Carbon Pastes and Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 19

75%,.the.C/SO.was.still.usable.with.slightly.distorted.baseline,.whereas.its.Nujol-based.test.partner.
started.to.leak.out.from.the.electrode.in.consequence.of.total.disintegration..Otherwise,.the.original.
study.[192].had.been.performed.with.a.sextet.of. Lukoil ® .polysiloxanes.of.the.[-O-Si(-CH 3 ) 2 -O-)] n .
and.[-O-Si(-CH 3 )(-CH=CH 2 )-O-] n .type.with.the.average.molecular.weight.of.500-15,000.g.·.mol −1 ,.
revealing.a.certain.increase.in.the.stability.of.the.individual.carbon.paste.mixtures.in.relation.with.
the.growing.molecular.weight.of.the.corresponding.SO.used.[188]..Yet.another.unpublished.study.
concerned.the.examination.of.a.CPE.prepared.from.SG.purchased.in.a.sport.shop.as.a.lubricant.for.
ly-ishing.sinking.lines..Despite.quite.a.ine.consistency,.the.resultant.paste.ultimately.failed.during.
electroanalytical.characterization.
The. remaining. differences. in. properties. of. both. PO-. and. SO-based. carbon. pastes. are. less.
evident. and. can. be. noticed. mainly. during. advanced. electrochemical. characterizations. (see,. e.g.,.
[221-223,226]). or. some. special. studies. with. the. aid. of. electrochemical. impedance. spectroscopy.
(EIS;. [227]). or. ohmic-resistance. measurements. (RM;. [228,229]).. Nevertheless,. the. resultant.
nuances.ascertained.during.these.experiments.are.also.worthy.of.mentioning.and.most.of.them.are.
of.interest.within.the.individual.sections.in.Chapter.3.
2.1.3.4 Halogenated Hydrocarbons and Similar Derivatives
Historically,.these.substances.represent.third.important.group.of.pasting.liquids;.and,.for.example,.
bromoform,.carbon.tetrachloride,.and.α-bromonaphthalene.were.among.the.binding.agents.that.had.
formed.the.very.irst.types.of.carbon.pastes.[1-3,7]..Since.then,.halogenated.derivatives.as.binders.
for.carbon.pastes.were.selected.only.occasionally,.which.is.the.case.of.α-bromonaphthalene.[40],.
p -dichlorobenzene.[230],.and. trans -1,2-dibromocyclohexane.[231],.the.latter.two.described.as.elec-
troactive.or.reactive.carbon.pastes,.respectively.
Note: . Except. for. Adams's. laboratory,. halogenated. hydrocarbons. and. similar. substances. are. not.
very.popular.among.electrochemists.working.with.CPEs,.which.can.be.understood.if.one.consid-
ers. that. these. compounds. are. often. highly. toxic;. some. of. them. are. also. proven. carcinogens.. In.
context.with.such.carbon.paste.mixtures,.the.authors.of.this.text.may.share.their.own.and.rather.ter-
rible.experience.with.carbon.pastes.prepared.from.halogenated.aliphatic.hydrocarbons..Apart.from.
rather. uncomfortable. work. in. a. ventilation. box. in. an. atmosphere. of. intensively. aromatic. vapors,.
the. resultant. CPEs. exhibited. markedly. incompact. consistency. with. unusually. rough. surface. and.
their.electrochemical.performance.was.also.very.average..Mainly,.however,.these.pastes.were.found.
extremely.aggressive.toward.to.the.electrode.bodies.used.for.their.housing,.in.that.case.a.less.resis-
tant.plastic.material.( Silon ® ).having.been.totally.destroyed.in.few.hours.of.use.[188].
2.1.3.5 Other Pasting Liquids and Mixed Binders
Occasional. use. of. atypical. pasting. liquids. can. be. documented. on. mixtures. made. of. (i). TCP.
[205,207]),.(ii).dioctyl.phthalate.(DOP;.[205,207,208]),.or.(iii).di-iso-nonyl.phthalate.(DINP;.[232])..
Due.to.a.chemical.activity.of.these.binders.exhibiting.noticeable.ion-exchanging.capabilities,.the.
resultant.CPEs.can.be.classiied.to.be.a. transient element .between.unmodiied.and.modiied.car-
bon.pastes.[75,84]..Similar.examples.are.also.the.carbon.paste.conigurations.based.on.(iv).NPOE.
[207,208].in.the.role.of.pasting.liquid.instead.of.its.typical.employment.as.a.plasticizer.for.electrode.
membranes.[159]..Due.to.the.presence.of.nitro.group,.this.binder.is.electrochemically.highly.active,.
and.hence,.its.applicability.seems.to.be.limited.to.current-free.potentiometry.and.related.measure-
ments;.nevertheless,.it.has.been.shown.that.typical.faradic.experiments.with.current.low.are.also.
feasible.if.the.polarization.range.is.properly.set.and.the.eventual.electrode.reduction.of.the.binder.
prevented.[207].
Another.liquid.binder.chosen.for.preparation.of.two-component.carbon.paste.was.(v).diphenyl.
ether.[233]..Further,.there.are.two.related.reports.on.the.use.of.(vi).glycerol.[234,235],.in.this.case,.
as. additional. stabilizer. and. in. mixture. with. ordinary. mineral. oil.. (The. authors. themselves. have.
speciied.their.coniguration.as.carbon.paste.with.“mixed.binder.”)