I have not used Sodium Carbonate in this particular case, but avoid it completely now with Rue extracts and Harmala separations. The main problem for me stemmed from its poor solubility. The best thing that happened to me with Rue extractions was reading the VDS protocol and switching to Ammonia for basing. Not sure how this would fit with Caapi though. NaOH is also very soluble and cleaner, but obviously much stronger. Nevertheless the concentration can be controlled, and so the pH, by dilution?