Chemically Modified Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 89

Insoluble.or.sparingly.soluble.salts.were.also.used.for.that.purpose.(e.g.,.lead.sulfate.for.oxalic.
acid.[811],.sodium.pyruvate.for.lactate.dehydrogenase.[1313],.mercury.oxalate.for.heavy.metal.ions.
[325],.magnesium.oxinate.for.Cu II .[1314])..On.the.other.hand,.copper(II).hexacyanoferrate.[1315].or.
copper(I).oxide.[1316].and.Meldola.blue.intercalated.in.calcium.or.barium.sulfates.[1317,1318].were.
exploited.for.electrocatalytic.purposes.

4.3.2 o rganiC and o rganoMeTalliC C oMpounds
4.3.2.1 Organic Ligands
A.large.variety.of.organic.ligands.have.been.used.for.the.chemical.modiication.of.CPEs,.and.
it.is.not.straightforward.to.provide.a.classiication..Hereafter.are.considered.molecular.ligands,.
macrocyclic/supramolecular. compounds,. and. polymeric. materials. (synthetic. macromolecular.
chelating.resins.and.natural.polymers.(or.biopolymers).with.anchoring.properties).
Organic.ligands.were.essentially.exploited.for.their.(expected).recognition.properties.in.order.
to.preconcentrate.target.analytes.(mainly.metal.ions).at.the.CPE.surface.to.enhance.the.sensitiv-
ity. of. their. electrochemical. detection.. The. vast. majority. of. applications. involved. voltammetric.
or.amperometric.detection.schemes,.but.potentiometric.determinations.have.also.been.reported.

4.3.2.1.1 Molecular Ligands
An.extraordinary.high.number.of.molecular.ligands.have.been.used.to.modify.CPEs..Most.of.them.
contain.N-.and.S-based.complexing.centers..They.have.been.classiied.here.on.the.basis.of.target.
analytes.

•. Mercury. species. (i.e.,. Hg II ). have. been. determined. at. CPEs. modiied. with. 1,5-diphenyl-

carbazide. [1319],. 2-mercapto-4(3H)-quinazolinone. [1320],. imidazole. [1321],. the. Schiff.
base.glyoxal.bis(2-hydroxyanil).[1322],.diethyldithiocarbamate.[1323],.tetraethyl.thiuram.
[1324],.the.Schiff.base.benzylbisthiosemicarbazone.[1325],.ethyl-2-(benzoylamino)-3-(2-
hydroxy-4-methoxyphenyl)-2-propenoate. [1326],. and. 4-nitrophenyldiazoamino-azoben-
zene.(Cadion.A).[1327].

•. Silver. (Ag I ). was. accumulated. at. CPEs. using. 2-iminocyclopentanedithiocarboxylic. acid.

[1328],. 2,2′-dithiodipyridine. [1329],. 2-mercaptoimidazole. [1330],. 2,3-dicyano-1,4-
naphthoquinone. [1331],. the. Schiff. base. glyoxal. bis(2-hydroxyanil). [1333],. N -benzoyl-
N ′, N ′-diisobutylthiourea. [1332],. N , N ′-diphenyl. oxamide. [1333],. (di)thiosalicylic. acids.
[1334],. Alizarin. violet. [690],. 3-amino-2-mercaptoquinazolin-4(3H)-one. [1335],. and.
1,11-bis(thiophenoxyl)-3,6,9-trioxaundecane.[1336].

•. Copper.species.(i.e.,.mainly.Cu II .but.also.Cu I ).were.analyzed.after.accumulation.at.CPEs.

containing,. for. Cu II . detection,. 2,9-dimethyl-1,10-phenanthroline. [1337],. diquinolyl-
8,8′-disulide. [1338],. salicylideneamino-2-thiophenol. [1339],. benzoin. oxime. [1340],.
1,2-bismethyl(2-aminocyclopentene-carbodithiolate)ethane. [1341],. pyruvaldehyde.
bis(N,N′-dibutylthiosemicarbazone). [1342],. 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyrimidi-
nethione.[1343],.tetraphenylporphyrin.[750],.salicylaldoxime.[1344],.2-mercaptobenzothi-
azole.[1345],.tetraethyl.thiuram.[1324],.naphthazarin.(5,8-dihydroxy-1,4-naphthoquinone).
[1346],.and,.for.Cu I .detection,.di(2-iminocyclopentylidinemercaptomethyl)disulide.[1347].
and.a.classical.analytical.reagent—rubeanic.acid.[1347].

•. Lead. species. (Pb II ). were. preconcentrated. using. benzoin. oxime. [1349],. diphenylthio-

carbazone. [814],. Schiff. base. N , N -bis[2-(2-iminoantipyrinephenoxy)ethyl]- p -tolu-
ene-sulfonamide. [1290],. pyruvaldehyde. bis(N,N′-dibutylthiosemicarbazone). [1342],.
bis[1-hydroxy-9,10-anthraquinone-2-methyl]sulide. [1351],. p -phenylenediamine. [1352],.
and.dithizone.[1353].

•. Cobalt. (Co II ). has. been. analyzed. at. CPEs. containing. 1,10-phenanthroline. [1354],.

2,2′-bipyridyl. [1355],. 1-nitroso-2-naphtholate. [1356],. 1-(2-pyridylazo)-2-naphthol. [1357],.