For any product under development, a huge amount of effort is put into characterizing the structure of that molecule. However, it is important to remember that the active ingredient is just a part of the totality, since we must consider “the product” as the entirety of what the patient will be exposed to. This means that any other components that have come through the manufacturing process with the active ingredient, such as inducers, antibiotics, antifoam agents or chemicals used specifically to modify the protein (such as in the case of PEGylation) also need to be considered.
This assessment of the residual levels of chemicals in the sample, taken at different production stages as well as in the final product, gives knowledge of the effectiveness of the purification process. This knowledge can then feed back into refinements to that purification process to minimize the levels of these residuals, the presence of which may be harmful to the patient either directly or indirectly through an adverse effect on the product. These impurities are described in ICH Q6B as “process related impurities” (1). Analytical guidelines, such as ICH Q6B, recognize process related impurities as components that should be monitored to ensure removal or reduction via the purification process to acceptable low levels.
Different chromatographic techniques can be employed for monitoring levels of residuals depending on the residual under investigation and frequently these can be combined with mass spectrometric detection in some form to give the best possible detection levels. However, the ability to detect a component by mass spectrometry relies on its ability to be volatilized and ionized in the source of the mass spectrometer. If the properties of the molecule under investigation are such that this is not possible then the molecule will not pass through the mass spectrometer and will not be detected.
Simple UV detection may also not be possible for some molecules, if a UV chromophore is not present in the chemical structure. Compounds such as certain types of antifoams and antioxidants and other polymeric species fall into this category and thus alternative detection methods such as evaporative light scattering detection (ELSD) should be considered.
ELSD is a detection mechanism that is considered as a universal detector and is compatible with chromatographic separation. It involves the production of an aerosol from the chromatography column eluant which then enters a drift tube where it is heated to evaporate the volatile mobile phase component. The desolvated analyte particles then pass across a light beam and the amount of scattered light is measured. The amount of scattered light is proportional to the amount of the component under investigation.
Analysis of polymers also requires the use of a robust chromatography system that is designed to cope with a variety of buffers, and potentially harsh solvents such as THF and Hexane, depending on the polymeric species under investigation. A combination of appropriate chromatographic separation and ELSD detection can give good levels of detection for what would otherwise be very challenging molecules in the absence of mass spectrometric detection for these non-volatile compounds.
While some molecules may not be detectable via mass spectrometry due to their non-volatile nature, Evaporative Light Scattering Detection (ELSD) offers a reliable alternative for assessing these challenging compounds. With its universal detection capability, ELSD allows for the precise quantification of a wide range of residuals, including antifoams, antioxidants, and polymeric species, ensuring thorough impurity testing across all stages of biopharmaceutical production.
At BioPharmaSpec, we specialize in advanced residual and impurity testing solutions, utilizing ELSD and other cutting-edge techniques to ensure your products meet the highest standards of purity. Contact us today to learn how our expertise can support your biopharmaceutical development.
