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We compile published spectroscopic data and [O III] magnitudes of almost 500extragalactic planetary nebulae (PNe) in 13 galaxies of various masses andmorphological types. This is the first paper of a series that aims to analyzethe PN populations and their progenitors in these galaxies. Although thesamples are not complete or homogeneous we obtain some first findings throughthe comparison of a few intensity line ratios and nebular parameters. We findthat the ionized masses and the luminosities in H$\beta$, L$_{H\beta}$, ofaround 30 objects previously identified as PNe indicate that they are mostlikely compact HII regions. We find an anticorrelation between the electrondensities and the ionized masses in M31, M33, and NGC 300 which suggests thatmost of the PNe observed in these galaxies are probably ionization bounded.This trend is absent in LMC and SMC suggesting that many of their PNe aredensity bounded. The He II/H$\beta$ values found in many PNe in LMC and some inM33 and SMC are higher than in the other galaxies. Photoionization modelspredict that these high values can only be reached in density bounded PNe. Wealso find that the brightest PNe in the sample are not necessarily the youngestsince there is no correlation between electron densities and the H$\beta$luminosities. The strong correlation found between L$_{H\beta}$-L$_{[O III]}$implies that the so far not understood cut off of the planetary luminosityfunction (PNLF) based on [O III] magnitudes can be investigated usingL$_{H\beta}$, a parameter much easier to study.

A study of extragalactic planetary nebulae populations based on spectroscopy. I. Data compilation and first findings