In recent years, revisions to the United States and European Pharmacopoeias have seen increased harmonisation between the two monographs, including both the surface/whole article and glass grains/powder tests, and an increasing emphasis placed upon the importance of assessing glass delamination risk.
A number of industry studies identified significant variations in the concentration of extracted elements analysed when performing the hydrolytic resistance glass surface test. These variations were attributed to differences in autoclaving procedures and have been addressed with the introduction of stricter requirements for autoclaves, including tight control over the thermal cycle, temperature monitoring, and both calibration and validation requirements. These changes came into effect in January 2019 with the implementation of version 9.6 of the European Pharmacopoeia (Pharmacopée Européenne) and are summarised at the end of this article.
Glass Technology Services were prepared for these changes through an ongoing strategic investment programme which saw the commissioning of a new autoclave as well as an expansion of their pharmaceutical services – ensuring continuity of service, extended capabilities and expanded capacity for its global pharmaceutical client base.
Glass Technology Services Ltd provides analysis, consultancy, testing and research and development support to all parts of the glass supply chain – from raw materials to the end consumer. The experts in glass pride themselves on their reputation, confidentiality and impartiality and are accredited to ISO 9001 and ISO/IEC 17025 standards.
Summary of changes to glass requirements in Ph. Eur Version 9.6
Autoclave requirements continue to be a focus in the European Pharmacopoeia, which now specifies that an autoclave must be capable to withstand a specified pressure and allow the connection of an external thermometer or thermocouple for independent measurements to be made for validation and calibration. Additional instructions allow operators to use the autoclaves own internal thermocouple – provided its calibration is proved to be valid over a defined timespan.
Thermal cycle; the updated monograph addresses reproduction of the thermal load as a means of ensuring conformity to the thermal cycle on a routine basis. This also allows for the testing of different size samples alongside one another. The rates for heating and cooling have been removed, however the thermal cycle itself remains unchanged.
Calibration and validation; a new section now outlines a suitable autoclave calibration procedure, which requires users to insert a temperature probe into filled vials of an intermediary size (e.g. 10ml), within an autoclave with the tray of the autoclave filled. This is in order to create a thermal load which can be re-created on an ongoing basis. Readings from within the filled vial must be used for the calibration and validation of the correct thermal cycle. For the first time the EP now stipulates that validation of the calibration must be carried out at regular intervals.
Glass Surface Test; the surface test has a revised list of limit values in table 3.2.1-3 with the “up to 1ml” category now split into two further categories, as summarised below. Matching categories are also introduced in tables 3.2.1.-7 for the flame spectroscopy method.
New filling categories added to 3.2.1.-7
Maximum vol 0.01M HCl per 100ml of test solution (mL) | ||
| Filling volume (mL) | Type I and II | Type III |
Up to 0.5mL | 3.0 | 30.0 |
Above 0.5 and up to 1mL | 2.0 | 20.0 |
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