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Samplepreparat)ontechn)ques
miniaturizeandautomatethesamplepreparationprocess9makingitless
labor-intensive9asthelimitofquantificationisloweredandtheamount
ofsolventsusedisminimized.Bearingthisinmind9theisolationmethods
usedsofararegraduallyreplacedbynewtechniqueswhichallowthere-
searcherstoisolateanalytesfromasampleintoasolidsorbentordirectly
intothemobilephase.Thetechniqueswhichdeserveamentioninclude
solidphasee[traction(SPE)9molecularlyimprintedpolymer-based6P()
microe[tractionintoapackedsorbent(MEPS)9solidphasemicroe[traction
(SPME)ormolecularlyimprintedpolymer-basedH[trIction(6P(-0IP
)
6P0(-0IP)śAnotherinnovativeapproachisliquid-liquide[tractionwhich
employsacollectionplateofasolidsorbent(SLE)[9912].
Mostoftheanalyticalmethodsusedarebasedontheapplicationofliq-
uidorgaseoussamples9whichrequirestheintroductionoftheirpartial
orcompleteseparationfromthematri[beforestartingtheactualanalysis.
Thechoiceofamethodisdeterminedbythephysicalandchemicalprop-
ertiesoftheanalyzedsubstances9thetypeofmatri[(biologicalsamples9
water9soil9air)andthefinalmethodofanalysis.Figure1providesaclas-
sificationofe[tractiontechniquesandunifiesthefundamentalprinciples
behinddierente[tractionapproaches.Inprinciple9e[haustivee[traction
approachesdonotrequirecalibrationbecausemostanalytesaretransferred
tothee[tractionphasebyemployingoverwhelmingvolumesofit.Inprac-
tice9however9confirmationofsatisfactoryrecoveriesisimplemented
inthemethodbytheuseofsurrogatestandards.Toreducetheamounts
ofsolventsandtimerequiredtoaccomplishe[haustiveremoval9batch
equilibriumtechniquesarefrequentlyreplacedbyflow-throughtechniques.
Thee[tractionprocedureisfollowedbyanalytesdesorptionintoasmall
volumeofasolvent9resultinginsubstantialenrichmentandconcentration
oftheanalytes.ThisstrategyisusedinsorbenttraptechniquesandinSPE
[9912].
Themostcommonandwidespreadsamplepreparationmethodissolid
phasee[traction.SPEoersawidefieldwithnumerousapplicationsand
wasoftenthetopicofdetailedpapersandreviews[194-11].Generally9dur-
ingthee[tractionprocess9anaqueoussamplepassesthroughanimmobi-
lizedphaseandisne[te[tractedbysuitableorganicsolvents.InSPE9sepa-
rationisbasedontheselectivedistributionofanalytesbetweenthesolid
20