A comparative study of a 600 W capacitively coupled microwave plasma (CMP) operated with different plasma gases (Ar, N(2) and air) with respect to the achieved detection limits for Fe, Cr, Zn, Ca and Mg have been carried out. Radially and axially resolved rotational temperatures (T(rot)), excitation temperatures (T(exc)) and electron number densities (n(e)) of these plasmas have been determined using OH (T(rot)), Fe (T(exc)) and Mg (n(e)) as thermometric species. The influence of different gas flow rates on T(rot), T(exc) and n(e), and of Li as an easily ionized element on T(exc) has been investigated.