A variety of physical processes leading to different types of pulsations and
chemical compositions is observed among A- and F-type stars. To investigate the
underlying mechanisms responsible for these processes in stars with similar
locations in the H-R diagram, an accurate abundance determination is needed,
among others. Here, we describe a semi-automatic procedure developed to
determine chemical abundances of various elements ranging from helium to
mercury for this type of stars. We test our procedure on synthetic spectra,
demonstrating that our procedure provides abundances consistent with the input
values, even when the stellar parameters are offset by reasonable observational
errors. For a fast-rotating star such as Vega, our analysis is consistent with
those carried out with other plane-parallel model atmospheres. Simulations show
that the offsets from the input abundances increase for stars with low
inclination angle of about 4 degrees. For this inclination angle, we also show
that the distribution of the iron abundance found in different regions is
bimodal. Furthermore, the effect of rapid rotation can be seen in the peculiar
behaviour of the H_beta line.Comment: accepted for publication in MNRAS, contains 6 tables and 8 figure