Errors Testing PO4 and Nitrate with RSPro

[Ghxst]

When testing NO3 the results are clear with a metal grey residue, when mixed it separates and clumps back. See pic

The PO4 appears to work and says I have 0.01. Would you agree with the That from the pic?


What can cause the metal grey, does it mean I have no nitrates, too high or just a bad test?

 

[2una]

I use the same kit & never seen that before - if i'm measuring my denitrator output that is also zero & don't do that.
Po4 looks about right but hard call working off a photo

 

[Ghxst]

Thank you ! Good to know it’s not normal.

The grey was also fizzing.

 

[XNavyDiver]

When testing NO3 the results are clear with a metal grey residue, when mixed it separates and clumps back. See pic

The PO4 appears to work and says I have 0.01. Would you agree with the That from the pic?


What can cause the metal grey, does it mean I have no nitrates, too high or just a bad test?

I get that same grey metal looking specks with the RSPro NO3 test. I have no idea what they are.

 

[Ghxst]

I get that same grey metal looking specks with the RSPro NO3 test. I have no idea what they are.

Does it do it even with a positive nitrate amount and color change?

 

[Lasse]

I have seen that too - both in coloured samples (nitrate) and not coloured (no nitrate). It comes and goes - even with the same batch of test

Sincerely Lasse

 

[dragon99]

Does it do it even with a positive nitrate amount and color change?

I get that also, it's from the step b powder.

Do you have anything kit to verify zero nitrates? Or a LFS to check it maybe

 

[XNavyDiver]

Does it do it even with a positive nitrate amount and color change?

Yes, maybe Randy has an answer for this?

 

[2una]

You guys seeing this in the older greyish colour box or the newer more black colour box?
I'm black box (algae control pro which has both No3 + Po4) - never seen that happening

 

[XNavyDiver]

You guys seeing this in the older greyish colour box or the newer more black colour box?
I'm black box (algae control pro which has both No3 + Po4) - never seen that happening

Black box.

 

[Ghxst]

Mines brand new.

 

[roberthu526]

I get the same residue when testing for nitrate. It dissolves after adding C if you have nitrate in the water. If you truely don’t have nitrate you will see this residue sitting there after 9 minutes.

 

[roberthu526]

What I have noticed is B dissolves in test water and releases a lot of bubble. The residue forms after adding C and it releases bubble again which makes the water cloudy. I think this is why Red Sea says wait for 9 minutes then swirl again then read the result so the color is not impacted by the bubbles.

 

[Ghxst]

Thanks everyone for the heads up and tips. I tried again and it did the same thing. I also have the 2 set kit in a black box. I tried with the lights out and on all day to see if something was using the NO3 and still clear with grey chunks. When I test again I’ll wait 9 extra mins but my instructions say the color is only stable 5 mins after the wait time.

 

[Ghxst]

I get that also, it's from the step b powder.


Do you have anything kit to verify zero nitrates? Or a LFS to check it maybe

I can bring it to a lab for ICP and field testing using a hach. I’ll test simultaneously to verify

 

[2una]

When I test again I’ll wait 9 extra mins but my instructions say the color is only stable 5 mins after the wait time.

Just checking

16ml water x 2
5 drop "A" - shake 15 sec
1 spoon "B" - shake 60 sec
1 spoon "C" - shake 15 sec
Wait 9min for reaction to do its thing.
Shake again - take reading

 

[Luno]

Just checking

16ml water x 2
5 drop "A" - shake 15 sec
1 spoon "B" - shake 60 sec
1 spoon "C" - shake 15 sec
Wait 9min for reaction to do its thing.
Shake again - take reading

That's correct also try shaking immediately like immediately immediately after using B and C. I've noticed if i put the spoon in cap and shake immediately the particles are less to none. If I let it sit for say 15 seconds while I put the cap on the powder bottle than put that cap on the vial and shake it it leaves more residue

 

[Randy Holmes-Farley Verified Community Expert]

I'm not sure exactly which method Red Sea uses, or what might cause this, but many kits use a cadmium metal (a grey metal) reduction method, and Hach says:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjrlbvLmc3XAhUM54MKHccnAfEQFggyMAI&url=https://www.hach.com/asset-get.download.jsa?id=7639983736&usg=AOvVaw1bU9pEKOoqloCwjXBB1SCj

"
The reagents that are used in this test contain cadmium. Rinse the sample cell immediately after use to remove all cadmium
particles. Collect the reacted samples for proper disposal.

A deposit of unoxidized metal will remain at the bottom of the sample cell after the reagent dissolves. The deposit will not
affect results."

 

[Ghxst]

Thanks Dr.! Exactly what I couldn’t find. I’ll use a magnetic stirer next time incase it’s an issue. I really wish the test kits had an option for weighing the regents too.

 

[Hans-Werner]

If Red Sea still uses cadmium for reduction of nitrate this has to be stated on the package. If there is no warning on the package they likely use zinc for nitrate reduction and it is zinc that forms the particles.