Does the FAS DPD Titrating reagent go stale?

[squibcakes]

I found my latest FC levels have jumped from 12 to 20 just by using a new bottle of Titrating reagent.

I know the instructions say to put lid cap back on to stop reagent going bad, but does the air in the bottle cause it to degrade over time - and if so does it cause the FC reading to be a lot lower (few drops required)?

What about the detection powder? I notice it gets a bit more grainy over time but it does dissolve okay.

Cheers

 

[YippeeSkippy]

The reagent should last about 18 months I believe? Does it have an expiration date on the bottle?

The powder does get darker and more grainy with moisture, but works just find. You can crush it up a bit in a mortar if you want.

Maddie

 

[squibcakes]

Hi Maddie,

I would have to check the bottle at home, but I'm sure it doesn't have expiry. Some of the other bottles do though. Any idea how an expired reagent would effect the test? (not sure how old mine was)

 

[duraleigh]

Note: This post appears to reference CCL's product in Australia......not the TFTestkits TF-100 or Taylor FAS/DPD......Is that correct, squibcakes?

 

[BrettClearChoiceLabs]

Most of the time an expired reagent should be weaker, so more drops are needed to make the reaction occur. Chemists feel free to correct me please.
With our DPD powder it turns grey after a while, and in water it then makes the water purple/grey or just cloudy. Up until that point though, you can just crush it up a bit like Maddie says.
We don't put expiry dates on our reagents as we're moving to "prepared on" dates, and so people can work out how long a reagent lasts for them. 12 months stored well is a good guide though.

As for air in the bottle, at a guess I'd say it would reduce the reagent over time but the impact should be pretty small?

 

[santacruzpool]

I mistakenly bought 2 sets of the DPD Powder and R-0871 back in spring/summer 2015 when we built our pool.

Come 2017 I started to really struggle with the test - the powder had turned dark grey and clumped up. Despite regrinding it at one point the test was very hard to see the end point.

When I purchased new DPD powder and R-0871 and it was like night and day - It was like comparing HDTV vs an old grainy video - it was easily an order of magnitude easier to do the test!

I plan to stick with fresh chemicals and hopefully won't see the same problems again - I think that it just degrades so slowly that you sort of forget how it was supposed to work.

 

[squibcakes]

Yes it’s the CCL kit not TF kit.

i also found with the powder the solution change at end of test is a bit blurred, or grey as you say but I think it gets me in the ball park.

ill try crushing the powder up too as it the bigger grains may not fill the spoon up properly and effect the test.