On the basis of best fit conditions in terms of pH, dielectric constant of medium, temperature etc., a new and simple kinetic-spectrophotometric method has been developed for nanogram determination of MnII in the range 1.23 – 190.98 ng cm-3 with molar extinction coefficient and Sandell’s sensitivity for various calibration curves developed being respectively, 55600 to 72340 L mol-1 cm-1 and 2.34 to 3.04 ng cm-2 using the reaction MnII catalysed periodate oxidation of p-phenetidine. Calibration curves in terms of absorbance at fix time vs [MnII] as well as in terms of initial rate or pseudo first order rate constant vs [MnII], were obtained and their characteristics are being presented and discussed. This reaction is already reported by us to be first order in reactants and catalyst with main reaction product 4-ethoxy-1, 2-benzoquinone.