Oxygen headspace is a non-destructive test method evaluating the oxygen concentration within closed containers at any point in the product-package life cycle. This is achieved through the use of tunable diode laser absorption spectroscopy. The laser’s wavelength is tuned to the absorption line of a gas under test (760 nm for oxygen, 1854 nm for moisture and 2000 nm for carbon dioxide) resulting in an electrical signal that varies with the intensity of transmitted radiation at the measurement site on the container’s surface.

The result is a measured change in the concentration of the target gas that correlates with the quantity of the gas present. This data can then be used to evaluate the container closure integrity (CCI) of the package and its contents. This can be accomplished through a CCI method that uses air headspace measurements or a CCI method using a sample with an oxygen-free headspace such as nitrogen.

Measuring Ammonia Levels: Exploring the Function of Ammonia Meters

Other headspace parameters such as equilibration time, vial shaking and sample loop volume can affect detector response and should be optimized for the application being tested. For example, to obtain a representative headspace oxygen analysis on a frozen food pack, the sample should be shaken gently and allowed to equilibrate for at least 10 minutes. This is a process that can be easily automated with modern headspace analyzers and is often incorporated into the sample preparation procedure.

Regardless of the method used, an oxygen headspace measurement is a valuable tool during lyophilization process development and stability studies. It is also an efficient way to monitor freeze-dried drug products during quality control testing. It allows for a comparison of initial headspace oxygen levels to the end-of-shelf-life specifications and provides insight into the amount of permeation through the package.