1 4 CO 2 is a radioactive byproduct of numerous clinical exams and enzymatic assays. Traditional methods for capturing and quantifying 1 4 CO 2 produce a large quantity of radioactive liquid organic waste, which is both difficult and expensive to handle. A polymeric membrane which can simultaneously capture and quantify 1 4 CO 2 has been developed to circumvent both problems. The membrane contains a quaternary amine trapping agent (Hyamine T M ) and an organic fluor for β - detection. A 12% (w/v) polysulfone/sulfonated polysulfone blend membrane containing 0.5 mmol of Hyamine T M captured 4.0 10 - 5 mmol/cm 2 of 1 4 CO 2 with a counting efficiency of 70%. The membrane retained all of the 1 4 CO 2 for at least a three-day period.