Simultaneous Determination of Different Phenolic Compounds Using Electrochemical Biosensor and Multivariate Calibration (original) (raw)
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Talanta, 2013
An approach based on the electrochemical detection of the horseradish peroxidase enzymatic reaction by means of square wave voltammetry was developed for the determination of phenolic compounds in environmental samples. First, a systematic optimization procedure of three factors involved in the enzymatic reaction was carried out using response surface methodology through a central composite design. Second, the enzymatic electrochemical detection coupled with a multivariate calibration method based in the partial least-squares technique was optimized for the determination of a mixture of five phenolic compounds, i.e. phenol, p-aminophenol, p-chlorophenol, hydroquinone and pyrocatechol. The calibration and validation sets were built and assessed. In the calibration model, the LODs for phenolic compounds oscillated from 0.6 to 1.4 Â 10 À 6 mol L À 1. Recoveries for prediction samples were higher than 85%. These compounds were analyzed simultaneously in spiked samples and in water samples collected close to tanneries and landfills.
Analytica Chimica Acta, 2003
A simple and reliable method for rapid evaluation of mixtures of phenolic compounds (phenol/chlorophenol, cathecol/phenol, cresol/chlorocresol and phenol/cresol) using a dual amperometric device is described. This new approach is based on the difference between the sensitivity of laccase and tyrosinase for different phenolic compounds. A multichannel potentiostat was used to monitor simultaneously laccase-and tyrosinase-based biosensors, and the data were treated using the partial least squares (PLS) chemometric algorithm. This system showed an excellent efficiency for the resolution of the phenolic mixtures. For example, in the phenol/chlorophenol mixture it was studied the determination of individual species in a concentration range from 1.0×10 −6 to 10.0×10 −6 mol l −1 obtaining relative standard deviations of 3.5 and 3.1% for phenol and chlorophenol, respectively. The excellent correlation between the estimated and the real concentrations can also be observed by the correlation coefficients (0.9958 and 0.9981 for phenol and chlorophenol, respectively). These results show that proposed methodology can be successfully employed to the simultaneous determination of phenolic compounds in mixtures, even in more diluted solutions.
Electrochemical biosensor-based devices for continuous phenols monitoring in environmental matrices
Journal of the Brazilian Chemical Society, 2002
Desenvolveu-se um método de análise em fluxo para a determinação contínua de compostos fenólicos em matrizes ambientais, usando-se uma membrana de diálise para amostragem e biossensores a base de lacase e tirosinase para a detecção destes compostos. A resposta dos biossensores frente a diferentes compostos fenólicos foi investigada. O biossensor a base de lacase mostrou uma alta sensibilidade para guaiacol e cloroguaiacol, enquanto que o biossensor de tirosinase foi mais sensível para fenol e clorofenol. Ambos os biossensores apresentaram respostas seletivas para concentrações destes compostos em níveis micromolares. Limites de detecção de 1,1 x 10-7 mol L-1 para guaiacol e de 1,9 x 10-7 mol L-1 para cloroguaiacol foram obtidos usando-se o biossensor a base de lacase. Empregando-se o biossensor a base de tirosinase obteve-se limites de detecção de 1,5 x 10-7 mol L-1 para fenol e de 9,0 x 10-8 mol L-1 para clorofenol. O método de análise em fluxo proposto apresentou um faixa linear de trabalho entre 1,0 mmol L-1 e 100,0 mmol L-1 , nas condições operacionais otimizadas dos biossensores (biossensor a base de lacase: pH 5,0 e potencial de trabalho 0 mV vs Ag/AgCl; biossensor a base de tirosinase: pH 5,0 e potencial de trabalho 50 mV vs Ag/AgCl). Uma amostra real de efluente papeleiro foi analisada pelo sistema proposto e pelo método colorimétrico de referência e os resultados discutidos. A flow system method for continuous determination of phenolic compounds in environmental matrices was employed using a dialysis membrane sampler and laccase-and tyrosinase-based biosensors as detector. The biosensors response to different phenolic compounds was investigated. The laccase-based biosensor showed high sensitivity to guaiacol and chloroguaiacol, while the tyrosinase-based biosensor was more sensitive to phenol and chlorophenol. Both of the biosensors presented highly selective measurements of micromolar concentration of these compounds. Detection limits around 1.1 x 10-7 mol L-1 for guaiacol and 1.9 x 10-7 mol L-1 for chloroguaiacol could be estimated for the laccase-based biosensor. Using the tyrosinase-based biosensor detection limits of 1.5 x 10-7 mol L-1 for phenol and 9.0 x 10-8 mol L-1 for chlorophenol were observed. The proposed flow method presented a linear response range between 1.0 mmol L-1 and 100.0 mmol L-1 , in the optimized operational conditions (laccase-based biosensor: pH 5.0 and 0 mV vs Ag/AgCl as working potential; tyrosinase-based biosensor: pH 5.5 and 50 mV vs Ag/AgCl as working potential). Real paper mill effluent sample was analyzed by this system and by the reference colorimetric method and the results were discussed.
Multienzyme electrochemical array sensor for determination of phenols and pesticides
Talanta, 2005
The screen-printed four-electrode system was used as the amperometric transducer for determination of phenols and pesticides using immobilised tyrosinase, peroxidase, acetylcholinesterase and butyrylcholinesterase. Acetylthiocholine chloride was chosen as substrate for cholinesterases to measure inhibition by pesticides, hydrogen peroxide served as co-substrate for peroxidase to measure phenols. The compatibility of hydrolases and oxidoreductases working in the same array was studied. The detection of p-cresol, catechol and phenol as well as of pesticides including carbaryl, heptenophos and fenitrothion was carried out in flow-through and steady state arrangements. In addition, the effects of heavy metals (Cu(2+), Cd(2+), Fe(3+)), fluoride (NaF), benzene and dimethylsulphoxide on cholinesterase activities were evaluated. It was demonstrated that electrodes modified with hydrolases and oxidoreductases can function in the same array. The achieved R.S.D. values obtained for the flow system were below 4% for the same sensor and less than 10% within a group of five sensors. For the steady state system, R.S.D.s were approximately twice higher. One assay was completed in less than 6min. The limit of detection for catechol using tyrosinase was equal to 0.35 and 1.7muM in the flow and steady state systems, respectively. On the contrary, lower limits of detection for pesticides were achieved in the steady state system-carbaryl 26nM, heptenophos 14nM and fenitrothion 0.58muM.
Phenols monitoring and Hill coefficient evaluation using tyrosinase-based amperometric biosensors
Bioelectrochemistry, 2004
Sensitive amperometric biosensors for phenols compounds, based on tyrosinase (polyphenoloxidase, PPO) immobilized on a Pt electrode in an electropolymerized poly-amphiphilic pyrrole matrix or cross-linked with glutaraldehyde, were constructed and compared. Steady-state amperometric measurements, performed at À 50 mV vs. SCE in aqueous phosphate buffer containing LiClO 4 0.1 M (pH 7) as well as in a chloroform solution containing 0.1 M C 6 H 5 CH 2 N(CH 3 ) 3 Cl, were used in order to compare the electroanalytical and kinetic parameters of the investigated amperometric biosensors in aqueous and nonaqueous media. It was established that the polypyrrole matrix has a higher efficiency for enzyme retention resulting in higher bioelectrode sensitivity, both in aqueous buffer (690 AA M À 1 ) and in chloroform (149 AA M À 1 ).
Amperometric biosensors precision improvement. Application to phenolic pollutants determination
Electrochimica Acta, 2014
Electrodes fouling associated with the electroenzymatic phenols determination was characterized in this work, applying various techniques such as cyclic voltammetry, amperometry, EQCM, and optical microscopy. An approach to overcome the fouling effects and hence to improve the precision of the phenolic compounds determination was suggested and tested. This approach consists of pulsed potential waveform application with a cleaning potential step of + 1.4 V vs. Ag, AgCl/KCl sat with a duration of 166.66 ms, while the determination was carried out at 0.0 V vs. Ag, AgCl/KCl sat applied for 66.64 ms. As a result a RSD of 2.97% for 0.6 mmol L À1 o-catechol determination was achieved, compared with 6.53% without the cleaning step application. The method was successfully used for the precise phenolic and triazine pollutants determination.
2002
An electrochemical biosensor for remote continuous monitoring of phenolic compounds in environmental analysis is described. The probe relies on rapid and sensitive amperometric detection at a submersible biosensor assembly, connected to a 50 ft long shielded cable. The enzymes laccase and tyrosinase were used as individual sensors and also as a bienzymatic sensor; these enzymes were immobilized chemically on the carbon fiber transducer. The analysis was based on the amperometric detection of the enzymatic products at a potential of 20.10 V vs. Ag/AgCl. Operational conditions were optimized to meet the requirements of remote operations. Tests with untreated river water spiked with phenolic compounds gave results similar to those obtained with synthetic buffer solutions. The remote laccase biosensor allowed the convenient quantification of guaiacol and chloroguaiacol at levels down to 22 and 9 nmol L 21 , respectively. The co-immobilization of laccase and tyrosinase allowed the efficient detection of a larger group of phenolic compounds.
Journal of Solid State Electrochemistry, 2020
In present study, a simple carbon paste electrode modified with iron oxide nanoparticles was used as an electrochemical sensor to analyze phenolic compounds. The combination of differential pulse voltammetry technique with partial least-squares multivariable analysis enabled simultaneous determination of six different compounds in phenolic mixtures (2,4-dimethylphenol, 2,4,6trichlorophenol, 2,4-dichlorophenol, 3-nitrophenol, 4-nitrophenol, and phenol). The proposed sensor was trained with standard mixtures to learn about fingerprint (current responses in voltammograms) before further applications in analysis of test mixtures and real samples. The results have shown that the proposed method is applicable to simultaneously detect six interested compounds with acceptable relative standard errors (less than 20% in most cases). These findings provide an effective tool for in situ and low-cost cost analysis of phenolic contaminants in water environments and phenolic compounds in foodstuffs.
Phenolic Compounds Determination Using Enzyme Modified Clark Type Electrode
MRS Proceedings, 2015
Public health and environmental protection concerns provoked by phenolic compounds pollution impose the development of sensitive, rapid and cost effective methods for in situ phenols monitoring. Given that biosensors based techniques could face these challenges, a variety of such devices was suggested and applied for phenolic compounds quantification. Their majority are based on the polyphenol oxidase (PPO) catalyzed phenols oxidation to catechol and then, to quinones, coupled with the registration of the quinones reduction current. Nevertheless, quinoid products polymerization involving electrode passivation corrupts the biosensors operational stability. Thus, to avoid this drawback, in this work is proposed another approach for phenolic compounds quantification based on the electrochemical detection of the oxygen depletion during PPO catalyzed catechol oxidation using a Clark type electrode with a disposable active enzyme membrane. The oxygen probe was modified in comparison to the commercial ones: its flat front allowed ensuring a good contact with the active enzyme membrane and the gold multicathode uniformly dislocated on the surface of the flat front permitted eliminating O 2 diffusional constraints. The active enzyme membrane was prepared by drop-coating of a mixture of PPO and gelatin onto a gelatin-saturated cellulose filter. A linear calibration graph for catechol determination was obtained in the range up to 0.7 mM with a slope of 0.902 A/mM, at pH 6.5 and ambient temperature. The steady-state response to catechol of the biosensor was reached in 120 s. The biosensor had an excellent reproducibility (RSD<3%) due to the reliable enzyme immobilization technique, allowing the preparation of active enzyme membranes with identical characteristics. The proposed biosensor provided stable response and free of interferences measurements since the unique possible electrochemical reaction is O 2 reduction. Another biosensor advantage is associated with the use of disposable prefabricated active enzyme membranes.
Composite Multienzyme Amperometric Biosensors for an Improved Detection of Phenolic Compounds
Electroanalysis, 2003
A biosensor design, in which glucose oxidase and peroxidase are coimmobilized by simple physical inclusion into the bulk of graphite-Teflon pellets, is reported for the detection of phenolic compounds. This design allows the ™in situ∫ generation of the H 2 O 2 needed for the enzyme reaction with the phenolic compounds, which avoids several problems detected in the performance of single peroxidase biosensors as a consequence of the presence of a high H 2 O 2 concentration. So, a much lower surface fouling was found at the GOD-HRP biosensor in comparison with a graphite-Teflon-HRP electrode, suggesting that the controlled generation of H 2 O 2 makes more difficult the formation of polymers from the enzyme reaction products. The construction of trienzyme biosensors, in which GOD, HRP and tyrosinase were coimmobilized into the graphite-Teflon matrix is also reported, and their performance was compared with that of GOD-HRP bienzyme electrodes. The practical applicability of the composite multienzyme amperometric biosensors was evaluated by the estimation of the phenolic compounds content in waste waters from a refinery, and the results were compared with those obtained by using a colorimetric official method based on the reaction with 4aminoantipyrine.