POLAROGRAPHIC STUDIES ON CO(II), NI(II), CU(II) AND ZN(II) COMPLEXES WITH PTEROYLMONOGLUTAMIC ACID

Differential pulse polarography (DPP) and cyclic voltammetry (CV) were used to study complex-forming reactions between metal ions such as Co(II), NI(II), Cu(II) or Zn(II) and pteroylmonoglutamic acid (PteGlu), commonly known as folic acid or vitamin B-9(B-c). In buffer solutions (Britton-Robinson's buffer), changes in peak potentials of the reversible electroreduction of folic acid on a dropping mercury electrode (DME) vs. pH were established. Based on polarographic measurements in unbuffered solutions, at the constant ionic strength mu = 1.00 (NaClO4), constant pH = 7.5 (+/-0.2) and constant temperature T = 298 (+/-0.2) K, it has been shown that all the metal ions under investigation form complexes with PteGlu. Stability constant values of the formed folic acid complexes were determined, using Casassas-Eek's method for calculation.