Characterization of Glass Delamination
Because the amount of material examined on a TEM grid is very small, representative sampling is always a concern. There might also be doubt that filtration of several drops of liquid will isolate enough particles of interest, particularly from samples that show little to no evidence of delamination by techniques such as light microscopy and SEM, both of which sample larger volumes. Current findings shown in Table 1 demonstrate positive identification of glass delami- nation flakes by TEM in samples where SEM analyses gave negative results. This is likely due at least in part to the ease of identifying particles in the TEM that are too small and thin to provide sufficient contrast in the SEM. The addition of TEM to the multi-technique methodology already brought to bear on identification of glass delamination, especially when coupled with the simple grid preparation method described here, increases the likelihood of positive identifications, and may possibly flag delamination while it is still in its early stages. Complicating factors such as flaking of coating layers and formation of secondary products, as well as presence of other types of small contaminant particles, may be better identified by x-ray spectrometry and electron diffraction in the TEM than by techniques currently employed.
Conclusion
Direct filtration of liquids onto holey carbon-coated TEM grids has been shown to be a fast and simple way in which to isolate representative samples of thin delamination
Join us for the inaugural Pre-Meeting Congress featuring the best biological and physical sciences microscopy and microanalysis research of young scientists.
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Saturday Technical Program
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Celebrate MSA’s 75th Anniversary with cocktails & dinner in St. Louis’ Ballpark Village - Great segue from the Pre-Meeting Congress to the start of M&M 2017!
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fl akes and residues. Characterization of materials associated with glass delamination by TEM/EDS can verify composition of isolated particulate in samples too thin or small for SEM/EDS analysis. Detection of smaller and thinner flakes easily observed in the TEM may also aid in earlier detection of glass delamination. Though SEM is of value for analysis of bulk glass and some types of associated particulate, this work demonstrates the benefit of TEM for unambiguous charac- terization of thin particulate and residues associated with glass delamination processes and provides an easy method for preparation of TEM grids, eliminating the difficulty of direct transfer of thin and fragile particulate and residues.
References [1] D Haines et al. , Contract Pharma 15 ( 2013 ) 92 . [2] USP General Chapter <1660>, “Evaluation of the Inner Surface Durability of Glass Containers,” U.S. Pharmacopeial Convention, Rockville, MD, 2012.
http://www.usp.org/sites/default/fi les/usp_pdf/ EN/USPNF/revisions/c1660.pdf .
[3] EF Schumacher et al. , Microsc Microanal 18 ( S2 ) ( 2012 ) 244 .
Saturday, August 5, 2017
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