Warning: Commercial pH Calibration Buffers can be way off!

[Boomer]

pH problems are among the most common problems in the Reef Chemistry forum here at RC. While I expect the vast majority of these problems are real, pH calibration is also a substantial issue.

A while back it was suggested to me that there may be a problem with certain commercial pH calibration buffers used by aquarists. So I set out to test a bunch by buying a variety of different brands and pHs from a variety of popular online vendors and an LFS. Some were intentionally expired, to see the effects of aging. I will report in detail on these tests next month in an article at reefkeeping.com

Frankly, however, I was shocked by the results, and feel the urgency to release some information right away.

One brand was so seriously in error that it could cause serious problems should aquarists use them and accept the results.

I'm not talking about small differences that only chemists or perfectionists would care about. I'm talking about a pH 4 buffer over pH 6, several pH 10 buffers from a single brand at pH 9.0, a pH 7 buffer at pH 7.5. These are serious errors.

I have reluctantly decided to not name the particular brands that performed poorly (even by email or PM, so please don't ask).

Instead, I will provide the list of brands below that indicate those brands that seem sufficiently accurate to me for reef aquarists to get useful results (although that does not imply that all samples from each listed brand were perfect):

Orion PerpHect packets
Milwaukee packets
Pinpoint packets
Hanna bottles and packets

So my recommendation is to use one of these brands, unless you have good reason to trust another brand.

Happy Reefing.

__________________
Randy Holmes-Farley

 

[mattseattle]

wow, Hanna is on your list. I had issues with the Hanna brand trying to calibrate my American Marine pH monitor. Did you test American Marine pH fluid? what were your results on that?

 

[Boomer]

As the post says, there will be no further comments

 

[Scooterman]

Thanks for the valuable information Boomer!

Glad I don't ever try to adjust my PH as of yet anyways!

 

[mojoreef]

That figures, I have been working with a few folks over the years and have noticed the problems reverted back to thier calibration tests. Took along time to figure that out to. I never even figured it would be a consistant flaw.

thanks for the post boomer

MIke

 

[NaH2O]

Thanks Boomer & RH-F. On calibration, I never thought some solutions could be that far off.

 

[cwcross]

I'll go one better here. I suggest not even to use electronic pH meters. They are generally a PITA. To properly care for a pH electrode it needs to be soaked in a strong solution of KCl to keep the electrode in good shape. Furthermore, calibrations should be two point and temperature compensated for accurate work (like two decimals of accuracy). This kind of accuracy is not warranted IMHO in a reef aquarium. This is especially true unless you measure at the same time in your light cycle every time and then log the results. A good pH test kit is generally more reliable unless you want to spend the necessary time to really use your meter correctly. Also it is much easier and less expensive.

Kind of like killing flies with hand grenades....Can be fun, but is it really necessary?

A good use for a pH meter in a reef aquarium is if you want to hook it up to a controller for some reason or another. a pH meter can output an analog signal and can therefore be useful. Also in this case the electrode won't run the risk of drying out as it is continually immersed in saline.

Sincerely...Collin

 

[mattseattle]

ok so you are talking more about those hand held ph meters than the ph monitors? i use an american marine pH monitor on my tank. It's a 2 decimal place monitor. I calibrate it or check the calibration monthly just to make sure it's on. So far after 4 months no change in it.

 

[cwcross]

ok so you are talking more about those hand held ph meters than the ph monitors? i use an american marine pH monitor on my tank. It's a 2 decimal place monitor. I calibrate it or check the calibration monthly just to make sure it's on. So far after 4 months no change in it.

No, just pH meters/monitors in general. Not saying they don't work. I've got them in all my laboratories in skads and we use them all the time. One is really nice and cost about 1500$. It does automatic temperature compensation, automatically calibrates itself, and has several different electrodes. I've got some little ones too that are the size of a pen and will fit in your shirt pocket.

Just not worth the money or time for an aquarium in my opinion. I'd rather spend the money on a nice coral or fish.

Just my preference though. Certainly nothing wrong with using an electronic meter. They are great for what they do. As boomer pointed out though.... Just a lot of problems reported for various reasons by those using them.

Best Regards...Collin

 

[mattseattle]

all good points. your original post mentioned probes drying out so i thought you were referring to the hand held meters more so than monitors. my probe is never out of water unless i'm calibrating it then it's only out for a second or two.

i went through this issue with calibration fluids a few months ago. i bought several different brands and they all had different calibration results. i'm glad that there is now an article out about it.

boomer - sorry about the PM earlier. it was early and i thought the article you posted was one you written but it was one by Randy.

 

[Boomer]

I could talk for hrs about pH meters, "the good the bad and the ugly"
but this as Collin said does it.

A good pH test kit is generally more reliable unless you want to spend the necessary time to really use your meter correctly.

I must say I was actual surprised by these testing out good,especially Hanna, as I don't care much for their stuff.

Pinpoint packets
Hanna bottles and packets

Just to throw in a short note about pH meters, for the heck of it. The higher the chloride concentration, the more wrong the meter is. We call this the "salt effect error". We are lucky the pH levels we see for NSW are uncorrected. The only time we really need the "real" pH is when doing Buch-Park equations. If you look in almost any chemical oceanography text you will see to pH stds, NIST-pH calibration solutions and NSW-pH solutions. We all use NIST, which is uncorrected but the pH values we see, in even in seawater textbooks, are NIST. So in all, it means nothing for us .

 

[NaH2O]

Did you test American Marine pH fluid?

Matt, I'm pretty sure American Marine is Pinpoint. Unless they have a different line of products?

 

[Scooterman]

Clear as Mud!

 

[mattseattle]

Nikki - thanks! Yeah I think you are right.

 

[Boomer]

Matt, I'm pretty sure American Marine is Pinpoint.

Yes, that is corret Nikki

Matt

See my reply at RC

 

[mattseattle]

thanks Boomer.