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Trace Analysis of Silicone Oil in Aqueous Parenteral Formulations and Glass Containers by Graphite Furnace Atomic Absorption Spectrometry

Tobias Mundry a, Peter Surmann b, and Thomas Schurreit a

Schering AG, Pharmaceutical Development a, Berlin, and Institute for Pharmacy, Humboldt University b, Berlin (Germany)

Medical grade silicone oils are widely used in pharmaceutical glass containers for parenterals for lubrication or hydrophobic deactivation of the inner glass container surfaces e.g. in prefilled syringes or injection vials. Since the amounts of silicone oil being used for heat curing glass siliconization usually are low, high sensitivity must be provided by the analytical technique when trace amounts of silicones migrated into the product are to be quantified. This is fulfilled by graphite furnace atomic absorption spectroscopy, and a method for poly(dimethylsiloxane) (silicone oil) was developed and validated for eight aqueous drug formulations and two silicone oils according to the ICH guidelines. The method was linear in the silicone concentration range between 10 and 60 µg/l with respect to the parenteral solutions with detection and quantification limits of 7 and 10 µg/l, respectively, and recovery rates between 80 and 120 %. Selectivity for organic silicon compounds is gained through separation of the analyte during sample preparation. Within the application field of the method are the silicone trace quantification of migrated silicones in aqueous drug formulations or the determination of silicone residues on thin film coated container walls. Particulate formation from silicone might be correlated with corresponding silicone levels found in the analyzed solutions.

Key words Atomic absorption spectrometry · Parenteral glass containers · Poly(dimethylsiloxane) · Silicone oil, trace analysis, validation