Phosphorus-31 nuclear magnetic resonance

³¹P has an isotopic abundance of 100 %, and a spin state of 1/2, making it NMR active. Due to the 2nI+1 rule, the phosphorus spectrum tends to be quite simple. That phosphorus is commonly found in organic compounds and coordination complexes (as phosphines), making it useful to measure ³¹P NMR spectra routinely.

85 % phosphoric acid is commonly used as a standard.