The present thesis describes a combination of pre-concentration technique needle trap device (NTD) and thermal-desorption in a photoionization time-of-flight mass spectrometer (PI-TOFMS) for analysis of gaseous organic compounds in complex gas mixtures. By variation of the adsorbent materials inside the needle trap and the variation of the ionization wavelengths (different photon energies), it is possible to measure various organic substances. Thus, the method is interesting and applicable for several analytical research fields (e.g. breath gas analysis).