I'm using an Elos alk that my wife bought for me. But when I test the tank water I'm getting a 7-8 reading. I always get 9-10 on my last Salifert. I had borrowed my friend Salifert tast kit. Atfer the testing I'm getting a 10.9 reading. Then I test using my Elos I'm getting 8.0. My question is which test kit is correct.
Elos and Salifert alk test
- Thread starter thi7b
- Start date
Cybernobbie
New member
I used the Salifert test kit and the readings were always too high. But i don´t trust the test kits anyway, because i have alk test kits from tropic marin and sera too and they all show different readings.
Now i check my test kits with a multi reference. If you compare the reference value with the current value from your test kit you know the true value.
I´m using the fauna marin multi reference. I´m from Germany, but i guess there are similar products in the US.
HighlandReefer
Team RC
Many alk kits are designed for freshwater and their label will state for both fresh & marine water. The Salifert kit is designed for marine water. If Elos is designed for freshwater, you will need to add about 10% to the number you get to determine the proper alk in marine water. Given your figures, if you add 10% to the Elos, it matches Salifert pretty close.
FWIW, the acid titration method described in Randy's article is the most accurate for determining alk in marine water & it's much cheaper then test kits you buy.
FWIW, the acid titration method described in Randy's article is the most accurate for determining alk in marine water & it's much cheaper then test kits you buy.
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EvMiBo
VictoriaConcordiaCrescit
FWIW, the acid titration method described in Randy's article is the most accurate for determining alk in marine water & it's much cheaper then test kits you buy.
I'll have to check this out, any link by chance? If not I'll find it eventually
btw, I use elos for most of my tests including alk.
HighlandReefer
Team RC
You can buy 0.1 N Sulfuric acid standard used as the titrant from: (you simply substitute the 0.1 N sulfuric acid for the 0.1 N hydrochloric acid with the same results)
Buying 0.1 N HCL can be difficult since there are shipping & other restrictions placed on it.
http://www.grainger.com/Grainger/it...est Instruments-_-Laboratory Supplies-_-4YNA6
It would be best to calibrate your pH meter using a 4 & 7 standard before you start the test. The pH test kits are not accurate enough for this procedure.
Easy part; Testing
Now take a sample of your aquarium water, you can use any volume but I like to use 100ml because my pH meter sits nicely in the cup without me holding it at this level. Stick in your pH meter to your sample. You should get the same reading you do when you stick it directly in your tank. If not start over with a clean sample container. Now draw up some 0.1 N HCl solution in to your 5ml syringe. And start dropping into your sample 0.5 mls at a time and watch your pH meter. You are adding a strong acid so your pH should fall rapidly. Once your pH hits 5 start to slow down and add a drop at a time until your pH hits 4.2 . The reason we are shooting for 4.2 is because this is the point where all available carbonates have been converted to carbonic acid. You would think this would be pH 7 but it's not as carbonic acid is a weak acid and you have to really saturate it etc. Anyway, once you have reached pH 4.2 you are done and now can calculate your total alkalinity.
Alk mg of CaC03 /L = A x N x 50,000 / mL of sample
Where A = ml of acid added
N = normality of your HCL
So if you added 4ml of 0.1 HCL before you hit a pH of 4.2
4*0.1*50,000 / 100 = 400 ppm CaC03 equivalents or your total alkalinity is 8 meg/L (mg/L / 50 = meg/L) or 22.4 dKH.
The above information was taken and corrected from this thread:
http://www.reefcentral.com/forums/showthread.php?t=1583884&highlight=acid+titration+alkalinity
Randy provides further details in this article:
What is Alkalinity
http://www.advancedaquarist.com/2002/2/chemistry
For converting ppm calcium equivalent to dKH or meq/L you can use this calculator:
http://www.saltyzoo.com/SaltyCalcs/AlkConv.php
Buying 0.1 N HCL can be difficult since there are shipping & other restrictions placed on it.
http://www.grainger.com/Grainger/it...est Instruments-_-Laboratory Supplies-_-4YNA6
It would be best to calibrate your pH meter using a 4 & 7 standard before you start the test. The pH test kits are not accurate enough for this procedure.
Easy part; Testing
Now take a sample of your aquarium water, you can use any volume but I like to use 100ml because my pH meter sits nicely in the cup without me holding it at this level. Stick in your pH meter to your sample. You should get the same reading you do when you stick it directly in your tank. If not start over with a clean sample container. Now draw up some 0.1 N HCl solution in to your 5ml syringe. And start dropping into your sample 0.5 mls at a time and watch your pH meter. You are adding a strong acid so your pH should fall rapidly. Once your pH hits 5 start to slow down and add a drop at a time until your pH hits 4.2 . The reason we are shooting for 4.2 is because this is the point where all available carbonates have been converted to carbonic acid. You would think this would be pH 7 but it's not as carbonic acid is a weak acid and you have to really saturate it etc. Anyway, once you have reached pH 4.2 you are done and now can calculate your total alkalinity.
Alk mg of CaC03 /L = A x N x 50,000 / mL of sample
Where A = ml of acid added
N = normality of your HCL
So if you added 4ml of 0.1 HCL before you hit a pH of 4.2
4*0.1*50,000 / 100 = 400 ppm CaC03 equivalents or your total alkalinity is 8 meg/L (mg/L / 50 = meg/L) or 22.4 dKH.
The above information was taken and corrected from this thread:
http://www.reefcentral.com/forums/showthread.php?t=1583884&highlight=acid+titration+alkalinity
Randy provides further details in this article:
What is Alkalinity
http://www.advancedaquarist.com/2002/2/chemistry
For converting ppm calcium equivalent to dKH or meq/L you can use this calculator:
http://www.saltyzoo.com/SaltyCalcs/AlkConv.php
HighlandReefer
Team RC
The other parameters we test for like nitrate and magnesium are more involved (than the alk test) as is demonstrated in this article:
Nitrate test
http://en.wikipedia.org/wiki/Nitrate_test
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HighlandReefer
Team RC
Jesse,
Do you know what pH your Elos alk kit changes color, at the end of the titration process?
Cliff
In a recent hobby test on the Hana thread, the API, Elos, LaMotte and Hanna Alk Checker meter( ones working correct) all tested about the same. The Salifert does *seem to read to high and others to low. I know for fact the LaMotte is FW and most of these others fall within a LaMotte reading +/- 2 - 8 ppm and that Salifert is + 30 ppm
It *seems to be this. Add 9 % to the, API, LaMotte, Elos, Hanna and subtract 9 % from the Salifert for correct seawater Alk. Hmm, sure is funny 9 + 9 = ~ 18 %
Actually:
4.2 pH / 4.5 pH = 9.33 %. We have just been rounding it up to 10%
Mean for Elos, LaMotte, Hanna 190 ppm ( with 9.3 % added) vs Salifert 186 ( with 9.3 % subtracted)
My post
In a recent hobby test on the Hana thread, the API, Elos, LaMotte and Hanna Alk Checker meter( ones working correct) all tested about the same. The Salifert does *seem to read to high and others to low. I know for fact the LaMotte is FW and most of these others fall within a LaMotte reading +/- 2 - 8 ppm and that Salifert is + 30 ppm
It *seems to be this. Add 9 % to the, API, LaMotte, Elos, Hanna and subtract 9 % from the Salifert for correct seawater Alk. Hmm, sure is funny 9 + 9 = ~ 18 %
Actually:
4.2 pH / 4.5 pH = 9.33 %. We have just been rounding it up to 10%
Mean for Elos, LaMotte, Hanna 190 ppm ( with 9.3 % added) vs Salifert 186 ( with 9.3 % subtracted)
My post
Unless the chemists here in RC would say that the LaMotte is not good for saltwater
It is not and Randy will tell you the same thing, as will Lamotte if you call them and ask or HACH. Randy brought this up long ago here.......
What is Alkalinity
http://www.advancedaquarist.com/2002/2/chemistry
The precise endpoint of a total alkalinity titration isn't always the same pH, but rather depends a bit on the nature of the sample (both its ionic strength and its alkalinity). For normal seawater, this endpoint is about pH = 4.2. In freshwater it depends strongly on the alkalinity, with an endpoint of pH = 4.5 for an alkalinity of 2.2 meq/L, and pH = 5.2 for an alkalinity of 0.1 meq/L.
Consequently, total alkalinity tests have been invented that determine how much acid is required to lower the pH into the 4-5 range. Later in this article I'll describe how these tests kits are measuring alkalinity.
4.2 / 4.5 = 9.3 % low, So at 10 dKH on a kit it will really be ~ 11 dKH. NSW is 2.33 Meq / l or 6.5 dKH. So, @ 10% low it will be 2.1 vs 2.33 and that is allot. A 10 % error is allot.
They only way we will know is when somebody get a certified Alk std and tests the meter/test kit, where that person is not affiliated with and company that makes meters or tests kits. I said it before if one wants to really know send kits and meter to ENC Labs for evaluation. NO you can not send them a sample of water for Alk as it can change, unless it an be kept cool enough. For 14 days it must be at or near 4C.
or if you have the time , equipment and patients
KH standards
Here is the information needed to make a KH standard.
* baking soda (sodium bicarbonate)
* sodium carbonate anhydrous
* a lab certified Alkalinity Standard Solution as NA2CO3 in 10mL Ampules From HACH
How accurate you want the standard is up to you.
If you want a more accurate standard than that you could use the alkalinity standard solution from HACH (NIST certified). The reason for the increase in accuracy is because all that needs to be done is the dilution part, the weighing process is removed, which eliminates any errors from moisture in the sample or an inaccurate scale.
To make a KH standard using baking soda you would need the following.
* distilled water
* baking soda (new and unopened would be best)
* .01 gram scale (a calibration weight)
* 500 ml graduated cylinder
* 50 ml graduated cylinder
1. Measure 3000 ml of distilled water using the 500 ml graduated cylinder and put it in a clean container. The container could be an empty 1 gallon distilled water bottle. (I found it easier to use 3000 ml, instead of the often suggested 5000 ml because you can make your standard with 1 gallon of distilled water instead of having to have a larger container or multiple containers)
To read the precise water level in the graduated cylinder.
-Place the cylinder on a flat surface.
-Make sure your eye is on a level plane with the of the meniscus.
-The meniscus is the half-moon curve formed at the surface of liquid.
-Water should be read from the bottom of the meniscus
2. Weigh 3.60 grams of baking soda, add it to the 3000 ml of distilled water and mix well, this will make a 40 dKH / KH standard.
3. Pour 450 ml of distilled water into the 500 ml graduated cylinder.
4. Pour 50 ml of the 40 dKH standard into the 50 ml graduated cylinder
5. Pour the 50 ml of 40 dKH standard into the 500 ml graduated cylinder and mix well, this will give you 500 ml of a 4 dKH standard.
6. If you want a 5 dKH standard instead of a 4 dKH - change step 3 from 450 ml to 400 ml and you will end up with 450 ml of a 5 dKH standard
Taylor makes a std more to our needs
http://www.hxworldwide.com/componen...0-taylor-reagent-pack-standard-solutions.html
LaMotte (one of the best only better by the HACH Digital Titrator)
The question is which LaMotte does one have as they make like 10 of them. Most are in 4 or 5 ppm increments or 0.28 dKH. For me cost wise and accuracy of a prove product, just follow the instructions get you reading in ppm and add 10% for seawater.
Last this, which prove my point over and over
http://reefgizmo.com/2010/10/the-hanna-hi-755-alkalinity-colorimeter-review/
And I do think it is very well down and I do not care what anybody says. It is a know FACT the the LaMotte iS for FW and NOT seawater and what does it show ~ 10% low of the Salifert which it should be
Salifert = 200 ppm sw
LaMotte = 170 ppm and add that ~ 10% 170 + 17 = 187 PPM sw
Hanna - 168 - 175 ppm and add ~10% = 185- 193 ppm sw and lets not forget the Hanna is +/- 10 ppm accuracy. So, 175 - 203 ppm.
So , if we assume the same for all at + /- 10%
Salifert = 200 ppm sw--------------190 - 210 sw
LaMotte = 187 ppm ....177 - 197 ppm sw
Hanna - 168 - 175 ppm ..... 175 - 203 ppm.
I will admit that the Salifert does seem to read higher than that 10 % ~ 18 % And that 200 should be more like ~ 185 ppm
So, any of them are with in that accuracy range. Meaning, on the right day, so to speak, all 3 could come up with 195 ppm sw
YOU HAVE TO LOOK AT ERRORS AND +/- ACCURACY AND NOT SOME NUMBER YOU SEE
Does that 10% work across the board. No, it varies slightly up or down down depending on organics, silica phosphate, borate, pH and Alk.
HighlandReefer
Team RC
Thanks Boomer for the detailed explanation. :thumbsup:
Jesse,
Do you know what pH your Elos alk kit changes color, at the end of the titration process?
No I do not. I can ask our chemist. I do know that the dkh numbers our kits read and the seawater lab numbers has always been within .3 dkh of each other.
HighlandReefer
Team RC
Jesse,
Very nice that you offer this information. I would like to know this information. Your assistance is much appreciated.
Very nice that you offer this information. I would like to know this information. Your assistance is much appreciated.
kgk
Purveyor of Cool
I see exactly, and I do mean exactly, the same thing with my Elos and Salifert tests. I just figured I was doing it wrong somehow. :hmm3:
this is me
Active member
I don't use Salifert anymore but when I used to have one, I tested against my Elos and the salifert's result was also higher than my Elos. I then buy a Sera kit and it tested the same as my Elos. I threw the Salifert and never looked back since.
I use Sera for my weekly check(because it's cheaper and offer the same result) and my Elos if my Sera reading is off from what I used to get for verification.
I use Sera for my weekly check(because it's cheaper and offer the same result) and my Elos if my Sera reading is off from what I used to get for verification.
James404
I <3 Acros
As cliff said before, most alk kits including the elos are designed for freshwater, whereas salifert is designed for marine use. The elos kit will read approx 10% lower then the salifert.
Thanks to Boomer and Cliff.
As said Salifert tends to read high due to the end point.
IMO What to look for in a test kit is consistency from batch to batch.
If we have to add 10% to Elos but the test kit is consistant that is no problem, but if you have a test kit that reads salt water but inconsistant that is no good either.
From my experience I found Elos to be very consistant from batch to batch.Therefore add 10% which is easy to do.
As said Salifert tends to read high due to the end point.
IMO What to look for in a test kit is consistency from batch to batch.
If we have to add 10% to Elos but the test kit is consistant that is no problem, but if you have a test kit that reads salt water but inconsistant that is no good either.
From my experience I found Elos to be very consistant from batch to batch.Therefore add 10% which is easy to do.
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