PT  - JOURNAL ARTICLE
AU  - Safia Lotfi
AU  - Fabio Montagner
AU  - Christian Proff
AU  - Sascha Dreher
AU  - Ulla Grauschopf
AU  - Chiara De Zorzi
AU  - Odra Pinato
AU  - Serena Panighello
AU  - Stefanie Funke
TI  - Method comparison study-One step forward towards robust silicone layer thickness measurements
AID  - 10.5731/pdajpst.2020.012567
DP  - 2021 Jan 01
TA  - PDA Journal of Pharmaceutical Science and Technology
PG  - pdajpst.2020.012567
4099  - http://journal.pda.org/content/early/2021/05/14/pdajpst.2020.012567.short
4100  - http://journal.pda.org/content/early/2021/05/14/pdajpst.2020.012567.full
AB  - In the past decades, the silicone layer thickness and its distribution on the inner glass barrels of prefilled syringes have been characterized in several studies. However, the limited number of adequate methods to characterize thin baked-on silicone layers and the destructive nature of some analytical techniques imply challenges on the inter-lab reproducibility of some methods. In this study, the measured silicone layer thickness of baked-on siliconized syringes was compared between two laboratories both equipped with white light reflectometry coupled to laser interferometry instrumentation (Bouncer, LE UT 1.0, LE UT 2.0). The quantity of silicone oil of a subset of those syringes was measured by Fourier transformed infrared spectroscopy. Glide force tests were realized as complementary measurements on both syringes analyzed by white light reflectometry coupled to laser interferometry instrumentation and on non-analyzed identical syringes from the same lot. The mean layer thickness was found to be slightly thicker when measured with LE UT 2.0 compared to the two other instruments, but overall comparable in between instruments. Silicone profiles of all prefilled syringes including limit of detection results replaced with 20 nm were comparable but values were slightly lower when measured with the Bouncer instrument. Increase of the layer thickness from the finger flange to the needle side was found for all syringes with all instruments (20 nm to 130-140 nm). Glide force results were similar except a difference in peak width in the break loose region between the laboratories. The mean quantities of silicone oil found by both laboratories were similar (65 μg/syringe and 69 μg/syringe). Overall, comparable results in between laboratories suggest a good reproducibility of the thickness measurement method as a result of thorough method understanding and defining key method parameters. Hence this study presents a robust inter-lab comparison between silicone layer thickness measurements which has been a lack in the literature up-to-now.