Does your calibration solution need calibrated?

[jason2459]

One of the very basic parameters that we need to maintain is that of salinity which can directly and indirectly effect all other parameters.

Reef Aquarium Water Parameters
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm


Being able to accurately test for and read what that salinity is can be challenging. There's many methods to be able to determine what your aquarium or new saltmix salinity is at.



For many years I've used many different devices including different probes, many different refractometers, digital refractometers, floating hydrometers, and even swing arm hydrometers.

All need and should at least be checked for calibration and if possible calibrated periodically and properly.

Refractometers and Salinity Measurement
http://reefkeeping.com/issues/2006-12/rhf/


I've used in the past a few different calibration solutions. It's important to know though that sometimes they are not accurate. Either when you first get them if bought pre-made or over time with any kind you have due to potential evaporation.

When purchasing I usually buy two to cross check each other. Usually there's a very slight and acceptable variation. Sometimes though there's large discrepancies. In the past 10 years or so I've maybe have had 3 or 4 bad bottles of calibration fluid sent to me.

Add one more to that count.


In comes the home brew calibration vs store bought

Article worth repeating
Refractometers and Salinity Measurement
http://reefkeeping.com/issues/2006-12/rhf/

In there is how to make your own solution. Along with in this article also by Randy Holmes-Farley

Reef Aquarium Salinity: Homemade Calibration Standards
http://www.reefkeeping.com/issues/2004-06/rhf/

I used canning and pickling salt as its only ingredient is salt (sodium chloride). Some kosher salts will work too. Morton's Kosher salt has an anti-caking agent in theirs. Used RO/DI for the water to mix the salt in.

I also picked up that bottle as it mixes up the 2L volume version easily (I still used my cylinder and scale)and the bottle keeps sealed from evaporation even when pouring a tiny bit out for use. It has a pop top for drinking

After mixing up here's the DIY calibration solution readings (used my digital refractometer for easy reading for this post. It was just calibrated to 0 with RO/DI.)

New bottle of 35ppt calibration solution.

And its reading

Not good. So, I added some RO/DI to bring it to 35ppt and realized why when I have 2L of perfectly good calibration solution I just made and tossed the small bottle out.

 

[bertoni]

Well, that result is discouraging. Other people have reported problems with the PinPoint solution, though, so it's not completely surprising. Making standard solutions that work well seems to be harder than one would think.

 

[Reef Frog]

Wow that's a big difference. Was that bottle new & did you cross check your meter with any other device or meter?

I never really worried about calibration solution being grossly inaccurate from the factory as I just assumed its relatively easy to do accurate cross checks on each batch. I guess not. At $10-$12 per bottle though this doesn't seem that hard to build the business around a reliable procedure. Talk about some bad quality control! I can imagine such negligence could be a huge potential liability. If I owned or managed that company is be scared to death of bad product leaving the building!

 

[dol13fan]

I recently had a bottle that was off by over 10PPT so the actually reading was 45 instead of 35. I think the solution does expired over time but never saw a date on one of the bottles. I only realized the discrepancy when I noticed the LFS water was reading much lower than mine. Anyway now I use distilled to calibrate.

 

[jason2459]

Well, that result is discouraging. Other people have reported problems with the PinPoint solution, though, so it's not completely surprising. Making standard solutions that work well seems to be harder than one would think.

It's happened a few times now for me. I think I'm done buying them and just sticking with the home brew. Considering that box of salt will probably last many years for me.

Wow that's a big difference. Was that bottle new & did you cross check your meter with any other device or meter?

I never really worried about calibration solution being grossly inaccurate from the factory as I just assumed its relatively easy to do accurate cross checks on each batch. I guess not. At $10-$12 per bottle though this doesn't seem that hard to build the business around a reliable procedure. Talk about some bad quality control! I can imagine such negligence could be a huge potential liability. If I owned or managed that company is be scared to death of bad product leaving the building!

Bottle was new. I trust my veegee more then any other device I test with. I check calibration periodically and rarely have to actually calibrate. It's been over a year I know since the last time I had to adjust it. So, when I put the calibration solution on my refractometer I knew right away it was bad.

I used the Milwaukee digital for this post only because it's a very easy to read display for pictures and a number most would understand. My probes wouldn't read that home brew calibration right with out adjustments for them which is in that Homemade Calibration Standards link I posted.

So yes, that bad bottle tested high with my veegee refractometer, Milwaukee digital refractometer, and pinpoint salinity probe.

I recently had a bottle that was off by over 10PPT so the actually reading was 45 instead of 35. I think the solution does expired over time but never saw a date on one of the bottles. I only realized the discrepancy when I noticed the LFS water was reading much lower than mine. Anyway now I use distilled to calibrate.

With any testing device I would check with a standard as close to the end point that is being tested for. For a refractometer I would still use a 1.0264/35ppt standard to check against. I would not use distilled or RO/DI to calibrate a non-seawater refractometer which many are that are sold to us in this hobby. I suggest reading that Refractometers and Salinity Measurement article by Randy which explains why.

 

[loudell]

I would be happy to measure that bottle of PINPOINT Calibration fluid against a new bottle of PINPOINT Standard and report the results...
Your discrepancy has several other possible/contributing avenues.

 

[jason2459]

I would be happy to measure that bottle of PINPOINT Calibration fluid against a new bottle of PINPOINT Standard and report the results...
Your discrepancy has several other possible/contributing avenues.

Well, old bottle still reads 36ppt on the Milwaukee and slightly over 35ppt on my veegee. Another bottle of AquaCraft standard reads 35 on the Milwaukee and slightly under 35ppt on my veegee.

 

[loudell]

Calibration by majority vote is not really scientific but suit yourself...

 

[jason2459]

Calibration by majority vote is not really scientific but suit yourself...

Not sure where the attitude is coming from but to be clear the DIY standard comes up perfect. I've also stated I'll be sticking with that standard. I'll also refer to this post where my feelings are in regards to measuring salinity.


[QUOTE="jason2459]Consistency is key. If you have established a resonable calibration protocol and fairly accurate method to determin salinity and stick with it you will be fine. If you believe you are reading 34-35ppt and maintain that level you should be just fine.

Corals can be found at various salinity levels. Salinity levels can change seasonally to daily. 35ppt is the canonical surface level average and a good number to set as the baseline to measure for. If you are not precisely there you should still be just fine.[/QUOTE]

 

[shifty51008]

just wanna double check:

3. Measure the full volume of a plastic 2-L Coke or Diet Coke bottle filled with purified freshwater (about 2104.4 g)

these measurements don't include the weight of the bottle correct? the 2104.4g is the water weight only?

 

[jason2459]

just wanna double check:

3. Measure the full volume of a plastic 2-L Coke or Diet Coke bottle filled with purified freshwater (about 2104.4 g)

these measurements don't include the weight of the bottle correct? the 2104.4g is the water weight only?

It would be the water volume and take note of his last comment. I'm not sure if the bottle has changed since the article.


From
Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

In particular, a plastic 2-L Diet Coke bottle filled to the absolute top contained 2104.4 grams (mL) of water. In a pinch, these containers may serve well as volume standards (at least until the company changes bottle styles).

 

[bertoni]

coleparmer.com lists graduated cylinders of 1000 ml capacity for $20-80, depending on the material. They might be useful.