Alkalinity Test bad batch?

[drawman]

Just curious if anyone has had a bad batch recently? Just performed about 6 tests they were all over the place within a 1dKH range. I certainly expect more precision than this. Fairly new bottle that is nowhere near close to expiring. FWIW, I've used this test kit for years and can't remember a bottle this bad.

 

[VTBig053]

I've been having issues with my Alk Pro refill kit purchased in early January. First of all, switching from the red to blue to the blue to green to yellow was an awful decision. Way too much margin for error trying to decipher between shades of blue and green.

I also have to test at least three times to get a consistent reading. I've had results vary by as much as 2dKH in successive tests. Maybe this is by design so we have to use more regeant and get another refill!

I've been considering making the investment in a hanna checker because of this.

 

[drawman]

I've had results vary by as much as 2dKH in successive tests.

Yeah that's a huge swing in precision. I said 1dKH for mine but it was actually a difference of 1.4dKH. Hopefully we both just got a bad batch but I am contacting the supplier about it you may want to do the same.

 

[GoVols]

Tim,
Do you have the new, Pro alk refill, that has the green endpoint color?

 

[drawman]

Tim,
Do you have the new, Pro alk refill, that has the green endpoint color?

Yes that's the one. FWIW, this is at least my fourth bottle that has the green endpoint color so I've used it extensively. Also I have very good color vision and have been using green (not yellow) as the endpoint.

It's odd to me that there is that much variability with different tests of the same sample. One test needs 0.1mL more for the titration to complete than another of the same sample. Hopefully it's a faulty batch and not a trend!

 

[mjlash22]

Alk testing is one of the few items I stray away from Red Sea kits for. I use the Hanna dKH checker and have had consistent results with that. I had the same issue when using Red Sea's test, never had consistent readings. I still use Red Sea kits for Mag and Calc.

 

[GoVols]

Alk testing is one of the few items I stray away from Red Sea kits for. I use the Hanna dKH checker and have had consistent results with that. I had the same issue when using Red Sea's test, never had consistent readings. I still use Red Sea kits for Mag and Calc.

I use the Hanna Alk checker too

 

[Randy Holmes-Farley]

FWIW, I wouldn't think a "bad batch" in an alk test would cause variable results, as opposed to them all being off in a particular direction (caused, for example, by incorrect concentration of the acid or degradation/misformulation of the dye to a different molecule with a different pH endpoint to the color change.

 

[drawman]

FWIW, I wouldn't think a "bad batch" in an alk test would cause variable results, as opposed to them all being off in a particular direction (caused, for example, by incorrect concentration of the acid or degradation/misformulation of the dye to a different molecule with a different pH endpoint to the color change.

Yes I agree I guess that's why I was so frustrated. You would think the titrant would still be precise (if not accurate). I follow a rather consistent and precise protocol and can assume a small amount of variability through operator error (color reading, etc.). That said, 0.1mL of difference in titrant used while measuring the sample sample is too much for me.

FWIW, I've switched to a Salifert kit so I'm hoping for better readings!

 

[GoVols]

FWIW, I wouldn't think a "bad batch" in an alk test would cause variable results, as opposed to them all being off in a particular direction (caused, for example, by incorrect concentration of the acid or degradation/misformulation of the dye to a different molecule with a different pH endpoint to the color change.

When I used to use the Red Sea Pro alk:
Red Sea Kev told me that it was not to certain endpoint color, but when you see a endpoint change, then stop the titration and take your reading.

He also said that overtime, oxygen can effect the endpoint color too