Chemically Modified Carbon Paste Electrodes - Electroanalysis with Carbon Paste Electrodes - page 96

(di)carboxylic. acid. [441,874,1535-1540],. ferrocenyl. surfactants. [207,1541],. 1-[4-(fer-
rocenylethynyl)phenyl]-1-ethanone. [1542-1547],. 2,7-bis(ferrocenyl. ethyl)luoren-9-one.
[879,1548-1550],.and.some.others.[1551-1553]).have.been.exploited.for.the.electrocatalytic.
detection.of.various.biologically.relevant.analytes.or.pollutants..These.mediators.could.be.
immobilized.onto.inorganic.particles.(e.g.,.zeolites.[876,1118].or.SiO 2 /Me x O y .[923,1103]).
before.incorporation.into.CPEs.or.associated.to.organic.or.inorganic.polymers.before.CPE.
modiication.[782,785,856,862,922,924,1554,1555]..Finally,.other.metallocenes.have.been.
exploited.in.CPE-based.immunoassays.with.electrochemical.detection.or.for.electrocataly-
sis.(i.e.,.cobaltocene.derivatives.[1556-1559]).

•. Complexes of phthalocyanine and porphyrin derivatives .. Phthalocyanines. are.

intensely. colored. macrocyclic. compounds. that. form. coordination. complexes. with.
many. elements. of. the. periodic. table.. Following. pioneering. works. by. the. Baldwin.
et al.. [882-885],. transition. metal. complexes. of. phthalocyanine. macrocycles. are. well-
known. electrocatalysts,. and. cobalt. phthalocyanine. (CoPc). in. particular. has. been.
widely. used. as. CPE. modiier. for. the. electrocatalytic. determination. of. biologically.
important. compounds. and. some. other. analytes. [324,555,560,652,653,886,889-894,.
897,898,901,902,904,905,908,914,915,917,929,931,933,1040,1560-1565].. Related. CoPc.
derivatives. used. in. CPEs. include. cobalt. octaethoxyphthalocyanine. [1566,1567].. This.
extraordinary. high. number. of. investigations. was. notably. applied. to. the. detection. of.
thiol. compounds,. saccharides,. amino. acids,. hydrazine,. or. hydrogen. peroxide.. CoPc-
modiied.CPEs.led.not.only.to.direct.electrocatalytic.determinations.but.they.also.prove.
to.be.useful.detectors.for.online.detection.of.various.analytes,.in.low.injection.analysis.
[324,902,905],.or.following.their.separation.by.high-performance.liquid.chromatography.
[882,884,886,889,890,892].or.capillary.electrophoresis.[555,556,1565]..Besides.CoPc,.other.
metal.complexes.of.phthalocyanine.macrocycles.have.been.introduced.into.CPEs.for.(bio)
sensing.purposes,including.complexes.ofiron.[1562,655,778,887,896,903,909,911,916,1568-
1570],. nickel. [651,895,900,1179,1180],. copper. [519,900],. molybdenum. [899],. manganese.
[912],. and. rare-earth. elements. [1571].. Of. related. interest. are. metalloporphyrins,. that. is,.
metal.complexes.of.heterocyclic.macrocycles.composed.of.four.modiied.pyrrole.subunits.
interconnected. at. their. α. carbon. atoms. via. methane. bridges,. which. have. been. used. as.
CPE.modiiers.for.electrocatalytic.determinations..For.species.used.in.CPEs,.the.porphy-
rinic.ring.(functionalized.or.not).contained.metal.species.such.as.iron.[1171,1572-1575],.
copper. [1112,1113,1574,1576-1578],. cobalt. [534,1176,1191,1195,1574,1579],. manganese.
[1572,1580],. as. well. as. of. nickel. and. zinc. [1574].. These. catalysts. can. be. incorporated.
(in the.original.form).as.such.in.the.CPE.matrix.or.previously.immobilized.in/on.inorganic.
particles.such.as.zeolites.[1112,1113].or.silica.gels.coated.with.thin.ilms.of.metal.oxides.or.
metal.phosphates.(see,.e.g.,.[206,534,1171,1176,1191]).

•. Schiff base complexes ..Schiff.bases.are.functional.groups.that.contain.a.carbon-nitrogen.

double. bond. with. the. nitrogen. atom. connected. to. an. aryl. or. alkyl. group. (probably. the.
most. well-known. chelating. ligand. of. this. family. is. salen,. a. name. originating. from. the.
contraction. for. salicylic. aldehyde. and. ethylenediamine).. Some. of. their. metal. complexes.
are.attractive.mediators.that.have.been.used.to.modify.CPEs..The.most.popular.are.cobalt.
salophen.(i.e.,.cobalt(II)- N , N ′-bis(salicylidene)-1,2-phenylenediamine,.the.salophen.name.
being.the.contraction.for.salicylic.aldehyde.and.phenylenediamine).[384,403,1581-1584].
and. cobalt. salophen. derivatives. [1585-1592],. while. some. other. metal. Schiff. base. com-
plexes.[536,1593-1596].were.also.of.interest..They.were.often.exploited.for.electrocatalytic.
purposes,.to.detect.some.principal.biologically.relevant.molecules.(mainly,.ascorbic.acid,.
dopamine,.and.uric.acid).as.well.as.various.pharmaceuticals.and.drugs.

•. Others/miscellaneous .. Other. two. families. of. metal. complexes. that. were. widely.

incorporated. into. CPEs. are. metal. phenanthroline. compounds. (iron(II,III). phenan-
throline.

derivatives. [68,546,547,1597-1599]. or. the. ruthenium(II). phenanthroline.