We present a detailed and uniform study of C , S , Zn and Cu abundances in a large set of planet host stars , as well as in a homogeneous comparison sample of solar-type dwarfs with no known planetary-mass companions .
Carbon abundances were derived by EW measurement of two C i optical lines , while spectral syntheses were performed for S , Zn and Cu .
We investigated possible differences in the behaviours of the volatiles C , S and Zn and in the refractory Cu in targets with and without known planets in order to check possible anomalies due to the presence of planets .
We found that the abundance distributions in stars with exoplanets are the high [ Fe/H ] extensions of the trends traced by the comparison sample .
All volatile elements we studied show [ X /Fe ] trends decreasing with [ Fe/H ] in the metallicity range -0.8 < [ Fe/H ] < 0.5 , with significantly negative slopes of -0.39 \pm 0.04 and -0.35 \pm 0.04 for C and S , respectively .
A comparison of our abundances with those available in the literature shows good agreement in most cases .