Lasses Dream Build

[Euphylliaphyle]

More testing experiments. Have test with Tropic Marin PO4 test pro and "the German Methode" to use Hanna to analyze PO4. I will say - with Hanna Marine Master - no good results and more unstable than Hannas own reagent. However - if I use TM PO4 pro the way it should be used - I get very stable results - but rather low - between 0.05 - 0.08

when Hanna (with Hanna´s reagent) report between 0.09-0.19 ppm.

Which analyze that´s nearest the true value - I do not know - but I will sen in an ICP rather soon - and after that I can compare - note - I send to OCEAMO and the do not use ICP for PO4 - they use another method

But still - I´m not very satisfied with Hanna and I decided to buy new sample cuvettes.

I did a comparison with my old cuvettes and the new one. At zero - they was equal but in a serie of three samplings - there was a different between new and old

The mean difference was 0.05 mg/L (ppm)!

Lesson learn - buy new cuvettes now and than

Sincerely Lasse

Lasse, what do you believe is the reason for the apparent cuvette deterioration? Glass staining? Micro scratches on outside? Etching on inside? Residue build-up? Something else?

 

[EnterName]

More testing experiments. Have test with Tropic Marin PO4 test pro and "the German Methode" to use Hanna to analyze PO4. I will say - with Hanna Marine Master - no good results and more unstable than Hannas own reagent. However - if I use TM PO4 pro the way it should be used - I get very stable results - but rather low - between 0.05 - 0.08

when Hanna (with Hanna´s reagent) report between 0.09-0.19 ppm.

Which analyze that´s nearest the true value - I do not know - but I will sen in an ICP rather soon - and after that I can compare - note - I send to OCEAMO and the do not use ICP for PO4 - they use another method

But still - I´m not very satisfied with Hanna and I decided to buy new sample cuvettes.

I did a comparison with my old cuvettes and the new one. At zero - they was equal but in a serie of three samplings - there was a different between new and old

The mean difference was 0.05 mg/L (ppm)!

Lesson learn - buy new cuvettes now and than

Sincerely Lasse

The accuracy of the phosphate test is ±5% of the reading ± 0.02ppm (∆ 0.04ppm).

If my math isn't off this means the 0.05ppm difference would be exactly what you would expect for your approx. 0.15ppm readings in that case:
+0.02ppm - (-0.02ppm) + 5% • 0.15ppm ≈ 0.05ppm

I know that Si interferes with the PO₄ test method over time, so maybe the glass itself reacts slowly and stains even when it is rinsed thoroughly after each use. I'm not sure how effective it is long-term but filling the vials with HCl from time to time seems to get rid of some of the blue staining more effectively than rinsing alone does.

I have gone through quite a few vials over the years and no matter how careful I am, it seems like the HannaChecker itself scratches the glass, which is very frustrating. Sooner or later the vials have to be replaced...

 

[Lasse]

I know that Si interferes with the PO₄ test method over time, so maybe the glass itself reacts slowly and stains even when it is rinsed thoroughly after each use. I'm not sure how effective it is long-term but filling the vials with HCl from time to time seems to get rid of some of the blue staining more effectively than rinsing alone does.

I will test to store the old vials with 0.1 N HCL for a while

Lasse, what do you believe is the reason for the apparent cuvette deterioration? Glass staining? Micro scratches on outside? Etching on inside? Residue build-up? Something else?

This is a problem - I get an off reading even if the differences in the average is within the margin of error. However - IMO - this is a real difference between these cuvettes. But why and how? If I fill them with RO water - both show 0.00 - it looks like its only when the dye comes in that I get a difference. after a test - I always fill them up with RODI water (after a rinse)

Glass staining?

Not likely - IMO

Micro scratches on outside?

Could be if they send part of the light beam apart from the reciver

Etching on inside? Residue build-up?

Difficult to believe this because I rinse every time and sometimes with acid.

Sincerely Lasse