We present a semi-empirical calibration between the metallicity ( Z ) of Seyfert 2 Active Galactic Nuclei and the N 2 =log ( [ N ii ] \lambda 6584/H \alpha ) emission-line intensity ratio .
This calibration was derived through the [ O iii ] \lambda 5007/ [ O ii ] \lambda 3727 versus N 2 diagram containing observational data and photoionization model results obtained with the Cloudy code .
The observational sample consists of 463 confirmed Seyfert 2 nuclei ( redshift z\ > \la 0.4 ) taken from the Sloan Digital Sky Survey DR7 dataset .
The obtained Z - N 2 relation is valid for the range 0.3 \ > \la \ > ( Z / Z _ { \odot } ) \ > \la \ > 2.0 which corresponds to -0.7 \ > \la \ > ( N 2 ) \ > \la \ > 0.6 .
The effects of varying the ionization parameter ( U ) , electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N 2 .
This result indicates the large reliability of our Z - N 2 calibration .
A relation between U and the [ O iii ] / [ O ii ] line ratio , almost independent of other nebular parameter , was obtained .