Is ICP magnesium test accurate?

[Miami Reef]

Red Sea Magnesium kit tested my magnesium above 1500

I purchased 2 different salifert magnesium kits, and they both showed 1400ppm

My ICP from ATI from a few months back said my magnesium was 1281ppm

I use instant ocean purple. I have NEVER dosed magnesium, besides for the small amount in tropic Marin balling part C that maintains the ionic balance with my 2 part.

I maintain my salinity at 35ppt.


Read these quotes from the thread where I asked for magnesium kit recommendations:

I would not be 100% confident in the accuracy of icp. I sent 2 tests in with samples of RODI taken from the same brute container at the same time and received totally different results.

To add to the above comment, magnesium can be especially wrong on ICP test. Due to this, some companies even use a different method for magnesium.

Is it true that ICP is not accurate with magnesium? I was under the impression that ICP was especially accurate with major elements.

I don’t chase numbers for magnesium, but it would be nice to know around where it is.

 

[The_Paradox]

Assuming the company had even half way decent GLP/GMP, MS will be several orders more accurate than a household titration test.

 

[Mattiejay6]

Given your description… it would seem that magnesium should be lower no? How accurate do you feel these at home tests are in comparison to lab tests?

Based on Christophs post about Oceamo and how he runs control samples before every test. I certainly feel comfortable with their accuracy.

the first guy you are quoting.. lots of missing variables to his post other than he sent in RODI water and he said both samples were way different. darn those silicates lol

 

[Miami Reef]

Given your description… it would seem that magnesium should be lower no?

Yes, especially since there was a recent thread on someone sending their freshly made sample of instant ocean to Oceamo. Our magnesium results were only 5ppm apart!: https://www.reef2reef.com/threads/oceamo-icp-ms-results-for-instant-ocean-batch-23108.992762/

I really believe my mag is around 1280, but it doesn’t make sense since @taricha said the salifert was really good!



I know I preformed the test accurately.

 

[Mattiejay6]

Yes, especially since there was a recent thread on someone sending their freshly made sample of instant ocean to Oceamo. Our magnesium results were only 5ppm apart!: https://www.reef2reef.com/threads/oceamo-icp-ms-results-for-instant-ocean-batch-23108.992762/

I really believe my mag is around 1280, but it doesn’t make sense since @taricha said the salifert was really good!



I know I preformed the test accurately.

… back when I tried using the salifert tests I always found they were pretty high.. I didn’t find it to be a reliable test and I never relied on it. with all of the context, you have given And in comparison with that fresh salt test. I’d say you should go with your gut and that the ati test is where you are.

 

[rtparty]

Here is the chart from Sanjay’s ICP experiment with 5 different companies.

Potassium is the top row in the 400s. Magnesium is in the middle at 1350ish and Sodium is the bottom row all around 10,500 to 11,000.

This shows that ICP is likely quite accurate and reliable with major elements. I would 100% believe ATI ICP over your home kits. Almost every Red Sea magnesium test kit I’ve tried over reports around 200ppm.

My Salifert kit was almost spot on with ICP results during my salt testing experiment. Then one day it went rogue and reads over 1500 no matter what salt I test. Like it expired 2 years early or something.

 

[taricha]

My salifert was within 20-30 below ATI.
That said, "Is ICP accurate for Mg" is a bit too vague. Sent one sample and got 1280 to 1480 for different ICP vendors.

I purchased 2 different salifert magnesium kits, and they both showed 1400ppm

My ICP from ATI from a few months back said my magnesium was 1281ppm

So I'd just call yours 1340 +-60 ppm, that is - close enough.

 

[Miami Reef]

My salifert was within 20-30 below ATI.
That said, "Is ICP accurate for Mg" is a bit too vague. Sent one sample and got 1280 to 1480 for different ICP vendors.



So I'd just call yours 1340 +-60 ppm, that is - close enough.

I think you might be right.

On October, 2022 (ATI ICP) my salinity was 35.5, and my magnesium was 1368ppm

I used the same salt brand, and I never dosed magnesium. I can say with certainty that the salifert was VERY precise. Both test kits test the exact same.

 

[The_Paradox]

I think you might be right.

On October, 2022 (ATI ICP) my salinity was 35.5, and my magnesium was 1368ppm

I used the same salt brand, and I never dosed magnesium. I can say with certainty that the salifert was VERY precise. Both test kits test the exact same.

That means they are consistent not precise.

 

[Miami Reef]

That means they are consistent not precise.

Precision and consistent is the same thing. You can be precise and not accurate, vise versa, both, or neither.

 

[The_Paradox]

Precision and consistent is the same thing. You can be precise and not accurate, vise versa, both, or neither.

That’s not correct. Consistency can be calibrated to be precise but does not mean it is inherently accurate. If you’re off 1MOA down every shot, you’re low.

 

[Miami Reef]

That’s not correct. Consistency can be calibrated to be precise but does not mean it is inherently accurate. If you’re off 1MOA down every shot, you’re low.

You can’t argue with me on this. I learned this in chemistry lab 101

Precision and accuracy are two ways that scientists think about error. Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other. Precision is independent of accuracy.

Practices of Science: Precision vs. Accuracy | manoa.hawaii.edu/ExploringOurFluidEarth

manoa.hawaii.edu

 

[Miami Reef]

That’s not correct. Consistency can be calibrated to be precise but does not mean it is inherently accurate. If you’re off 1MOA down every shot, you’re low.

I think we are saying the same thing. Forget about the word consistency.

Precision is how close your results are to each other. Accuracy is how close you are to the true target. You can be precise, but not accurate.

The chart I posted above is correct (With the darts on the board)

 

[The_Paradox]

Wait, I think we are saying the same thing.

People (in general) mix terms here too often. Confidence/repeatability can be high while still being inaccurate. Your two tests could be very consistent and adjusted/correlated to an accurate number.

 

[Randy Holmes-Farley]

For reasons i do not understand, the Red Sea magnesium kit seems to give folks more trouble than other brands, nd often seems to read high.

Maybe they are not properly sorting calcium from magnesium.

 

[Dan_P]

Red Sea Magnesium kit tested my magnesium above 1500

I purchased 2 different salifert magnesium kits, and they both showed 1400ppm

My ICP from ATI from a few months back said my magnesium was 1281ppm

I use instant ocean purple. I have NEVER dosed magnesium, besides for the small amount in tropic Marin balling part C that maintains the ionic balance with my 2 part.

I maintain my salinity at 35ppt.


Read these quotes from the thread where I asked for magnesium kit recommendations:





Is it true that ICP is not accurate with magnesium? I was under the impression that ICP was especially accurate with major elements.

I don’t chase numbers for magnesium, but it would be nice to know around where it is.

We (@Rick Mathew , @taricha ) will soon present data to confirm the ICP could have problems with Mg.

 

[Ef4life]

For reasons i do not understand, the Red Sea magnesium kit seems to give folks more trouble than other brands, nd often seems to read high.

Maybe they are not properly sorting calcium from magnesium.

Well the instructions are very specific on the Red Sea pro and it takes time to do the test properly, my guess is most don’t actually take the time to do it the correct way.

I use the Red Sea pro and my magnesium tests are always consistent, and if I do a test and then add a set amount of magnesium I can then retest, and it increases the amount I added within +/- 50ppm. Plenty good enough

 

[Miami Reef]

Well the instructions are very specific on the Red Sea pro and it takes time to do the test properly, my guess is most don’t actually take the time to do it the correct way.

I use the Red Sea pro and my magnesium tests are always consistent, and if I do a test and then add a set amount of magnesium I can then retest, and it increases the amount I added within +/- 50ppm. Plenty good enough

Not true for me. I followed the directions to the T, but I still had these issues.

 

[Randy Holmes-Farley]

Well the instructions are very specific on the Red Sea pro and it takes time to do the test properly, my guess is most don’t actually take the time to do it the correct way.

I use the Red Sea pro and my magnesium tests are always consistent, and if I do a test and then add a set amount of magnesium I can then retest, and it increases the amount I added within +/- 50ppm. Plenty good enough

That may be, but your reported experience is also still consistent with it reading high.

 

[Reefahholic]

For reasons i do not understand, the Red Sea magnesium kit seems to give folks more trouble than other brands, nd often seems to read high.

I will echo what Randy said. I find Red Sea test kits to report extremely high values on ICP. Definitely do not stop at first color change. Make sure you go at least 3-4 drops past that to get a “complete” color change for more accuracy.