Carbon Paste as an Electrode Material - Electroanalysis with Carbon Paste Electrodes - page 69

carbon.pastes.with.nonconducting.pasting.liquids.and.not.the.faradic.transformations.in.the.bulk.
of.strong.electrolyte-based.CPEEs,.except.for.special.carbon.paste.mixtures.of.the.CILE.type,.
also.containing.conductive.ionic.liquids.and.which.have.occupied.rapidly.the.signiicant.position.
within.electroanalysis.with.CPEs.

3.4.2.1 Extraction and Reextraction
The.hydrophobic.character.of.the.liquid.binder.makes.possible.the.extractive.transport.associated.
with.penetration.of.species.into.the.bulk.of.carbon.paste.matrix,.which.has.become.a.typical.process.
occurring.with.this.kind.of.electrode.material.[20,748]..Extraction.capabilities.represent.perhaps.the.
most.distinct.difference.between.CPEs.and.traditional.solid.electrodes.that.are,.in.principle,.inap-
plicable.to.similar.experiments.(except.for.special.conigurations.with.additional.membranes.and.to.
some.extent.with.mercury.electrodes;.see.discussion.in.[157]).
Typically,. extraction. at. carbon. pastes. (see. Figure. 3.6). is. appreciated. as. quite. an. attractive.
feature.in.practical.measurements.[732,740],.and.only.exceptionally.one.can.meet.some.critical.
comments.considering.this.process.as.a.complicating.or.even.unwanted.factor.[211]..Basically,.
the. distinction. can. be. made. between. processes. restricted. to. the. electrode. surface. only. and.
“genuine”. extractive. behavior,. where. species. migrate. appreciably. from. the. surface. into. the.
electrode.bulk.

1 1

2 2

3 3

(A) (B)

Graphite particles Species extracted

Pasting liquid Species re-extracted

(after electrochemical
transformation)

FIGURE 3.6 Typical. pathway. of. extraction. (A). and. the. subsequent. re-extraction. (B). at. carbon. paste-
based.electrodes..A.schematic.view..1-3,.three.consecutive.situations..(Redrawn.and.colorized.according.to.
Kalcher, K.. et. al.,. Heterogeneous. electrochemical. carbon. sensors,. in. The Encyclopedia of Sensors ,. Vol. 4,.
Eds.. C.A.. Grimes,. E.C.. Dickey,. and. M.V.. Pishko,. American. Scientiic. Publishers,. Stevenson. Ranch,. CA,.
2006,.pp..283-429.)