borate and boron

[Randy Holmes-Farley]

"...When boron is that high, then the borate alkalinity becomes very significant, at 1-2 meq/L, and can readily mislead aquarists interested in carbonate alkalinity." This is a straw man. His other review indicated that, at less than four times the level of natural seawater, we begin to deal with toxicity issues, which presumably render moot the question of boron alkalinity.

:lol:

Well, the straw man is apparently the old Seachem salt mix. Perhaps it predates you, and if true, perhaps ask some of the old timers that work there about it. Leo told us that the high borate was to provide pH stability, and that was more important than any other hypothesized concerns about it, which he claimed were minimal.

In fact, I started my first reef tank with Seachem salt mix more htan 10 years ago. When I saw Leo Morin state on Compuserve's Fishnet the high borate levels and the reason for them, it was the last bucket I ever used.

 

[gmorin]

Ok, I've just been made aware of this thread now and feel compelled to clarify a few things.

1) Our borate kit does not measure total boron, it measures only available borate. It is a pH endpoint titration based procedure... pretty standard stuff, nothing propietary there. I apologize for the confusion George's prior statement added to this whole discussion... I've clarified this with George and it was an unfortunate honest mistake (one of those brain farts we sometimes have, you know, like if you divide by 2 when you meant to multiply by 2 <doh!>). Anyway... it sometimes happens to the best of us.

2) I apologize if George's post came off a bit too strong. He is very passionate about our products and our company - definitely a desirable trait in any employee - but I can see how the tone might have seemed stronger in a text based forum such as this.

3) However, George's contentions were still on point, which is distilled down to this: We are perplexed as to why in the review of the Seachem borate kit you compared the effectiveness of our kit against "hypothetical" values that you calculated from an equation and used that calculated value as the absolute standard of correctness. However in the review of the Salifert kit your comparison there was based solely on actual ICP results of the samples (i.e. real world values). Our contention would be the latter is the more valid way to test... so why was that method not used in the Seachem review (or the calculated method not used in addition in the Salifert review). Two clearly different methods of evaluation begs the question: Why?

Also, I would note above you mentioned a kit should be within 10% of actual values for borate to be useful... however in your Saliftert review you said 30% was plenty good enough... and coincidentally, that is the exact value by which their kit differed from the standard result. That does not beg a question... but it sure seems like an odd coincidence, don't you think?

And lastly, regarding borate ion competition. Come on Randy, do you really think we would be bucking the system and putting borate at levels above NSW in our salt for no reason whatsoever? I mean, if it really did nothing we'd have dropped it out long ago for all the grief you and others have given us for it .

-Greg Morin

 

[Randy Holmes-Farley]

In one case he preordains a result

That's funny. You make it sound like I had no reason to pick that value other than how the Salifert test kit result came out in another review. Why would I prefer the Salifert kit? Kickbacks? Some unstated association with Salifert? Rather a thinly veiled accusation that is utterly baseless. I receive no compensation from any aquarium company aside from the online magazines and forums that I write for.

My reason was stated in the Salifert kit review article:

"In natural seawater, boron is present at about 4.4 ppm total boron. My aquarium, and the Instant Ocean salt mix that I use seem to run significantly higher (6-8 ppm). I donââ"šÂ¬Ã¢"žÂ¢t consider that difference to be important, or at least not requiring any action on my part. I would only recommend folks do anything about boron if it were very low (less than about 3 ppm where you loose any buffering that the borate provides) and higher than about 15 ppm, where it can begin to cloud the interpretation of total alkalinity tests and approach the point where it can become toxic.

So that is the standard that Iââ"šÂ¬Ã¢"žÂ¢m setting for evaluating the usefulness of this test kit. While great precision and accuracy are desirable attributes of any test kit, it is not especially important in a boron test kit (relative to, say, a calcium kit where an uncertainty of 33% might be a critical problem)."

http://www.advancedaquarist.com/issues/sept2003/chem.htm

folks can agree or disagree as they wish. The reasoning is there for all to see.

George: DO YOU DISAGREE?

Or do you just want to plant the idea that I had some benefit from promoting your competitors kit?

Did I use a different standard for the Seachem kit?

The Seachem kit provided grossly inaccurate borate alkalinity, by a factor of 2-8 or so. That seems a larger error than the Salifert kit. Maybe if you had called it a total boron kit, it would have gotten exactly the same marginal blessing as the Salifert kit:

"The Salifert boron kit does an acceptable job of determine whether aquarists are at risk, especially on the high side. Consequently, Iââ"šÂ¬Ã¢"žÂ¢d recommend it for aquarists that are using Seachem salt mix, have used it in the past, have otherwise used additives containing boron, or who just want to be sure that they do not have a problem. "

The biggest criticism of the Seachem borate alkalinity kit is that it guided folks to get carbonate alkalinity by subtracting the borate alkalinity from the total alkalinity. That led to serious errors, IMO. The Salifert kit gave no such guidance, and so folks only had some uncertainty in the total boron level. They do not need to know that precisely, IMO. They do need to know carbonate alkalinity accurately and precisely, if they are going to use it.

 

[Randy Holmes-Farley]

Greg:

I think I have addressed all the points that you brought up except the new assertion that it is not a total boron kit.

So to be sure before I spend a lot of time thinking and writing about it, you are claiming that it should be reporting borate alkalinity, and not total boron?

So the same natural seawater sample acidified with HCl from pH 8.2 to pH 7.2 will give a far lower answer?

 

[boxfishpooalot]

<a href=showthread.php?s=&postid=6644368#post6644368 target=_blank>Originally posted</a> by Randy Holmes-Farley


before I blast back

I will come back with an approriate response in due time.

I too wish to know what part of Boron this kit measures. I use it, but have the same concerns as Randy. Total or not...

 

[Randy Holmes-Farley]

Before I go into another discussion that looks at the exact values that I got with the Seachem borate alkalinity kit vs what I believe they should have been, let me ask a simple question:

George or Greg, have you ever experimentally validated that your kit accurately measures borate alkalinity in seawater? If so, how did you do it? I can't think of any way except essentially what I did, but I would be thrilled to hear about results doing some other type of validation.

 

[Randy Holmes-Farley]

So since I have established (I believe) that George's concerns about salinity and temperature confounding my analysis of the Seachem borate alkalinity are unfounded, let's see how it performed relative to what it claims and recommends for aquarists. I'll do the same for the Salifert kit,and folks can determine for themselves if my conclusions were as biased as George claims.


In my review of the Seachem borate alkalinity kit, I tested 4 samples. All had salinity of approximately 35 ppt. Fresh Instant Ocean, my aquarium water, and Instant Ocean spiked with a known amount of borax.

The samples had, by my independent measure of boron and calculation of borate alkalinity using known, accepted parameters for the boric acid pKa:


Tank water....0.18 meq/L
Instant Ocean...0.18 meq/L
Spiked Instant Ocean....4.2 meq/L


What did the kit report?

Tank water....0.4-0.8 meq/L
Instant Ocean...0.6-1.5 meq/L
Spiked Instant Ocean....3.5 meq/L

Those borate alkalinity values are:

Tank water....2.2 to 4.4 times higher than actual
Instant Ocean...3.3 to 8.3 times higher than actual
Spiked Instant Ocean.... 0.8 times the actual value


The error seems rather substantial there. More than I thought was useful for aquarists. In fact, misleading.

The kit directions then state that aquarists should

"Instructions - Carbonate Alkalinity

1. Subtract the borate alkalinity result from the total alkalinity result. This is the carbonate alkalinity."

OK, so for the first two, I tested total alkalinity, both with my own high precision titration, and also with the Seachem total alkalinity part of that same kit. They gave essentially the same answers (showing the Seachem results):

Tank water....2.4 meq/L total alkalinity
Instant Ocean...3.9 meq/L total alkalinity

And so doing the suggested subtraction gives:

Tank water....1.6 - 2.0 meq/L carbonate alkalinity
Instant Ocean...2.4-3.3 meq/L carbonate alkalinity

What is the "real" carbonate alkalinity for these samples? Doing the same subtraction using my determination of borate alkalinity and my determination for total alkalinity:

Tank water....2.0 meq/L carbonate alkalinity
Instant Ocean...3.8 meq/L carbonate alkalinity

While the value is close for the tank water, it is not close enough to be useful for the IO sample. It is farther off for that sample than assuming there is no borate alkalinity.

In fact, the only reason it is close for the tank water is that there is so little borate alkalinity that being off by a factor of 2 to 4 for the borate alkalinity does not make much difference. Ignoring the borate alkalinity entirely (simply assuming it is zero) gives an equally accurate value (2.4 meq/L).


Based on the errors of a factor of 0.8 to 8 fold in the reported borate alkalinity, I concluded in the review that

"The Seachem borate alkalinity kit attempts to perform a very difficult task: that of determining the borate alkalinity of marine aquarium samples in the presence of a background of bicarbonate and carbonate alkalinity. Unfortunately, in my hands it falls short of providing accurate and useful values to aquarists. "



IMO, that is still a reasonable conclusion, and I stand by it.

I will go over what I found and concluded about the Salifert total boron test in a subsequent post for folks to decide if the results seem biased.

 

[gmorin]

So the same natural seawater sample acidified with HCl from pH 8.2 to pH 7.2 will give a far lower answer?

Yes, the available borate will be lower at 7.2 than at 8.2, so the answer will likewise be lower.

 

[Randy Holmes-Farley]

OK, thanks. I assumed that in my recent posts.

Now here's a discussion of my data and conclusions on the Salifert kit that you feel was biased.

The Salifert Boron Test Kit
http://www.advancedaquarist.com/issues/sept2003/chem.htm


Like was done for the Seachem borate alkalinity kit, I tested my reef aquarium water and fresh IO, both at 35 ppt salinity, and an IO sample spiked with extra borate.
In addition, I tested some diluted samples to see if the kit worked at lower salinity and lower boron levels.

The samples were determined by me using ICP to contain:


Tank Water ...................................................5.5 ââ"šÂ¬Ã¢â‚¬Å“ 6.5 ppm
Tank Water diluted 50% with RO/DI water .....2.3 ââ"šÂ¬Ã¢â‚¬Å“ 3.3 ppm(calculated)
Instant Ocean..................................................7 ââ"šÂ¬Ã¢â‚¬Å“ 8 ppm
Instant Ocean Diluted 50% with RO/DI water...3.5 ââ"šÂ¬Ã¢â‚¬Å“ 4 ppm (calculated)
Instant OceanSpiked with Borax (pH = 8.42).....95 ââ"šÂ¬Ã¢â‚¬Å“ 105 ppm

I then used the Salifert kit without any of the pH corrections that it suggests,and found:

Tank Water .................................................4.5 ââ"šÂ¬Ã¢â‚¬Å“ 5 ppm
Tank Water diluted 50% with RO/DI water ....2 ââ"šÂ¬Ã¢â‚¬Å“ 3 ppm
Instant Ocean(pH = 7.93)..............................5 ââ"šÂ¬Ã¢â‚¬Å“ 5.5ppm
Instant OceanDiluted 50% with RO/DI water...2 ââ"šÂ¬Ã¢â‚¬Å“ 2.5 ppm
Instant OceanSpiked with Borax ....................95 ââ"šÂ¬Ã¢â‚¬Å“ 105 ppm

When I did their pH correction, the results did not appreciably change.

How good are they? The ratios of the midpoints of the ranges found were

Tank Water .................................................0.8x
Tank Water diluted 50% with RO/DI water ....0.9x
Instant Ocean(pH = 7.93).............................0.7x
Instant OceanDiluted 50% with RO/DI water...0.6x
Instant OceanSpiked with Borax ....................0.96x

None of these samples were off by as much as a factor of 2. All were closer than the Seachem borate alkalinity kit (in which each sample was off by several fold), although they are reporting something different from each other.

Is it perfect? No. I said in my review:

"The ability of this kit to accurately measure boron is not perfect, as can be seen from the data. Some samples were off by as much as 30%. "

My final summarizing conclusion was:

"Boron is an element that is not typically high on the list of maintenance requirements for most reefkeepers, and with good reason. Nevertheless, it is something that can be a concern if it is either too high, risking toxicity, or too low, creating larger pH swings than necessary. The Salifert boron kit does an acceptable job of determine whether aquarists are at risk, especially on the high side. "

IMO, that conclusion is justified by the data,and I reject the assertion that I was biased toward this kit over the Seachem borate alkalinity kit.