Electroquímica analítica
Transcript of Electroquímica analítica
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Electroquímica analíticaPrincipios:
Condiciones operatorias I y IIModelo difusional
Cinética electródicaCinética de transferencia de masa
Cinética química acoplada
Alejandro BaezaFQ UNAM
1FQ UNAM Alejandro Baeza 2007
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2FQ UNAM Alejandro Baeza 2007
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(+) (-)
mV
Equilibrio
electroquímico
δδδδ δδδδ
Interfases cargadas =electrodos
Se forma La doble capaelectrica
3FQ UNAM Alejandro Baeza 2007
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(+) (-)Se rompe el
Equilibrio
Electroquímico:
Migración iónica.
Se enriquece
imigratoriaI
δδδδ δδδδ
Interfases cargadas =electrodos
Se enriquecela doble capaEléctrica.
v
(+) (-)
imigratoria=icapacitiva
4FQ UNAM Alejandro Baeza 2007
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+ -
-´+ +
C/s = I
- -´+ +
Esfera internaEsfera externa
-
+
-
5FQ UNAM Alejandro Baeza 2007
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CONDICIONES OPERATORIAS6FQ UNAM Alejandro Baeza 2007
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¿cuál es la relación entre corriente, resistencia yel potencial impuesto externamente
Para una disolución iónica?
Los iones se muevenLentamente.
Los electrodosSe polarizan:
7FQ UNAM Alejandro Baeza 2007
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8FQ UNAM Alejandro Baeza 2007
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LOS ELECTRODOS Y LAS CELDAS
Iamperímetro
Sistema de 2 electrodos:
potenciostáto
9FQ UNAM Alejandro Baeza 2007
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10FQ UNAM Alejandro Baeza 2007
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11FQ UNAM Alejandro Baeza 2007
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electrodo
12FQ UNAM Alejandro Baeza 2007
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Condiciones operatorias (I)
1) Los electrodos: 3
EA: Gran superficieET: MICROELECTRODOER: (dE/dI) 0 ET: MICROELECTRODOER: (dE/dI) 0
1) Electrolito soporte inerte
2) Régimen hidrodinámico controlado
13FQ UNAM Alejandro Baeza 2007
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Régimen hidrodinamico controlado:
I/Régimen convectivo laminar
II/
Sin agitar
III/Flujo continuo
ultramicroelectrodos
14FQ UNAM Alejandro Baeza 2007
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15FQ UNAM Alejandro Baeza 2007
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16FQ UNAM Alejandro Baeza 2007
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17FQ UNAM Alejandro Baeza 2007
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Antecedentes: celda convencional
HMDE
“hanging mercury
dropping electrode
Volumen: 30 mL
18FQ UNAM Alejandro Baeza 2007
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H.Prado, P. Diaz. J.L. Ortiz and Alejandro Baeza
Polarographic determination of Km´ and of glutathione reductaseCurrent Separations 20-4(2004)117-122 19FQ UNAM Alejandro Baeza 2007
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Electrodos giratorios de disco: EGDRégimen hidrodinámico (convectivo laminar) 20FQ UNAM Alejandro Baeza 2007
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21FQ UNAM Alejandro Baeza 2007
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22FQ UNAM Alejandro Baeza 2007
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Electroquìmica
De flujo
23FQ UNAM Alejandro Baeza 2007
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Microcelda para ASV
SIN AGITACIÓNREGIMEN DE
DIFUSIÓN PURA
24FQ UNAM Alejandro Baeza 2007
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UME
SIN AGITACIÓN
¡REGIMEN CONVECTIVO!
25FQ UNAM Alejandro Baeza 2007
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ITIES
26FQ UNAM Alejandro Baeza 2007
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27FQ UNAM Alejandro Baeza 2007
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100 mL
28FQ UNAM Alejandro Baeza 2007
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29FQ UNAM Alejandro Baeza 2007
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30FQ UNAM Alejandro Baeza 2007
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¿cuál es la relación entre corriente, resistencia y
el potencial impuesto externamente?
Resistencia ideal:¡Ley de Ohm!
E=IR
E
I31FQ UNAM Alejandro Baeza 2007
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ERET
32FQ UNAM Alejandro Baeza 2007
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Química Analítica
Determinación Analítica
Metodologìa Analítica
Metodos quìmicos Metodos Fisicoquìmicos
Analísis Químico(mediciòn, monitoreo, caracterización)
(reacción químico) (interacción energìa-materia)33FQ UNAM Alejandro Baeza 2007
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CONDICIONES OPERATORIAS (II)
METODOLOGIA ELECTROANALÍTICA
PERTURBACIÓN SISTEMA RESPUESTA
34FQ UNAM Alejandro Baeza 2007
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imposición
de
potencial
E=f(t)
imposición
de
corriente
I=f(t)
programa
perturbación
potenciostático
pulsos
de
potencial
potenciodinámico
barridos
de
potencial
E=f(t)
galvanostático
pulsos
de
corriente
galvanodinámico
barrridos
de
corriente
I=f(t)
35FQ UNAM Alejandro Baeza 2007
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Programaperturbación
Patrón de Respuesta
Pulsos de
potencialCronoamperometría
(I)E = f(t)
Pulsos de
corrienteCronopotenciometría
(E) = f(t)corriente (E)I = f(t)
Barrido de
potencialVoltamperometría
I = f (E)
Barrido de
corrienteVoltamperometría
E = f (I)36FQ UNAM Alejandro Baeza 2007
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37FQ UNAM Alejandro Baeza 2007
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galvanostato
38FQ UNAM Alejandro Baeza 2007
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39FQ UNAM Alejandro Baeza 2007