Spectrophotometric Determination of Iron(II) and Cobalt(II) by Direct, Derivative, and Simultaneous Methods Using 2-Hydroxy-1-Naphthaldehyde-p-Hydroxybenzoichydrazone : Figure 6

Figure 6: Second-order derivative spectra of (a) [Fe(II)-HNAHBH] and (b) [Co(II)-NAHBH]. Amount of Fe(II) (μg mL⁻¹): 0.055, 0.11; Co(II) (μg mL⁻¹): 3.53; 4.719.