The preconcentrator consists of {TAIL ~ a substrate} with passageways, a conductive material coated to the top and {HEAD ~ the bottom} of the substrate and an adsorbent coating covering the entire substrate 
The preconcentrator consists of { TAIL ~ a substrate } with passageways , a conductive material coated to the top and { HEAD ~ the bottom } of the substrate and an adsorbent coating covering the entire substrate
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH