Upcoming article: DIY pH buffers

[Randy Holmes-Farley]

Sounds good! I haven’t had a chance to work on this yet as I don’t have an ro/di yet. :)

 

[Miami Reef]

Sounds good! I haven’t had a chance to work on this yet as I don’t have an ro/di yet. :)

What do you mean by “work on this?”

I thought we had all the instructions in this thread.

Are you planning on finding the exact amounts required to make the stock solutions?

 

[Randy Holmes-Farley]

What do you mean by “work on this?”

I thought we had all the instructions in this thread.

Are you planning on finding the exact amounts required to make the stock solutions?

Was mostly going to do what you did and keep track of amounts, etc. Nothing wrong with what you did. :)

 

[Miami Reef]

Was mostly going to do what you did and keep track of amounts, etc. Nothing wrong with what you did. :)

I needed about 60g. I want to try it again, but I want to make a carbonate solution to add instead of dry solids.

 

[Miami Reef]

@Randy Holmes-Farley

Would you have added dry solids or used a carbonate solution if you made it yourself?

 

[Randy Holmes-Farley]

@Randy Holmes-Farley

Would you have added dry solids or used a carbonate solution if you made it yourself?

I think I’d be inclined to add a solution, but either way works. :)

 

[Miami Reef]

What strength would you make the carbonate solution?

0.2M as well? Higher?

I want to remake it tonight for fun.

 

[Rollnwthdatide]

I think I like the old-fashioned science better.

Using the RpB Method has two downfalls, in my current opinion:

1) It requires buying 7 & 10 solutions, which is a catch-22.

2) It involves trusting those pH packets and their companies. It would be ironic if you made new standards with a solution you don’t trust; if the initial standard isn’t trustworthy, future standards with that calibrated probe would also be untrustworthy.

Why wouldn't you trust the companies as they have robust quality control methods that easily test and confirm their lots. It's not hard make consistent pH buffers at scale.

 

[Randy Holmes-Farley]

What strength would you make the carbonate solution?

0.2M as well? Higher?

I want to remake it tonight for fun.

The concentration is not really important. Higher gives better buffering and stability, and for our purposes where we measure pH at high ionic strength, it has no real downside to be high. 0.2 M is good. If we were measuring pH in very dilute solutions, lower may be better because there are salinity complications in both calibrating and measuring pH. It’s another case of looking too deeply shows up complications that are usually brushed aside.

 

[Miami Reef]

Why wouldn't you trust the companies as they have robust quality control methods that easily test and confirm their lots. It's not hard make consistent pH buffers at scale.

A Comparison of pH Calibration Buffers by Randy Holmes-Farley - Reefkeeping.com

FWIW, I showed in this article a while back (20 years) that some commercial buffers that i bought online and from an lfs were seriously off. Best to use reliable brands for pH calibration.

One pH 10 was only 9.01, and some pH 7 were in the pH 7.5 range. One pH 4 buffer was pH 6.1.

My opinion of RpB has changed once I’ve learned its usefulness and limitations.

You can’t make new standards out of air, which was my initial expectation. I didn’t want to trust any hobby-grade company. I wanted to cut the middleman out.


However, you CAN create decent duplicates of a good quality standard to save money. That seems useful to me.

I don’t buy low-quality pH standards. In fact, the article listed above is how I chose the standards I use today.

 

[Rollnwthdatide]

Are pH buffers that expensive to even waste time making your own? Imo, no. I bought some bottles off Amazon for $22 that will last me a until their expiration date(contain 4, 7 and 10 solutions). It's all lot controlled and tested with all documentation for it according to NIST standards. I compare my results to the COA that's supplied and also test it with another pH probe i use when making nutrient solutions for plants. Works great.

 

[gbroadbridge]

Devils advocate.

I think I paid $40 for a Hanna set of 3 x 250ml (4.01, 7.01, and 10.01) buffers which would be strongly buffered and certainly will last a couple of years once opened if tightly closed and stored in the cellar.

Seems like a lot of work to DIY, and you need the reference buffers anyway.

 

[Randy Holmes-Farley]

Are pH buffers that expensive to even waste time making your own? Imo, no. I bought some bottles off Amazon for $22 that will last me a until their expiration date(contain 4, 7 and 10 solutions). It's all lot controlled and tested with all documentation for it according to NIST standards. I compare my results to the COA that's supplied and also test it with another pH probe i use when making nutrient solutions for plants. Works great.

Try reading my tests and see how many were inaccurate.

 

[Rollnwthdatide]

Try reading my tests and see how many were inaccurate.

I did. But you didn't list brands to stay away from, which would be useful for people that want to avoid them and if someone wished to try and reproduce your results they'd know what to test.

I've worked as a QC scientist in the medical industry before so that's why I always go for companies that follow NIST standards and protocols in addition to providing a COA for all reagents.

 

[Randy Holmes-Farley]

I did. But you didn't list brands to stay away from, which would be useful for people that want to avoid them and if someone wished to try and reproduce your results they'd know what to test.

I've worked as a QC scientist in the medical industry before so that's why I always go for companies that follow NIST standards and protocols in addition to providing a COA for all reagents.

The fact that bad ones exist makes the effort potentially worthwhile from a cost perspective, by buying a quality product once and reproducing it yourself, and not having to rely on the cheapest standards from Amazon which might be of uncertain accuracy or shelf life. :)

 

[Freenow54]

pH buffers are very simple to make, and are surprisingly expensive to buy. For that reason, I thought DIY pH buffers would be a good article in the future. Easy to make, last a good while in a cheap closed soda bottle, and one can easily make a lot at once.

What I don't know is what pH values people really need these days. Obviously we want to bracket the pH in reef tank, with something like 7 and 10.

Many pH meters allow you to use most any pH values you want to calibrate, and can use more than 2 buffers.

But the simpler devices are usually only 2 (just one is a bad idea), and often they are fixed.

So what fixed values do people need?

One reason I'm asking is that a surprisingly large numbers of inexpensive buffer packet sets are 4, 7, and 9.18. I've never personally used a meter that needed pH 9.18, but they may exist.

Are there common reefing pH meters that need pH 9.18 for calibration? If so, its easy to make. if not, I won't bother since some do require pH 10.

TIA.

Sorry to ask this but need to know/. What does your bulkhead fitting wrench look like?

 

[Rollnwthdatide]

The fact that bad ones exist makes the effort potentially worthwhile from a cost perspective, by buying a quality product once and reproducing it yourself, and not having to rely on the cheapest standards from Amazon which might be of uncertain accuracy or shelf life. :)

That's why I check my standards with two other probes and two different sets of pH buffers (easy to take an aliquot to the lab to test) and then compare to the CoA before they're put in use in addition to doing periodic checks every 6months. I may be a bit out of the norm just because I use pH measurements for more than just my reefing and need to ensure I have accurate readings

Posting the companies would help though. No sense in making hobbyists find out for themselves.

 

[Miami Reef]

Posting the companies would help though. No sense in making hobbyists find out for themselves.

Maybe the companies would come after him? I’ve always wondered which were the bad companies and why they were anonymous.

I have chosen not to name two brands that I deemed not suitably accurate for use as a standard. One of these was grossly inaccurate, and could lead to serious problems if its buffers were used to determine and subsequently "correct" the pH in a reef aquarium (or in a CaCO3/CO2 reactor).

 

[Randy Holmes-Farley]

The studies were done too long ago to have much bearing on today’s likely suppliers. It’s just an indication of likely possible issues.

 

[Miami Reef]

The studies were done too long ago to have much bearing on today’s likely suppliers. It’s just an indication of likely possible issues.

I understand the study is old and likely irrelevant for many of the brands; time has changed.

I’m just curious why they were left out at the time of publication. Did they leave threats like (Seachem?) did to you?