Sterile buffer solution containing sodium phosphate, sodium chloride, potassium phosphate and potassium chloride with 0.05% TWEEN 20.Sterile filtered using 0.1um filterDNase, RNase and protease free.Sterility validated using USP <71> Test for SterilityDoes not contain calcium, magnesium, phenol red or sodium pyruvate. IBI 1X PBST (1X PBS) with TWEEN 20 (0.05% TWEEN 20) is a ready-to-use sterile solution in a 1 liter bottle that is ideal for use in immunoassay procedures such as Western Blotting and ELISAs in microtiter plate wells.IBI 1X PBST is mixed and bottled in our liquid production facility here in Dubuque, Iowa. Our high output pure water system produces endotoxin free and nuclease free water at a rate of 100 gallons per/hr. This water is the basis for all of our liquid blending production here at IBI.