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Fundamentals
therelativenumberofoccupiedadsorptioncentersdependsontheconcen-
trationoftheadsorbedsubstanceinthesolution.Atconstanttemperature9
theamountofadsorptiondependson
-theamountofthesubstancetobeanalyzedinthesolution9
-type9size9andstructureofliquidphasemolecules(adsorbate)9
-typeandsurfacepropertiesofthestationaryphase(adsorbent).
Accordingtothenatureofthebondingforces9twotypesofadsorp-
tioncanbementioned9i.e.thechemicalone(chemisorption)9duringwhich
thebondingforcesaresohighthattheprocessisirreversible9andthephysi-
calone9inwhichtheseforcesaremuchsmaller(e.g.vanderWaalsforces)
andtheprocessisreversible(theadsorbatecanbeeasilyremovedfrom
theadsorbentsurfaceduetoitsunstablebindingintheinteractionzone
oftheactivecenters)[1].
Theadsorptionprocessislimitedbythetransitiontimeoftheanalyte
particlesfromtheliquidphasetotheactivesitesofthesurface.Thisphe-
nomenonproceedsuntiltheanalyteconcentrationinthesolutionisindy-
namicequilibriumwiththeconcentrationofthesubstanceintheinnersur-
faceoftheadsorbent.Thephenomenonofadsorptionfromtheliquidphase
onporousmaterialsisadiusionprocesswhichinvolvesthefollowing
stages:
-transportoftheanalyteparticles(biologicallyactivesubstance)to
theboundarylayerliquidphase(solution)-stationaryphase(adsor-
bent)9
-diusionintheboundarylayernearthestationaryphasesurface9
-diusionintheadsorbentpores9
-surfacediusion9
-specificadsorption-bindingoftheanalytemoleculesintheactive
centersofthestationaryphase.
Traceanalysis
Traceanalysisisanimportantpartofchemicalanalysisandisbecoming
anobjectofinteresttoever-growingranksofanalysts.Insolvinganalyti-
caltasksinthisfield9increasinglycomplicatedmonitoringandmeasuring
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