Electroanalysis with Carbon Paste–Based Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 197

investigated.with.respect.to.their.interaction.with.double-stranded.and.single-stranded.deoxyribo-
nucleic. acid. (dsDNA. and. ssDNA). [293,2764].. They. show. some. protective. effect. against. dsDNA.
cleavage.by.Cu-phenanthroline.and.hydrogen.peroxide.
Hydroquinone. is. oxidized. by. Co-phthalocyanine. [633]. or. by. laccase. (on. magnetic. core-shell.
nanoparticles).[979].or.polyphenol.oxidase.from.apple.tissue.[2765].. Moraxella .spp..can.degrade.
p -nitrophenol.to.hydroquinone,.which.can.be.oxidized.electrochemically;.this.system.was.used.to.
construct.a.microbial.carbon.paste.biosensor.for. p -nitrophenol.[2440].
Phenol. can. be. oxidized. directly. at. carbon. paste. electrodes. at. rather. positive. potentials.
[548,1903,2766,2767]. and. its. redox. transformation. is. often. accompanied. by. distinct. adsorp-
tion. effects. [3,27].. Ionic. liquids. [461],. polyamide. [2768],. CTAB. [1101,2769],. silica. gel. [1150],.
montmorillonite. [1101,2770],. sepiolite. [824],. mesoporous. TiO 2 . [994],. bentonite. [2696],. and.
β-cyclodextrin. [1411]. improve. the. conditions. for. accumulation. and. oxidation.. Procaine. hydro-
chloride. [2413]. and. over-oxidized. polymers. [2412]. improve. the. electron. transfer.. RuO 2 . and.
colloidal. Pt. [2771]. and. co.phthalocyanine. [2772]. act. as. electrocatalysts. for. oxidation.. HRP. cata-
lytically. oxidizes. phenol. with. the. aid. of. hydrogen. peroxide. [1181,1192,1525,2785].. This. system.
also. works. with. resveratrol,. a. “magic”. stilbene. compound. with. life. prolonging. and. anti-aging.
effects. in. the. popular. literature. [775].. Extracts. of. soybean. seed. hulls. [2777]. or. eggplant. (“gilo”.
for.rutin. and. H2Q). [2791]. can. be. a.source.of. the.peroxidase..Phenols. and. its.compounds. can. be.
enzymatically.oxidized.by.tyrosinase,.often.in.combination.with.supporters.and.electron.acceptors.
[194,384,573,898,979,1258,1265,1275,1798,1800,2125,2410,2773-2776,2778-2784].. Mushroom. or.
plant.tissue.may.serve.as.pools.for.polyphenol.oxidase.[194,283,898,1258,1265,2564,2783].
Cu(II)-. and. Mn(II)-phthalocyanines. were. used. as. biomimetic. agents. which. should. mimic. in.
combination. with. histidine. and. hydrogen. peroxide. dopamine. β-hydroxylase. to. oxidize. phenolic.
compounds. [519,912].. As. a. pathway. oxidation. of. the. phthalocyanine. is. assumed. which. in. con-
sequence. oxidizes. the. phenol;. electrochemical. monitoring. is. achieved. by. reducing. the. generated.
quinoid..The.sensors.are.called.enzymeless.biosensors,.but.in.fact.they.are.not.biosensors.
p -Aminophenol,. hydroquinone,. and. catecholamines,. such. as. DA,. epinephrine,. and. norepi-
nephrine,.can.be.detected.with.quinoprotein.glucose.dehydrogenase;.electrochemical.detection.is.
achieved.by.oxidation.of.the.phenols.at.0.5.V.vs..Ag/AgCl;.the.signal.is.ampliied.by.electron.trans-
fer.from.the.enzyme.to.the.quinoid.as.an.electron.acceptor.[2786]..Quercetin.adsorbs.on.carbon.
paste.and.can.be.determined.with.adsorptive.differential.pulse.anodic.stripping.voltammetry.[366].
Redox. compounds. in. olive. oil. and. wines. can. be. used. for. bitterness. or. adulteration. criteria.
[918,1571,2163,2787,2788]..For.wines,.the.array.with.different.phthalocyanines.in.combination.with.
statistical.evaluation.may.act.as.an.electronic.tongue.(see.Section.7.4.2).
Rosmarinic.acid.[2789]. and. rutin. [2790].are.catalytically.oxidized.with.transition. metal.com-
plexes. in. the. presence. of. hydrogen. peroxide;. the. sensors. should. somehow. mimic. the. action. of.
peroxidase.and.red.kidney.purple.acid.phosphatase..Thymol,.zearalenone,.and.zearalenole.can.all.
be.oxidized.directly.at.unmodiied.carbon.paste.electrodes.used.as.amperometric.detectors.in.low.
systems.[2627,2792].
8.4.5 C arbohydraTes and r elaTed C oMpounds
Table.8.19.surveys.analytical.methods.with.carbon.paste.electrodes.for.the.determination.of.sugars.
and.related.compounds.
Alditols. and. saccharides. can. be. catalytically. oxidized. with. Co-phthalocyanine. [882,889,890]..
Aldoses.can.be.determined.enzymatically.with.pyrroloquinoline.quinone.(PQQ)-dependent.aldose.
dehydrogenase,.where.the.reduced.form.PQQH 2 .is.electrochemically.reoxidized.with.ferrocene.as.
a.mediator.[1735,2793,2794].
Metal.oxides.can.catalyze.the.oxidation.of.carbohydrates;.typical.representatives.are.Co-oxides.
[1230,2706],.copper.oxides.and.hydroxides.[1225,1226,1229,2706],.NiO.(nanoparticles).[1231,2706],.
Ni(OH) 2 .[497],.and.RuO 2 .[1218,1221,2706]..The.metals.can.be.present.also.in.complexed.form,.for.