Pitfalls in Measurement of 14CO2 Activity from Glucose-6-14C and Two Corrective Procedures

Abstract

Summary Studies on the validity of measured activity of ¹⁴CO₂ from glucose-6^-14C trapped in KOH, Hyamine or KOH suspended in Cab-O-Sil were carried out in dioxane-based scintillation solutions. The counts obtained with KOH were low, unstable and showed a progressive increase becoming rather stable after 5 days. Contrary to this, Hyamine, or KOH in Cab-O-Sil produced high counts which were reproducible for at least 2 wk. Poor solubility of K₂¹⁴CO₃ in Bray's solution is a likely reason for the initial low counts of ¹⁴CO₂ trapped in KOH. The use of Hyamine or KOH in Cab-O-Sil is therefore a better method for the measurement of ¹⁴CO₂ activity. In addition to counting stability, Cab-O-Sil suspensions have low settling rates, no opacity and almost negligible self-absorption and hence, would be considered as a method of choice.