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

Figure 1: First-order derivative spectra of [Fe(II)-HNAHBH]. Amount of Fe(II) μg mL⁻¹: .