dex higher, depending on which ionization correction approach we use (see § \[sec:tot\_ab\]). Hence, the iron abundances derived for these 5 PNe have this additional amount of uncertainty.

We calculate the uncertainties of the physical conditions and the ionic and total abundances of O and Fe using Montecarlo simulations, which assume that the errors in the line intensities follow Gaussian distributions. The line intensity errors are those given in the references listed in Table \[tab:1\]. Each Montecarlo run samples the Gaussian distributions of all the lines in order to provide new values for [$T_{\rm e}$]{}, [$n_{\rm e}$]{}, and all the ionic and total abundances described in § \[sec:ionic\_ab\] and § \[sec:tot\_ab\] below. The errors listed for the calculated quantities define a confidence interval of 68$\%$ (equivalent to one standard deviation in a Gaussian distribution).

Table \[tab:1\] presents the physical conditions and their associated uncertainties for our sample PNe. The values are similar to the ones obtained in @DelgadoInglada_09 for the objects in common. The highest differences are for the values of [$n_{\rm e}$]{}, and there are two reasons for that. First, we use here one more diagnostic ratio for the density, \[\] $\lambda3726/\lambda3729$. Second, whereas @DelgadoInglada_09 derive the final [$n_{\rm 