ICP Calcium vs. Test Kit

[msderganc]

Just browsing through some of the ICP results over the past few weeks, I've only noticed one below 400ppm. Most are 440-460+.

My test came back with 438ppm, even though my test kits are reading 400. I have another test in, and I should get the results back any day. I let my Ca levels (at least by two test kits) go down to about 365 since my target is really about 400-410, so I'm interested to see what ICP reads this time.

Those of you who have done the Triton test - could you please post your measured Ca vs. the ICP Ca? My hypothesis is that there's about a 30-40ppm systematic disparity between the two.

 

[Keithcorals]

I noticed the same thing but I also noticed the setpoint for calcium from Triton is 440 and they are from what I understand basing their set points on what they found in natural seawater from reefs. I know I've read a few place that natural sea water has a calcium level around 400. It would be nice to hear from Triton on this.

Salifert Ca 440
Triton Ca 463

I also have another test sent out right now I'll post the results when I get them

 

[Nano sapiens]

Salifert (Low-Res) Ca 460
Triton Ca 491

~30 mq/l difference.

I noticed this discrepancy, too. NSW is typically close to 400 mg/l, but reef hobbyists tend to keep a somewhat elevated level so perhaps that is why Triton is showing 440.

 

[FarmerTy]

Red Sea - 420 ppm
Triton - 495 ppm

I prefer to trust tritation based tests on Ca so I default to my own test results for Ca versus Triton's results.

 

[jgalen0025]

Red Sea - 420 ppm
Triton - 495 ppm

I prefer to trust tritation based tests on Ca so I default to my own test results for Ca versus Triton's results.

Thats funny because the error with titration based testing is pretty high. With some kits it can be up to greater than 10% A reading of 440 is actually 440+/- 44ppm. The Triton testing based on Ehsan's publication is much more accurate in and of itself.

"Given the inherent uncertainties of our test kits, and a degree of variation from the user, most hobbyist grade test kits will have an uncertainty (i.e., a likely range of error) on the order of at least 5-10% of the value being measured, and much higher in some situations."
~Skeptical Reefkeeping

 

[Randy Holmes-Farley]

FWIW, the variability in kit calcium levels on the same water can be huge.

Check this article where they tested a bunch of kits on the same water sample.

The range is shocking!

Aquarium Chemistry: An Attempt to Test Test Kits ? Advanced Aquarist | Aquarist Magazine and Blog

 

[FarmerTy]

Thats funny because the error with titration based testing is pretty high. With some kits it can be up to greater than 10% A reading of 440 is actually 440+/- 44ppm. The Triton testing based on Ehsan's publication is much more accurate in and of itself.

"Given the inherent uncertainties of our test kits, and a degree of variation from the user, most hobbyist grade test kits will have an uncertainty (i.e., a likely range of error) on the order of at least 5-10% of the value being measured, and much higher in some situations."
~Skeptical Reefkeeping

The approved EPA method for Calcium is titration based.

http://www.caslab.com/EPA-Methods/PDF/EPA-Method-2152.pdf

Though this test is for freshwater. As I understand it, ICP can detect down to very low levels for Calcium in freshwater but with all the interference in saltwater, you basically have to dilute the sample and extrapolate your readings. At least this is what I understood from speaking with a fellow environmental scientist. I'll defer to the experts on this though as I'm not a chemist.

 

[msderganc]

FWIW, the variability in kit calcium levels on the same water can be huge.

Check this article where they tested a bunch of kits on the same water sample.

The range is shocking!

Aquarium Chemistry: An Attempt to Test Test Kits ? Advanced Aquarist | Aquarist Magazine and Blog

I do understand that there is significant error possible in home test kits, but if we are all (10%+) lower than the ICP, that would point to a systematic bias either in the home kits or in the ICP. A more normal distribution would be anticipated with some higher and some lower if it were just uncontrollable error.

 

[Randy Holmes-Farley]

I do understand that there is significant error possible in home test kits, but if we are all (10%+) lower than the ICP, that would point to a systematic bias either in the home kits or in the ICP. A more normal distribution would be anticipated with some higher and some lower if it were just uncontrollable error.

True, but if that were the case, then the article I posted must be way wrong in its assessment of kits since the values ranged over more than a factor of two.

 

[msderganc]

True, but if that were the case, then the article I posted must be way wrong in its assessment of kits since the values ranged over more than a factor of two.

Yeah, I've always halfway doubted that article because the range is so extreme. It was like he gave it to people who had never seen a test kit before to do the testing. Plus, he indicated that the actual water level was 338 ppm. There are a lot over that, and a lot under that number, which would indicate some portion of random error.

When I test my water among three (and sometimes four) test kits (Red Sea, Salifert, Hanna, and sometimes LaMotte) and all of them are within 5-10ppm of each other, and repeatably so, it makes me think that there is some fundamental difference in what the titration is measuring vs. what the ICP is measuring. I would love Triton to weigh in on this. Just in this thread there are a half dozen similar reports about calcium in particular.

 

[Randy Holmes-Farley]

FWIW, I did see a confidential test on a seawater sample with known calcium content (not a reef tank sample; not tested with a test kit) and it did read a bit higher than the guaranteed concentration. I don't know how the "standard" concentration was determined, but I expect the guarantee was based on ICP. Unfortunately, that's all I can say about that test.

With regard to the ICP method itself, this was my experience with it in relation to the Salifert kit in an old article of mine:


For initial testing I chose to use as the "standard" a sample of artificial seawater that was mixed to an approximate salinity of S=35. I mixed a 44-gallon batch using Instant Ocean artificial salt mix and reverse osmosis/deionized (RO/DI) water to a conductivity of 52.7 mS/cm, and allowed it to settle for three weeks. I then proceeded to measure its calcium concentration by ICP-AES (inductively coupled plasma-atomic emission spectroscopy, an $80,000 analytical instrument. I was somewhat disappointed with my inability to use this sophisticated technique to get a precise answer. Despite taking five different samples and analyzing them at eight different emission wavelengths using two different calibration methods (five standard additions of known calcium concentrations to each sample, as well as comparison to a fixed 1000 ppm commercial calcium standard), I was unable to get consistent values. Some of the samples were acidified or filtered through submicron filter membranes to determine if solid materials were impacting the result (they were not). Overall, I took more than 200 measurements, each involving three replicate observations of the emission intensity. Nevertheless, the result was not very satisfying, with a substantial variation occurring between the different values. The average of every measurement taken was 336 ppm. With the uncertainty involved, however, I'd conclude that the true value was probably 340 ± 40 ppm. I also measured the same sample once with a Salifert brand test kit and got 330 ppm calcium.

 

[msderganc]

FWIW, I did see a confidential test on a seawater sample with known calcium content (not a reef tank sample; not tested with a test kit) and it did read a bit higher than the guaranteed concentration. I don't know how the "standard" concentration was determined, but I expect the guarantee was based on ICP. Unfortunately, that's all I can say about that test.

With regard to the ICP method itself, this was my experience with it in relation to the Salifert kit in an old article of mine:


For initial testing I chose to use as the "standard" a sample of artificial seawater that was mixed to an approximate salinity of S=35. I mixed a 44-gallon batch using Instant Ocean artificial salt mix and reverse osmosis/deionized (RO/DI) water to a conductivity of 52.7 mS/cm, and allowed it to settle for three weeks. I then proceeded to measure its calcium concentration by ICP-AES (inductively coupled plasma-atomic emission spectroscopy, an $80,000 analytical instrument. I was somewhat disappointed with my inability to use this sophisticated technique to get a precise answer. Despite taking five different samples and analyzing them at eight different emission wavelengths using two different calibration methods (five standard additions of known calcium concentrations to each sample, as well as comparison to a fixed 1000 ppm commercial calcium standard), I was unable to get consistent values. Some of the samples were acidified or filtered through submicron filter membranes to determine if solid materials were impacting the result (they were not). Overall, I took more than 200 measurements, each involving three replicate observations of the emission intensity. Nevertheless, the result was not very satisfying, with a substantial variation occurring between the different values. The average of every measurement taken was 336 ppm. With the uncertainty involved, however, I'd conclude that the true value was probably 340 ± 40 ppm. I also measured the same sample once with a Salifert brand test kit and got 330 ppm calcium.

Wow, thanks for that.

 

[fjsdvm]

I am glad to see all the responses to my post yesterday when I asked 64Ivy if he had a disparity between his kit measured Calcium and the Triton results. I am not surprised to see that many are reporting that their kit values are lower. As stated, I run the Red Sea Calcium Pro kit test on a regular basis. I happen to own a veterinary hospital and am fortunate to have a very nice blood chemistry analyzer (Idexx Catalyst DX). When I first started using the Red Sea test I compared my test kit results with the analyzer and found that Calcium levels reported in both the test kit and analyzer were consistently within 2% agreement. Of all the kit tests that I run, I find the Calcium Pro to be very easy perform without error and the color change to be quick and obvious (this is probably also true in regards to the Salifert test kit). Certainly there are other titration test kits (Sr+/Fe+ etc) which have more complicated procedural protocols with color changes which occur slowly. I think the majority of advanced reef keepers run their calcium tests accurately and with valid results. Yes, we definitely need more responses to get a statistically significant answer and I think we need to continue to pursue the apparent disparity between kit testing and ICP so that we can develop a set of "normal" values for each. I do think the information we get from ICP testing is very important, we just do not know how to interpret it completely at this time.

 

[dgrigor02]

Who really cares ? even 40ppm +/- or even 60ppm +/- it doesn't really matter. As long as your confident it's above 360ppm is really all that matters.

If your looking for growth, there are far more important factors to concentrate on than whether your calcium ppm is 400 or 500ppm or anywhere in between.

 

[msderganc]

Who really cares ? even 40ppm +/- or even 60ppm +/- it doesn't really matter. As long as your confident it's above 360ppm is really all that matters.

If your looking for growth, there are far more important factors to concentrate on than whether your calcium ppm is 400 or 500ppm or anywhere in between.

Well that's exactly the issue. I could be shooting for (and measuring) 390ppm calcium, and really be at 350ppm.

If the ICP is higher than reality, a lot of people could adjust their tanks down and cause problems. Given the results posted so far, it's not that the test is +/-40, it's that it is always higher than what we're measuring.

The second, and more disturbing, implication is that the ICP isn't as accurate as it's been sold, at least for our purposes.

 

[swk]

Red Sea - 430
Triton - 464

 

[Sangheili]

RS calc: 425
Triton calc: 413

I tend to test on end color change not beginning so my test could be 20-40 high.

 

[dgrigor02]

Well, I've been pretty successful in this hobby with all kinds of inhabitants over that last 18years believing the titration test kit, so I really don't care if the triton is giving a higher reading than what I get with my test kit. If my test kit was so far off that I'm actually below 360ppm I would have seen signs of low calcium by now by observation.

So like others have said, just keep moving forward with what has got you this far. Just go with the lower of the two readings ( if you really worried take a sample to a friend or lfs and have it double checked ) and focus on other key factors for growth etc. Like nitrate/phosphates, alkalinity, lighting, flow the list goes on and on.

 

[FarmerTy]

I think this post was more to see if there is a correlation of ICP values being generally higher than home titration kit values. I don't think anybody discussing here is worried as much of implications to the tank, but more curious about the discrepency of values between the two test types. I think we all generally know that 420 or 460 doesn't really matter, as long as it's within accepted parameters.

 

[Ehsan@triton]

Hey guys, maybe I can help you with that a bit.

1. The fluctuations showing up out of our data, in terms of Ca and Mg testing at hom , are quite high. Like Randy said before the Article is not realy far out... but the bigest problem seems not to be the chemicals or different test it is more the human user.

2. For Analytikal reasons therefor you wil get the best results with a "Photometer" to get out the Human error.

3. In our ICP Method your Tests are not tested only once, like Randy said ICP-OES testing of seawater is very difficult. Your tests are actualy caried out 6X and the averge out of them is taken as the result.
Each time we test your for example Calcium, inreality it is detected/tested 2400 Times to create one of the 6 testresults.... So in simple words you can say we test your calcium 2400 x 6 = 14400 Times and then take the average.
This kind of testing make the result quite Accurate... but it is also needed as the conditions are not always Perfect.
So we can say for Calcium we have a + / - 5ppm deviation in the range of 100ppm - 550ppm HTS (High troughput Seawater) copared to a certified standard and NSW and the TRITON Dt controles. but we would also accept a +/- 10ppm.

4.You can addapt the "Methode of often testing" to your own testing if you want. By testing more often and takeing the average you can significantly lower the magnitude of every test method . When you use the human eye as an detector you should also let your Family test some times and take the average then.

5. The 440 setpoint has more a practical reason. in seawater we normaly detect 410, but in the reeftank we think its better to have a smal buffer... as some people forget about dosing or dosingpumps are broken... our Tank is at 480ppm Ca.

6. But the higest instance is still your Tank the testings are only tools to help you decide the right things, so no chasing Nr. like always I would say ( even having my ICP over here)


Hope that helps sorry for the english
All the best Ehsan