Stability of methyl p-hydroxybenzoate (methylparaben) to gamma radiolysis

The stability of methyl p-hydroxybenzoate during 60Co γ-radiolysis was studied in the solid state and in 10 μM water solution. The work was undertaken as a model to be extended to radiolytic sterilization of pharmaceutical preparations. Only in water moderate decomposition was observed at high doses (50 KGy, whilst at 5 kGy sterilization was verified. Methylparaben labelled with carbon-14 on the carboxyl group provided the decomposition yield by the reverse isotope dilution method; mass balances were drawn and mechanisms suggested