title: Conversion rate of para-hydrogen to ortho-hydrogen by oxygen: implications for PHIP gas storage and utilization.
abstract: OBJECTIVE
  To determine the storability of para-hydrogen before reestablishment of the room temperature thermal equilibrium mixture.
  
  
  METHODS
  Para-hydrogen was produced at near 100% purity and mixed with different oxygen quantities to determine the rate of conversion to the thermal equilibrium mixture of 75: 25% (ortho: para) by detecting the ortho-hydrogen (1)H nuclear magnetic resonance using a 9.4 T imager.
  
  
  RESULTS
  The para-hydrogen to ortho-hydrogen velocity constant, k, near room temperature (292 K) was determined to be 8.27 ± 1.30 L/mol · min(-1). This value was calculated utilizing four different oxygen fractions.
  
  
  CONCLUSIONS
  Para-hydrogen conversion to ortho-hydrogen by oxygen can be minimized for long term storage with judicious removal of oxygen contamination. Prior calculated velocity rates were confirmed demonstrating a dependence on only the oxygen concentration.
authors.affiliation: Department of Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Los Angeles, CA, 90048, USA, wagners@cshs.org.
authors.forename: Shawn
authors.initials: S
authors.lastname: Wagner
mesh_terms: D003287:Contrast Media / Q000138:chemical synthesis* / Q000302:isolation & purification*; D004355:Drug Stability; D004356:Drug Storage / Q000379:methods*; D006859:Hydrogen / Q000737:chemistry* / Q000302:isolation & purification*; D007700:Kinetics; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen / Q000737:chemistry*; D013113:Spin Labels / Q000138:chemical synthesis
chemical_list: D003287:Contrast Media; D013113:Spin Labels; D006859:Hydrogen; D010100:Oxygen