here is some info from Randy about the Hanna calibration fluid

I hope folks realize that this sort of "calibration" does not by any stretch of the imagination demonstrate that you get accurate readings from the Hanna. It should be called a color standard for checking the electronics, not an alkalinity standard, which would require adding reagents to it and using the normal alk check procedure.

And about the DIY recipe

FWIW, Hanna does not do an ordinary alkalinity titration, but uses a slightly different method. I expect it is a one point "titration" like described here:

https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lom3.10253
Essentially, they add an amount of acid similar to that needed in an ordinary alkalinity titration, and then use the color to determine the pH, and back calculate what the alkalinity would have been to give that pH with that amount of added acid.

Without seeing some data on how the dye they use responds (in terms of absorbance and also pKa), I cannot be sure this method is reliable for the Hanna, and would be wary of over interpreting the Hanna accuracy based on it.

You can get there with one additional step if you have another kit

1. Carefully check your normal kit for accuracy.
2. Use it to measure tank water or new salt water
3. use the Hanna to measure that same tank water or new salt water and compare.

 

[FlyPenFly]

Yeah, I think ultimately it's just a matter of zero-ing out as much error as possible but also taking into account what is practical in that you can commit to doing it regularly.

 

[Spieg]

I have a bunch of these vials. When I first read about this issue, I pulled them all out and compared them and they're all pretty identical. I find those cheap plastic (disposable) mass produced syringes are more likely to be off than I do the glass vials... If you really want to get it down to a gnats-butt level of accuracy (probably not necessary for hobbyists), you need to go buy a precisely calibrated scale and get a tare-weight of the syringe or vial to be able to accurately determine how much water is actually contained.

 

[92Miata]

I have a bunch of these vials. When I first read about this issue, I pulled them all out and compared them and they're all pretty identical. I find those cheap plastic (disposable) mass produced syringes are more likely to be off than I do the glass vials... If you really want to get it down to a gnats-butt level of accuracy (probably not necessary for hobbyists), you need to go buy a precisely calibrated scale and get a tare-weight of the syringe or vial to be able to accurately determine how much water is actually contained.

Mine aren't identical at all. They vary by a couple of millimeters. I'd guess that either all of yours were made by the same subcontractor, or something along those lines.

And I'd be astounded if they were more accurate than syringes. Syringes are regulated. Hobby test kits aren't.

 

[K7BMG]

All valid verbal points.
But thats the just the thing isn't it. Its all verbal and based on assumption without facts.

Where are the test results backing up the verbal rhetoric in these arguments.

Has anyone here done the work and proved the theory they are making themselves and shared the results.

I had an issue with the Hanna salinity checker.
In my thread I tested two units against three other methods and came to the conclusive fact that both my checkers were dead on consistant.
But both also were exactly .002 in the result in comparison to my othe three.
Proof provided by facts not assumptions.

Just saying......

 

[Spieg]

Syringes are regulated. Hobby test kits aren't.

I'm sure medical grade syringes are regulated. I doubt hobby test syringes from China are regulated any more than the glass vials... If they were regulated, this would not happen;

 

[K7BMG]

I'm sure medical grade syringes are regulated. I doubt hobby test syringes from China are regulated any more than the glass vials... If they were regulated, this would not happen;

See proof not verbal rhetoric

 

[92Miata]

See proof not verbal rhetoric

Proof of what?

That some unknown epoxy syringe he picked up from who knows where isn't accurate? Great. Nobody is arguing that cheap Chinese non-medical syringes are accurate.

Real medical syringes are like $.10-30 a piece. Just buy some.

 

[K7BMG]

Proof of what?

That some unknown epoxy syringe he picked up from who knows where isn't accurate? Great. Nobody is arguing that cheap Chinese non-medical syringes are accurate.

Real medical syringes are like $.10-30 a piece. Just buy some.

Ha ha understood.

But is that really needed?
I know I am not going to spend that much on syringes.

We saw that @90's reefer just tested his alk with a known differance of sample water by .5ml.
The results were.
7.56 and 7.39.
Thats a differance of .17 less than the margin of error on the device alone.
I feel most here would not be overly concerned, and not enough to start spending $10.00 $30.00 dollars on a lab grade syringes.

If we really want to get serious and precisely accurate the we would have better results following regimented cleaning procedures, and be in a fairly sterile area with controled temps.

We all should have the Seneye unit to test ammonia as well.
This is only $400.00 something plus monthly replacement cards at some $30.00 each because we all know the API kits are unreliable.

I get that we all want exacting test results. I know I do but the expectation needs to match reality.

My reality and I will venture a guess is that the majorities reality, is that the expense for the outcome of the result is just not there.

Maybe I am tired of fighting the fight after 59 years of life.
I have been on your bandwagon for years.
Hate that they wont give truth in advertising.
Hate that our test kits are what they are, and that every test kit or measuring tool will get a different result.
Why cant the various test kits no matter the brand or way they do the test accuratly read the sample given?
Why should the same container of saltwater used as a sample for six different brands and or methods not yeald the exact same out come.
Its the same water used right! and its contents has not changed.

This IMO should be fought over with dilligance vs the fact that a cuvettes or syringes are accurate.

 

[Spieg]

Proof of what?

That some unknown epoxy syringe he picked up from who knows where isn't accurate? Great. Nobody is arguing that cheap Chinese non-medical syringes are accurate.

Real medical syringes are like $.10-30 a piece. Just buy some.

Epoxy syringe... REALLY? Both of the syringes I pictured came from hobby-grade marine test kits. Why should I have to go buy a syringe when I paid good money for a test kit?

 

[SMSREEF]

I have been on your bandwagon for years.
Hate that they wont give truth in advertising.
Hate that our test kits are what they are, and that every test kit or measuring tool will get a different result.
Why cant the various test kits no matter the brand or way they do the test accuratly read the sample given?
Why should the same container of saltwater used as a sample for six different brands and or methods not yeald the exact same out come.
Its the same water used right! and its contents has not changed.

Very good points. I just had more faith in Hanna than the others. Thus, I held them to a higher standard. I probably should not have done that.
you are right that our technique probably has more to do with any inaccurate results that a couple mm off on the tube.

 

[Velcro]

Syringes are not very accurate either and susceptible to user error. If you aren’t weighing the water added to the vial, you really don’t know how much you are actually adding via the syringe.

Yes they are. Density plays little role in volumetric measurements of seawater.

 

[DeputyDog95]

My vials' 10ml lines vary as well, which would clearly cause an accuracy issue of being either high or low depending on where the line was mis-printed. I see no point in trying to "re mark" the vials. If you have to be super accurate filling the vial, I would rather put the energy into the accuracy of the sample amount and then squirt it into the cuvette, completely ignoring the line.

Instead of printing on the vials since they can't seem to do it with any consistency... Why not just include a 10ml plastic bulb pipette from a known source they trust? They put smaller plastic bulb pipettes in some of their kits... So much simpler than trying to manage the work of a 3rd party vendor and probably significantly easier to get better accuracy with injection molded plastic pieces.

I went ahead and bought a lab grade 10ml mechanical pipette off Amazon. Similar to the small one they use in the Ca kit (that one measures like a 10th of an ml), just bigger. It was like $40.

One variable removed from the testing process for more easily repeatable, consistent results.