The ability to rapidly detect {TAIL ~ a trace amount} of lead species on {HEAD ~ site} is very desirable 
The ability to rapidly detect { TAIL ~ a trace amount } of lead species on { HEAD ~ site } is very desirable
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH