In which of the following process of refining, pure metal has less affinity with oxygen than impurity

Cupellation method is used to separate noble metals like gold and silver from base metals like lead,copper,zinc etc., present in the ore. If a metal has low oxygen affinity, then the purification of metal may be carried out by cupellation.For example separation of pure silver from impurity lead.  During cupellation,impurity lead has more affinity to oxygen and converted to PbO, while pure silver metal don't reacts with oxygen and don't changes to its oxide,hence silver shines.