The next-generation neutrino experiment, DUNE, will utilize a high-intensity neutrino beam produced to measure electron-neutrino appearance and muon-neutrino disappearance with its 40 kilotons (fiducial mass) liquid argon far detector. Liquid argon purity is crucial to use liquid argon time projection chambers (LArTPC) in DUNE’s large detectors. A purity monitor is a miniature TPC that measures the lifetime of photoelectrons generated by its UV-illuminated gold photocathode to measure the purity of liquid argon. ProtoDUNEs are full-scale DUNE prototype LArTPCs built at CERN
and perform beam tests. The following will discuss the design, implementation, and results of liquid argon purity monitors deployed in ProtoDUNE.