Figure 5: Selected 31P NMR patterns and calibration curve for phosphite with NMR data. A: NMR patterns for 4 different standards (8, 100, 250, and 500 ppb) containing 4 different species (hypophosphite, phosphite, phosphate, pyrophosphate). 8 and 100 ppb standards (0.258 and 3.229 µM/L) are not detected in the present analytical conditions. B: Calibration curve for phosphite with peak integral data with a R2 value nearly 1.