Instrumental Measurements with Carbon Paste Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 133

or. the. polymeric. matrix,. which. worsens. the. electron. transfer. between. electrode. surface. and.
analyte,.resulting.in.signal.broadening.

6.2.2 s Tripping V olTaMMeTry
Stripping.voltammetry,.in.the.former.U.S.S.R..and.some.Central.European.countries.also.known.
as.inverse.voltammetry,.employs.in.its.classical.arrangement.a.preconcentration.(preelectrolysis.or.
deposition,.respectively).to.accumulate.the.target.species.on.the.electrode.surface.before.measure-
ment,.which.can.be.DCV,.DPV,.or.any.other.voltammetric.method.
Most.typical.applications.are.the.preconcentration.of.zinc,.cadmium,.lead,.or.copper,.alone.or.
in. combination,. as. amalgams. at. the. hanging. mercury. drop. electrode.. The. most. important. is. the.
immobilization.of.the.target.species.at.the.electrode.surface,.resulting.in.an.accumulation.and.conse-
quently.in.a.decrease.in.the.detection.limit..In.order.to.avoid.diffusion.effects,.the.solution.is.usually.
stirred.during.this.step..For.settling.the.solution,.stirring.is.usually.stopped.for.some.10-20.s.(with.
the.potential.still.applied).before.the.measurement.starts.to.provide.quiet.current.responses..The.so-
called.medium.exchange.approach.is.possible.but.is.hardly.performed.in.the.classical.technique..The.
ensuing.measurement.can.be.performed.either.in.cathodic.or.anodic.direction.depending.on.the.pre-
concentrated.system,.named.consequently.as.cathodic.or.anodic.stripping.voltammetry.(CSV,.ASV).
Characteristic.for.stripping.analysis.is.the.decoupling.of.the.mass.transfer.process.in.the.direc-
tion.of.the.electrode.from.the.measurement;.nevertheless,.reaction.products.are.still.subject.to.mass.
transfer.away.from.the.surface.in.case.they.are.not.sorbed..Modiied.electrodes.have.signiicantly.
broadened.the.applicability.of.stripping.analysis.to.analytes,.which.cannot.be.preconcentrated.by.
means.of.electrolysis..In.such.cases,.chemical.preconcentration.can.improve.the.analytical.situation..
Here,.a.chemical.reaction.is.the.basis.of.the.immobilization.of.the.analyte.at.the.electrode.surface.
Often,.it.can.be.done.under.open.circuit.conditions.without.a.potential.applied;.sometimes.an.
electric.ield.may.also.support.the.accumulation.process..Chemical.preconcentration.is.often.com-
bined.with.an.exchange.of.the.analyte.medium.by.the.measurement.medium.with.obvious.advan-
tages:.the.interaction.time.can.be.well.controlled,.and.both.media.can.be.optimized.with.respect.to.
their.composition.independently.from.each.other..Electroactive.components.from.the.analyte.solu-
tion.not.showing.an.afinity.for.the.carbon.paste.or.the.modiier.will.be.separated.

•. Adsorptive stripping voltammetry (AdSV) ,.introduced.by.Kalvoda.(see,.e.g.,.[168].and.refer-

ences.therein),.is—in.its.simplest.form—the.accumulation.of.the.analyte.by.adsorption.to.the.
electrode.surface..In.a.more.common.variant,.an.adsorbant.or.reactant.present.on.the.surface.
immobilizes.the.target.species.by.interacting.with.it..Reactants.can.also.be.added.directly.to.
the.analyte.solution.modifying.the.electrode.surface. in situ ;.that.is,.from.the.sample.solution,.
which.is.added.directly.to.the.analyte.solution.and.modiies. in situ .the.surface.of.the.electrode.
in.order.to.accumulate.the.target.species..Typical.examples.are.the.preconcentration.of.Ni.
or.Co.as.oxime.complexes.at.the.electrode.surface.with.the.subsequent.reduction.of.the.Me II .
atom.during.measurement..Also.here,.the.potential.applied.controls.the.adsorption.process.

•. Adsorptive catalytic stripping voltammetry (AdCtSV) ,. propagated. by. Bobrowski. et. al..

(again,.see.[168]),.is.an.interesting.variant.with.the.measurement.combined.with.a.cata-
lytic.process,.where.an.additional.reagent,.oxidant.or.reductant,.converts.the.product.of.the.
electrochemical.reaction.at.the.electrode.surface.again.to.its.initial,.preconcentrated.state.
yielding.an.increased.current.response.via.a.catalytic.cycle.

•. Adsorptive transfer stripping voltammetry (AdTSV) . is. in. fact. AdSV. with. a. medium.

exchange.between.the.accumulation.and.the.measurement.step..At.least.some.authors.use.
this.term.in.such.a.context..It.was.originally.suggested.by.Palecek's.group.[1921].in.DNA.
detection.for.the.technique.to.add.a.small.volume.of.a.solution.to.the.surface.of.the.elec-
trode;.after.some.time,.during.which.the.target.analytes.adsorb.at.the.interface,.the.solution.
can.be.washed.off,.and.the.electrode.inserted.to.the.electrochemical.cell.