conversion of pure form of compounds into their oxides

conversion of pure form of compounds into their oxides   (09/15/2011, 8:51 AM)

I want to perform ash elemental analysis of ETP sludge for Al2o3.Fe2o3,Cao,Mgo,Na2o,K2O,Min o,p2o5,So3.I have method to analyse to find pur forms like ca,mg,Al,Phosphorous .My question is how can I convert these results into their oxides once my analysis is over?
Pl. guide me.