\begin{table}%t5
%\centering
\par
\caption {\label{tab_micro}Abundance and metallicity differences when adopting the microturbulent velocity yielded by the \ion{N}{ii}~lines ($\xi=7$~km~s$^{-1}$), instead of the adopted value estimated from the \ion{O}{ii} features 
($\xi=12$~km~s$^{-1}$).}
\begin{tabular}{lc} 
\hline\hline
$\Delta \xi$              & From 12 to 7~km~s$^{-1}$ \\\hline
$\Delta$He/H              & +0.025\\
$\Delta\log \epsilon$(C)  & +0.04 \\ 
$\Delta\log \epsilon$(N)  & +0.13 \\ 
$\Delta\log \epsilon$(O)  & +0.16 \\ 
$\Delta\log \epsilon$(Ne) & +0.03 \\ 
$\Delta\log \epsilon$(Mg) & +0.15 \\ 
$\Delta\log \epsilon$(Al) & +0.11 \\ 
$\Delta\log \epsilon$(Si) & +0.10 \\ 
$\Delta\log \epsilon$(S)  & +0.02 \\ 
$\Delta\log \epsilon$(Fe) & +0.06 \\ 
\hline
${\rm [N/C]}$             & +0.09\\
${\rm [N/O]}$             & --0.03\\
\hline
$Z$                       & +0.0027 \\
\hline
\end{tabular}
\end{table}