Electrochemical Investigation with Carbon Paste Electrodes and Sensors - Electroanalysis with Carbon Paste Electrodes - page 166

7.4.2 s eleCTed T heMes aCross The F ield

7.4.2.1 Carbon Pastes as Substrates for Electropolymerized Films
As.already.emphasized.in.the.historical.survey.and.in.association.with.the.newest.trends,.the.cur-
rently.abundant.applications.of.carbon.pastes.in.the.form.of.supports.for.electrolytically.deposed.
polymeric.layers.cannot.be.overlooked..Since.a.pioneering.report.of.this.[2160],.especially.the.last.
2.years.have.seen.a.whole.series.of.such.studies.[129-138,433],.conirming—among.others—the.
good.adhesive.property.of.hydrophobic.carbon.pastes.for.irmly.attaching.polymeric.structures.that.
alter.the.carbon.paste.surface.with.respect.to.its.overall.nature.and.quality.
The. macromolecular. structures. are. obtained. by. controlled. polymerization. of. substituted.
anilines. (e.g.,. N -methylaniline. [132],. N , N -dimethylaniline. [129,133],. and. o -anisidine. [2160]),.
including. the. native. aniline. [138],. or. other. related. compounds. (e.g.,. o -aminophenol. [131],.
1,5-diaminonaphthalene. [130],. 5-amino-1,10-phenanthroline. [433],. indole. [134],. or. an. amino.
ester.[136])..Compact.ilms.can.be.formed.by.means.of. potentiostatic deposition .[129].or,.more.
often,.in.the.potentiodynamic.mode—by. repetitive potential cycling .[132,133,2160].in.solutions.
containing.the.respective.monomer.and,.usually,.more.concentrated.mineral.acid.(e.g.,.5%.H 2 SO 4 .
[135].or.1.M.HCl.[138]).
In.most.cases,.the.polymerized.ilms.formed.at.the.CP-surface.serve.to.house.the.modiier(s).of.
choice.(e.g.,.Fe II/III .[129],.Ni II .[130],.Pt 0 .[134],.or. Patton & Reeder' s.modiier.with.−SO . −. and.−COO − .
functional.groups.[135])..However,.the.same.effect.can.also.be.accomplished.by.selecting.the.proper.
monomer—a. compound. that. already. contains. the. reactive. functional. group(s). in. built. inside. the.
molecule.(see.[137].and.2-amino-5-mercapto-1,3,4-thiadiazole.used.therein).
In.conclusion,.the.presence.of.polymerized.layers.at.the.CP-surface.enables.to.increase.both.selec-
tivity.and.sensitivity.due.to.intentionally.introduced.electrocatalytical.sites.[129-133,136]),.which.can.
be.realized.by.the.polymer.itself.(via.its.functional.groups.[135,137].or.via.immobilization.of.special.
modiiers.[130-132,134],.including.some.more.resistant.enzymes.(e.g.,.GOD.[138,433]).

7.4.2.2 Carbon Pastes as Electronic Tongues
Some. advantageous. properties. of. carbon. pastes. could. not. remain. unnoticed. during. the. devel-
opment. of. multichannel. sensing. assemblies,. the. so-called. ETs. or. noses,. respectively.. The.
recent. years. have. spawned. a. quintet. of. reports. concerning. carbon. paste-based. conigurations.
[584,765,2161-2163].
As.illustrated.in.Figure.7.6,.sophisticated.sensing.systems.of.ETs.[2164].are.based.on.measure-
ment.and.subsequent.evaluation.of.multiple.signals,.when.some.speciic.features.can.be.monitored,.
mathematically. or. statistically. analyzed. and. correlated,. for. example,. by. means. of. the. method. of.
partial least squares .( PLS ;.[584]).or.using. principal component analysis .( PCA ;.[2162]),.and.thus.
ultimately.distinguished.
Regarding. the. constructions. with. carbon. paste,. the. respective. assemblies. have. served. for. (i).
qualitative. analysis. of. potable. waters,. some. soft. drinks,. and. beers. [584];. (ii). recognition. of. ive.
fundamental. tastes. (namely,. sweet,. bitter,. salty,. acidic,. and. umami. [765]);. (iii). classiication. of. a.
series.of.red.wines.through.the.release.of.speciic.compounds.that.characterize.the.process.of.aging.
of.oak.barrels.and.whose.different.properties.has.allowed.one.to.identify.also.the.country.of.origin.
[2163]);.(iv).analysis.of.white.wines.depending.on.the.local.climate.and.different.quality.of.grapes.
[2162],.enabled.by.a.sextet.of.carbon.pastes.modiied.with.three.rare-earth.phthalocyanines.(of.the.
Me III (Pc) 2 .type).and.three.different.perylenes..The.last.construction.could.then.be.employed.for.(v).
evaluation. of. the. overall. bitterness. of. extra-virgin. olive. oils. [2163],. when. the. assembly. of. CPEs.
bulk.modiied.with.the.individual.olive.oils.differing.in.their.bitterness.relect.the.redox.behavior.
of. the. compounds. of. interest—in. this. case,. electroactive. polyphenols—present. in. the. individual.
olive.oils..These.oils.were.mechanically.admixed.into.a.carbon.paste.of.otherwise.identical.carbon-
to-pasting-liquid.composition.and.used.for.preparation.of.nine.different.CPEs.forming.the.proper.
sensing.array.