A small study from me how zinc dose may affect nitrate measurement

[JonasRoman]

Hi. @Randy Holmes-Farley and I had a discussion few weeks ago, and I promised investigate in which way the reagent-zinc dose in a nitrate test is crucial or not for the test result. Here is my test, summarized in a small article.

Randy or someone responsible for the forum , feel free to relocate this to the article threads, or if you find it more appropriate somewhere else:-)

Its a very easy study, and a follow up would be interesting to do with higher nitrate concentrations , as I think the "break point" where zinc dose is crucial depends also on nitrate conc. A nitrate test is probably designed to have an excess amount of zinc-reagent for all nitrate values up to the tests "roof". Up to that value an overdose of zinc will have no negative effect on accuracy, but a too low dose will have when the "new" zinc dose is that low so its lower the "roof" below your true nitrate value. Where that limit is hard to know, so its always most safe to be careful when dosing the zinc powder.



Jonas

 

[Subsea]

Jonas,
I am more interested in what does inorganic zinc accomplish in the organic world. While inorganic zinc & copper are both below the lower detection limit of my ground water at 900’ in Middle Trinity Aquifier; Ward Lab showed 2ppm of copper & 5ppm of zinc in the biomass of Gracilaria Parvispora grown in my 10KG mariculture system in greenhouse.

Because I don’t test my reef systems, it’s more academic and not pragmatic to me. However, good fortune on your quest.

Hi. @Randy Holmes-Farley and I had a discussion few weeks ago, and I promised investigate in which way zinc dose is crucial or not for nitrate tests. Here is my test, summarized in a small article.

Randy or someone responsible for the forum , feel free to relocate this to the article threads, or if you find it more appropriate somewhere else:-)

Its a very easy study, and a follow up would be interesting to do with higher nitrate concentrations , as I think the "break point" where zinc dose is crucial depends also on nitrate conc. A nitrate test is probably designed to have an excess amount of zinc for all nitrate values up to the tests "roof". Up to that value an overdose of zinc will have no negative effect on accuracy, but a too low dose will have when the "new" zinc dose is that low so its lower the "roof" below your true nitrate value. Where that limit is hard to know, so its always most safe to be careful when dosing the zinc powder.



Jonas

 

[JonasRoman]

Jonas,
I am more interested in what does inorganic zinc accomplish in the organic world. While inorganic zinc & copper are both below the lower detection limit of my ground water at 900’ in Middle Trinity Aquifier; Ward Lab showed 2ppm of copper & 5ppm of zinc in the biomass of Gracilaria Parvispora grown in my 10KG mariculture system in greenhouse.

Because I don’t test my reef systems, it’s more academic and not pragmatic to me. However, good fortune on your quest.

@Subsea , another subject for another thread maybe, zink as trace in corals. important for the enzyme carbanhydras that convert co2 to hco3 for calcification in coral, but alo opposite, convert hco3 to c02 for the algue.

This article is about nitrate tests which use zink as reagent you know

 

[JonasRoman]

Some have misunderstood my article, its not about zinc in tank.

The study is about to find out how crucial the zinc-reagent dose are when we do a nitrate test. @Randy Holmes-Farley and I had a discussion if the reagent amount of zinc powder in the nitrate test was supercrucial. I promised find out. So did this test.

Jonas

 

[Dan_P]

Hi. @Randy Holmes-Farley and I had a discussion few weeks ago, and I promised investigate in which way the reagent-zinc dose in a nitrate test is crucial or not for the test result. Here is my test, summarized in a small article.

Randy or someone responsible for the forum , feel free to relocate this to the article threads, or if you find it more appropriate somewhere else:-)

Its a very easy study, and a follow up would be interesting to do with higher nitrate concentrations , as I think the "break point" where zinc dose is crucial depends also on nitrate conc. A nitrate test is probably designed to have an excess amount of zinc-reagent for all nitrate values up to the tests "roof". Up to that value an overdose of zinc will have no negative effect on accuracy, but a too low dose will have when the "new" zinc dose is that low so its lower the "roof" below your true nitrate value. Where that limit is hard to know, so its always most safe to be careful when dosing the zinc powder.



Jonas

How did you determine zinc is the reducing agent in this test?

 

[JonasRoman]

How did you determine zinc is the reducing agent in this test?

Zinc is what you use in many nitrate tests as reducing agent. In this test I use Focustronic reagents for nitrate tests in MTE, but same basic design is in most nitrate test kits. Sometimes cadmium is used but seldom due to more hazardous to use. So, the methid itself is well known, the small sttudy from me is to just find out if the zinkreagent dose is supercrucial for accurrate results from the nitrate test. And I think the findings are interesting.
Jonas

 

[Dan_P]

Zinc is what you use in many nitrate tests as reducing agent. In this test I use Focustronic reagents for nitrate tests in MTE, but same basic design is in most nitrate test kits. Sometimes cadmium is used but seldom due to more hazardous to use. So, the methid itself is well known, the small sttudy from me is to just find out if the zinkreagent dose is supercrucial for accurrate results from the nitrate test. And I think the findings are interesting.
Jonas

Are there visible particles of zinc in the reagent and does it need to be vigorously mixed before using?

 

[JonasRoman]

Are there visible particles of zinc in the reagent and does it need to be vigorously mixed before using?

1)yes
2) yes

 

[Dan_P]

1)yes
2) yes

Thank you for the confirmation.

 

[Malcontent]

Is the zinc insoluble? If so then you have to be quick between shaking and dosing otherwise it might settle. This might actually be more important than vigorous shaking (think snow globes).

 

[JonasRoman]

Thank you for the confirmation.

@Dan_P the crucial stirring and other physical factors that may effect is identical as a machine is doing that. So I only changed the dose of the zinc reagent. See pic from my text:-).

 

[JonasRoman]

Is the zinc insoluble? If so then you have to be quick between shaking and dosing otherwise it might settle. This might actually be more important than vigorous shaking (think snow globes).

@Malcontent Exact. All those moments are identical in my study as a machine is handle that. So waiting time etc is 100% identical in all tests.

 

[JonasRoman]

Same questions from several. All moments (shaking, dosing, waiting time, photometric reading) are performed by a robot (mastertronic E) that I have coded, so only variable is the no of drops. Everything else is identical performed. Also, the cuvette is never touched or repositioned, its a fixed mount. So photometric readings properties are identical.
So only variable is zincreagent dose, which was the purpose of the study.

Jonas

 

[Lasse]

IMO - What the test show is that with your waiting time programmed into the machine - your test need a special amount of zink in order to be stable. I´m sure that if you vary the waiting time instead for the amount of zink dosed - you should get a different result. IMO - the waiting time is the crucial parameter because it is very little of the nitrate that will be reduced into nitrite in this method and it is time depended.

Sincerely Lasse

 

[Dan_P]

@Dan_P the crucial stirring and other physical factors that may effect is identical as a machine is doing that. So I only changed the dose of the zinc reagent. See pic from my text:-).

Very sound approach.

Do you have a feeling about how consistent the stirring is? I have wondered but never tested the effect of varying the shaking during the zinc reduction step.

 

[JonasRoman]

Very sound approach.

Do you have a feeling about how consistent the stirring is? I have wondered but never tested the effect of varying the shaking during the zinc reduction step.

The stirring is very consistent as thats controlled digital with an exact same speed and time. Overall, yes the stirring is very very important, which is obvious when you do the tests manual (manual tests) where the shaking of zinc reagent is crucial. BUT, up to a limit, above that further shaking has no influence.

Jonas

 

[Malcontent]

When I was a kid I would try to shake snow globes increasingly violently but it didn't make the snow storm last much longer. It would settle quickly as soon as I stopped.

People always talk about how necessary it is to violently shake the API nitrate test but I suspect dispensing the drops ASAP after shaking is more important.

 

[JonasRoman]

When I was a kid I would try to shake snow globes increasingly violently but it didn't make the snow storm last much longer. It would settle quickly as soon as I stopped.

People always talk about how necessary it is to violently shake the API nitrate test but I suspect dispensing the drops ASAP after shaking is more important.

Actually not so crucial to be superfast, as the high viscosity makes the zink particles to stay evenly distributed for at least 5 min. The most important is to shake vigorously (ofcourse dispense immediately but its not about seconds).

 

[Malcontent]

Actually not so crucial to be superfast, as the high viscosity makes the zink particles to stay evenly distributed for at least 5 min. The most important is to shake vigorously (ofcourse dispense immediately but its not about seconds).

Ah, interesting. I should dump out some API solution into a clear container and see how it behaves.

 

[Randy Holmes-Farley Verified Community Expert]

Hi. @Randy Holmes-Farley and I had a discussion few weeks ago, and I promised investigate in which way the reagent-zinc dose in a nitrate test is crucial or not for the test result. Here is my test, summarized in a small article.

Randy or someone responsible for the forum , feel free to relocate this to the article threads, or if you find it more appropriate somewhere else:-)

Its a very easy study, and a follow up would be interesting to do with higher nitrate concentrations , as I think the "break point" where zinc dose is crucial depends also on nitrate conc. A nitrate test is probably designed to have an excess amount of zinc-reagent for all nitrate values up to the tests "roof". Up to that value an overdose of zinc will have no negative effect on accuracy, but a too low dose will have when the "new" zinc dose is that low so its lower the "roof" below your true nitrate value. Where that limit is hard to know, so its always most safe to be careful when dosing the zinc powder.



Jonas

Thanks for posting this, Jonas. I needed to wait till I had access to my computer to easily read a pdf.

One of the questions this relates to is how precise folks need to be in measuring out components for nitrate kits, which we discussed and which I expect is the reason for this study.

To that end, do you know how the drops used here relate to the amount of zinc normally present in any given hobby nitrate kit, and whether the commercial kit test may be above or near (or below) the break point in the line?

Thanks!

Randy