5H4-2 recognizes the terminal methoxy group of methoxy-PEG. It does not recognize the polyoxyethylene “backbone” or PEG chains that lack the terminal methoxy group. We purify the antibody using a method that do not involve low pH elution from protein G or A. This gives a slightly lower purity product but the active antibody content is increased by ~3-fold. This antibody pairs well with our anti-PEG monoclonal 9B5-6-25-7 in ELISA. It was developed and manufactured at Life Diagnostics, Inc.