The OES analyzes {HEAD ~ light} captured from a spark emission stand through which {TAIL ~ the fluid sample} is flowed 
The OES analyzes { HEAD ~ light } captured from a spark emission stand through which { TAIL ~ the fluid sample } is flowed
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH