12-Molybdophosphoric Acid as an Analytical Reagent for Greater Celandine (Celadonium) Alkaloids

The conditions for determining the total greater celandine alkaloids resulting from a plant by acid infusion were studied. The interaction between the organic cations of alkaloids and the heteropoly anion PMo₁₂O^3- ₄₀ with the formation of a sparingly soluble stable associate of total celandine alkaloids was examined using UV and IR spectroscopy and quantum-chemical calculations. The associate composition (Alk)₃PMo₁₂O₄₀ was found by amperometric titration, and the ionic solubility product was calculated to be equal to (3.0 ± 0.2) × 10^–27 at P = 0.95 and n = 5. The synthesized associate was used as an electrode-active substance in the development of an ion-selective electrode with a plasticized membrane that is reversible and selective for the organic cations of greater celandine alkaloids. Procedures for determining total alkaloids in extracts, infusions, and medicinal forms were developed using potentiometry with ion-selective electrodes and amperometric titration.