Fig. 6. Solution ³¹P NMR spectra of aromatic orthophosphate esters used in the measurement of phosphatase activity added to a soil extract (0.25 M NaOH and 0.05 M EDTA) that had been lyophilized and redissolved in D₂O and 1 M NaOH. The methylumbelliferyl compounds were dissolved in D₂O and 1 M NaOH only.