ASAS offers three screening assays, based on GSH- and GSSG-trapping, to detect protein-reactive extractables

Extracts of packaging or single use material are treated with GSH and/or GSSG, the reaction products are identified using high-resolution accurate LC-MS.
Extractables, which can be converted into reactive species (pro-electrophiles) by e.g. aging processes or γ-irradiation, are trapped with GSH after electrochemical activation.
Results of the GSH/GSSG screening will help sponsors to fulfill FDA demands, as described in Guidance for Industry Immunogenicity Assessment for Therapeutic Protein Products. Details can be found here: screening assays ASAS