What is the way to test for organically bound phosphorus (phosphate)?

Document ID

Document ID TE7404

Published Date

Published Date 18/04/2018
Question
What is the way to test for organically bound phosphorus (phosphate)?
Summary
How to test for organically bound phosphorus.
Answer
The Phosphorus for Water, Wastewater and Seawater outlines the different phosphorous types Hach offers tests for, and how those tests work.
The applicable part to this question is below:
 
Condensed phosphates plus orthophosphate can be determined by acid hydrolysis using sulfuric acid, followed by the reactive phosphorus test for the appropriate range. A small amount of organically bound phosphorus will be included in this measurement. The results of the test are reported as acid-hydrolyzable phosphorus. Total phosphorus (orthophosphate, condensed and organically bound) can be determined by acid oxidation with persulfate, followed by the reactive phosphorus test. Organically bound phosphate can then be determined by subtracting the acidhydrolyzable phosphorus.

In summary, subtracting an Acid-Hydrolyzable phosphorus result (Ortho+Condensed) from a Total phosphate result (Ortho+Condensed+Organic) will give a result for Organically bound Phosphate. However some Organically bound phosphorus will be included in the Acid-Hydrolyzable phosphorus result so the recovery is expected to be low. How low is unknown and will be dependent on the sample matrix (what organically bound phosphates are in the sample).

Methods:
Phosphorus, Acid Hydrolyzable Digestion-Acid Digestion Method 8180
Phosphorus, Acid Hydrolyzable-PhosVer™ 3 with Acid Hydrolysis TNT Method 8180
Phosphorus, Total Molybdovanadate Method with Acid Persulfate Digestion HR TNT Method 10127
Phosphorus, Total, Digestion-Acid Persulfate Digestion Method 8190
Phosphorus, Total-PhosVer® with Acid Persulfate Digestion TNT Method 8190