clay and 1-butyl-3-methylimidazolium-hexafluorophosphate

Pt-Pd bimetallic alloy nanoparticles (NPs) dispersed in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (Pt-Pd-BMI·PF6) were employed together with a peroxidase (PO) enzyme from cauliflower immobilized on nanoclay for the development of a new biosensor for polyphenol determination by square-wave voltammetry (SWV). The biosensor demonstrated good repeatability and reproducibility, low limit of detection (LOD = 3.7 × 10(-7) mol L(-1) for caffeic acid (CA)), and adequate lifetime and stability (maintaining over 80% of the response over 80 days of evaluation, and allowing over 600 measurements by SWV for each electrode). Under optimized conditions, the proposed biosensor was applied in the determination of the bioelectrochemical polyphenolic index (BPI) for samples of commercial white wine, using CA as the phenolic compound standard. The recovery of CA from wine samples ranged from 95.5 to 108.3%. The values for the polyphenolic content obtained using the proposed biosensor showed a good correlation (r = 0.990) with those obtained with the reference spectrophotometric method (Folin-Ciocalteu method). Therefore, the proposed biosensor represents a useful tool for the rapid and accurate monitoring of polyphenolic content in wine samples and may also be applicable to other beverage samples, such as juices and teas.

Topics: Aluminum Silicates; Biosensing Techniques; Brassica; Clay; Electrochemistry; Enzymes, Immobilized; Imidazoles; Ionic Liquids; Metal Nanoparticles; Models, Molecular; Molecular Conformation; Palladium; Peroxidase; Platinum; Wine

Halloysite clay nanotubes were used as a support for the immobilization of the enzyme peroxidase from clover sprouts (Trifolium), and employed together with platinum nanoparticles in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (Pt-BMI·PF(6)) in the development of a new biosensor for the determination of catecholamines by square-wave voltammetry. Under optimized conditions, the analytical curves showed detection limits of 0.05, 0.06, 0.07, 0.12 μM for dopamine, isoproterenol, dobutamine and epinephrine, respectively. The biosensor demonstrated high sensitivity, good repeatability and reproducibility, and long-term stability (18% decrease in response over 150 days). A recovery study of dopamine in pharmaceutical samples gave values from 97.5 to 101.4%. The proposed biosensor was successfully applied to the determination of dopamine in pharmaceutical samples, with a maximum relative error of ±1.0% in relation to the standard (spectrophotometric) method. The good analytical performance of the proposed method can be attributed to the efficient immobilization of the peroxidase in the nanoclay, and the facilitation of electron transfer between the protein and the electrode surface due to the presence of the Pt nanoparticles and ionic liquid.

Topics: Aluminum Silicates; Biosensing Techniques; Catecholamines; Clay; Electrochemistry; Enzymes, Immobilized; Hydrogen-Ion Concentration; Imidazoles; Ionic Liquids; Metal Nanoparticles; Nanotubes; Peroxidases; Platinum; Trifolium