Phosphate mismath between Hanna Phosphate ULR and ICP test - old cuvettes?

[Neko]

Same water sample, but I got Phosphate mismatch between Hanna Phosphate ULR and ICP test.

ICP test result is 0.03
Hanna Phosphate ULR result is 0.08

(1) In order to see where the difference come from, today I tested with brand new cuvettes, and compared with the test I'm doing with old cuvettes. The new cuvettes shows 0.12. The old cuvettes shows 0.25. This is huge difference!

(2) I also checked the history (ICP test vs. Hanna Phosphate ULR).

ICP test Hanna checker
8-28-2023 0.03 0.08
4-19-2023 0.01 0.02
1-19-2023 0.02 0.01

In above results, I understand it's time to replace cuvettes to get accurate number. Old cuvettes shows higher number than actual. In my eyes, it does not tell difference between old cuvettes and new cuvettes. Both looks similar (I know my cuvettes for alkalinity test is blue tinted).

Any experience sharing would be helpful.

 

[Propane]

I was concerned about this so I immediately rinse mine and store them with rodi. Can you buy just the cuvettes?

 

[ryshark]

Same water sample, but I got Phosphate mismatch between Hanna Phosphate ULR and ICP test.

ICP test result is 0.03
Hanna Phosphate ULR result is 0.08

(1) In order to see where the difference come from, today I tested with brand new cuvettes, and compared with the test I'm doing with old cuvettes. The new cuvettes shows 0.12. The old cuvettes shows 0.25. This is huge difference!

(2) I also checked the history (ICP test vs. Hanna Phosphate ULR).

ICP test Hanna checker
8-28-2023 0.03 0.08
4-19-2023 0.01 0.02
1-19-2023 0.02 0.01

In above results, I understand it's time to replace cuvettes to get accurate number. Old cuvettes shows higher number than actual. In my eyes, it does not tell difference between old cuvettes and new cuvettes. Both looks similar (I know my cuvettes for alkalinity test is blue tinted).

Any experience sharing would be helpful.

I think the ICP reads less because the water is in the vial for days before being tested and in that time I think the phosphate dissipates.

 

[BaliReefBox]

yes you can buy cuvette in a pack of 2. For what they are they are kinda expensive.

 

[Reefahholic]

Same water sample, but I got Phosphate mismatch between Hanna Phosphate ULR and ICP test.

ICP test result is 0.03
Hanna Phosphate ULR result is 0.08

(1) In order to see where the difference come from, today I tested with brand new cuvettes, and compared with the test I'm doing with old cuvettes. The new cuvettes shows 0.12. The old cuvettes shows 0.25. This is huge difference!

(2) I also checked the history (ICP test vs. Hanna Phosphate ULR).

ICP test Hanna checker
8-28-2023 0.03 0.08
4-19-2023 0.01 0.02
1-19-2023 0.02 0.01

In above results, I understand it's time to replace cuvettes to get accurate number. Old cuvettes shows higher number than actual. In my eyes, it does not tell difference between old cuvettes and new cuvettes. Both looks similar (I know my cuvettes for alkalinity test is blue tinted).

Any experience sharing would be helpful.

Which ICP analysis was used?

Also, I’ve seen that Hanna Phosphate ULR consistently reads higher on ICP. I do not trust it. On the flip-side the Hanna Phosphorus ULR is very close and accurate.

 

[naterealbig]

I was concerned about this so I immediately rinse mine and store

Yep, a best-practice. With RODI of course to minimize residual solids once dry.

Can you buy just the cuvettes?

Sure can, as someone else mentioned. You can buy them cheaper if you don't need the graduated vial. No problem if you are measuring exactly 10 ml of sample, independent of the graduation (also, a best practice). (I use a syringe).

 

[gbroadbridge]

Same water sample, but I got Phosphate mismatch between Hanna Phosphate ULR and ICP test.

ICP test result is 0.03
Hanna Phosphate ULR result is 0.08

(1) In order to see where the difference come from, today I tested with brand new cuvettes, and compared with the test I'm doing with old cuvettes. The new cuvettes shows 0.12. The old cuvettes shows 0.25. This is huge difference!

(2) I also checked the history (ICP test vs. Hanna Phosphate ULR).

ICP test Hanna checker
8-28-2023 0.03 0.08
4-19-2023 0.01 0.02
1-19-2023 0.02 0.01

In above results, I understand it's time to replace cuvettes to get accurate number. Old cuvettes shows higher number than actual. In my eyes, it does not tell difference between old cuvettes and new cuvettes. Both looks similar (I know my cuvettes for alkalinity test is blue tinted).

Any experience sharing would be helpful.

Biological and chemical reactions in the sample during transit to the ICP lab almost always result in Phosphate being consumed before testing, resulting in lower readings.

The Hanna measurement is likely more correct than the ICP.

This is a quite common occurence.