Quantifying the Vial Capping Process: Re-examination Using Micro-Computed Tomography

Robert Ovadia; Philippe Lam; Vassia Tegoulia; Yuh-Fun Maa

doi:10.5731/pdajpst.2019.010363

Abstract

A vial capping process for lyophilization stopper configurations was previously quantified using residual seal force (RSF). A correlation between RSF and container closure integrity (CCI) was established, and component positional offsets were identified to be the primary source of variability in RSF measurements. To gain insight into the effects of stopper geometry on CCI, serum stoppers with the same rubber formulation were investigated in this study. Unlike lyophilization stoppers that passed CCI (per helium leak testing) even with RSF of 0 N due to their excellent plug seal, serum stoppers consistently failed CCI when RSF was <15.8 N. When the plug was removed, both types of stoppers exhibited a comparable critical lower RSF limit (19−20 N), below which CCI could not be maintained. When CCI was retested at later time points (up to six months), some previously failed vials passed CCI, suggesting that CCI improvement might be related to rubber relaxation (viscous flow), which can fill minor imperfections on the vial finish. To confirm component positional offsets are the primary sources of RSF variability, a novel quantification tool − micro-computed tomography (micro-CT) − was used in this study. Micro-CT provided images for quantification of positional offsets of the cap and stopper that directly correlated with RSF fluctuations. Serum stoppers and lyophilization stoppers are comparable in RSF variations, although lyophilization stoppers are more robust in CCI. The use of micro-CT provides a non-destructive and innovative tool in quantitatively analyzing component features of capped vials that would otherwise be difficult to investigate.

Received May 8, 2019.
Accepted August 14, 2019.

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