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Can test kit results be trusted when on PPS Pro?

4K views 5 replies 5 participants last post by  ray-the-pilot 
#1 ·
Hi all,

I've been running with PPS Pro for a couple months now. When running PPS Pro, can the results from a Nitrate and Phosphate test kit be trusted? I'm using API test kits and the results seem off.

Thanks,
-Dave
 
#2 ·
How old are the test kits? They might be old if they are not giving any good results. Chemical degradation these days.. :p
 
#5 ·
API test kits can yield results all over the scale from kit to kit. Many will only register in a narrow band. You must calibrate them to know where your real values are being indicated by which color.
The kit may be new to you but who knows how long and under what conditions it sat on a shelf some where.
 
#6 ·
I too have found that kit results vary from lot to lot. The problem is that the color that develops is not consistent, while the color scale is always the same. The result is that same sample will read higher or lower than the correct value.
You can work around this by always running three samples. The first is a blank which is just distilled water. The second is a reference sample that you make up to your target concentration. The third is your sample. Run all three together. Then compare them to the color chart.
It is easy to tell if your sample is darker or lighter than your reference. This will immediately tell you which way you may want to go. Here is how to estimate the concentration of your sample.
Compare the reference sample to the color chart. If the color chart indicates 25 ppm and your reference is actually 15 ppm then your correction factor is 15/25.
Then compare your tank sample to the color chart. If it reads 15 ppm then the corrected value is:

15 ppm x 15/25 = 9 ppm

Obviously doing three samples instead of one will use up your reagents faster but your results will be more reliable.
 
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