DQ
UFSCar
LABORATÓRIO DE ANALÍTICA
•BIOANALÍTICA
•BIOSSENSORES
•ELETROANALÍTICA &
•SENSORES
Detecção Amperométrica/Voltamétrica em Sistemas FIA
e Cromatográficos Empregando Eletrodo de Diamante
Dopado com Boro
Orlando Fatibello Filho
Departamento de Química, Universidade
Federal de São Carlos,
Caixa Postal 676, 13560-970 São Carlos – SP
[email protected]; www.ufscar.br/labbes
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Financial Support and Acknowledgements
Prof. Dr. Romeu C. Rocha-Filho (DQ-UFSCar)
Prof. Dr. Leonardo S. Andrade (DQ-UFG-Catalão)
Dr. Roberta Antigo Medeiros (DQ-UFSCar)
M.Sc. Bruna Cláudia Lourenção (DQ-UFSCar)
Prof. Dr. Quezia B. Cass (DQ-UFSCar)
Prof. Dr. Adriana Evaristo de Carvalho (DQ-UFMS)
Prof. Dr. Élen R. Sartori (DQ-UEL)
Prof. Dr. Giancarlo Richard Salazar-Banda (ITP-Un. Tiradentes)
Prof. Dr. Luis A. Avaca (Guarujá, SP)
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Boron-doped diamond electrode
 corrosion stable in very aggressive media
 very low and stable background current
 very low adsorption of organic/inorganic species
 extreme electrochemical stability in both alkaline and
acid media
 high response sensitivity
 very wide working potential window (3.5 V)
K. Pecková et al. Critical Reviews in Analytical Chemistry. 39 (2009) 148
3
Approximate potential ranges for platinum, mercury, carbon and
boron-doped diamond (BDD) electrodes
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Experimental
 Working electrode: Boron-doped diamond film (8000 ppm) on a silicon
wafer from Centre Suisse de Electronique et de Microtechnique SA
(CSEM), Neuchatêl, Switzerland
Electrochemical pre-treatments
 Cathodic pretreatment: –1.0 A cm–2 for 180 s in a 0.5 M H2SO4 solution
 Anodic pretreatment: +1.0 A cm-2 for 180 s in a 0.5 M H2SO4 solution
Counter electrode: Pt wire
Reference electrode: Ag/AgCl (3.0 M KCl)
Potentiostat/galvanostat: Autolab PGSTAT-30 (Ecochemie) controlled
with the GPES 4.0 software
L.S. Andrade, G. R. Salazar-Banda, R. C. Rocha-Filho, O. Fatibello-Filho, Cathodic
Pretreatment of Boron-Doped Diamond Electrodes and Their Use in Electroanalysis, In:
Synthetic Diamond Films: Preparation, Electrochemistry, Characterization, and Applications,
5
(Eds. E. Brillas and C. A. Martínez-Huitle), John Wiley & Sons, Inc., Hoboken, NJ, USA, 2011.
Electrochemical pre-treatments
Characteristics of the procedure:
 simple and rapid
 low cost
 good intra- and inter-day repeatabilities
Cathodic pre-treatment
Anodic pre-treatment
Hydrogen-terminated BDD
(HT-BDD)
Oxygen-terminated BDD
(OT-BDD)
G.R. Salazar-Banda, L.S. Andrade, P.A.P. Nascente, P.S. Pizani,
R.C. Rocha-Filho, L.A. Avaca. Electrochimica Acta, 51 (2006) 4612.
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Potentiostat/galvanostat: Autolab
PGSTAT-30 (Ecochemie)
Flow Injection analysis system
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Flow electrochemical cell
Working electrode :
BDD
8000 ppm; 0.33 cm2
Counter electrode :
stainless steel tube
Reference electrode
Ag/AgCl
(3.0 mol L–1 KCl)
E. M. Richter et al. Quim. Nova, 26(6) (2003) 839.
L. Andrade et al. Anal. Chim. Acta 654 (2009) 127.
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Results and discussion
Simultaneous Square-Wave Voltammetric Determination of
Phenolic Antioxidants (BHA and BHT) in Food Using a
Boron-Doped Diamond Electrode
OH
O
C (C H 3 ) 3
O
C (C H 3 ) 3
H 2O
OCH3
H 3O
C (C H 3 ) 3
+
2
e-
2H 2 O
C H 3O H
OCH3
O
BHA
OH
O
C (C H 3 ) 3
(C H 3 ) 3 C
H 2O
CH3
C (C H 3 ) 3
(C H 3 ) 3 C
+
H 3O
+
2
e-
CH3
BHT
BHA = butylated hydroxyanisole; BHT = butylated hydroxytoluene
R.A. Medeiros, R.C. Rocha-Filho, O. Fatibello-Filho, Food Chemistry, 123 (2010) 886.
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H 3O
+
1.6
I / 
1.2
0.8
0.4
0.0
0.4
0.6
0.8
1.0
1.2
E / V vs. Ag/AgCl (3.0 M KCl)
SWV curves obtained on an anodically (dashed line) and a cathodically (solid line)
pre-treated BDD electrode, using a mixture of 10 µM BHA and 10 µM BHT.
Supporting electrolyte: aqueous-ethanolic (30 % ethanol, v/v) 10 mM KNO3
solution (pHcond. = 1.5 adjusted with conc. HNO3).
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OH
BHA
C (CH 3 ) 3
OCH3
OH
BHT
C (CH 3 ) 3
(C H 3 ) 3 C
CH3
BHA: 0.60 – 10 M; LOD = 0.14 M
BHT: 0.60 – 10 M; LOD = 0.25 M
Highlight:
LODs lower than those
previously reported
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Flow injection simultaneous determination of BHA and BHT
with multiple pulse amperometric detection at a BDD electrode
2,5
1,6
(A) - BHA
2,0
(B) - BHT
1,2
I/
1,5
I/
1,0
0,5
0,4
0,0
0,3
0,8
0,0
0,4 0,5 0,6 0,7 0,8 0,9
-1
E/V vs. Ag/AgCl (KCl 3,0 mol L )
1,0
0,7 0,8 0,9 1,0 1,1 1,2 1,3
-1
E/V vs. Ag/AgCl (KCl 3,0 mol L )
Voltamogramas hidrodinâmicos obtidos para o BHA 0,10 mmol L-1 (A) e BHT 0,10 mmol
L-1 (B), utilizando o eletrodo de BDD; vazão 2,4 mL min-1 e Vamostra = 350 µL
R.A. Medeiros; B.C. Lourenção; R.C. Rocha-Filho, O. Fatibello-Filho; Anal. Chem.,
82 (2010) 8658.
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(A) MPA waveform applied to the cathodically pretreated BDD working electrode as a
function of time. (B) Flow-injection pulse amperometric responses in triplicate for
solutions containing 50 μmol L-1 BHA or BHT or both analytes simultaneously at this
concentration. Supporting electrolyte: aqueous ethanolic (30% ethanol, v/v) 10 mmol L-1
KNO3 solution (pHcond =1.5) adjusted with concentrated HNO3); flow rate 2.4 mL min-1;
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injected volume 250 μL.
FIA-MPA amperograms obtained after injections of solutions containing BHA (0.050-3.0
μmol L-1) and BHT (0.70-70 μmol L-1) simultaneously or different samples of mayonnaise
(A-D). Supporting electrolyte: aqueous ethanolic (30% ethanol, v/v) 10 mmol L-1 KNO3
solution (pHcond =1.5) adjusted with concentrated HNO3); flow rate 2.4 mL min-1;
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injected volume 250 μL.
Faixa linear: BHA - 0,050 a 3,0 µmol L–1
BHT - 0,70 a 70,0 µmol L–1
(I = IEdet.1, para o BHA)
I/µA= 0,00619 + 0,0559 [c/(µmol L–1)]; r = 0,998
(I = IEdet.2 – IEdet.1, para o BHT)
I/µA= 0,144 + 0,0503 [c/(µmol L−1)];
r = 0,999
Limites de Detecção: BHA: 3,0  10-8 mol L-1
BHT: 4,0  10-7 mol L-1
Tabela-Resultados obtidos para o estudo de repetibilidade intra e entre-dias
intra-dias
RSDa (%)
BHA (mol L-1)
7,0 × 10-8
5,0 × 10-7
3,0 × 10-6
BHT (mol L-1)
7,0 × 10-7
6,0 × 10-6
7,0 × 10-5
entre-dias
RSDb (%)
3,8
2,5
2,9
5,1
3,9
4,2
8,9
2,0
1,8
8,5
5,3
3,6
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Tabela- Resultados obtidos na determinação simultânea de BHA e BHT em
produtos alimentícios empregando-se HPLC e MPA-FIA
a
b
BHA
BHT
Erro (%)b
Erro (%)b
2,1 ±0,2 1,1±0,1 1,2±0,3
5,0
9,1
1,7±0,2
1,6±0,1
1,3±0,2 1,3±0,2
-5,9
0,0
3
2,3±0,2
2,2±0,2
1,8±0,2 1,8±0,3
-4,3
0,0
4
2,3±0,1
2,1±0,3
1,4±0,2 1,3±0,1
-8,7
-7,1
Amostras
BHA (mg/100 g)
BHT (mg/100 g)
Maionese
HPLCa
HPLCa MPAa
1
2,0±0,1
2
MPAa
n=3
Erro (%) = 100 × (valor amperométrico - valor HPLC) / valor HPLC
teste t-pareado
BHA: texp = 1,54 e BHT: texp = 1,66 tcrítico = 3,18
R.A. Medeiros; B.C. Lourenção; R.C. Rocha-Filho, O. Fatibello-Filho; Anal.
Chem., 82 (2010) 8658.
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Paracetamol (A) and caffeine (B) in pharmaceuticals
Differential pulse voltammetry
Paracetamol: 0.50 – 83 M
LOD = 0.049 M
Caffeine: 0.50 – 83 M
LOD = 0.035 M
Highlight:
LODs lower than those reported; higher sensitivity
and larger linear concentration range of the AC
17 M
38 M
B.C. Lourenção, R.A. Medeiros, R.C. Rocha-Filho, L.H. Mazo, O. Fatibello-Filho.
Talanta, 78 (2009) 748.
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A Simple Strategy for Simultaneous Determination of
Paracetamol and Caffeine Using Flow Injection Analysis with
Multiple Pulse Amperometric Detection
W. C. Silva, F.P. Pereira, M.C. Marra, D. T. Gimenes, R.R. Cunha, R.A.B. da Silva,
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R. A.A. Munoz, E. M. Richter, Electroanalysis, 23 (2011) 2764.
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Simultaneous differential pulse voltammetric determination of
ascorbic acid and caffeine in pharmaceutical formulations
using a boron-doped diamond electrode
DPV responses for 0.029 M AA and 0.79 M caffeine in 0.1 M H2SO4 on (1)
cathodically pretreated BDD electrode and (2) glassy-carbon electrode.
B.C. Lourenção, R.A. Medeiros, R.C. Rocha-Filho, O. Fatibello-Filho.
Electroanalysis, 22, 1717 (2010)
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Repeatability study
50
45
GC
60
35
50
30
40
I/A
I/A
40
70
25
20
BDD
30
20
15
10
10
0.4
0.6
0.8
1.0
1.2
E/V vs Ag/AgCl
1.4
1.6
0
0.4
0.6
0.8
1.0
1.2
1.4
1.6
E/V vs Ag/AgCl
Repeatability study for 0.029 M Ascorbic acid (n = 10) + 0.79 M caffeine
in 0.1 M H2SO4
Highlight:
higher repeatability of the BDD
RSD = 8.7 % for glassy-carbon (GC) electrode
electrode
RSD = 1.0 % for boron-doped diamond (BDD) electrode
B.C. Lourenção; R.A. Medeiros; R.C. Rocha-Filho; O. Fatibello-Filho;
Electroanalysis, 22 (2010) 1717
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Sampling
Rate = 30 h-1
(A) Diagram of the multicommutated stop-flow system: V1 and V2: solenoid valves;
A: sample or standard solution; C: carrier solution (BR buffer pH 7.0).
(B) Transient DPV signals in triplicate for sulfamethoxazole (1.0 – 8.0 mg L–1) and
trimethoprim (0.2 – 1.6 mg L–1) determination in pharmaceuticals.
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Conclusions
 HT-BDD electrodes present an improved electrochemical activity
towards many analytes
 Background current for HT-BDD electrodes is one order of magnitude
lower than that for glassy-carbon electrodes, leading to an improved
signal-to-background ratio
 HT-BDD electrodes present higher sensitivity, precision, and accuracy,
and lower LOD and response time than glassy-carbon electrodes
 No deactivation of the BDD electrode was observed in the flow
injection system / HPLC coupled with amperometric/voltammetric
detection
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Profs. Romeu
Dr. Adriana
Leonardo
Dr. Élen
Quezia
M.Sc. Bruna
Giancarlo
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M.Sc. Roberta
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