Help with CYA and comparing to Standard!

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I just did a test with the solutions that I have and it's right on where 50 ppm is obscured, 60 ppm I can faintly see the black dot, 40 ppm is also obscured, but I have older reagent and standard solution. I was going to post photos, but the 40 ppm doesn't show the black dot well because I didn't get it to focus properly and it has to be focussed well since it's a little subtle (at least enough that it's tough for a camera unless in clear focus). I can't hold it in one hand and both focus and shoot at the same time with the other. I need some sort of clamp (or another person) to hold it in front of me so I can take the picture. I'll see if I can get my wife to hold the tube while I take the pictures.

[EDIT] I've got pictures of the 50 ppm CYA Standard Solution at the 50 ppm mark, the 60 ppm mark, and the 70 ppm mark (I took the pictures in the order 60 then 50 when adding to the tube and then poured back and went to 70, but I show them in the 50,60,70 order below). The photos still don't do justice to how it actually looks from a waist-high distance since the 50 ppm one really isn't visible while the 60 is definitively (if not clearly) showing a black dot. When I looked at 40 ppm it looked the same as 50 so 50 is truly the measurement and matches the standard. [END-EDIT]

50 PPM Standard at 50 PPM line (is it visible? barely, but really? unsure? yes, that's it!):
https://www.troublefreepool.com/~richardfalk/pool/50_PPM_CYA.JPG

50 PPM Standard at 60 PPM line (it is visible, though not strongly so):
https://www.troublefreepool.com/~richardfalk/pool/60_PPM_CYA.JPG

50 PPM Standard at 70 PPM line (it's pretty darn visible):
https://www.troublefreepool.com/~richardfalk/pool/70_PPM_CYA.JPG
 
I just received my CYA standard and a brand-new bottle of CYA reagent, and I too believe the dot is extremely visible at the 50ppm mark. I am certain I used it correctly, filling the test bottle to the bottom of the label with standard, filling to the top of the label with reagent, shaking vigorously for 30 seconds, letting it sit for 30 seconds, and shaking for 10 seconds more before dispensing into the tube. At 50 it's very clear. At 40 it's mostly gone, and at 30 completely gone.
 
So we need to figure out if the standard is wrong or the reagent or if there is something unique about certain pool water that is causing a problem (seems unlikely as we would have heard about this before over the years). For shaking, I just tilt back and forth the entire time during the 30 seconds. I don't do it vigorously though I don't think that matters.
 
Mine looks exactly like the picture in post #11 with the standard reagent purchased about 2 weeks ago from TFtestkits.net. I mix shaking vigorously and gently back and forth during the 30 seconds, then I shake vigorously before pouring into the CYA cylinder.
 
chem geek said:
So we need to figure out if the standard is wrong or the reagent or if there is something unique about certain pool water that is causing a problem (seems unlikely as we would have heard about this before over the years). For shaking, I just tilt back and forth the entire time during the 30 seconds. I don't do it vigorously though I don't think that matters.
Click to expand...
Wow! Mine definitely does not look like that! Could it possibly be the tube?

also... Why would the pool water affect anything? It's the standard that I'm having trouble with.
 
ned8377 said:
I would have to agree with the above. I ordered the Taylor test kit to compare with the TFTest Kit. Taylor shows my CYA to be higher than TFTest Kit.

So, I tried an experiment. When I used the TFTest Kit reagent with the Taylor comparitor I could see the dot all the way up - much further than when using the Taylor reagent. Also, test strips show CYA to be higher at 30-50. Why, when using Taylor reagent, does Taylor show CYA at about 35 and TFTest Kit, when using TFTest Kit reagent, shows it about 22 before you can't see the dot. Then when I substitute the TFTest Kit reagent and use it with the Taylor comparitor it shows about 22 before I can't see the dot. So, what I am saying is that there is a difference in the reagents. I'm not saying one is right or accurate and the other one is wrong, just that there is a difference. Something else, though, the strips show the CYA to be 30-50. It makes me wonder that the true CYA must be above 30.
Click to expand...

Could someone duplicate what I did above and compare the Taylor Reagent to the TFTest Kit Reagent? In my experiment the Taylor Reagent was closer to what the strips were saying. I also switched the reagents between test kits and the Taylor seemed stronger or made the dot disappear quicker on both comparitors.
 
I assume this test works because the reagent causes the sample to become opaque in proportion to the level of CYA present. Roughly correct?

Is anyone aware of an attempt to characterize the opacity using an LED and photo diode? It seems to me this would be relatively easy to implement. I have a small design and engineering firm and I could mock something up, but I don't want to walk a well trod path if I can avoid it.

Are standards other than 50ppm available?
 
So I educated myself a bit on this test. This thread was helpful:

Turbidity measurement (was ) [Archive] - Trouble Free Pool

Last year some folks from Johns Hopkins and Cornell published an open-source, low cost (~$30) turbidity meter that correlates 99.5% to commercial meter readings in our region of interest (100-400 NTU):

http://www.mdpi.com/1424-8220/14/4/7142/pdf

We actually have a ring-based pulse oximeter design that might do this quite well. When we get some downtime we'll do some experimenting.
 
I have a Taylor K-1721 kit I use for testing CYA. I had some Taylor CYA agent left that I bought last season as well as a couple bottles of the TFTestkit CYA reagent that I purchased this spring.

Comparing the two, the TFTestkit version tested a solid 10ppm higher than the Taylor version. Since they are suppose to be the same thing, I don't know why the results were different. Perhaps the age of the reagents was a factor (I thought the CYA reagent should be good for a couple of years; I keep all my test supplies in the house).

Just thought I'd share my experience.
 

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No. We've got 2 or 3 people reporting lower CYA compared to the standard and Dave has been contacting them. It's important not to have the tube lit by direct sunlight, but from the photos it looked like the test was done correctly yet the dot was quite visible. So unless there's a problem with the reagent, the standard, or how they were measured and mixed, we haven't solved this one yet. Dave isn't able to reproduce it and I didn't either though I wasn't using recent standard nor reagent.
 
chem geek said:
So we need to figure out if the standard is wrong or the reagent or if there is something unique about certain pool water that is causing a problem (seems unlikely as we would have heard about this before over the years). For shaking, I just tilt back and forth the entire time during the 30 seconds. I don't do it vigorously though I don't think that matters.
Click to expand...

Richard..in your post with the pictures, you had a phrase waist high. Is that simply where you were holding it it, or is the 'reading' supposed to be taken with the eye some set distance away from the tube? If so, my eyes couldn't see an obscured black dot at far away?
 
You are supposed to hold it away from your face. If you look too close, you will make out the black dot a little better. Also waist high has your body block the sun. The photos in the posts before mine were better at showing where one should hold it and view it.
 
chem geek said:
You are supposed to hold it away from your face. If you look too close, you will make out the black dot a little better. Also waist high has your body block the sun. The photos in the posts before mine were better at showing where one should hold it and view it.
Click to expand...

Ok. Thanks. I typically do my testing sitting on the coping with the vials sitting ther with me, so th distance is about right,
 
chem geek said:
No. We've got 2 or 3 people reporting lower CYA compared to the standard and Dave has been contacting them. It's important not to have the tube lit by direct sunlight, but from the photos it looked like the test was done correctly yet the dot was quite visible. So unless there's a problem with the reagent, the standard, or how they were measured and mixed, we haven't solved this one yet. Dave isn't able to reproduce it and I didn't either though I wasn't using recent standard nor reagent.
Click to expand...

Thanks. I guess I'd better buy the "standard" reagent, for peace of mind, since I don't have a lot of faith in the validity of my current reagent.
 
So one thing that came up in another thread is that it's possible that the use of clarifiers (including Polyquat 60 which is a clarifier) or flocculants might precipitate the CYA in the tube if one lets it settle and that could result in a lower reading. The goal is to create a melamine cyanurate suspension and not have it settle so the cloudiness in the tube should be consistent from top to bottom and not be more dense or precipitated at the bottom.
 
I think it is because the tube is separate, lightweight, and larger. Compare the Taylor K-2006 tube where you look at the hard to read scale on the back side of the left tube vs. the TF-100 tube that is clearly marked, reads down to 20 ppm (the Taylor K-2006 only reads down to 30 ppm) and is more easily handled IMHO. This tube comes from the standalone Taylor K-1720 test kit, but here again the CYA Test from TFTestkits is more economical using that same tube but a lot less expensive for the same volume (8 oz.) of CYA reagent.
 

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