Do you use the kit supplied vials ....

Bilk

New member
to measure water for testing or another graduated container or syringe to measure water to be tested?

Presently using Elos tests. Some require filling to the 10ml mark and others require 5ml, for which there is no mark. When checking the 10ml marks on the Elos vials against another reference, it is not 10ml from what I can tell. I say that because the mark is sort of a Nike swoosh and not just a straight line, so there isn't really a reasonable way to judge the correct measure.

I've been using a graduated cylinder for measuring. Does anyone feel this will throw off the test? Were the tests developed for 10ml or the swoosh mark? The difference appears to be an ml or two, but that represents a significant percentage of the measured quantity.

PS Had these Elos kits and will probably replace with Red Sea Pro unless there is a better recommendation. Once upon a time I only used LaMotte kits as they were the "non hobbyist" kits that seemed to be much more precise, but since then the hobby kits have really gotten much better.
 

disc1

-RT * ln(k)
Which tests? For titration style tests like calcium, magnesium, or alkalinity the sample volume is incredibly critical. For colorimetric tests like nitrate or phosphate the actual sample volume isn't a big deal as long as it is close.
 

Bilk

New member
Which tests? For titration style tests like calcium, magnesium, or alkalinity the sample volume is incredibly critical. For colorimetric tests like nitrate or phosphate the actual sample volume isn't a big deal as long as it is close.
All of the above. I actually don't use the test kit vials for any testing. I use test tubes and I measure fluids with a graduated cylinder and/or a syringe. The Elos vials have a stylistic marker that is ill suited for something that's supposed to have some scientific reliability.

So if the test requires 10ml of water, I fill a graduated cylinder to the 10ml mark (accounting for the meniscus) and then pour into a test tube. The test tube is easier for mixing as well. They're taller. However I can see that it may effect a test where the color change needs to be matched against a reference. It won't effect a titration test as that will occur no matter the container.
 

disc1

-RT * ln(k)
However I can see that it may effect a test where the color change needs to be matched against a reference. It won't effect a titration test as that will occur no matter the container.

You've got that backwards. With a titration you are counting ions. How much water that many ions is dissolved in is the concentration. So you have to know exactly how much sample you started with or you cannot turn that into a concentration. So sample volume is absolutely critical to a titration.

With a colorimetric test you are measuring concentration more directly. Since the concentration doesn't change depending on how much volume you have there and the reagents are all added in excess, the colorimetric test will work just the same in 5mL as it will in 5.5mL. The only thing that make a difference to the color is the path-length of the light going through the sample. So as long as the sample is in a test tube with the same diameter, the light passes through the same amount of sample getting to your eyes no matter how deep the sample is in that container. So for colorimetric tests, you can be off quite a bit with the sample volume and still get a good answer.
 

ReachTheSky

Active member
I think the Nike swoosh might be referring to the meniscus - or the crescent shape the surface of the water creates. Match the bottom of the crescents and you'll be fine.
 

Bilk

New member
You've got that backwards. With a titration you are counting ions. How much water that many ions is dissolved in is the concentration. So you have to know exactly how much sample you started with or you cannot turn that into a concentration. So sample volume is absolutely critical to a titration.

With a colorimetric test you are measuring concentration more directly. Since the concentration doesn't change depending on how much volume you have there and the reagents are all added in excess, the colorimetric test will work just the same in 5mL as it will in 5.5mL. The only thing that make a difference to the color is the path-length of the light going through the sample. So as long as the sample is in a test tube with the same diameter, the light passes through the same amount of sample getting to your eyes no matter how deep the sample is in that container. So for colorimetric tests, you can be off quite a bit with the sample volume and still get a good answer.
I understand what you're saying and I guess I didn't say what I meant very well. The titration test is fine in any container as long as the volume being tested is correct. The colorimetric test results can be effected, or at least misinterpreted, as you stated.

I guess what I'm asking is, do they mean 10ml or do they mean fill it to the line? Because that line certainly isn't 10ml from what I can tell.
 

Bilk

New member
I think the Nike swoosh might be referring to the meniscus - or the crescent shape the surface of the water creates. Match the bottom of the crescents and you'll be fine.
Ok that sounds like a reasonable assumption/method, but that also doesn't equate to 10ml as is required for the tests. It's more like 11.5ml.
 

Signal151

New member
My advice is always measure. I also have a few ELOS kits and in comparing two of their vials I found the line isn't even printed at the same height on both vials! I use syringes to measure all my fluids when testing.
 

ReachTheSky

Active member
Ok that sounds like a reasonable assumption/method, but that also doesn't equate to 10ml as is required for the tests. It's more like 11.5ml.
I see your point. It's a bit odd that the marking would be that inaccurate. I wouldn't be able to tell you for sure which one you should follow but if I had to leave it to chance, I would bet on their test being developed around a 10ml standard vs. mass-produced vials that they likely outsource.
 

Bilk

New member
My advice is always measure. I also have a few ELOS kits and in comparing two of their vials I found the line isn't even printed at the same height on both vials! I use syringes to measure all my fluids when testing.

Yeah I just discovered that as well. I think Elos produces some well designed, well thought out products, but the vial isn't one of them. I guess I'll just keep using the graduated cylinder/syringe approach. Will probably go with RSP tests after these are spent. I have Hanna checkers for Ca,Alk and PO4, but like to have back up tests to confirm.
 

disc1

-RT * ln(k)
I understand what you're saying and I guess I didn't say what I meant very well. The titration test is fine in any container as long as the volume being tested is correct. The colorimetric test results can be effected, or at least misinterpreted, as you stated.

I guess what I'm asking is, do they mean 10ml or do they mean fill it to the line? Because that line certainly isn't 10ml from what I can tell.

I read you now. So to me the answer is to measure out the samples for titration using something you know. Even if it is a little off from what they expected you to use at least it is consistent. And for the color tests just use their vial since the volume doesn't really matter that much anyway.
 

rburns24

Member
I use veterinary syringes for my Hanna tests. The lines on some of my vials have been worn off from cleaning, but it doesn't matter, because I have never used them. An accurate syringe makes vial lines irrelevant.
 

Bilk

New member
I use veterinary syringes for my Hanna tests. The lines on some of my vials have been worn off from cleaning, but it doesn't matter, because I have never used them. An accurate syringe makes vial lines irrelevant.
Yeah I found the lines on the Hanna supplied vials to be off as well. These kits aren't free or cheap and the vials are the least expensive part. I'm kind of amazed these companies can't provide an accurate instrument to perform their tests in.
 
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