It is preferable that {TAIL ~ least possible impurity} is contained in {HEAD ~ the EL forming substance} 112 
It is preferable that { TAIL ~ least possible impurity } is contained in { HEAD ~ the EL forming substance } 112
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH