Abundance determination in PNe: How to deal with large chemical inhomogeneities

Abundance determinations in planetary nebulae (PNe) are crucial for understanding stellar evolution and the chemical evolution of the host galaxy. We discuss the complications involved when the presence of a metal-rich phase is suspected in the nebula. We demonstrate that the presence of a cold region emitting mainly metal recombination lines necessitates a detailed treatment to obtain an accurate assessment of the enrichment of this cold gas phase.