Investigation of the colour reaction of phenols with the MBTH Reagent

Gasparič, J.; Svobodová, D.; Pospı́šilová, Marie

doi:10.1007/bf01213034

Cited by 24 publications

(6 citation statements)

References 12 publications

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“…[55] The color in the visible part of the UV/VIS region should be attributed to the formation of conjugated covalent bond system indicated by dashed lines. Quite importantly, this colored adduct is insoluble in water and readily soluble in organic solvents, [42] which should favor its retention in the polymer film avoiding its leaching to aqueous phase. To optimize the MBTH concentration, several biosensors were constructed by varying the MBTH concentration in the polymer mixture between 0.5 and 3 mg/ml.…”

Section: Biosensor Compositionmentioning

confidence: 99%

“…[39][40][41] Since the oxidative coupling of this reagent was described with phenols, aromatic amines, heterocyclic bases, and compounds with active methylene groups, to form highly colored products, MBTH was introduced into analytical chemistry as a sensitive reagent for the detection and photometric determination of carbonyl compounds resultant from enzyme catalyzed oxidation of phenolic compounds. [42] This work presents the first construction and testing of an optical disposable biosensor for catechol determination integrating: (a) previously synthesized porous anionic PA6 microparticles (PA6 MP) in which laccase is immobilized by physical adsorption, embedded in (b) a semipermeable polymer matrix that contains the optical indicator MBTH and permits catechol diffusion, preventing at the same time the enzyme leakage. The sensing scheme is divided into two steps: (a) biological recognition based on the catalytic oxidation of catechol by laccase and (b) optical transduction by formation of a pink-colored adduct between the oxidation product (o-benzoquinone) and MBTH chromophore (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Optical biosensor for catechol determination based on laccase‐immobilized anionic polyamide 6 microparticles

Cano‐Raya

Dencheva

Braz

et al. 2020

J of Applied Polymer Sci

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This work presents the preparation, optimization, and testing of an enzymebased optical biosensor for catechol determination. The sensing area is attached to a glass support and contains: anionic polyamide 6 (PA6) porous microparticles supporting laccase from Trametes Versicolor, embedded in a Pebax ® MH1657 polymer binder that contains the optical indicator dye 3-methyl-2-benzothiazolinone hydrazone (MBTH), responsible for the optical transduction. The catechol analyte, after its enzymatic oxidation, forms o-benzoquinone that can be detected by oxidative coupling with MBTH giving rise to a colored product. The latter can be quantified measuring the UV/VIS absorbance at 500 nm. The PA6 microparticles performed as useful laccase carriers reaching high immobilization yields of up to 99.8% and preserving the enzyme catalytic activity. This permitted the preparation of a new biosensor presenting a detection limit of 11 μM and responding linearly to up to 118 μM of catechol. Biosensor applicability was tested in spiked natural water samples from river and spring. The recovery rates observed were in the range of 97-108% that proves the good accuracy of the proposed biosensor.

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Section: Biosensor Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optical biosensor for catechol determination based on laccase‐immobilized anionic polyamide 6 microparticles

Cano‐Raya

Dencheva

Braz

et al. 2020

J of Applied Polymer Sci

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“…Again, hydroxylamino aromatics would be readily oxidized, and the resulting nitroso aromatics could then react with and mask amine products (37,38). Therefore, to detect the possible formation of aromatic amines at low concentration, we reacted NR with p-HABA instead of p-NBA to focus directly on the reaction in question, and we have refined a sensitive direct chromogenic probe for aminoaromatic products that can be applied in the presence of hydroxylamines without any workup or exposure to air (33,34).…”

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confidence: 99%

Understanding the Broad Substrate Repertoire of Nitroreductase Based on Its Kinetic Mechanism

Pitsawong

Hoben

Miller

2014

Journal of Biological Chemistry

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Background: Nitroreductase reduces a broad range of nitroaromatics. Results: Steady-state and pre-steady-state kinetics were combined with tests for aminoaromatic product formation. Conclusion: Both half-reactions occur via a simple mechanism lacking detectable gating steps consistent with the broad substrate repertoire. Significance: Nitroreductase does not generate p-aminobenzoic acid and, therefore, appears not to reduce nitro groups to amines.

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“…As follows from our earlier TLC studies of the phenol -MBTH reactions in acid medium [37], the MBTH can be attached to the aromatic ring either in ortho or para position relative to the phenolic OH group and thus for phenols with both 2-and 4-positions free two coloured reaction products are formed at the same time. In view of this fact three different phenols, namely 2,6-xylenol (2,6-X), unsubstituted phenol (P) and 4-cresol (4-MP) were selected as model compounds that can bind MBTH (i) exclusively in para position, (ii) either in para or ortho position and (iii) only in ortho position respectively (see the scheme below).…”

Section: Resultsmentioning

confidence: 91%

Spectrophotometric study of reactions of substituted phenols with MBTH in alkaline medium: The effect of phenol structure on the formation of analytically useful coloured products

1998

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The oxidative coupling reactions of unsubstituted phenol, 4-cresol, 2,6-xylenol and another fourteen substituted phenols with MBTH in alkaline medium containing potassium hexacyanoferrate (Ill) as the oxidant were examined by spectrophotometry. The maximum yield and stability of coloured species was attained at optimum pH 9.0-t-0.5. Stoichiometry of the reactions involving a four-electron transfer was confirmed. The coloured products were stable in an aqueous alkaline medium containing 50% (V/V) of a water-miscible organic solvent and they could be quantitatively extracted into chloroform. Absorption maxima Amax of the reaction products ranged between 495 nm and 610 nm depending on the phenol structure and their molar absorptivities fell within the range 2,500-47,000L mol-lcm -1 in aq. 50% ethanol. The calibration graphs were rectilinear for 2 to 20 gM phenol or 2,6-xylenol (r=0.9994-0.9997; n=6) and the RSD values were ~1.8% (n = 10) when determining 10 gmolL -1 of the analytes. The reactivity of the phenols with MBTH (and hence the yield of the coloured species in alkaline medium) depending on the analyte structure decreased in the order: 2,6-dialkylphenols or 4-halogenated 2,6-dialkylphenols>2-alkyl, 2-alkoxy or 2-arylphenols and 1-naphthol>unsubstituted phenol or 2-naphthol=2-halogenated phenols>4alkylphenols and 4-halogenated phenols>2-nitrophe-no1>2,4-or 3,4-dialkylphenols. For some 4-halogenated phenols the elimination of halogen upon coupling with the MBTH was observed.

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Investigation of the colour reaction of phenols with the MBTH Reagent

Cited by 24 publications

References 12 publications

Optical biosensor for catechol determination based on laccase‐immobilized anionic polyamide 6 microparticles

Optical biosensor for catechol determination based on laccase‐immobilized anionic polyamide 6 microparticles

Understanding the Broad Substrate Repertoire of Nitroreductase Based on Its Kinetic Mechanism

Spectrophotometric study of reactions of substituted phenols with MBTH in alkaline medium: The effect of phenol structure on the formation of analytically useful coloured products

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