PAN is a metal indicator and colorimetric reagent for heavy metal and rare earth metal ions. This reagent is slightly soluble in acidic solutions and soluble in alkaline solutions. Its proton dissociation constants are reported to be pKa1=2.9 and pKa2=11.6 (μ=0.1, NaClO4, at room temperature). The aqueous solution is yellow at pH<12 and red at pH>12. The distribution constants, logKD, of chloroform/water and carbon tetrachloride/water are reported to be 5.4 and 4.0, respectively.
Chelate titration: Bi, Cd, Ce, Cu, Ga, In, TI, UO2(II), Zn
Solvent extraction colorimetru: Ag, Bi, Cd, Co, Cr, Cu, Fe, Ga, Hf, Hg, In, Ir, Mn, Nb, Ni, Os, Pd, Pt, Rh, Ru, Sb, Ti, Tl, UO2(II), VO(II), Zn, Zr, rare earth metals
* M=metal ion, L=PAN
Table 2 Photometric Detection Conditions Using PAN