A range of coordination and organometallic compounds have been analysed by quadrupole ion-trap mass spectrometry using various photoionisation methods. Atmospheric-pressure photo ionisation (APPI), which combines atmospheric-pressure chemical ionisation (APCT) with a photolysis lamp, was compared with the new technique photo-assisted electrospray ionisation (PAESI). Additionally, the atmospheric pressure matrix-assisted laser desorption ionisation (AP-MALDI) was also evaluated and compared to MALDI quadrupole ion-trap time-of-flight (MALDI-QIT-TOF) mass spectrometry. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).