RecruitingViability Assessment Using FMN Measured in Perfusate and Bile During Normothermic Machine PerfusionDiscarded perfusate samples will be collected from donors after circulatory death (DCD) or donors after brain death (DBD) organs during the machine perfusion period prior to transplantation by the study team. FMN will be measured as is standard of care for all machine perfusion liver transplant cases at Cleveland Clinic. Participating centers will be provided with sample collection and shipping instructions to ensure sample preservation in accordance with IATA guidelines. Samples from outside sites will not be stored for future research and will be discarded once analysis is completed. After the collection of the samples from machine perfusion, the transplant procedure will continue according to standard process.