If GetItemInfo works then so does GetitemFamily, they both rely on the item being cached.
If I understand what you're trying to do here, and you only want items that are at least epic quality and aren't considered enchanting materials, then you can try something like this..
Lua Code:
local _, item, quantity, quality = GetLootSlotInfo(i)
if quality >= 4 and bit.band(GetItemFamily(GetLootSlotLink(i) or '') or 0, 0x0040) == 0 then