Difference In DPD-FAS Reagents and Wildly Different Results

[DBB]

I started the summer off with a new Taylor DPD-FAS test kit (K-2006). As the summer wore on, I started to need refills on some of them, so I oredered Taylor reagents in larger quantities frm Amazon, and refilled the bottles in the kit, as needed.

Prior to refilling the R-0871 chlorine reagent, my FC read 3.6. The next day's test with the new reagent yielded a FC reading of 12.2. My FC readings have been in the high side ever since. B

oth have expiration dates well into 2016 and 2017, and have been stored indoors out of the heat.

What gives? I'm not sure what to think, and have lost confidence in my test results.

-DBB

 

[pabeader]

Do you still have the listing from when you bought the refills? Could you post a pic of the R-0871 bottle?

 

[JoyfulNoise]

One thing I would say is this - it is not typically good practice to refill the dropper bottles from larger refills. In other words, once you finish a 0.75 or 2 oz bottle, it is better to throw the used bottle away and just get a new one. If you want to have ample supplies on hand, Taylor does often sell their 0.75 and 2 oz reagents in 12-packs.

The reason being is that some of the indicator dyes can go bad as well as some of titrants and you really should not mix old chemicals with new ones.

The purpose of some of those really large reagent bottles (like the 16oz bottle of R-0013 reagent or the 1/4lb container of DPD powder) is meant more for commercial testing facilities or pool stores where they might be doing 100+ tests per day.


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[chem geek]

See Recognizing a Compromised Reagent where for the R-0871 it says the following:

R-0871/R-0872 FAS-DPD Titrating Reagent (for chlorine/bromine)

This solution should be colorless. As it degrades, the color will become increasingly yellow.

If the FAS-DPD is exposed to higher temperatures or to sunlight it will degrade more quickly. It should be kept at room temperature and away from sunlight.

 

[DBB]

Understood re: mixing old with new, but both had expiration dates well out into 2016. I only purchased the 2oz bottle as a refill. The K-2006 test kit came with .75oz bottles - I refilled the .75oz bottle because I wanted to keep everything handy in the case, and it was more cost-effective to purchase th 2oz size. A 12 pack would most likely go bad before I could use it all.

DBB

- - - Updated - - -

If the FAS-DPD is exposed to higher temperatures or to sunlight it will degrade more quickly. It should be kept at room temperature and away from sunlight.

Ive kept everything at room temps. The only exceptions would be the temperatures experienced during shipping. Regardless, the new reagent does not appear yellow at all.

DBB

 

[chem geek]

Well, you should contact the vendor where you bought the bad FAS-DPD reagent and either get a replacement or at least let them know it appears they sold a degraded or flawed reagent.

 

[BuckeyeChris]

I bought a 2 oz of the 0871, and I just use that for the test. The drops are, from what I can tell, the same size. I took out the acid demand bottles, moved the ph test into the same column as the FC CC bottles, and just lay the new 2 oz bottle across the top of the second column. The lid will still close.

 

[DBB]

Well, I just did a test, only this time I used the new reagent by itself; in other words, as received from the vendor, without having been mixed with the little bit of R-871 that was left in the original Taylor K-2006 kit. The results were high, comparable with what I got with the mixed.

So, it seems that there are only a couple of conclusions I can draw:

-The new reagent is bad, or was diluted by the vendor, or
-The reagent included with the original Taylor kit was off.

For the record, the expiration date on the .75oz bottle that came in the kit was 8/16, while the 2.0 replacement reagent expires in 7/16.

The replacement reagent was listed on Amazon as R-871-C; I've not seen the "C" designator before, but I assume that just stands for the chlorine test version.

Any other thoughts?

-DBB

 

[JoyfulNoise]

All 2oz reagents are labelled with the "C" designator for "Commercial" since the commercial version of the K-2006 uses all 2oz reagent bottles (and costs a lot more than the residential "A" version of the K-2006)

Which vendor did you get that bottle from on Amazon? Taylor does not sell directly through Amazon, only through 3rd parties. Taylor only sells directly from its website.

It is possible that the vendor did not store the reagent properly. Do you live in a hot area? Did the package sit out in the mailbox too long? Heat is another factor. I typically try to order my reagents only when it's cool out so that shipping temps are not a major issue.


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[DBB]

PST Pool Supplies was the Amazon vendor. And yes, I live in North Central Texas, so you could say it gets hot here... At the time of the order, it was in the high 90s/low 100s, and did sit in the mailbox for a bit, but is this stuff so unstable that a few hours in the heat would be enough to throw it off? As mentioned earlier, it is clear, and hasn't gone yellow at all.

I guess the next thing to try would be to purchase a bottle from Leslie's to compare. But who knows how this stuff is distributed and shipped to the local pool store? I could see it sitting in the sun in a truck at a dock somewhere; I doubt that these get shipped refrigerated, and if these reagents are that sensitive to heat, can any of us rely on our test results...?

I'm confused by your comments, though, that the "C" commercial version is more expensive - the pricing on Amazon was less, which is why I went there to purchase to start with. The larger sized bottles were more cost effective than the .75oz bottles. Leslie's doesn't stock the .75 oz bottles, either. I guess maybe you're talking about the actual full commercial kit?

 

[JoyfulNoise]

Too hot or too cold can be an issue. If you go to the Taylor website, they actually warn against shipping products during freezing conditions which, I think, is worse for the chemicals. But excessive heat can also degrade reagent products as well.

Yes, the "C" designation is for "commercial" and the K-2006-C kit is more expensive than the K-2006-A. Taylor uses several different types of suffices for its reagent bottles. If you go to the Taylor website and look through their Pool/Spa section, you'll see what I mean.


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