Phenolic compounds sensors

Yang SM, Li YM, Jiang XM, Chen ZC, Lin XF (2006) Horseradish peroxidase biosensor based on layer-by-layer technique for the determination of phenolic compounds. Sensor Actual B Chem 114(2) 774-780. doi 10.1016/j.snb.2005.07.035... 

Reproducible electrochemical analysis of phenolic compounds by high-pressure liquid chromatography with oxygen-terminated diamond sensor... 

A multitude of publications describe enzyme sensors for the detection of phenolic compounds, reflecting the large variety of possible configurations. 

Sotomayor, M. D. P. T. Tanaka, A. A. Kubota, L. T., Development of an amperometric sensor for phenol compounds using a Nafion (R) membrane doped with copper dipyridyl complex as a biomimetic catalyst,./. Electroanal. Chem. 2002, 536, 71-81... 

An enzyme sensor based on tyrosine can be used for assay of phenolic compounds at the millimole-per-liter level.103 The method is based on the following reactions ... 

Timur, S., Pazarlio lu N., Pilloton R., and Telefoncu A., Detection of phenolic compounds by thick film sensors based on Pseudomonas putida, Talanta, 61, 87-93, 2003. 

Voltammetric sensors based on chemically modified electrodes (conducting polymers, phthalocyanine complexes) with improved cross-selectivity were developed for the discrimination of bitter solutions [50], The performance and capability were tested by using model solutions of bitterness such as magnesium chloride, quinine, and four phenolic compounds responsible for bitterness in olive oils. The sensors gave electrochemical responses when exposed to the solutions. A multichannel taste sensor was constructed using the sensors with the best stabilities and cross-selectivities and PCA of the signals allowed distinct discrimination of the solutions. 

Phenolic compounds are found in most fruits and vegetables. These endogenous compounds show interesting properties such as antioxidant activity, enzymatic inhibition and free radical scavenging action [42]. In particular, catechol is a diphenol compound of interest in the food industry and has been involved in ghal cell toxicity. Thus, there is a great appeal to produce novel sensors of higher stability and lower cost for catechol detection [43]. 

Regardless to the material used, electrochemical sensors suffer from several drawbacks, one of the most known is the passivation of its surface [31]. The oxidation of electroactive substances involves the formation of oxidized material at the electrode surface which blocks further reaction at the electrode [32]. For instance, during the electrochemical detection of biological analytes in matrices with a high content of phenolic compounds, the surface of the electrode is contaminated and the subsequent analysis is compromised [33]. 

Reaction of 3.40, 3.41, 3.43 or 3.51 with 1-methylimidazole, pyridine, amine " and tributylphosphine afforded cationic pillar[5]- and pil-lar[6]arenes (3.52-3.56). A pillar[5]arene with 10 ionic liquids (imidazolium cations 3.53) was produced in the liquid state at 25 °C by choosing an appropriate counter anion. A pillar[5]arene with 10 phosphonium cations (3.56) is amphiphilic and acts as a substrate-selective phase-transfer catalyst. Oxidation of linear alkane 1-hexene to 1-pentanal by KMn04 vwis >99%, whereas that of the branched alkene, 4-methyl-l-hexene, was only 31%, even under ideal conditions. An etherification reaction between an allqrl-halide and phenolic compounds is a good method to synthesize functionalized pillar[5]arene. Etherification of pillar[5]arene containing 10 bromide with a coumarin derivative with a phenolie moiety gave a pillar[5]arene eanying 10 coumarin moieties (3.57) 3.57 aeted as a fluorescence sensor for methyl parathion. Pillar[5]- and pillar[6]arenes with 10 and 12 bromide moieties should be good key compounds for the synthesis of various functionalized pillar[5]- and pillar[6]arenes. 

The work reported the applicability of a voltammetric BioET to the monitoring of different phenolic pollutants present in wastewaters. Voltammetric responses obtained from an array of bulk-modified (bio)sensors, containing enzymes such as tyrosinase and laccase, were combined with chemometric tools such as ANNs for building the quantitative prediction model. The four voltammetric electrodes prepared consisted in one blank electrode plus three (bio)composite electrodes modified with tyrosinase, tyrosinase-i-laccase and Cu nanoparticles. This choice was intended as to maximize the response of the (bio)sensor array towards phenolic compounds. That is, on one side, tyrosinase and laccase were chosen as they are extensively used for the development of amperometric biosensors aimed to the detection of phenolic compounds on the other side, copper nanoparticles were also considered due to the well-known catalytic properties of nanoparticles and the importance of copper in the two enzymes used. To fully exploit all the information... 

The main function of the receptor is to provide the sensor with a high degree of selectivity for the analyte to be measured. While most chemical sensors are more or less selective (specific) for a particular analyte, some are, by design and construction, only class specific, e.g., sensors or biosensors for phenolic compounds, or whole-cell biosensors used to measure the biological oxygen demand. 

Increased selectivity and prevention of passivation of the BDD surface may be also achieved by its modification. An enzyme-based amperometric sensor was proposed for detection of phenolic compounds by Notsu et al. BDD was anod-ically polarized for the introduction of hydroxyl groups onto its surface, then treated with (3-aminopropyl)triethoxysilane (APTES), and finally coated with a tyrosinase film cross-linked with glutaraldehyde. Tyrosinase catalyzes oxidadmi of phenol and various phenol derivatives to o-benzoquinone derivatives via catechol derivatives and thus the quinones generated are ready to be reduced electrochemically at an appropriate potential and obtained reduction currents serve as good analytical signals for the determination of the phenol derivatives. Bisphenol A and 17-/ -estradiol were detected at —0.3 V vs. Ag/AgCl with the detection limit of 1 pmol in FIA. However, the biosensor retained its activity only for a few days due to weak bonding of APTES to BDD surface. 

Similar results were obtained with a Pseudomonas putida biosensor [113]. Phenol-induced cells showed little cross reaction to other compounds. This sensor did not react to benzoate. Detection of benzoate is possible only with cells grown on benzoate. 

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