title: Application of EPR spectroscopy to examine free radicals evolution during storage of the thermally sterilized Ungentum ophthalmicum.
abstract: Free radicals formed during thermal sterilization of the Ungentum ophthalmicum were examined by an X-band EPR spectroscopy. The influence of storage time (15 min; 1, 2 and 3 days after heating) on free radical properties and concentrations in this sample was determined. Thermal sterilization was done according to the pharmaceutical norms. The first-derivative EPR spectra with g-values about 2 were measured with magnetic modulation of 100 kHz in the range of microwave power 2.2-70 mW. The changes of amplitudes (A) and linewidths (ΔBpp) with microwave powers were evaluated. Free radicals in concentration ∼1017spin/g were formed during heating of the tested Ungentum. Free radical concentration decreased with increase in storage time, and reached values ∼1017spin/g after 3 days from sterilization. The tested U. ophthalmicum should not be sterilized at a temperature of 160 °C because of the free radicals formation, or it should be used 3 days after heating, when free radicals were considerably quenched. Free radical properties remain unchanged during storage of the Ungentum. The EPR lines of the U. ophthalmicum were homogeneously broadened and their linewidths (ΔBpp) increased with increase in microwave power. EPR spectroscopy is useful to examine free radicals to optimize sterilization process and storage conditions of ophthalmologic samples.
authors.affiliation: a Department of Biophysics , School of Pharmacy and Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia , Sosnowiec , Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Ramos
authors.affiliation: a Department of Biophysics , School of Pharmacy and Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia , Sosnowiec , Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Pilawa
mesh_terms: D060433:Administration, Ophthalmic; D004356:Drug Storage / Q000379:methods / Q000592:standards; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000032:analysis*; D006358:Hot Temperature; D009883:Ophthalmic Solutions / Q000592:standards*; D013242:Sterilization / Q000379:methods / Q000592:standards*
chemical_list: D005609:Free Radicals; D009883:Ophthalmic Solutions
keywords: EPR spectroscopy; Ungentum ophthalmicum; free radicals; storage; thermal sterilization