Introduction to Electrochemistry and Electroanalysis with Carbon Paste–Based Electrodes - Electroanalysis with Carbon Paste Electrodes - page 6

carbon.or.graphite.particles.in.suitable.binders..Regarding.CPEs,.the.latter.is.represented.by.pasting.
liquid.that.stays.in.the.liquid.state.even.after.preparation.of.the.carbon.paste.mixture;.whereas,.in.
SPEs,.the.original.luid.agent.is.solidiied.during.the.machining.of.the.inal.product..Thus,.although.
the.resultant.properties.of.a.CPE.and.the.selected.SPE.can.be.quite.different,.the.method.of.eventual.
modiication.is.nearly.the.same,.including.the.direct.mixing.of.the.two.main.components.with.the.
modifying.agent..If.such.modiication.is.to.be.used.for.the.irst.time.and.hence.tested.in.advance,.it.
is.evident.that.the.whole.process.for.SPEs.(including.model.measurements).can.be.simulated.with.
CPEs,. which. is. advantageous. because. the. corresponding. procedure. with. a. CPE. is. usually. much.
simpler..Yet.another.factor.in.favor.of.this.strategy.is.the.fact.that.SPEs.are.typically.made.in.special.
machines.as.integrated.series.(sets).of.many.electrodes.[74].and.their.repeated.fabrication.just.for.
testing.would.became.unacceptable.from.the.economical.point.of.view.
Besides.SP(C)Es,.there.are.a.number.of.other.carbon.composite.materials.for.which.the.respec-
tive.sensing.units.are.called.“carbon.paste-like”.or.“pseudo-carbon.paste”.electrodes,.often,.by.the.
authors.themselves..Some.of.them.have.already.been.introduced.in.the.previous.sections.[33,62,63]);.
further.types.and.prototypes.have.been.proposed.newly.[76-79]..One.of.such.composites.was.a.mix-
ture.of.carbon.powder.with.melted.phenanthrene.[76],.when.the.hot.liquid.homogeneous..mixture.
was.cooled.down,.thus.giving.rise.to.a.granular.mass.that.could.be.stored.for.later.use..Then,.before.
use,. a. portion. of. such. granules. was. melted. up. and—as. a. luid—packed. into. an. ordinary. carbon.
paste.holder..Alternatively,.this.solid-like.carbon.paste.material.could.be.modiied.like.common.car-
bon.paste.mixtures,.either.by.incorporating.a.modiier.into.the.mixture—again,.in.melted.form—or.
in situ .if.the.modifying.agent(s).tended.to.decompose.at.higher.temperatures.
Other.types.of.“solid-like”.CPEs.were.polyethylene-based.carbon.paste.solid-like.mixture.[77],.
with. the. modiier. added,. and. the. relatively. popular. parafin. wax-based. carbon. composites. (see,.
e.g.,. [78,79]),. continuing. in. the. concept. of. a. pioneering. prototype. by. Crow. and. his. “carbon. wax.
electrode”.(CWE.[80])..In.these.cases,.the.electrode.material.itself.is.obtainable.in.the.same.way.as.
for.the.previously.described.phenanthrene-s-CPE,.and.its.later.modiication.can.also.be.performed.
analogically.
Similar.to.the.previous.decade,.the.1990s.with.CPEs.were.also.surveyed.in.some.contemporary.
reviews.[81,82],.highlighting.the.signiicance.of.new.technologies.in.the.area.and.the.lexibility.of.
carbon.paste.as.being.“ready.for.things.to.come.”
1.1.9 2000-2001: C arbon p asTes and n eW T eChnologies
The.arrival.of.a.new.millennium.coincided.with.rapidly.increasing.applicability.of.materials.that.
had.been.developed.with.the.aid.of.new.technologies..In.electroanalysis.with.carbon.pastes,.they.are.
represented.mainly.by.two.major.groups.of.modiiers.[83]:.(a).complexants.and.(b).redox.electrocat-
alysts,.including.mediators.for.biosensing,.when—from.the.chemical.point.of.view—the.individual.
compounds.typically.belong.to.the.so-called.inorganic.or.organic.hybrids;.e.g.,.various.(I).cations.
of.the.[Me N (A) a (B) b ] m+ .type.(where.“Me”.is.a.metal.of.the.iron.or.platinum.groups,.“A”.inorganic.
ligand,.and.“B”.organic.molecule.or.vice.versa).or.(II).heteropoly-anions.based.on.Si IV ,.P V ,.and.As V .
as.central. atoms,. Mo VI ,. W VI ,. and. V V . as.metals.in. oxo-anionic. ligands,. both. in. combination. with.
voluminous.organic.and.organometallic.cations.as.well.as.neutral.organic.molecules.
These. complex. structures. offer. numerous. attractive. properties. owing. to. their. multifunctional.
nature,.coupling.in.one.the.mechanical.stability.of.the.inorganic.lattice,.chemical.reactivity.of.the.
organic.moiety,.and.its.lipophilicity,.which.ensures.good.adhesion.of.the.voluminous.molecule.to.
the.hydrophobic.carbon.paste.surface.or.bulk,.respectively.[84].
Incorporations. of. these. substances. and. materials. into. various. CPE. conigurations. cannot,. of.
course,.be.conined.to.a.couple.of.years.as.evoked.by.the.title.of.this.section,.because.their.applica-
tions.have.been.or.are.of.interest.for.many.years—before,.as.well.as.after,.the.commencement.of.
the. year. 2000.. This. is. also. emphasized. in. two. recent. reviews. [83,84]. analyzing. for. the. irst. time.
the.phenomenon.called.“carbon.paste.vs..new.technologies”.and.mapping.in.detail.the.respective.