Chemistry Reference
In-Depth Information
electrophoresis.(CE).[555-557].and.this.trend.stays.on.[558-562],.adopting.yet.further.related.tech-
niques.[563]..Among.CE.setups,.one.can.highlight.an.unprecedented.combination.of.a.chemically.
modiied.carbon.paste.with.a.dual.electrode/dual.channel.detection.system.[560].consisting.of.two.
working.electrodes.and.two.amperometric.detectors,.the.whole.assembly.enabling.the.simultaneous.
determination.of.four.different.analytes.
With. regard. to. the. electrochemical. techniques. so. far. combined. with. CP-detectors,. dominant.
is. of. course. the. amperometric. mode. (see,. e.g.,. [46,97,280,436,548,564-567]),. but. there. are. also.
occasional.reports.on.the.choice.of.voltammetric.ramps.[65,310,568],.potentiometry.[569,570],.or.
electrochemiluminescence.measurements.[389,462,571,572].
Carbon.paste-based.detectors.are.appreciated.for.(i).easy.regeneration.and.renewal.of.the.elec-
trode. material,. as. well. as. for. (ii). lexibility. in. modiications. manageable. with. various. classical.
reagents,. newly. synthesized. materials,. or. even. various. biological. tissues.. Both. these. advantages.
are.fully.exploited.in.a.construction.shown.in.Figure.2.11.(Scheme.“A,”.redrawn.from.illustrations.
published.in.[573]).
The.igure.depicts.the.design.of.a.dual.enzymatic.detector.for.FIA,.where.a.well.(3).served.as.a.
reactor.with.carbon.paste.modiied.with.a.mushroom.tissue,.whereas.the.second.hole.(2)—placed.
in.parallel—was.the.working.electrode.containing.the.native.paste.with.immobilized.redox.media-
tor.. The. paste. in. both. illing. wells. could. be. fully. exchanged. and. thus. effectively. renewed. [573]..
Moreover,. such. regeneration. can. be. accomplished. directly. during. measurements. if. the. construc-
tion.employs.two.parallel.reactors;.when.the.irst.one.is.in.use,.the.second,.at.the.same.moment,.is.
appropriately.regenerated.[574]..On.the.other.hand,.some.constructions.of.low.detectors.can.also.be.
quite.simple.with.a.possibility.to.incorporate.the.standard.piston-driven.CP-holder—see,.e.g.,.[114].
and.Figure.2.11,.Scheme.“B.”
Relatively.serious.drawback.of.CP-detectors.is.their.limited.stability.in.media.with.organic.sol-
vents,.such.as.mobile.phases.in.HPLC.and.CE..However,.usually.helpful.would.be.the.choice.of.
more.resistant.mixtures,.such.as.those.made.of.new.carbon.materials.(e.g.,.GC.powders.[114]).or.
some.solid-like.carbon.pastes.[78,308,310,318,575].
1
1
3
2
2
7
6
3
4
4
5
6
5
(A)
(B)
FIGURE 2.11
Typical.constructions.of.carbon.paste-based.detectors..(A).Dual.detector.with.enzyme-.modiied.
carbon.paste.reactor.(Redrawn.from.Bonakdar,.M..et.al.,.
J. Electroanal. Chem
.,.266,.47,.1989):.1,.electric.plug; 2,.
working.electrode;.3,.enzymatic.reactor;.4,.Telon.seal;.5,.outlet;.and.6,.inlet;.(B).electrochemical..wall-jet.detec-
tor.employing.the.piston-driven.CPE.(After.Zima,.J..et.al.,.
Rev. Chim. (Bucharest)
,.55,.657,.2005): 1,.piston.head.
and.electrical.contact;.2,.Telon.electrode.body;.3,.steel.piston;.4,.carbon.paste.illing;.5,.inlet.from.HPLC;.6,.
Pt-counter.electrode;.and.7,.reference.electrode..(Redrawn.and.colorized.from.Kalcher,.K. et.al.,.Heterogeneous.
electrochemical.carbon.sensors,.in.
The Encyclopedia of Sensors
,.Vol..4,.Eds..C.A. Grimes,.E.C. Dickey,.and.
M.V..Pishko,.American.Scientiic.Publishers,.Stevenson.Ranch,.CA,.pp. 283-429,.2006.)
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