  This work presents a uniform and homogeneous study of chemical abundances of
refractory elements in 101 stars with and 94 without known planetary
companions. We carry out an in-depth investigation of the abundances of Si, Ca,
Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al. The new comparison sample, spanning
the metallicity range -0.70< [Fe/H]< 0.50, fills the gap that previously
existed, mainly at high metallicities, in the number of stars without known
planets. We used an enlarged set of data including new observations, especially
for the field ``single'' comparison stars. The line list previously studied by
other authors was improved: on average we analysed 90 spectral lines in every
spectrum and carefully measured more than 16600 equivalent widths (EW) to
calculate the abundances. We investigate possible differences between the
chemical abundances of the two groups of stars, both with and without planets.
The results are globally comparable to those obtained by other authors, and in
most cases the abundance trends of planet-host stars are very similar to those
of the comparison sample. This work represents a step towards the comprehension
of recently discovered planetary systems. These results could also be useful
for verifying galactic models at high metallicities and consequently improve
our knowledge of stellar nucleosynthesis and galactic chemical evolution.
