Electroanalysis with Carbon Paste–Based Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 173

25 3

(a)

20

(a)

2

15

(b)

10

1

(b)

5

0

0

0 5 10

Accumulation time (min)

15 20 0 10

Accumulation time (min)

20 30

(A) (B)

FIGURE 8.2 Inluence. of. the. silica. structure. incorporated. into. a. carbon. paste. electrode. on. the. voltam-
metric. response. of. cyclam-functionalized. silica. samples. to. Cu(II),. recorded. as. a. function. of. accumulation.
time.. (a) Mesostructured. SBA15-cyclam.and. (b). non-ordered. silica. gel. K60-Cyclam..Preconcentration. was.
carried.out.in.(A).1.0.×.10 −6 .M.and.(B).1.0.×.10 −8 .M.Cu(II).solutions.(0.1.M.citrate.buffer,.pH.6.4)..Square-
wave.voltammograms.recorded.in.3.M.HNO 3 .after.60s-electrolysis.at.−0.5.V..(Redrawn.and.rearranged.from.
Stephanie,.G.R..et.al.,. Electroanalysis ,.21,.280,.2009.)

2 μA

CN -

SCN -

Br -

Cl -

F -

+0.8 +0.4

E [V] vs. Ag/AgCl

0 -0.4

FIGURE 8.3 A.set.of.voltammograms.obtained.by.analyzing.the.[AuX 4 ] − .complexes.for.subsequent.evalu-
ation. of. the. corresponding. stability. constants,. β ( AuX ) .. See. inscriptions.. Experimental conditions :. CPE. con-
taining.tricresyl.phosphate.as.the.binder.(“C/TCP”.type);.DPCSV,.deposition.conditions:. E DEP .=.+1.0.V.vs..
ref,. t DEP .=.30.s,.scan.rate:.20.mV.·.s −1 ,.Δ E .=.+50.mV;.stripping.limits:. E INIT .=.+1.0.V.and. E FIN .=.−0.5.V.vs..ref.;.
s.e.:.(a).0.1.M.H 2 SO 4 .+.0.1.M.KX.(where.“X,”.F,.Cl,.Br,.and.SCN;.equimolar.mixture.(1:1),.pH.∼.0.5-1.0);.
(b) 0.01.M.KOH.+.0.1.M.KCN.(pH.∼12);. c [Au(III)].=.1.×.10 −5 .mol.·.L −1 ..(Assembled.after.Švancara,.I.,.Carbon.
paste. electrodes. in. electroanalysis,. Hab. dissertation. (in. Czech),. University. of. Pardubice,. Pardubice,. Czech.
Republic,.2002.when.using.some.data.from.Švancara,.I..and.Vyt ˇ as,.K.,. Anal. Chim Acta ,.273,.195,.1993.)

When. possible,. the. detection. by. direct. voltammetry. or. anodic. stripping. voltammetry,.
whether.associated.or.not.to.a.preceding.chemical.accumulation.step,.was.applied.but.this.was.
not.always.possible.due.to.“poor.electrochemistry”.of.some.of.these.species.at.carbon.surfaces.
and/or. the. respective. large. overpotential.. For. instance,. reduction. of. Hg 2+ . can. be. quite. easily.
performed.on.CPE,.that.of.Cd 2+ .is.still.possible.but.the.corresponding.signal.is.situated.close.