CYA Reading after using R-7065 50ppm sample

[JoyfulNoise]

Well, I will say this - If you are reading 40ppm with a 50ppm standard, then technically speaking you're within the margin of error for the test as the testing tolerance is +/-10ppm (unless taylortechnologies says otherwise). The R-0013 reagent is basically 0.1-5% melamine in a low pH (5.8) buffered water solution. The low pH is necessary in order to force all of the cyanurate anions to be cyanuric acid since the first acid dissociation constant, pK_a1 = 6.8. So the only possible compromise of the reagent could be if the test water had so much alkalinity in it that the R-0013 could not push the pH below 6.8 as that would interfere with the formation of the melamine-cyanurate acid-adduct (the particulates that cause turbidity). There is plenty of melamine in solution (even at 0.1% the amount of melamine present would 10-20X higher than the amount of CYA found in pool water) to react with the cyanuric acid so small differences in sample water/reagent volume should have no practical effect on the test.

Again, lighting is key and I have to say I have never used the round test vial (#9193) for CYA, I have always used the #9056 or #9058 comparator blocks. The internal cross-section of the #9056/58 comparator is square, not round like the #9193, but I'm not sure that it should matter much as long as the graduation marks on the tube are properly calibrated.

As far as I've experienced, I have always gotten readings consistent with my CYA dosing. I have not tried the R-7065 standard, so I can not comment on that.

 

[Saturn94]

Well, I will say this - If you are reading 40ppm with a 50ppm standard, then technically speaking you're within the margin of error for the test as the testing tolerance is +/-10ppm (unless taylortechnologies says otherwise). The R-0013 reagent is basically 0.1-5% melamine in a low pH (5.8) buffered water solution. The low pH is necessary in order to force all of the cyanurate anions to be cyanuric acid since the first acid dissociation constant, pK_a1 = 6.8. So the only possible compromise of the reagent could be if the test water had so much alkalinity in it that the R-0013 could not push the pH below 6.8 as that would interfere with the formation of the melamine-cyanurate acid-adduct (the particulates that cause turbidity). There is plenty of melamine in solution (even at 0.1% the amount of melamine present would 10-20X higher than the amount of CYA found in pool water) to react with the cyanuric acid so small differences in sample water/reagent volume should have no practical effect on the test.

Again, lighting is key and I have to say I have never used the round test vial (#9193) for CYA, I have always used the #9056 or #9058 comparator blocks. The internal cross-section of the #9056/58 comparator is square, not round like the #9193, but I'm not sure that it should matter much as long as the graduation marks on the tube are properly calibrated.

As far as I've experienced, I have always gotten readings consistent with my CYA dosing. I have not tried the R-7065 standard, so I can not comment on that.

Would the presence of borates affect the ability of R-0013 to push pH low enough for a proper result?

 

[JoyfulNoise]

Would the presence of borates affect the ability of R-0013 to push pH low enough for a proper result?

No. Borates have very low buffer capacity at low pH. They are strongest when the pH is high and rising.

 

[Saturn94]

No. Borates have very low buffer capacity at low pH. They are strongest when the pH is high and rising.

Thanks.

 

[gemphx]

Well, I just received my new test kit refill, and I ordered the standard. In order to read at 50, I had to stand with my back to the sun, and the turn very slightly so that I wasn't completely with my back to the sun.

 

[Holydoc]

I just wanted to say that I just received the R-7065 sample with results from my test showing 50ppm. I performed this test in the morning, setting the vial on a bar that is waste height, the sun on my back, and the shade from my body on the vial. I did not touch the vial with my hands. I just let it sit on the bar as I added drops while staring at the dot from above. I moved my head back and forth once I thought I could not see the dot to ensure it was obscured. So close to the 50ppm line, I was amazed.

At least I now know my technique is correct. Thanks TFTESTS for the chance to verify our techniques for this very tough test.

 

[jblizzle]

Hmm, so maybe the key is to have the vial sitting on a surface and not holding it in the air.

 

[Marlahoutex]

If it's sitting on a surface then no light is coming in from the bottom. Maybe that's the difference?

 

[JoyfulNoise]

Peehaps it's a good idea to check your tubes. My Taylor comparator has a big white sticker with a black dot on the bottom and the sticker completely covers the bottom of the tube. I imagine the round tubes should be designed the same way. Just do a sanity check and make sure the sticker is in place and covers/fits over the entire bottom of the tube.