Instrumental Measurements with Carbon Paste Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 143

1

2

3

4

5

6 7

8

9 10

11 12

13

100 mV

0.5 mL

Δ E (mV)

450

400

350

300

0 2 4 6 8 10 12 14

n C

FIGURE 6.9 Potentiometric. ion-pair. formation-based. titrations. of. quaternary. ammonium. salts. of. the.
[CH 3 (CH 2 ) 10 COOCH 2 CH 2 N(CH 3 ) 2 −R] + Br − . type. using. NaBPh 4 . as. the. titrant. showing. the. dependence. of.
the. titration. end-point. break. on. the. lipophilicity. of. the. cation.. A. set. of. titration. curves. (above). and. the.
“Δ E [mV]. vs.. n C ”. plot. (below).. 1-13,. actual. number. of. titration. curves. corresponding. to. the. number. of.
carbon. atoms. ( n C ). in. the. alkyl. chain. R. of. the. salt.. Experimental conditions :. titrations. in. the. automated.
mode;.tricresylphosphate-containing.carbon.paste;. c (salts).=.1.×.10 −5 .mol.·.L −1 ,. c (titrant).=.0.01.mol.·.L −1 ..
(Redrawn.from.Vytˇas,.K..et.al.,.A.low.ohmic.resistance.sensor.for.potentiometric.titrations.of.tensides,.in.
XXVII Seminar on Tensides and Detergents. Proceedings (in Czech) ,.Novaky,.Slovakia,.1994,.pp..35-48.)

6.4.2 C hronopoTenTioMeTry and s Tripping C hronopoTenTioMeTry
These. techniques. whose. stripping. modiications. have. been. recently. in. the. centre. of. interest. in.
passionate. debates. on. their. proper. classiication. and. terminology. [1977]. offer. an. interesting.
alternative.to.other.electrochemical.measurements,.which.is.also.relected.in.electroanalysis.with.
CPEs—see.the.already.cited.studies.(e.g.,.[13,26,91,92,108,190,209,210,254,341,366,588,626,629,
630,684,710,711]),.contributions.within.this.section.(plus.related.items.[1978-1999]),.and.some.others.
in.Chapter.8,.surveyed.in.the.respective.tables.
Chronopotentiometry.uses.a.three-electrode.coniguration.in.which.a.small.constant.current.is.
impressed.between.the.auxiliary.and.working.electrodes,.and.the.potential.of.the.working.electrode.
vs..reference.electrode.is.measured.as.a.function.of.time,.that.is,. E .=. f ( t ).and.known.as. E - t .curve(s)..
The.operation.is.done.in.unstirred.solution,.and.thus,.an.electroactive.substance.is.transported.by.
diffusion.only.[1978-1980]..From.the.corresponding.chronopotentiogram,.the.so-called. transition
time ,.“ τ ,”.can.be.evaluated..During.this.interval,.the.concentration.of.the.reacting.substance.on.the.