Method Comparison Study-One Step Forward toward Robust Silicone Layer Thickness Measurements.

Area of Science:

• Pharmaceutical Manufacturing
• Materials Science
• Analytical Chemistry

Background:

• Accurate characterization of silicone layer thickness on prefilled syringes is crucial for drug delivery.
• Existing methods for analyzing thin, baked-on silicone layers present challenges in reproducibility.
• Inter-laboratory comparisons are needed to validate analytical techniques for silicone layer characterization.

Purpose of the Study:

• To compare silicone layer thickness measurements between two laboratories using white light reflectometry coupled to laser interferometry.
• To assess the inter-laboratory reproducibility of silicone layer thickness characterization on baked-on siliconized syringes.
• To correlate silicone layer thickness with glide force performance and silicone oil quantity.

Main Methods:

• White light reflectometry coupled to laser interferometry (Bouncer, LE UT 1.0, LE UT 2.0) for silicone layer thickness measurement.
• Fourier transform infrared spectroscopy for quantifying silicone oil quantity.
• Glide force testing to evaluate syringe functionality.

Main Results:

• Comparable silicone layer thickness profiles were observed between laboratories, with slight variations noted for the Bouncer instrument.
• A consistent increase in silicone layer thickness from the finger flange to the needle side was detected across all instruments (20 nm to 130-140 nm).
• Mean silicone oil quantities were similar between laboratories (64 µg/syringe and 69 µg/syringe), and glide force results were comparable.

Conclusions:

• The study demonstrates good inter-laboratory reproducibility for silicone layer thickness measurements on prefilled syringes.
• Thorough method understanding and defined parameters contribute to robust and comparable analytical results.
• This work addresses a gap in the literature by providing a validated inter-lab comparison for silicone layer thickness analysis.