  Massive stars play an important role in the Universe. Unlike low-mass stars,
the formation of these objects located at great distances is still unclear. It
is expected to be governed by some combination of self-gravity, turbulence, and
magnetic fields. Our aim is to study of the chemical and physical conditions of
dense clumps in several high-mass star-forming regions. We performed
observations towards 5 high-mass star-forming regions (L1287, S187, S231,
DR21(OH), NGC7538) with the IRAM 30 m telescope. We covered the 2-3 and 4 mm
wavelength band and analyzed the lines of HCN, HNC, HCO$^+$, HC$_3$N, HNCO,
OCS, CS, SiO, SO$_2$ and SO. Using astrodendro algorithm on the 850 $\mu$m dust
emission data from the SCUBA Legacy catalogue, we identified dense gas clumps
and determined their masses, H$_2$ column densities and sizes. Furthermore, the
kinetic temperatures, molecular abundances and dynamical state were obtained.
The Red Midcourse Space Experiment Source survey (RMS) was used to determine
the clump types. We identified $\sim$20 clumps. We found no significant
correlation between line width and size, but the linewidth-mass and mass-size
relationships are strongly correlated. Virial analysis indicated that the
clumps with HII regions and young stellar objects (YSOs) are gravitationally
bound. Furthermore, it was suggested that significant magnetic fields provide
additional support for clump stability. The molecular abundances decrease from
YSOs to submm and HII regions.
