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Detection of total phenol in green and black teas by flow injection system and unmodified screen printed electrode.

de Mattos IL, Zagal JH - Int J Anal Chem (2011)

Bottom Line: Results were reported as gallic acid equivalents (GAEs).The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample), and allows the analysis of about 35-40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement.Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química de Los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Sucursal Matucana, Santiago 9170022, Chile.

ABSTRACT
A flow injection system using an unmodified gold screen-printed electrode was employed for total phenol determination in black and green teas. In order to avoid passivation of the electrode surface due to the redox reaction, preoxidation of the sample was realized by hexacyanoferrate(III) followed by addition of an EDTA solution. The complex formed in the presence of EDTA minimizes or avoids polymerization of the oxidized phenols. The previously filtered tea sample and hexacyanoferrate(III) reagent were introduced simultaneously into two-carrier streams producing two reproducible zones. At confluence point, the pre-oxidation of the phenolic compounds occurs while this zone flows through the coiled reactor and receives the EDTA solution before phenol detection. The consumption of ferricyanide was monitorized at 360 mV versus Ag/AgCl and reflected the total amount of phenolic compounds present in the sample. Results were reported as gallic acid equivalents (GAEs). The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample), and allows the analysis of about 35-40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement. Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

No MeSH data available.


Flow-cell (model FC2) and screen-printed electrode developed by BVT Technologies (Czech Republic). A, R, and W refer to auxiliary, reference, and working electrodes. In the present flow-cell does not exist the light emitting diode (LED) as specified in the figure.
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fig1: Flow-cell (model FC2) and screen-printed electrode developed by BVT Technologies (Czech Republic). A, R, and W refer to auxiliary, reference, and working electrodes. In the present flow-cell does not exist the light emitting diode (LED) as specified in the figure.

Mentions: Cyclic voltammetry was performed using a PS potentiostat system (Palm Instruments BV, The Netherlands) connected to a PC. A three-compartment electrochemical cell containing three electrodes in the form of an electrochemical sensor type AC1.W.R (BVT Technologies, Czech Republic) was used. The sensor was formed on a corundum ceramic base and on this surface, the working, the reference, and the auxiliary electrodes were placed as illustrated in Figure 1. Its compositions were: AuPd (98/2), Ag/AgCl (60/40), and AuPd (98/2%), respectively.


Detection of total phenol in green and black teas by flow injection system and unmodified screen printed electrode.

de Mattos IL, Zagal JH - Int J Anal Chem (2011)

Flow-cell (model FC2) and screen-printed electrode developed by BVT Technologies (Czech Republic). A, R, and W refer to auxiliary, reference, and working electrodes. In the present flow-cell does not exist the light emitting diode (LED) as specified in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3065041&req=5

fig1: Flow-cell (model FC2) and screen-printed electrode developed by BVT Technologies (Czech Republic). A, R, and W refer to auxiliary, reference, and working electrodes. In the present flow-cell does not exist the light emitting diode (LED) as specified in the figure.
Mentions: Cyclic voltammetry was performed using a PS potentiostat system (Palm Instruments BV, The Netherlands) connected to a PC. A three-compartment electrochemical cell containing three electrodes in the form of an electrochemical sensor type AC1.W.R (BVT Technologies, Czech Republic) was used. The sensor was formed on a corundum ceramic base and on this surface, the working, the reference, and the auxiliary electrodes were placed as illustrated in Figure 1. Its compositions were: AuPd (98/2), Ag/AgCl (60/40), and AuPd (98/2%), respectively.

Bottom Line: Results were reported as gallic acid equivalents (GAEs).The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample), and allows the analysis of about 35-40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement.Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química de Los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Sucursal Matucana, Santiago 9170022, Chile.

ABSTRACT
A flow injection system using an unmodified gold screen-printed electrode was employed for total phenol determination in black and green teas. In order to avoid passivation of the electrode surface due to the redox reaction, preoxidation of the sample was realized by hexacyanoferrate(III) followed by addition of an EDTA solution. The complex formed in the presence of EDTA minimizes or avoids polymerization of the oxidized phenols. The previously filtered tea sample and hexacyanoferrate(III) reagent were introduced simultaneously into two-carrier streams producing two reproducible zones. At confluence point, the pre-oxidation of the phenolic compounds occurs while this zone flows through the coiled reactor and receives the EDTA solution before phenol detection. The consumption of ferricyanide was monitorized at 360 mV versus Ag/AgCl and reflected the total amount of phenolic compounds present in the sample. Results were reported as gallic acid equivalents (GAEs). The proposed system is robust, versatile, environmentally-friendly (since the reactive is used only in the presence of the sample), and allows the analysis of about 35-40 samples per hour with detection limit = 1 mg/L without the necessity for surface cleaning after each measurement. Precise results are in agreement with those obtained by the Folin-Ciocalteu method.

No MeSH data available.