The University of Iowa

Radionuclide Safety Guideline for S-35

Physical Data

  • Radiation: Beta (100% abundance)
  • Energy: Max: 157.47 keV; Average 48.8 keV


  • Physical: 87.44 days
  • Biological: 623 days (unbound); 90 days (bound) 
  • Effective: 44 - 76 days (unbound)


  •  26 cm in air unshielded

External Hazard

  • Not an external hazard

Internal Hazard

  • Critical Organ: Testis
  • Internal uptake results in exposure to the whole body.

Skin & Eye Hazard

  • Avoid skin contamination.

Safety Guidelines 

  • Plexiglas 1 cm thick is recommended as shielding material. Thinner Plexiglas, although adequate to reduce exposure, does not have good mechanical properties.
  • Dosimeters cannot detect S-35 beta radiation due to its low energy.
  • Wear a lab coat and disposable gloves when working with S-35. Change gloves frequently.
  • Avoid direct eye contact - work behind a Plexiglas shield or wear safety glasses.
  • Methionine, cysteine and trans-label compounds can form volatiles during storage, thawing and incubation resulting in contamination.
  • Radiolytic breakdown may occur during the freezing process and during thawing. As much as 1 mCi of S-35 can be released per 8 mCi vial of
    S-35 amino acid.
  • Source vials should be opened and used in an operating fume hood.
  • Vent S-35 amino acid stock vials with an open-ended, charcoal-filled disposable syringe. Activated charcoal has a high affinity for S-35 vapors. 

Updated 1/2013