Membrane-based scintillation proximity assays I. Detection and quantification of ¹⁴CO₂

¹⁴CO₂ is a radioactive byproduct of numerous clinical exams and enzymatic assays. Traditional methods for capturing and quantifying ¹⁴CO₂ 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 ¹⁴CO₂ has been developed to circumvent both problems. The membrane contains a quaternary amine trapping agent (Hyamine^TM) and an organic fluor for β^- detection. A 12% (w/v) polysulfone/sulfonated polysulfone blend membrane containing 0.5 mmol of Hyamine^TM captured 4.0 × 10^-5 mmol/cm² of ¹⁴CO₂ with a counting efficiency of 70%. The membrane retained all of the ¹⁴CO₂ for at least a three-day period.