ICP test results vs. Hobby Grade!!!

[MERKEY]

UPDATE:
So I did what I said I was going to do. Slowly raise my calcium and alk. added trace elements, and dosed Red Sea Reef energy AB+, followed by rods food.
The day before my short tent pinwheel looked like this(here he’s eating a shrimp)

After doing all my dosing, I went to sleep, woke up, went to work, and came home to THIS:

i have never seen it look like this, not even in the LFS when I bought it. It’s like on steroids lol. So, I’m happy

Thats a huge improvement

 

[Lasse]

This digestions occurs in sulfuric acid at high temps for hours.

Yes - and if you did not tighten the cap with force before the start of the process - you have a burned ceiling above the diggester At least I had that in my old Lab

Sincerely Lasse

 

[Lasse]

It is important to stress once again that Hannas HI736 do not measure P - it only measure PO4-P - it means the P part of the inorganic PO4 molecule. In a stored sample PO4 can be biological transformed to forms that the Hi734 (or other Hanna P or PO4 Checkers can not measure) - therefore - the HI735 report lower P content in a stored sample because it only report PO4-P - not other forms of P. ICP measure all forms of P - therefore it does not change with storage if the sample is evenly homogenized.

Sincerely Lasse

 

[Dan_P]

Where? you do not misunderstand the word accuracy with 95% confidence interval?

Sincerely Lasse

Hanna reports the +/- ppm +/- % of the reading for each instrument type. This amounts to two standard deviations.

 

[Rick Mathew]

Hopefully this helps put the P issue to bed. I have a reference below that hopefully will clarify things.

with regard to Total "P"... the Hanna meter will never give you total P and i believe that is acknowledged in the instructions. To get total P you can't shake and read. You have to "digest" the sample for hours at 300 degrees C to break down the organics. For example.. DNA is full of phosphorus.. but make a DNA sample in water and the hanna meter ain't gonna show that because "shake with no bake" is not gonna break DNA down into phosphate which is what the meter is looking for. The assumption with the hanna process is "most" of the P containing organics are broken down into PO4 during that shake.. but not all. For the purposes of a reef tank none of that probably matters and i don't see the need for doing phos by ICP when you have Hanna ULM unless you are doing research. The more complex P we don't read with the hanna is likely inconsequential.

Now that hopefully everyone sees that the hanna method cannot guarantee total P let's looks at ICP vs. Colorimetric (Hanna). In the real world where data counts samples must be digested for the colorimetric analysis of Total P to be effective. This digestions occurs in sulfuric acid at high temps for hours. In ICP.. your sample is aspirated into a plasma at 6,000 kelvin (temp of the sun). In theory ALL of the organic P is broken down at that temperature which is why ICP values should be greater than or equal to a hanna value. If your Hanna sample was "digested" prior to analysis then now you can make the argument the values should be equal between Hanna and ICP.

Here is the abstract for the reference below. Keep in mind colorimetric analysis is "digested" when comparing to ICP.

The possibility that P concentrations in extracts, digests, and water samples might be different when measured with inductively coupled plasma spectrometry (ICP) as compared to colorimetric procedures has been debated since the introduction of ICP instruments. The ability of ICP to measure several elements simultaneously has increased interest in multi-element extracts for routine soil testing and likely reduced the use of the colorimetric approach. However, colorimetric procedures offer some advantages, such as increased sensitivity and lower instrumentation costs, and it is unlikely that ICP will completely displace colorimetric procedures. The commonly held belief is that ICP would measure greater P concentrations than colorimetric procedures because the high temperature environment of the plasma would allow the measurement of organic P compounds or other soluble P complexes that would not be measured colorimetrically. Differences in P concentrations measured by these two methods may have implications for agronomic and environmental P testing. The purpose of this paper is to discuss potential differences in P determination by ICP versus colorimetric procedures.

https://sera17dotorg.files.wordpress.com/2015/02/sera-17-icp-vs-color-methodology-position-paper-2005.pdf

Nice find on the paper...Good read!

So I will start with a quote from the Summary and Conclusions of this paper

"The method of P determination used in water samples and extracts of soils and by-products can influence the reported concentrations. For most sample types, ICP is slightly greater than colorimetric analyses, but the two methods are well correlated for high P samples. However, extreme caution needs to be used for samples with low P concentrations (e.g., 60 mg/kg extractable P), as the difference may be as great as 5 fold. "

This matches quite nicely with my understanding of what to expect, as you well point out above. I should expect that any measurement taken by a Hanna Instrument would not pick up total P. Where as the ICP testing would pick up total P. This would necessarily mean, as the paper you provided states, the ICP measurement will be slightly greater in total P than that of the Hanna Instrument. I seems according to the paper that as you move down in concentration the difference get greater.

This is exactly what I expected when I sent in my first ICP test and compared it to my Hanna results, but to my surprise the ICP reported a lower value for P and PO4....not by a small amount by close to 50% (My measurement 20 ppb P ....ICP 10 ppb P) I concluded that my measurement was incorrect so I went back to my retained sample of the test I sent for ICP analysis and retested....Sure enough I got a lower reading 12 ppb----close enough! So that should have been the end of the story, but it was not lucky!!.. I continued to send in ICP tests every 90 days (Started in 2017) and I saw exactly the same results...Not every time but by far the majority.... ICP lower P than Hanna Hi-736 ...Retest the retain...looks good.

Call me a slow learner ....It took me almost 2 years to stop and ask the question what is going on? I am either the worlds worst (but consistent) Tester or there is something I am missing. I had seen on this forum several discussions about the same observation...ICP tests lower then Hanna Tester and didn't really follow them until @taricha made a statement that caught my attention "maybe the sample is not stable" ...That set me down this "Rabbit Hole"....And literally 100's of tests later here we are...My first posting ( https://www.reef2reef.com/threads/sample-storage-and-its-impact-on-phosphate-measurement.696800/) was the beginning of my trip to "Wonderland" but only the beginning. I basically set our to understated what impact storing a sample has on my test results... My basic conclusion for myself was not to store samples for any length of time in any type of container....Which is as it turns out was well known before I went down the "Rabbit Hole"....My bad should have done more looking...none the less I got really good at the test, ....But it still did not answer my question "Why do my ICP tests come out consistently lower than my Hanna results?" According to my understanding this should not be happening and if I read the paper you provided correctly they agree...Should not be lower only higher or at best equal to.

I proposed in my first post, where I reported the depletion of P (PO4) during storage when tested with a Hanna Checker, that this depletion could be an explanation of why my (as well as others) ICP tests for P were lower than my Hanna Checker....This speculation has taken me down an even deeper "Rabbit Hole"...on containing Biofilms...Metal immobilization by biofilms and all kind of exciting stuff. My work on this second "Rabbit Hole" is almost completed and it was focused on the "Missing P" issue and how I might correct it....

I do not characterize this a an ICP testing issue, but an overall protocol issue relating to the sampling . As the information you provide and the article I have suggest water sampling is no trivial issue....Can't just "dip and go"....One has to consider type of container, preservation requirements etc. based on the elements you are testing . As you very well pointed out some elements and compounds are "rugged" and can be handled accordingly but others like P...PO4.. NO2 are much more demanding in the sample handling...This is like a whole science unto itself!

Does ICP testing overcome these sampling issues? Can a vendor hold a sample for several days and still get the same test results?...I can for sure say my testing methods can not. I contend that this sampling problem does impact ICP test results for some elements. Some how, way beyond my understanding, it has to do with Bio-activity and biofilms that prevent the availability of some amount of P in this case from being available to the current test protocols...This is the focus of my second trip to "Wonderland"


So this is a very long winded way of saying ....I am not quite yet settled on the matter.

Respectfully

rick

 

[Rick Mathew]

It is important to stress once again that Hannas HI736 do not measure P - it only measure PO4-P - it means the P part of the inorganic PO4 molecule. In a stored sample PO4 can be biological transformed to forms that the Hi734 (or other Hanna P or PO4 Checkers can measure) - therefore - the HI735 report lower P content in a stored sample because it only report PO4-P - not other forms of P. ICP measure all forms of P - therefore it does not change with storage if the sample is evenly homogenized.

Sincerely Lasse

Hey Lasse would you happen to know the homogenization procedure....I can always ask a vendor if you don't know

thanks

rick

 

[Lasse]

They report the accuracy but do not say if it is in the 95 % confidence interval or not. Nowhere in the paper I have seen is the confidence interval for their accuracy mentioned. It could be in the 100 % or in the 50 % - what do I know. The term accuracy is not the same as the variation reported is in a 95 % confidence interval. It could be (but if - it is normally stated that the ± is inside a 95 % confidence interval) and it could not be.

But the problem is also that every sold Hanna checker is its own machine and should this be serious (with your way of seeing things) - every single checker should have it own variation based on 95 % confidence interval noted.

What does it means if the ± x ppm (ppb in some cases) is inside a 95 % confidence interval? It also means that - in average - of 20 measurements - 1 is off records. IMO - after have done a lot of repetitive test on repeatability - around every teenth test is off record. And I have not test the other leg of accuracy - the precision.

Sincerely Lasse

 

[Lasse]

@Rick Mathew - I do not know where to begin.

But try to follow this two paths

1) Assume that it is the ICP test that give the right answer - and the Hanna checkers consistently showing too much. In your world - the truth is what Hanna checker show - thats not that way in my world

2) You still use the PO4 instability caused of biological processes as a prove that the ICP analyse of elemental P is wrong.

Try to follow this example - the true PO4 level is 0,307 ppm. Hence the phosphorus (elemental P or PO4-P) part of this is 0.1 ppm. (and the O4 part 0.207 ppm) We store this sample for 5 days. Bacteria and other biological processes use P in the PO4 molecule in order to build biomass. Let us say that half of the PO4-P will be in the form of bacteria biomass. Its remain 0.05 ppm PO4-P - or 0.153 ppm as PO4. If you analyse with a checker - you will read 0.153 ppm PO4. But the 0.05 ppm P that you miss in the checker analyse has not leaved the earth - it is still in the sample tube but as organic P in this case. When the content in the tube is homogenized before the ICP test - even this P will be analysed of the ICP machine and you will get the result 0.1 ppm P. The total content of P have not been changed - only the species of P has been changed to forms not possible for the Hanna checker to analyse.

Sincerely Lasse

 

[Rick Mathew]

@Rick Mathew - I do not know where to begin.

But try to follow this two paths

1) Assume that it is the ICP test that give the right answer - and the Hanna checkers consistently showing too much. In your world - the truth is what Hanna checker show - thats not that way in my world

2) You still use the PO4 instability caused of biological processes as a prove that the ICP analyse of elemental P is wrong.

Try to follow this example - the true PO4 level is 0,307 ppm. Hence the phosphorus (elemental P or PO4-P) part of this is 0.1 ppm. (and the O4 part 0.207 ppm) We store this sample for 5 days. Bacteria and other biological processes use P in the PO4 molecule in order to build biomass. Let us say that half of the PO4-P will be in the form of bacteria biomass. Its remain 0.05 ppm PO4-P - or 0.153 ppm as PO4. If you analyse with a checker - you will read 0.153 ppm PO4. But the 0.05 ppm P that you miss in the checker analyse has not leaved the earth - it is still in the sample tube but as organic P in this case. When the content in the tube is homogenized before the ICP test - even this P will be analysed of the ICP machine and you will get the result 0.1 ppm P. The total content of P have not been changed - only the species of P has been changed to forms not possible for the Hanna checker to analyse.

Sincerely Lasse

Lassie thank you for the reply...let me play back what I think you said by using an example.

1) I take a tank sample and measure it on my HI-736 and get a P (PO4-P) value of say 24 ppb (.074 PPM PO4)

2) I then send the sample to an ICP vendor and 4 later (3 days in transit one day testing) they test the sample...They should get some value equal to or higher than the 24 ppb I got because my Hanna Check will not pick up the organic phosphate portion...Lets say 30 ppb (.09 ppm PO4) for example.

3) I have a sample retain of the sample tested in step #2 of the example also stored for 3 days and I test it on my HI-736 I will get a value even lower than my initial reading (24 ppb) because of the some portion of the PO4-P will be covered to biomass...Lets say around the 50% you used...10 ppb.

4) I now send the same water sample that I have kept in storage for an addition period of time in the sample tubes to an ICP vendor. They test the sample and should get some value close to the 30 ± ppb they got in step 2 of the example

5) I test the water sample sent in step # 4 on my HI-736 I will find even a lower measurement than I got in step # 3 < 10
ppb

My Data Table would look like this

PPB P​	INITIAL​	DAY 3​	EXTENDED TIME​
MY MEASUREMENT	24 ± 5 PPB​	10 ± 5 PPB​	8 ± 5 PPB​
ICP MEASUREMENT	30 ± ? PPB​	30 ± ? PPB​	30 ± ? PPB​

Does this capture your example?

Thanks Again

Respectfully

rick

PS In my world the Hanna Checkers are not the truth...They are data and just like any data subject to skepticism

 

[4sylvester]

Try to follow this example - the true PO4 level is 0,307 ppm. Hence the phosphorus (elemental P or PO4-P) part of this is 0.1 ppm. (and the O4 part 0.207 ppm) We store this sample for 5 days. Bacteria and other biological processes use P in the PO4 molecule in order to build biomass. Let us say that half of the PO4-P will be in the form of bacteria biomass. Its remain 0.05 ppm PO4-P - or 0.153 ppm as PO4. If you analyse with a checker - you will read 0.153 ppm PO4. But the 0.05 ppm P that you miss in the checker analyse has not leaved the earth - it is still in the sample tube but as organic P in this case. When the content in the tube is homogenized before the ICP test - even this P will be analysed of the ICP machine and you will get the result 0.1 ppm P. The total content of P have not been changed - only the species of P has been changed to forms not possible for the Hanna checker to analyse.

Sincerely Lasse

This is a great example and follows conservation of mass. P cannot be created or destroyed but it can change form.

 

[4sylvester]

Does ICP testing overcome these sampling issues? Can a vendor hold a sample for several days and still get the same test results?...I can for sure say my testing methods can not. I contend that this sampling problem does impact ICP test results for some elements. Some how, way beyond my understanding, it has to do with Bio-activity and biofilms that prevent the availability of some amount of P in this case from being available to the current test protocols...This is the focus of my second trip to "Wonderland"

Respectfully

rick
[/QUOTE]


LOL.. dooms day stock? haha. ICP is a destructive analysis. When the sample hits that plasma it decomposes instantly. That is why it doesn't discriminate. It doesn't know the difference between an organophosphate, DNA, or free phosphate PO4. In theory... ICP will be greater than or equal to hanna but i am not surprised we don't observe this. There are real world problems to consider. First let me point out i am chemist and not a biologist so excuse my ignorance in the bio arena.

In the environmental world samples for most metals can be stored for 6 months with no change in integrity. The only requirement is that the sample is digested in acid prior to ICP. It doesn't matter if you test the same day or 6 months later you must digest. The reason for that is simple... over time metals can change the form they take. Lead is always lead but over time lead chloride might "precipitate" out of solution. You can't load a solid onto ICP so that gets left behind. We see this all the time. Samples sit and solids form and fall to the bottom. That is why digestion is a requirement. Acid and heat break up those insoluble precipitates. The metals go back into solution which is introduced to the ICP at time of analysis.

Now let's consider free phosphate in your reef sample you ship off for ICP. You have tons of bacteria in that sample. Those bacteria may assimilate phosphate or incorporate phoshpate into cellular growth. you free PO4 is gone.. its now an organic form within bacteria. Could that bacteria stick to the sample container? Sort of like when you put tap water in a dog bowl? AFter a few days bacteria grows on the bowl and it gets slimy? If that is what is happening with your sample then that portion of the sample would not get sucked up into the ICP. This is just speculation but unless you digest the sample or analyze it immediately you allowing for all sorts of changes to occur. If you have any changes to the uniform concentration of the sample it will affect the results.

 

[4sylvester]

My Data Table would look like this

PPB P​	INITIAL​	DAY 3​	EXTENDED TIME​
MY MEASUREMENT	24 ± 5 PPB​	10 ± 5 PPB​	8 ± 5 PPB​
ICP MEASUREMENT	30 ± ? PPB​	30 ± ? PPB​	30 ± ? PPB​

rick

PS In my world the Hanna Checkers are not the truth...They are data and just like any data subject to skepticism

Yes what you propose is very feasible. ICP results will stay constant in theory. Your Hanna results? not so sure because you have two processes going on. Yes, you could have bacteria consuming phosphate. But what about trace amounts of fish food that hasn't decomposed yet? That could make phosphate go up over time as it decomposes. I guess it depends if decomposition is occurring faster than bacterial consumption of phoshpate. this might be a worthy experiment. This is why PO4 must be analyzed as soon as possible.

 

[Rick Mathew]

Does ICP testing overcome these sampling issues? Can a vendor hold a sample for several days and still get the same test results?...I can for sure say my testing methods can not. I contend that this sampling problem does impact ICP test results for some elements. Some how, way beyond my understanding, it has to do with Bio-activity and biofilms that prevent the availability of some amount of P in this case from being available to the current test protocols...This is the focus of my second trip to "Wonderland"

Respectfully

rick

LOL.. dooms day stock? haha. ICP is a destructive analysis. When the sample hits that plasma it decomposes instantly. That is why it doesn't discriminate. It doesn't know the difference between an organophosphate, DNA, or free phosphate PO4. In theory... ICP will be greater than or equal to hanna but i am not surprised we don't observe this. There are real world problems to consider. First let me point out i am chemist and not a biologist so excuse my ignorance in the bio arena.

In the environmental world samples for most metals can be stored for 6 months with no change in integrity. The only requirement is that the sample is digested in acid prior to ICP. It doesn't matter if you test the same day or 6 months later you must digest. The reason for that is simple... over time metals can change the form they take. Lead is always lead but over time lead chloride might "precipitate" out of solution. You can't load a solid onto ICP so that gets left behind. We see this all the time. Samples sit and solids form and fall to the bottom. That is why digestion is a requirement. Acid and heat break up those insoluble precipitates. The metals go back into solution which is introduced to the ICP at time of analysis.

Now let's consider free phosphate in your reef sample you ship off for ICP. You have tons of bacteria in that sample. Those bacteria may assimilate phosphate or incorporate phoshpate into cellular growth. you free PO4 is gone.. its now an organic form within bacteria. Could that bacteria stick to the sample container? Sort of like when you put tap water in a dog bowl? AFter a few days bacteria grows on the bowl and it gets slimy? If that is what is happening with your sample then that portion of the sample would not get sucked up into the ICP. This is just speculation but unless you digest the sample or analyze it immediately you allowing for all sorts of changes
to occur. If you have any changes to the uniform concentration of the sample it will affect the results.
[/QUOTE]

Yes my doomsday stash...

You speculation about the "Slim" film is exactly what I suspect...and what ever the ICP test protocols it doesn't pick it up in the pr-sample preparation for "destruction "...I have some experiments that look at this very question...

Thanks for your reply

rick

 

[4sylvester]

You speculation about the "Slim" film is exactly what I suspect...and what ever the ICP test protocols it doesn't pick it up in the pr-sample preparation for "destruction "...I have some experiments that look at this very question...

rick
[/QUOTE]

Yes, no chance ICP vendors are not digesting samples reef samples. My company doesn't run P by ICP otherwise i would run some experiments myself. We run P by EPA Method 365.4 which is digestion followed by automated colorimetric analysis.

 

[Lasse]

Still - all assume that the Hanna Checker always is the standard and show the right value. That´s not my experiences with all checkers and especially the ULR versions. I noted this in november after trying to press down my PO4 for months. My HI774 show around 0.08 and 0.1 and whatever I done - it did not go down. My corals stop to grow, my chaeto stop to grow and I notice for the first time in this nearly 4 years old aquarium small patches of cyanobacteria/dinoflagellates. My eyes screamed nutrient deficiency - my HI774 screamed to high PO4. I sent in a Triton test - get back 6 µg/L (0.006 mg/L or 6 ppb) of P (0.018 mg/l PO4). I also take with a sample to my job and analyse it there with a HI713 - both me and @Sallstrom analyse it. It was inline with the Triton test. I slowly rise my PO4 level - last test it was around 0.06 ppm PO4 (Triton and 0.14 my HI774) After this - I have purchase a Red Sea Pro PO4 test kit and for the moment it shows between 0.08 - 0.12 and my HI774 show between 0.16 and 0.22 ppm. I will soon send in a new Triton test and have also purchased a distant test that analyse PO4 with colourimetric methods.

My growth is good for the moment - the pictures below shows my green monty the 17/6 and 29/6. They are below different lighting but compare the white edge.

What I will say is that at least my HI774 has a rather good repeatability but the precision is 0.08 ppm wrong.

Sincerely Lasse

 

[Ulm_nano_diybudgetreef]

Very interesting topic and points raised. I'm meant to get an ICP test done specifically to look for leaching.

Any reccommendations?

As from what I'm reading doesn't look like theres much point. Water changes and a close eye on things will probably be the best indicator.

 

[Randy Holmes-Farley]

Very interesting topic and points raised. I'm meant to get an ICP test done specifically to look for leaching.

Any reccommendations?

As from what I'm reading doesn't look like theres much point. Water changes and a close eye on things will probably be the best indicator.

Leaching of what from what?

 

[Ulm_nano_diybudgetreef]

Leaching of what from what?

Metals from volcanic rock

 

[Randy Holmes-Farley]

Metals from volcanic rock

ICP is the way to test, and Triton is a reasonable choice.

 

[Rick Mathew]

Still - all assume that the Hanna Checker always is the standard and show the right value. That´s not my experiences with all checkers and especially the ULR versions. I noted this in november after trying to press down my PO4 for months. My HI774 show around 0.08 and 0.1 and whatever I done - it did not go down. My corals stop to grow, my chaeto stop to grow and I notice for the first time in this nearly 4 years old aquarium small patches of cyanobacteria/dinoflagellates. My eyes screamed nutrient deficiency - my HI774 screamed to high PO4. I sent in a Triton test - get back 6 µg/L (0.006 mg/L or 6 ppb) of P (0.018 mg/l PO4). I also take with a sample to my job and analyse it there with a HI713 - both me and @Sallstrom analyse it. It was inline with the Triton test. I slowly rise my PO4 level - last test it was around 0.06 ppm PO4 (Triton and 0.14 my HI774) After this - I have purchase a Red Sea Pro PO4 test kit and for the moment it shows between 0.08 - 0.12 and my HI774 show between 0.16 and 0.22 ppm. I will soon send in a new Triton test and have also purchased a distant test that analyse PO4 with colourimetric methods.

My growth is good for the moment - the pictures below shows my green monty the 17/6 and 29/6. They are below different lighting but compare the white edge.

What I will say is that at least my HI774 has a rather good repeatability but the precision is 0.08 ppm wrong.

Sincerely Lasse

Very nice Monti Sir...I also have a rather large green Monti...