Carbon Pastes and Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 26

“by. force”. some. macromolecules. such. as. DNA. for. their. easier. oxidation. [298,299],. to.
increase. again. the. mass. transport. [300],. or. to. accomplish. an. immunoassay. [301-303])..
Regarding.the.irst.cases.[298,299],.the.respective.sensing.systems.have.also.been.intro-
duced.under.a.special.term—as.a.“magnetic.carbon.paste.(electrode).”

2.2.2 s peCial T ypes oF C arbon p asTe -b ased e leCTrodes

2.2.2.1 Carbon Paste Electroactive Electrodes
A. group. of. carbon. paste-based. electrodes. appearing. irstly. in. its. typical. form. in. the. mid-1970s.
[38,304],.but.having.had.the.principally.similar.predecessors.a.decade.ago.[14,15,29].or.even.essen-
tially.identical.conigurations.yet.before.[305],.comprises.the.carbon.paste.mixtures.with.qualita-
tively. different. compositions.. Namely,. in. the. CPEE. conigurations,. the. originally. insulating. and.
chemically.inert.pasting.liquid.is.being.intentionally.replaced.by.a.strong.inorganic.electrolyte,.such.
as.concentrated.solutions.of.mineral.acids.or.alkaline.hydroxides.[83].
A.rather.speciic.area.of.CPEEs,.concentrated.in.a.collection.of.more.than.100.scientiic.papers.
[7]. and. already. widely. reviewed. [151,170,306,307],. is. not. only. worthy. of. mentioning. here,. but.
deserves.special.attention—thanks.to.a.variety.of.attractive,.as.well.as.unique.applications—which.
is.accomplished.by.means.of.a.separate.section.(see.Section.7.2).

2.2.2.2 “Solid,” “Solid-like,” and “Pseudo” Carbon Paste Electrodes
It. is. not. surprising. that. the. growing. diversity. of. carbon. pastes. has. also. motivated. numerous. sci-
entists.to.prepare,.test,.and.popularize.further.related.mixtures,.in.which.the.traditional.oils.were.
replaced.by.alternate.binders..Many.of.the.resultant.electrode.substrates.had.exhibited.consistency.
markedly.thicker.than.that.of.classical.CPEs.(being.like.peanut.butter.as.speciied.by.Adams.[2]),.
giving.rise.to.the.terms.used.as.headline.of.this.section..Here,.the.individual.examples.can.be.briely.
presented,.when—except.for.a.few.cases—the.denotation.“solid”.or.“solid-like”.CPE.is.authentic.
and.come.from.the.authors'.reports.
The. oldest. prototypes. of. an. s-CPE. were. those. combining. purposely. graphite. powder. with. (i).
silicone.rubber.[32,65,308-310].that.had.gotten.their.inal.consistency.after.cold.vulcanization,.hav-
ing.been.recommended.for.measurements.in.both.stationary.and.hydrodynamic.conditions..Similar.
s-CPEs. designed. as. amperometric. sensors. or. detectors. were. then. made. of. (ii). highly. molecular.
polyvinylchloride.(PVC;.[65]),.(iii).chloroprene.rubber.+.alkyl-phenyl.resin.(at.the.1:1.ratio.[310]),.
or.related.(iv).butadiene.rubber.(caoutchouc;.[311])..Other.types.of.s-CPEs.were.based.on.(v).par-
afin.wax.[36].or.(vi).ceresin.wax.[37],.which.can.be.easily.melted.(both.beneath.100°C.[38,80]),.
mixed. with. graphite. powder,. and. then. left. to. cool. down. into. ine. solid. dispersions.. At. present,.
wax-impregnated. electrodes. can. be. crowned. as. the. most. frequently. employed. s-CPEs. (see. also.
[78,79,222,312-317])..Notably.high.resistance.in.organic.solvents.has.been.shown.for.a.solid-like.
paste. mixture. prepared. from. (vii). poly(chlorotriluoroethylene). oil. (or. wax,. respectively),. known.
under.a.trademark. Kel-F ® .[66,318,319]..Reportedly,.the.respective.detectors.could.be.used.in.HPLC.
being.immersed.in.mobile.phase.containing.up.to.70%.ACN.
The.remaining.types.of.s-CPEs.have.already.made.an.ephemeral.appearance..Among.them,.one.
can.present.electrodes.made.from.the.melted.and.solidiied.(viii).phenanthrene.[76],.(ix).polyeth-
ylene.([77],.yet.with.a.modifying.agent.as.the.third.component),.(x).polypropylene.(forming.a.very.
dense,.sticky,.and.dificult-to-handle.mass.[188,320]),.and,.inally,.(xi).3,3′,5,5′-tetramethylbenzidine.
[321]—a.polymeric.binder.capable.of.hosting.either.bulk-incorporated.or.surface-attached.enzymes.

Note: . In.association.with.carbon.paste-like.mixtures,.one.should.not.forget.a.large.family.of. screen
printed (carbon) electrodes ,. SP(C)Es .[74,83],.belonging.to.most.typical. carbon heterogeneous elec-
trodes .or,.else,. carbon composite electrodes ..Besides.some.related.characteristics.with.CPEs,.their.
sensing. proper—carbon. ink,. formed. by. graphite. powder. and. a. polymeric. resin. (hardener)—has.
been.occasionally.called.“carbon.paste”.(see,.e.g.,.[83,97,290,322,323])..(Similar.materials.seem.to.