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Increasing Specificity of the API tests

swyftfeet

swyftfeet

Member
Joined
29 Oct 2021
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Location
WNY
Probably a very odd question but can you double specificity of the liquid test kits by adding either half the number of the drops or double the amount of water, meaning after doing so I would double the resulting match on the card?
contra:
If I added double the drops or half the water would I half the color match?

Are the Test kits linear in this fashion?
 
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swyftfeet said:
Probably a very odd question but can you double specificity of the liquid test kits by adding either half the number of the drops or double the amount of water, meaning after doing so I would double the resulting match on the card?
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Hi @swyftfeet

I'm not familiar with the use of the word "specificity" when used in this context.

swyftfeet said:
If I added double the drops or half the water would I half the color match?
Click to expand...
I have to confess to not fully understanding your question and the only API tests with which I'm familiar are KH and GH. If you want to improve the resolution of these two parameters, API gives instructions on how to do this.

swyftfeet said:
Are the Test kits linear in this fashion?
Click to expand...
See above.

JPC
 
All I have a brand new tank that I'm keeping a journal on. I'm trying to track ammonia levels after water changes and what not.

the problem is I personally cannot perceive very well the difference on the ammonia chart of the 0.25 the 0.5 and 1.0. they look very similar under most lighting conditions to me.

So I was trying to make the color change more drastic yet mean something on a linear scale that would be easier to identify.

y= mx +b where b is 0 (no change in color)

2y = 2mx

that was my thinking...

so if the relationship was linear if doubled the drops in 5ml, then I would expect a 1ppm to look like a 2ppm.

I was always worse than bad at chemistry, so I was asking if I lost my marbles.

@jaypeecee Sorry if I misused the term specificity. I often do. I thought increasing the specificity meant making it more sensitive.
Biology
  • the narrowness of the range of substances with which an antibody or other agent acts or is effective
 
These drop by drop kits always worry me. Instructions say look down the test tube for comparison but you see photos on this forum of side on shots but the comparisons are like chalk and cheese. Always the look down comparision is always several stages darker by several points. Not a good indication for new comers by any means.
Dirk
 
so I keep rereading what I am typing and maybe my equation was left without enough explanation...

I will preface that I know jack-all about the chemistry of testing kits or how they work besides: magic drops make color happen. They proclaim to measure some aspect of the water in ppm based on a test sample size of 5ml.

If I use the same number of drops in 2.5 ml, then it would seem that the color match on the provided scale scale would match to double the actual ppm. meaning the real value of 2ppm would look like 4ppm. Likewise if I used double the drops on 5ml.

Alternatively, If I used double the volume of water or half the drops, then the color match would have to be doubled.

This would only work like this if the color change could be expressed as a linear eqn.

since the 0 color change indicates 0ppm the y intercept is 0.

Anywho, in the end it doesnt really matter as I am going to wait till ammonia = 0, I feel like i'm circling the rabbit hole here trying to explain concept that seems obvious to me thinking about it. But I am also failing spectacularly at communicating it.
 
Kelvin12 said:
These drop by drop kits always worry me. Instructions say look down the test tube for comparison but you see photos on this forum of side on shots but the comparisons are like chalk and cheese. Always the look down comparision is always several stages darker by several points. Not a good indication for new comers by any means.
Dirk
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Pretty sure the look down tube tests are the JBL type that use wide test containers, the API in narrow tubes should be measured side on.
 
swyftfeet said:
failing spectacularly at communicating it.
Click to expand...

I had another whole useless post written out when I finally realised (maybe?) what you want.
You dont want a smaller more sensitive reading. You want a bigger one (duh) :facepalm:
All the advice I can find on test kit use only allows for (smaller) readings that need to be multipled later to get the actual result.
The API ammonia test did not have any useful FAQ that I could find, but the JBL ammonia did, and they appear to use the same color gradient, and therefore I would assume they are based on the same ingredients and reaction. So usage advice for JBL ammonia should then theoretically apply to API ammonia as well.

See FAQ further down on this page
They do not mention doing double drops, but then again the question on their FAQ was for when readings were outside the scale.

You could try it and report back your findings, but to save time and headache I would just wait for it to read a clear 0 as you say.
The hobby has many rabbitholes, and it is sometimes best not to go down too deep ;)
The 0 reading is a very distinct warm yellow compared to the greenish yellow hues of the scale.
With practice you should be able to tell it quite immediately.
 
Hufsa said:
You dont want a smaller more sensitive reading. You want a bigger one
Click to expand...

Exactly, they want a larger/stronger colour change for a smaller change in parameters.

Interested to know the answer to this myself, I don't test often but I really struggle with the subtle changes to most kits and have to get others to try and figure it out. KH/GH are about the only ones I can reliably do.
 
Hi all,
I'm going to tell you the simple answer is to have plenty of plants in active growth, and then you can ignore ammonia (NH3), it is never going to build up to toxic levels.

I have access to <"an analytical lab">, but even then there are some issues and I don't test for ammonia in the aquariums.
swyftfeet said:
All I have a brand new tank that I'm keeping a journal on. I'm trying to track ammonia levels after water changes and what not.

the problem is I personally cannot perceive very well the difference on the ammonia chart of the 0.25 the 0.5 and 1.0. they look very similar under most lighting conditions to me.
Click to expand...
You really need a much <"more sensitive measurement method">. Testing for any gas (NH3) <"is problematic">, but with ammonia/ammonium you can convert it to the ammonium ion by lowering the pH (or into NH3 gas by raising the pH).

The two colorimetric methods available are <"the Nessler method"> in which potassium, mercury, and iodine react with to create a yellow-brownish colored compound and the salicyate method in which "free ammonia reacts with hypochlorite to form monochloramine. Monochloramine reacts with salicylate, in the presence of sodium nitro-ferricyanide, to form 5-aminosalicylate, a blue-colored compound". The color intensity of the final compound is proportional to the concentration of NH3/NH4+ in the sample, in both cases.

<"An ion selective electrode"> would do, but they are expensive bits of kit and you still need to convert all the <"TAN to the ammonium ion (NH4+)">, or to NH3, before you can get a reading.

cheers Darrel
 
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Nick potts said:
Exactly, they want a larger/stronger colour change for a smaller change in parameters.

Interested to know the answer to this myself, I don't test often but I really struggle with the subtle changes to most kits and have to get others to try and figure it out. KH/GH are about the only ones I can reliably do.
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Yay! i don't have to be the guy shouting "I'm not crazy" as the load me into the back of the panel van.

Ok, I feel better that someone is understanding me. The color swatches on the test kit ranges from 0 -> 8ppm, what I am trying to do is make that color range represent 0->4ppm.

if my actual sample is:
0 should appear as 0
0.25ppm actual should match the 0.5 color patch,
0.5ppm actual it should appear as 1 color patch
1 it should appear as 2 color patch and so on.

I'm trying to make it easier on my eyes since the colors change would be more significant for a smaller range which I called doubling the specificity...

Thank you all for the information and attention, I'll read those links. I really do get intimidated by chemistry, so there is an opportunity to slay that dragon here I guess.

I don't think I know any more (yet) than when I started, but I think that's more a reflection on the student than the teachers.
 
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this is my dilemma. Is that 0.25, 0.5 or 1. Lmao

Doesnt help that they used an inkjet CMYK printer to generate the color swatch. Even worse the heads arent even aligned. /sigh

Not that it terribly much matters it isn’t 0.

But I was trying to keep a diary.
284E133B-4903-421C-995A-633F6CC11DA2.jpeg
 
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DaveWatkin said:
Pretty sure the look down tube tests are the JBL type that use wide test containers, the API in narrow tubes should be measured side on.
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Hi @DaveWatkin

You can see from the pictures below how the JBL test kits are used:

www.jbl.de

JBL PROAQUATEST PO4 Phosphate Sensitive

Determines phosphate value for perfect plant growth or possible cause of algae growth in freshwater/marine water & ponds
www.jbl.de www.jbl.de

I like this comparator system. The only exception to the colour comparator (that I know of) in the JBL range is the potassium (K) test kit, which is based on turbidity (cloudiness) but this, again, is done by viewing the tube from above. I can't be certain but my guess is that JBL test kits are very probably manufactured by Macherey-Nagel.

JPC
 
swyftfeet said:
Doesnt help that they used an inkjet CMYK printer to generate the color swatch. Even worse the heads arent even aligned. /sigh
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Wow that print sucks big time, my eyes cant decide if they want to focus on the lighter lines or the darker ones within the color 😂
Based on the picture id say slightly more than 0.5 (~0.6) but pictures can lie.

swyftfeet said:
But I was trying to keep a diary.
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No diary for you lol!
I guess it will have to be "Dear diary, API sucks, forum is no help. >0 Ammonia"
 
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