TABLE 2.

Fe(II) inorganic and organic speciation at equilibrium

LigandFe(II) species% of total Fe(II)
SpeciesaChargepH 6pH 7pH 8
CitrateFe2+ (aqueous)29.15.91.5
Fe-CIT (aqueous)−188.992.338
Fe-CIT2 (aqueous)−401.80
Fe(II)-CO3 (solid)Solid0060.5
PicolinateFe2+ (aqueous)221.615.31.5
Fe-PIC (aqueous)152.349.89.8
Fe-PIC2 (aqueous)026.134.914
Fe(II)-CO3 (solid)Solid0074.7
NTAFe2+ (aqueous)250.50
Fe-NTA (aqueous)−19599.5100
Fe(II)-CO3 (solid)Solid000
NoneFe2+ (aqueous)29516.62.5
Fe-HCO3 (aqueous)151.80
Fe(II)-CO3 (solid)Solid081.497.5
  • a CIT, citrate; PIC, picolinate.