New Regents Reading Much Higher?

[ctrav]

So I ordered new refills for water testing and they are much different. Example: I tested my CH with last years R-0012 and results were 375-400, then I tested with new R-0012 and results were 500-525! I waited 3 days and retested with the exact same results from both R-0012's. Mind you the old R-0012 is a year old...

Any ideas as to what is going on with such different numbers? Should I call Rebecca at TFTestkits?

I don't see the need to drain some of the water since we are starting to get high outside temps (mid to high 90's) so normal evaporation and pool use will take care of it.

Thanks for your thoughts...

 

[JoyfulNoise]

The indicator dyes (R-0008 and R-0011L) are the most susceptible to aging. They will tend to get "clumpy" like curdled milk and stick to the sides of the bottle.

The R-0012 can go bad from oxidation if it is left exposed to air (or you suck lots of air into the bottle....best to apply consistent steady pressure to create a droplet stream so you don't "breath" air into the bottle). However, it's not very susceptible to "aging" effects, ie, it is stable in the bottle.

Honestly, the CH test is a difficult one to get right and people make two classic mistakes - fading endpoint due to metal contamination (solution turns sort-of-blue but goes back to purple) OR they do not let the blue color fully develop and end the test too early. I have found that lighting is key for this test and it's best done when you are in a bright outdoor space. You get the best color development that way. Also, the CH test is not really intended for CH levels above 800ppm. The reason being is that the R-0011L dye is a chelating agent and it captures calcium ions to make the color go from blue to red. If you have too high concentration of calcium ions, you may not have enough dye in the test to fully chelate all the calcium. As well, if the dye concentration is too high, that can cause problems too. Complexometric titrations are very tricky to do right because it's not based on a pH change but a very sensitive competitive reaction between different strength chelation compounds (EDTA/CDTA versus Eriochrome Black) so, if you don't follow the protocol exactly or you are outside the intended ranges, results can vary.

I think your reagents are probably fine if they are only a year old. You just need to practice the test more....

 

[Dirk]

The indicator dyes (R-0008 and R-0011L) are the most susceptible to aging. They will tend to get "clumpy" like curdled milk and stick to the sides of the bottle.

The R-0012 can go bad from oxidation if it is left exposed to air (or you suck lots of air into the bottle....best to apply consistent steady pressure to create a droplet stream so you don't "breath" air into the bottle). However, it's not very susceptible to "aging" effects, ie, it is stable in the bottle.

Honestly, the CH test is a difficult one to get right and people make two classic mistakes - fading endpoint due to metal contamination (solution turns sort-of-blue but goes back to purple) OR they do not let the blue color fully develop and end the test too early. I have found that lighting is key for this test and it's best done when you are in a bright outdoor space. You get the best color development that way. Also, the CH test is not really intended for CH levels above 800ppm. The reason being is that the R-0011L dye is a chelating agent and it captures calcium ions to make the color go from blue to red. If you have too high concentration of calcium ions, you may not have enough dye in the test to fully chelate all the calcium. As well, if the dye concentration is too high, that can cause problems too. Complexometric titrations are very tricky to do right because it's not based on a pH change but a very sensitive competitive reaction between different strength chelation compounds (EDTA/CDTA versus Eriochrome Black) so, if you don't follow the protocol exactly or you are outside the intended ranges, results can vary.

I think your reagents are probably fine if they are only a year old. You just need to practice the test more....

Matt, not sure this is hijacking or not, may apply to OP's issues. The CH test is my second most challenging one (CYA! Booo!!!). It's not always clear to me when CH test is over, and the blue seems to develop over time. Am I imagining that? It's as if I put in enough drops to get past purple, so it looks blue, but if I let it sit for a bit, it gets even bluer? Which then makes me doubt the number of drops, like maybe a drop or two back, if I had waited, would have eventually gone from purple to blue. Is there a length of time between drops that you can recommend, so that you can better determine when the blue fully develops?

 

[JoyfulNoise]

It’s best if the drops are added as a continuos drip, about one drop per second or two. This is why having the SpeedStir makes a huge difference - it lets you go hands free so you can more easily count drops.

You want to count until the blue stops changing, that’s the end-point. It doesn’t matter what the solution does after that point. If you want a “crisper” end point and you “sort of” know what your CH is, then you can use the fading-endpoint protocol to help. Let’s say you know your CH is going to be around 400ppm and you’re using a 10mL sample volume (25ppm/drop). So your transition will likely occur at drop #16. Before adding the R-0010, you add 8 drops of R-0012, then you add the 10 drop of R-0010, then 3 drops of R-0011L, then you start counting drops. When the blue color stops changing at drop #7 you then record the total drop count as 15 drops and your CH is 375ppm. When you do it that way, you are more likely to see a sharper endpoint in the test.

 

[jimim]

The indicator dyes (R-0008 and R-0011L) are the most susceptible to aging. They will tend to get "clumpy" like curdled milk and stick to the sides of the bottle.

The R-0012 can go bad from oxidation if it is left exposed to air (or you suck lots of air into the bottle....best to apply consistent steady pressure to create a droplet stream so you don't "breath" air into the bottle). However, it's not very susceptible to "aging" effects, ie, it is stable in the bottle.

Honestly, the CH test is a difficult one to get right and people make two classic mistakes - fading endpoint due to metal contamination (solution turns sort-of-blue but goes back to purple) OR they do not let the blue color fully develop and end the test too early. I have found that lighting is key for this test and it's best done when you are in a bright outdoor space. You get the best color development that way. Also, the CH test is not really intended for CH levels above 800ppm. The reason being is that the R-0011L dye is a chelating agent and it captures calcium ions to make the color go from blue to red. If you have too high concentration of calcium ions, you may not have enough dye in the test to fully chelate all the calcium. As well, if the dye concentration is too high, that can cause problems too. Complexometric titrations are very tricky to do right because it's not based on a pH change but a very sensitive competitive reaction between different strength chelation compounds (EDTA/CDTA versus Eriochrome Black) so, if you don't follow the protocol exactly or you are outside the intended ranges, results can vary.

I think your reagents are probably fine if they are only a year old. You just need to practice the test more....

thst is what I noticed also woth this test. U got to give each drop time so u see the change and not add extra drops. It’s not an instant change and the lighting is so important.

- - - Updated - - -

It’s best if the drops are added as a continuos drip, about one drop per second or two. This is why having the SpeedStir makes a huge difference - it lets you go hands free so you can more easily count drops.

You want to count until the blue stops changing, that’s the end-point. It doesn’t matter what the solution does after that point. If you want a “crisper” end point and you “sort of” know what your CH is, then you can use the fading-endpoint protocol to help. Let’s say you know your CH is going to be around 400ppm and you’re using a 10mL sample volume (25ppm/drop). So your transition will likely occur at drop #16. Before adding the R-0010, you add 8 drops of R-0012, then you add the 10 drop of R-0010, then 3 drops of R-0011L, then you start counting drops. When the blue color stops changing at drop #7 you then record the total drop count as 15 drops and your CH is 375ppm. When you do it that way, you are more likely to see a sharper endpoint in the test.

ok thats new new to me. So is it better to do it that way?

 

[JoyfulNoise]

thst is what I noticed also woth this test. U got to give each drop time so u see the change and not add extra drops. It’s not an instant change and the lighting is so important.

- - - Updated - - -



ok thats new new to me. So is it better to do it that way?

The best way to do it is the way that works best for you and gives you consistent results. Using a steady stream of drops with a SpeedStir tends to mix in the reagents fastest and the color should develop/change quickly enough between droplets.

 

[jimim]

I just did the test that way. I got the same number. 325 for my ch. last time I tested last week I got 350. I don’t get the chrisper part. It just changed with less drops this time the change still looks the same to me. A slight fade from pinkish to blue.

- - - Updated - - -

The best way to do it is the way that works best for you and gives you consistent results. Using a steady stream of drops with a SpeedStir tends to mix in the reagents fastest and the color should develop/change quickly enough between droplets.

ues I use the speed stirrer. I personally have no idea how I would do these tests without it.

 

[JoyfulNoise]

I just did the test that way. I got the same number. 325 for my ch. last time I tested last week I got 350. I don’t get the chrisper part. It just changed with less drops this time the change still looks the same to me. A slight fade from pinkish to blue.

- - - Updated - - -



ues I use the speed stirrer. I personally have no idea how I would do these tests without it.

If both test methods work, then use the method that’s easiest for you. A one drop difference in the test is insignificant, the results are essentially the same.

 

[ctrav]

Thanks Matt...I just found it odd as I did not have an issue until the new order. Since I am out of the old I will go with the new numbers after 2-3 more tests with new one!

 

[Dirk]

It’s best if the drops are added as a continuos drip, about one drop per second or two. This is why having the SpeedStir makes a huge difference - it lets you go hands free so you can more easily count drops.

You want to count until the blue stops changing, that’s the end-point. It doesn’t matter what the solution does after that point. If you want a “crisper” end point and you “sort of” know what your CH is, then you can use the fading-endpoint protocol to help. Let’s say you know your CH is going to be around 400ppm and you’re using a 10mL sample volume (25ppm/drop). So your transition will likely occur at drop #16. Before adding the R-0010, you add 8 drops of R-0012, then you add the 10 drop of R-0010, then 3 drops of R-0011L, then you start counting drops. When the blue color stops changing at drop #7 you then record the total drop count as 15 drops and your CH is 375ppm. When you do it that way, you are more likely to see a sharper endpoint in the test.

Thanks, Matt. I'll give that a try.