Ati icp oes

[nathanemmerich]

Sent out a water sample to ati. Along with the icp they analyzed for phosphate. Came back at 2ppm. I have two phosphate test kits. The basic ati saltwater test kit reads 0ppm. My seachem phosphate kits read 0ppm and reads the 1ppm standard spot on.

What to trust? I do have cheato growth and algae in the display....

[bertoni]

I wouldn't particularly trust the ATI numbers. There's an article on the subject if you're interested in some reading. Algae growth is fairly common with zero measured phosphate, in any case. Some GFO might be able to outcompete the algae for phosphorus, if you'd like to work on that.

[Tripod1404]

Ati icp results have always been very close to what I measure with hanna ULR phosphorous kit. For the last test i sent to them, they measured phosphate at 0.02ppm and the phosphate value (with hanna) for the same data that I prepared the water samples is 0.02ppm as well.

[Dan_P]

Originally Posted by nathanemmerich

Sent out a water sample to ati. Along with the icp they analyzed for phosphate. Came back at 2ppm. I have two phosphate test kits. The basic ati saltwater test kit reads 0ppm. My seachem phosphate kits read 0ppm and reads the 1ppm standard spot on.

What to trust? I do have cheato growth and algae in the display....

You'll have to look into ICP analysis a little further to answer this question. Call or email the vendor for clarification.

Our test kits only detect phosphate. ICP probably detects phosphorous. Phosphorous in the ICP test can originate from phosphate but also from any other form of molecule such as organic phosphates and phosphate polymers. What you might conclude from the two tests is that while your water is low in phosphate other forms of phosphate are present and possibly bioavailable. Even if the ICP method detects phosphate, it can still originate from molecules our test kits cannot detect.

[Tripod1404]

Originally Posted by Dan_P

You'll have to look into ICP analysis a little further to answer this question. Call or email the vendor for clarification.

Our test kits only detect phosphate.

Not all. Hanna URL phosphorous reader detect all sources of phosphorous.

[Dan_P]

Originally Posted by Tripod1404

Not all. Hanna URL phosphorous reader detect all sources of phosphorous.

That is not correct. It only detects orthophosphate, PO4.

[Tripod1404]

Originally Posted by Dan_P

That is not correct. It only detects orthophosphate, PO4.

I see. I always thought it measured total elemental phosphorus and we converted to equivalent amounts of phosphate. It turns out it measures phosphate and displayed the results in equivalent amounts of phosphorus (or in other words, amount of phosphorus found in that much of phosphate) and we convert it back to phosphate. Thanks for forcing me to research this .

But even than, arent organic phosphates short lived and readily removable by a protein skimmer. So they would either degrade down to phosphate or will be skimmed out. I would think they account for a very little fraction of total soluble phosphate.

I dont think OP can have 2 ppm of total phosphorous and nearly 100% of it is organic phosphate.

ATI ICP also list phosphorus and phosphate separately. So I think in ops case, it is the phosphate our test kits measure.

[Dan_P]

Originally Posted by Tripod1404

ATI ICP also list phosphorus and phosphate separately. So I think in ops case, it is the phosphate our test kits measure.

Best to talk with the vendor about the meaning of their results, where the PO4 number came from and why the discrepancy between them and solution test. Hopefully customer service folks respond :-)

[bertoni]

There are total phosphorus kits available (Each has one), although they are more dangerous and time-consuming than orthophosphate tests. It's possible that organic phosphorus in the water column is skimmed well, but there's no good way to be sure. The effectiveness of skimmers is largely unknown and hard to test convincingly.