{P31}H1 Experiment

For P31-containing compounds, 1D H1 spectra can be collected with or without P31 decoupling so that P31 coupled H1 peaks can be identified and the coupling constants can also be measured. P31 decoupling can be achieved either with a broadband decoupling scheme (to cover multiple P31 peaks) or with a weak CW power to decouple one P31 peak or multiplet at a time. For high-resolution H1 spectrum when the acquisition (and decoupling) time is long (>1 sec), selective P31 decoupling with weak power is preferred in order to minimize probe and sample heating.

Pulse sequence

H1 P31 decouple sequence


Step 1: Lock and shim

Step 2: Collect H1 spectrum without P31 decoupling

Step 3: Load parameters and tune X-channel for P31

Step 4: Set and submit experiment

Step 5: Processing

Step 6: Finishing up: tune probe X-channel to C13 and recable


  • 1% CH3I (99% C13-labeled) + 1% trimethyl phosphite in cdcl3
  • Data collected in Dec 2010
H1 P31 dec

Bottom: P31-coupled H1 spectrum

  • CH3I reacts with trimethyl phosphite to form (CH3)P(=O)(OCH3)2 with the P31 direct bonded CH3 partially C13 labeled. The P31-coupled methyl esters give a doublet peak at 3.75ppm. The direct P31 coupled CH3 appears between 1.3 to 1.7ppm: the outer two are from 13C-attached H1 separated by C-H coupling constant of ~130Hz, and the center doublet is from C12-attached H1.
  • The three peaks between 2.0 and 2.4ppm are from 12CH3I and 13CH3I.

Top: P31-decoupled H1 spectrum

  • P31 decoupling collapses the P31-coupled CH3 peak at 3.7ppm and between 1.3 to 1.7ppm and causes no effect on the CH3I peaks.

H. Zhou updated Dec 2010