Extraction is effected by equilibrating {HEAD ~ homoionically saturated ion exchange resin beads} with a sample of {TAIL ~ the complex matrix} under study 
Extraction is effected by equilibrating { HEAD ~ homoionically saturated ion exchange resin beads } with a sample of { TAIL ~ the complex matrix } under study
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH