Carbon Pastes and Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 23

2.2 CLASSIFICATION OF CARBON PASTES AND CARBON PASTE ELECTRODES

2.2.1 T radiTional T ypes oF C arbon p asTe -b ased e leCTrodes
Regarding.classical.carbon.paste.mixtures.with.two.main.constituents,.the.classiication.of.the.hith-
erto.existing.types.can.be.made.according.to.three.different.criteria:.(i).the.physicochemical.char-
acter.of.the.binder,.(ii).consistence,.and.via.(iii).the.status.whether.or.not.the.respective.carbon.paste.
is.anyhow.modiied.
In.the.irst.category,.one.has.the.following:

•. Common (classical) carbon paste electrodes ..Mixtures.made.of.spectral.graphite.powders.

and. of. liquid. binders. represented. by. chemically. and. electroinactive. organic. substances,.
such. as. parafin. or. SOs.. These. CPEs. are. the. most. frequent. type,. representing. around.
80%-90%. carbon. paste-based. electrodes,. sensors,. and. detectors. reported. to. date. and.
belonging.to.the.two-component.conigurations.[2,3,56,82,83,69,83,166,167].

With.respect.to.the.consistence,.the.carbon.pastes.can.be.sorted.in.this.way:

•. “ Dry ” or “ wet ” CPEs ..Such.carbon.paste.mixtures.differ.signiicantly.from.the.content.of.

the.binder,.that.is,.from.the.“carbon-to-pasting-liquid.ratio”.used,.which.is.schematically.
depicted.in.Figure.2.4.showing.also.the.corresponding.cyclic.voltammograms.for.a.model.
redox.pair.that.conirm.that.too.dry.mixtures.may.suffer.from.less.favorable.signal-to-noise.
ratio.(see.“Dry.CPE”)..Although.this.classiication.is.not.very.common,.it.can.occasionally.
be.found.in.some.special.studies.[68,175,220,244].or.in.the.early.papers.(see,.e.g.,.[190]).

Graphite Pasting liquid

70

20

50

10

30

0

10

-10

-10

3/4- 3/4-

[Fe(CN) 6 ] [Fe(CN) 6 ]

-30
-0.8

-20
-0.8 -0.3

E [ V ] vs. Ag/AgCl

0.2 0.7 -0.3

E [ V ] vs. Ag/AgCl

0.2 0.7

(A) (B)

FIGURE 2.4 Microstructure.of.(A).“dry”.and.(B).“wet”.carbon.paste.mixtures.(a.scheme,.cross.sections).
with. the. corresponding. cyclic. voltammograms. for. the. [Fe(CN) 6 ] 3/4− . redox. pair.. Experimental conditions :.
Carbon.paste.from.spectral.carbon.powder.(C).and.silicone.oil.(SO),.dry.mixture:.0.5.g.C.+.0.2.mL.SO,.wet.
mixture:.0.5.g.C +.0.4.mL.SO;.CV,.polarization.potential:.from.−1.0.to.+1.0.V.vs..Ag/AgCl.and.back,.scan.rate:.
20.mV.·.s −1 ;.0.2.M.KCl;.c[K 4 Fe(CN) 6 ].=.0.005.mol.·.L −1 ..(Drawings.and.voltammograms.from.authors'.archives.)