Effect of NaOH-EDTA extraction time on the degradation of phosphate compounds

A chemical extraction of soil organic- and poly‑phosphorus (P) with a 0.25 M NaOH +0.05 M ethylenediaminetetraacetic acid (EDTA) solution is the most widely accepted method for ³¹P NMR measurements. The chemical preservation is often questioned because of inconsistent extraction time (4–16 h) among researchers. In this study, the effect of extraction time on the degradation of common P compounds (phytic acid, pyrophosphate, 2-aminoethylphosphonic acid, adenosine 5′-triphosphate disodium, and tripolyphosphate) was investigated using a spectrophotometric method. No degradation was observed up to 16 h in most of the compounds except for tripolyphosphate. The hydrolytic degradation of tripolyphosphate was retarded initially due to a high ionic strength of the extractant but became apparent after 8 h.