Repeat scintillation measurements (0-96 h) of 14CO2 trapped in NaOH of varying molarity and CO2 saturation using five different scintillation cocktails
Repeat scintillation measurements (0-96 h) of vials containing mixtures of NaOH samples (with 14CO2) and five different scintillation cocktails. The NaOH samples resemble samples typically obtained in experiments investigating the mineralization of 14C-labelled substances using base trapping of CO2. The NaOH is either 1 M or 0.35 M and saturated with CO2 either 5% or 50%. NaOH sample and scintillation cocktails are mixed at two different ratios.
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Scintillation vials were prepared with 5 different scintillation cocktails (Ultima GoldTM, Ultima GoldXR, Optiphase HiSafe 3, Hionic Fluor (all PerkinElmer) and Rotiszint Eco Plus (Carl Roth)) and different volumes of 0.35 M or 1 M NaOH saturated either 5% or 50% with CO2. NaOH samples have a 14C-activity of around 45,000 DPM ml-1 from 14CO2. All scintillation measurements were conducted in 6-ml plastic scintillation vials (PerkinElmer) at room temperature. NaOH solutions and scintillation cocktails were mixed to a total volume of 4 ml directly in the vial by carefully inverting each vial 50 times. The vials were immediately measured in a Tri-Carb 2910 TR scintillation counter (PerkinElmer) with a DPM assay including two counting regions, A and B, at 0–156 keV and 4–156 keV, respectively, and using the tSIE quench indicating factor. The static controller was active, coincidence time 18 ns and delay before burst 75 nsec. All samples were counted to a counting error below 1.00% using the two sigma percent terminator function (with 95% confidence, the true value is within a range of ± 1.00%). Control measurements were done using NaOH solutions without 14C-activity. The counting efficiency determined by the tSIE factor was validated using the internal standardization method with 14C-O standard capsules of 1,701 Bq (102,100 DPM).