How does Triton's N-Doc measure phosphorus?

[malfist]

I've sent off a tank sample for Triton's N-DOC test and it's phosphorus reading is significantly different than my testing of phosphate at home with a hanna checker.

Triton's N-DOC says my phosphorus is barely detectable at 4.554 µg/l, however, my hanna checker requires a dilution to read and gives me a reading of 1.54 ppm of PO4.

Now, I know that phosphorus and phosphate aren't the same, and µg/l aren't directly convertible to ppm without going beyond my grasp of chemistry (I think I'd have to do something with mols?), but a scenario where P is barely detectable and PO4 requires a dilution to read shouldn't be possible.

Also, reading the Triton Tech Paper about the NDOC, it mentions that the testing method is a "CHNS elemental analyser", not knowing what that is, I found it's wikipedia page and a page by a manufacturer it notes that it's primarily for detection of Carbon, Hydrogen, Nitrogen, and Sulfur. It says specifically that for detection of other elements "CHNS analyzer may not be the best individual choice"

So I'm curious, how does Triton measure phosphorus in the NDoc process and how reliable is it?

 

[Randy Holmes-Farley Verified Community Expert]

There are a number of ways to measure phosphorus, and if they do not say one cannot be sure.

 

[Dan_P]

I've sent off a tank sample for Triton's N-DOC test and it's phosphorus reading is significantly different than my testing of phosphate at home with a hanna checker.

Triton's N-DOC says my phosphorus is barely detectable at 4.554 µg/l, however, my hanna checker requires a dilution to read and gives me a reading of 1.54 ppm of PO4.

Now, I know that phosphorus and phosphate aren't the same, and µg/l aren't directly convertible to ppm without going beyond my grasp of chemistry (I think I'd have to do something with mols?), but a scenario where P is barely detectable and PO4 requires a dilution to read shouldn't be possible.

Also, reading the Triton Tech Paper about the NDOC, it mentions that the testing method is a "CHNS elemental analyser", not knowing what that is, I found it's wikipedia page and a page by a manufacturer it notes that it's primarily for detection of Carbon, Hydrogen, Nitrogen, and Sulfur. It says specifically that for detection of other elements "CHNS analyzer may not be the best individual choice"

So I'm curious, how does Triton measure phosphorus in the NDoc process and how reliable is it?

NDOC measures organic and inorganic carbon, and total nitrogen. Are you sure they are measuring phosphorous? Their web site says phosphorous is measured separately.