Alk test mix & match - API/Salifert

[Mr. Ugly]

Posted this on my club forums a few days ago. Still have some more tests to do, but how about if some people here see how it works for them?
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Ok, just got done playing around with 3 API alk kits and the last of my Salifert.

I ran the Salifert in high resolution mode and came up with 2.86 meq/L for one sample. That works out to 8dKH.

Running the API kits according to the directions multiple times gives me 10dKH for the same sample.

I decided to rerun the titrations using the API reagent, but out of a Salifert syringe for more precise measurement. An API drop is about .039 ml vs. a Salifert drop at .019 ml. (I measured the volume of a bunch of drops of each and divided by the number of drops.)

Going to the bright yellow endpoint, which still actually had a hint of green, I used .36 ml of reagent. This worked out to about 9.25 dKH. The API kit reads at least 1.25 dKH higher than the Salifert for that alk level.

I reran the API/Salifert reagent/syringe combo a few times and found that API and Salifert kits agree if I go by the first hint of API color change and subtract .02 ml. from the total volume used.

I'll run another batch of tests on some fresh RC, but for now I'll be using API reagents out of the Salifert syringe and tip.

I made up a chart for Salifert(low res) and API using volume of reagent and meq/L alk.


ml. Salifert API
reagent (meq/L) (meq/L)
0.01 0.11 0.09
0.02 0.23 0.18
0.03 0.34 0.27
0.04 0.46 0.37
0.05 0.57 0.46
0.06 0.69 0.55
0.07 0.80 0.64
0.08 0.91 0.73
0.09 1.03 0.82
0.10 1.14 0.92
0.11 1.26 1.01
0.12 1.37 1.10
0.13 1.48 1.19
0.14 1.60 1.28
0.15 1.71 1.37
0.16 1.83 1.47
0.17 1.94 1.56
0.18 2.06 1.65
0.19 2.17 1.74
0.20 2.28 1.83
0.21 2.40 1.92
0.22 2.51 2.01
0.23 2.63 2.11
0.24 2.74 2.20
0.25 2.86 2.29
0.26 2.97 2.38
0.27 3.08 2.47
0.28 3.20 2.56
0.29 3.31 2.66
0.30 3.43 2.75
0.31 3.54 2.84
0.32 3.65 2.93
0.33 3.77 3.02
0.34 3.88 3.11
0.35 4.00 3.21
0.36 4.11 3.30
0.37 4.23 3.39
0.38 4.34 3.48
0.39 4.45 3.57
0.40 4.57 3.66
0.41 4.68 3.75
0.42 4.80 3.85
0.43 4.91 3.94
0.44 5.02 4.03
0.45 5.14 4.12
0.46 5.25 4.21
0.47 5.37 4.30
0.48 5.48 4.40
0.49 5.60 4.49
0.50 5.71 4.58

 

[Mr. Ugly]

Ugh... sorry on the chart formatting. Copy and paste didn't come across very well.

 

[Mr. Ugly]

And a reply to someone that had asked about speed of testing between API and Salifert.
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I haven't used them before. What makes them fast?

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Hehe... I'm faster with Salifert alk than with API

Salifert has the extra step of adding 1 drop of indicator solution before the titration, but that's no biggie.

People that like Elos probably will like API. Same count the drop testing method. Ok for trending parameters, but no good for fine tuning your kalk/2part/Ca reactor.

The Salifert syringe gives really good control, so I can work fast without having to worry about extra drops coming out like with the API bottle. Also, the Salifert vial is large so that it's fast to mix and titrate at the same time. I'll bring test kits to demo at the next meeting if you like.

If you use the API kit the way it was designed, you have to cap and uncap the skinny vial as you add drops and mix... messy and slow. You could do the finger flick method, but the vial is small enough that you don't get good mixing when you're close to the endpoint.

I actually don't like API or Elos, in case people couldn't tell by now

I'm just using API because Salifert is hard to find right now. And I found a way to make the API kit usable for me.

I use the API reagent with the Salifert syringe and tip. I don't use the dropper bottle. I use the large vial from the Salifert kit so I can mix while titrating. I stop titrating at the first hint of green, not yellow. And I take my endpoint to be .02ml(1 Salifert drop) less.

I use SeaChem for Ca and lately for Mg. I prefer Salifert Mg, but same problem with availability.

People on the RC Chem forum talk crap on the SeaChem, saying that it reads low for Ca. I'm able to get the same readings with SeaChem Ca as others get with Salifert Ca. The thing to remember is to go to the bright blue endpoint with SeaChem.

I like the Salifert tips. I use them with my SeaChem kits. A drop out of a Salifert tip is ~.02 ml. You can do half drops at ~.01 ml pretty easily.

 

[Mr. Ugly]

And in reply to test procedure and doubling or tripling up on sample volume.
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I bought 3 kits with the intent to triple up on volumes.

I did a few runs doubled up on the sample size. It was ok. Even the Salifert test vial starts getting a little too full, and it was kind of a hassle going to 20-30 drops. I didn't bother with 3x sample size. Counting 40+ drops... eeesh!

API says to go to bright yellow endpoint, which ends up reading way high for me with this batch.

Anyway, use the Salifert syringe and tip. The lines are every .01 ml, and you can estimate to .005 ml. That's 8x resolution of the standard API method, and 4x the resolution of API's "more accurate" method.

You don't have to lose count of a crazy number of drops. Makes it easy to titrate and chew gum at the same time

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Also, shake up the API reagent like crazy before you use it.

I read somewhere about some test kits having problems unless you do that. At least one person said that about API.

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Also, I use a 5ml syringe for measuring the water sample volume.