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Which test kit to measure chlorine?

anewbie

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1,424
So this is a bit different than most posts but maybe someone here has some first hand experience. My project is finally nearing completion and one aspect is filtering water through carbon to remove chlorine. I want to test the water flowing through the system to ensure 'all' the chlorine is removed. My question is which test it has suitable sensitivity - my vague understanding is any chlorine over 0.0001 ppm is harmful to the long term health even if it doesn't immediately kill the fish. Is there expertise here in this area that can suggest a suitable test kit. I've found one paper that seems like the right beast but someone with first hand experience would be a bonus.
 

MacZ

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3,119
Location
Germany
If you were in Europe I'd say any test strips (Sera, JBL, even Tetra and any similar ones) would do as all of them have a field for Cl2 which is sensitive enough to show a positive or negative result.
0.0001mg/l is laboratory grade sensitivity. Unless you order from a lab supplier you won't find anything of that sensitivity in the aquarium trade.
 

anewbie

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1,424
I know hanna-761 is suppose to work well; and the cost isn't horrible. The stated sensity is 1 part per billion ppb; The acutal device one time cost is $70 and then the cost per test is around 0.36cents.

I worry about strip accuracy; the strips that @Ben Rhau linked I worry about the accuracy i think it is 1ppm - isn't 1ppm still toxic?

The strips mentioned are like 0.68 per test but of course no upfront cost.
 

Ben Rhau

Apisto Club
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573
Location
San Francisco
The strips have two ranges based on how long you wait. 1 - 10 ppm, or 0 - 1 ppm. I don't use them often, and it's always undetectable for me after RODI. I mostly just use it to know when my DI resin will be exhausted. I'm sure the meter also works-- never used it.

-B
 

anewbie

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Messages
1,424
The strips have two ranges based on how long you wait. 1 - 10 ppm, or 0 - 1 ppm. I don't use them often, and it's always undetectable for me after RODI. I mostly just use it to know when my DI resin will be exhausted. I'm sure the meter also works-- never used it.

-B
Yea it is this sort of uncertainty that make me frett - did i wait long enough; is the chemical still accurate - esp if make 1 or 2 test a year - did i read the colour accurately - i'm not saying it is a bad test - but - for example I *hate* api liquid test since some of the colours are so difficult to accurately read - esp for nitrate which i test frequently. Is it really 15 or 20 or 40.
 

Ben Rhau

Apisto Club
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573
Location
San Francisco
I always run a positive and a negative control:

Positive: tap
Negative: distilled water
Test: RODI output

If I can't tell the difference between the negative and the test treatment, I'm comfortable with it, especially since I know the stages are supposed to work. It's definitely faster and easier than API liquid tests, which I also dislike.

I do think meters also have their downsides. With both pH and TDS, they swing around a lot, so I need to make several measurements to get a stable reading. And they need to be calibrated.

There's no one best way to do this. If you prefer the meter, I'm sure that's also a fine solution.

Cheers
 

anewbie

Well-Known Member
Messages
1,424
I always run a positive and a negative control:

Positive: tap
Negative: distilled water
Test: RODI output

If I can't tell the difference between the negative and the test treatment, I'm comfortable with it, especially since I know the stages are supposed to work. It's definitely faster and easier than API liquid tests, which I also dislike.

I do think meters also have their downsides. With both pH and TDS, they swing around a lot, so I need to make several measurements to get a stable reading. And they need to be calibrated.

There's no one best way to do this. If you prefer the meter, I'm sure that's also a fine solution.

Cheers
It isn't a meter in the same sense of a pen meter. It is basically a reader of the colour that converts it to a numerical value (if that make sense); that is my take on the hanna testers. I don't think they can be calibrated like the pens can be calibrated. You mix the water with an agent - put it in the reader via inserting the test tube with the mix and it gives the value. Smudges on the test tube can influence value so they recommend you hold the test tube with a cloth and not touch it directly.
 

MacZ

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3,119
Location
Germany
So it does the same as the teststrip reader apps many aquarium supply companies have released (like JBL proscan and the like). You do a strip (or drip) test and the meter scans the colour.
 

anewbie

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1,424
So it does the same as the teststrip reader apps many aquarium supply companies have released (like JBL proscan and the like). You do a strip (or drip) test and the meter scans the colour.
I guess - but one difference is it has the accuracy of a liquid test which for some people say are more accurate than test strips.
 

MacZ

Well-Known Member
Messages
3,119
Location
Germany
I guess - but one difference is it has the accuracy of a liquid test which for some people say are more accurate than test strips
If you go by the stuff you get from the aquarium trade:
It's not even the accuracy or precision.
E.g. a pH drip test sold by your average aquarium supply company has a standard deviation of +/- 0.5 pH-points, the softer the water the bigger the deviation: Up to 1.5 points, depending on the quality of the reagents.
Same goes for pool test kits among which these test strip readers are quite common.

The aquarium specific strips are designed to tell you whether a certain thing is present and if you're lucky whether it's a lot or a little. The colour scales are not very precise and have big steps. They are quick tests after all.
Liquid tests do have charts with smaller steps, but that doesn't make them much more precise or accurate. We all have nuances in our perception of colour and a partial colour blindness might make a test completely useless. I for example know my left eye has a less intense perception of red, so if a test is on the spectrum of reddish tones I'm in trouble.

In summary one can still say that tests designed and sold for hobbyist use are "good enough" but should never be taken too serious unless measuring or handling errors are ruled out and the testkit is not off yet.

If you are looking for actual precision and accuracy a look into lab equipment is advisable.
 

Ben Rhau

Apisto Club
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573
Location
San Francisco
The guy who wrote that article I linked to used a Hach kit, which is lab quality but also colorimetric. He’s a commercial scientist, and it met his standards.

My preference was for something that was “good enough” and didn’t take up much space. I don’t need precision, I just want to be able to detect chlorine in the tap and see that my test sample is indistinguishable from distilled water.
 

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