A new apparatus designed for the study of vapour-liquid equilibria (VLE) of small molecules at temperatures down to 77 K and pressures up to 40 MPa was built, set-up and used up to 2.8 MPa. It is based on the 'static-analytic' method using two pneumatic capillary sampling devices, which allow taking small and reliable in-situ samples and performing direct analyses through gas chromatography. Accurate P, x, y isothermal data obtained for the O-2-N-2 and Ar-N-2 mixtures are well represented by the Soave-Redlich-Kwong equation of state (SRK-EoS). The conclusions which can be drawn from the comparison with literature data are the following: maximum deviations on pressure, temperature and vapour phase composition, between literature experimental data and the calculated ones (using our binary interaction parameters) are not larger than 3.3%, 0.12 K and 4.2%. We also point out inconsistencies in several literature data.