Ozone Generation during High-Voltage Leak Detection: Fiction or Reality?

Abstract

In order to further clarify if and how much ozone is generated during high-voltage leak detection and to identify measures to reduce the impact of ozone generation on product quality, a highly sensitive analytical system was employed to investigate the generation of ozone at different operational conditions of high-voltage leak detection integrity testing. The analytical system is based on oxidation of Iodide ions in solution and identification of the Iodine formed by N, N-Diethyl-p-phenylendiamine (DPD) according to DIN 38403. Sensitivity of the system was found suitable to detect ozone levels as low as 0.025 ppm (mg/L). High-voltage leak detection process parameters-inspection speed, high voltage, filling level of the ampoule, and exposure time to the ampoule to high voltage-were varied between maximum and minimum values applicable in integrity testing of different ampoule sizes. For variation of exposure time, ampoules were repetitively tested by the leak testing machine to achieve a maximum exposure time of the ampoule up to 24 s (exposure time during production ≤2.4 s). No ozone was detected during the study under all inspection conditions. Even repeated exposure of the ampoules to high-voltage leak detection did not result in generation of measurable ozone levels. It has to be concluded that high voltage leak detection is not prone to causing oxidation of the drug products. For drug products in ampoules, 100% integrity testing is requested both by European and US regulations. Detection of integrity defects like small holes or cracks in the ampoule can be performed by numerous methods. Due to automation requirements, only three methods have been used during routine production-vacuum decay, head space infrared spectroscopy, and high-voltage leak detection. High-voltage leak detection is the most common method used in the pharmaceutical industry for 100% integrity testing of ampoules, but resent publications showed considerable oxidation of an air-sensitive active pharmaceutical ingredient during the integrity testing process. It was assumed that ozone generated in the inside of the vial due to exposure of the product to the high voltage during the testing process may be responsible for this result. As ozone is a very aggressive and non-selective oxidant, this result posed a serious thread not only to this product but also to the quality of many other products subjected to integrity testing by high-voltage leak detection.

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