Concentrating test water

[Kettle2]

I would like to concentrate some aquarium water in order to get a lower range on my test kit. I have considered either boiling off some of the water or allowing it to evaporate. Would these methods impact on the accuracy of the test?

 

My concern in relation to allowing the water to evaporate naturally is that the parameters (specifically nitrate and phosphate) may change in the time it takes to evaporate.

 

Any feedback or comments would be appreciated.

[PaulBuxton]

My concern would be that it would't just concentrate the chemicals. If you evaporate the water then you are increasing the salt content which may affect the solubility of the chemicals you are testing for.

Note I am not a chemist so might be talking nonsense!

[jedimasterben]

Buy better test kits.

[Kettle2]

I have good test kits, I would just like to obtain a better resolution than what I can presently.

[jedimasterben]

What 'good' test kits don't have a fine enough resolution for what reefkeepers need?

[Mariaface]

Right, but what Ben said was to get a better one, in order to get a better resolution. There exist low range phosphate/nitrate test kits, and you wouldn't have to deal with accounting for odd things happening due to precipitation and whatnot. If you're trying to measure in ppt instead of ppm, you may just want to send a water sample to a lab, or invest in a professional test kit instead of a hobby test kit.

[Kettle2]

If you don't know, just say you don't know. I'm not going to argue with you over whether you think my desire to obtain a better resolution in testing is valid or not.

[jedimasterben]

What I'm getting to is that you can't really do what you're wanting with hobby-grade test kits. You're getting into big bucks ($$$) if you're wanting anything better. What parameters are so important that you need higher resolution?

[Mariaface]

It's true, I have no clue if phosphate -or whatever- itself is going to precipitate out of the solution or if something else is going to hamper your hobby-grade test kit's ability to get an accurate result. But even if nothing did happen to the water outside of becoming more concentrated (unlikely, considering how close calcium and alk/carbonate already are to precipitation in our tanks), how were you planning on evaporating away an exact amount of the sample water in order to measure accurately? Is finding out a way to cause exactly half of the H2O in the solution to evaporate really worth getting to divide the result by two? What would that be, the difference between .01 and .02 ppm? Your hobby grade test kit (assuming it's a good one) should already get you there, so what's the issue?

 

Wanting a better test resolution is completely valid, and I understand it. It's just not always feasible when you're already at a great accuracy/precision.

[tibbsy07]

This won't work. The chemicals in the test kits are designed to work in a certain amount of water. If you concentrate the chemicals in the water and then add the same amount of test reagents, you will effectively just see more of whatever you are testing for. If you add less reagents, then there is no point. If you want lab grade results, you need to spend the money on lab grade supplies