Electroanalysis with Carbon Paste–Based Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 199

-4

CH 2 OH

I AD

C O OOH

H

H

C C

H

OOH

-3

C C

HHO

H

H OOH

-2

-1

0

0 50 100 150 200 250 300

C GLU [mg L -1 ]

FIGURE 8.16 Testing. of. a. new. CP-biosensor. with. GOD. immobilized. onto. the. electropolymerized. ilm..
Calibration. of. glucose. (GLU). at. the. mg.·.L −1 . level.. Experimental conditions :. Nujol. oil-based. carbon. paste.
coated.with.polyaniline.ilm;.hydrodynamic.amperometry.(HA),.detection.potential,.−300.mV;.phosphate.buf-
fer.(pH.7.5),. c (GLU).=.10-300.ppm.(introduced.to.the.solution.as.the.adequate.additions.of.stock.standard.
solution)..(An.outtake.from.Stoces,.M..et.al.,. Int. J. Electrochem. Sci .,.submitted.paper,.2010.)

Enzyme-induced. precipitation. of. Cu(II)-. and. Nd(III)-hexacyanoferrate(II). starts. with. ferri-
cyanide,. which. is. an. electron. acceptor. from. FADH 2 . of. GOD. (in. solution). forming. [Fe(CN) 6 ] 4− .
which. then. precipitates. with. the. counterion. [1008,1009].. CuO. catalyzes. the. oxidation. and.
the. reduction. of. hydrogen. peroxide. [2833].. Mn-perovskite. [1249]. and. manganese. oxides.
[1234,1874,2834]. mediate. the. oxidation. of. hydrogen. peroxide. to. oxygen;. manganese. oxides.
in. lower. oxidation. states. can. be. electrochemically. reoxidized. to. MnO 2 . again.. Metal. oxides. as.
mediators. for. detecting. H 2 O 2 . were. studied. in. [2835].. Platinum. metals,. their. alloys,. and. copper.
were. widely. used. [285,291,375,405,609,611,612,754,838,873,1035,1256,1260,1262,1263,1266,1267,.
1281-1283,1711,1789,1854,1949,2733,2837];. they. can. be. applied. in. dispersed. form. of. metalized.
graphite. particle,. as. powder. and. as. micro-. and. nanoparticles.. At. positive. potentials,. platinum.
metals. mediate. the. oxidation. of. H 2 O 2 . to. O 2 ,. at. negative. the. reduction. to. H 2 O.. The. studies. also.
revealed.high.thermal.[291,2707].and.acid.[1854].stability.of.the.enzyme.GOD..Efforts.to.avoid.
oxygen.depletion.by.the.enzymatic.action.resulted.in.addition.of.myoglobin.as.an.oxygen.pool,.or.
in.the.use.of. Kel-F .or.siloxane.as.pasting.liquids.that.can.dissolve.O 2 .[611,873,1789,2837]..Iron.
nanoparticles.on.carbon.nanotubes.(carbon-iron.nanocomposite).may.transfer.electrons.directly.
to.GOD.in.a.third-generation.biosensor.[2712],.similar.to.gold.nanoparticles.[941,1270,1274];.here.
catalytic. effects. of. the. Au-nanoparticles. on. the. reduction. of. oxygen. are. also. assumed. [1274]..
A nanostructured.perovskite.immobilizes.GOD.well,.but.the.catalytic.action.is.done.by.ferrocene.
[1250]..Tetrathiafulvalene.(TTF,.2,2′-bis-1,3-dithiolylidene).can.be.oxidized,.acting.as.an.electron.
acceptor.[1486,2841-2843,2846,2847]..Tetracyano-quinodimethane.(TCNQ,.2,5-cyclohexadiene-
1,4-diylidene).is.readily.reduced.to.a.blue.anionic.radical.and.is.therefore.also.a.useful.oxidant.
for.FADH 2 .in.GOD.[1493,2844-2846]..Both.TTF.and.TCNQ.together.form.a.blue.salt.with.high.
conductivity,.“organic.metal”;.it.can.be.used.to.build.a.third-generation.glucose.biosensor.which.
is.less.stable.than.the.one.with.TTF.alone.[2846]..Quinones.are.another.group.of.organic.electron.
acceptors. in. biosensors. with. GOD. [1438,1440,1448,1450,1456,1757,. 1759,2848,2852].. One. assay.
uses. a. silicagel. particle. with. immobilized. modiiers. as. a. microreactor. implanted. on. the. CPE.