Influence of nafion in titania sol-gel matrix on analytical characteristic of amperometric phenol biosensor based on tyrosinase

For detection of phenolic compounds a simple amperometric biosensor based on tyrosinase immobilized in titania sol- gel/Nafion composite was employed. Titania sol-gel was mixed with Nafion (v/v) in ratios 1:1 (TiO 2 /NF-1/1) and 2:1 (TiO 2 /NF-2/1), v/v. Morphology of immobilization composites was characterized by scanning electron microscopy. Analytical performance of biosensors with Nafion and based only on titania sol-gel (TiO 2 ) was compared. Apart from sensitivity, linear range and detection limit also repeatability, reproducibility and storage stability were evaluated. The biosensor based on titania sol mixed with Nafion in ratio 1:1 (v/v) exhibited the best analytical parameters in terms of sensitivity: 2.84 μA L μmol –1 , corresponding LOD, 0.056 μmol L –1 , and the long-term stability within 20 days: it re- tained 80% of initial activity

Detection of NADH and ethanol at a graphite electrode modified with titania sol-gel/Meldola’s Blue/MWCNT/Nafion nanocomposite film

For electrocatalytic determination of NADH, a graphite electrode modified with titania sol-gel/Meldola’s Blue/MWCNT/Nafion nanocomposite was proposed. The composition of the matrix film was optimised in terms of the content of carbon nanotubes and Nafion. Incorporation of a redox mediator, Meldola’s Blue, into the nanocomposite film enabled electrocatalytic determination of NADH at a low potential, −50 mV. For determination of ethanol, alcohol dehydrogenase (ADH) was immobilized into the matrix layer. Experimental conditions affecting the biosensor response were examined, including enzyme loading, temperature of measurement and pH of background electrolyte. Assessments of the analytical characteristics of the biosensor were performed with respect to sensitivity, limit of detection, operational stability, repeatability and reproducibility. The proposed biosensor showed electrocatalytic activity toward oxidation of ethanol with sensitivity of 2.24 µA L mmol^{^{-1}}, linear range from 0.05 to 1.1 mmol L^{-1}, and limit of detection of 25 µmol L^{-1}. The apparent Michaelis-Menten constant was 1.24 mmol L^{-1}, indicating a high biological affinity of ADH/titania sol-gel/Meldola’s Blue/MWCNT/Nafion electrode for ethanol. The developed biosensor was tested in determinations of ethanol content in alcoholic beverages

Polypyrrole layers electrodeposited from TRIS buffer solution as matrix of tyrosinase biosensor

A novel supporting electrolyte – tris(hydroxymethyl)aminomethane hydrochloride (TRIS) buffer solution was used to obtain polypyrrole (PPy) layers based on the anodic oxidation of pyrrole. Influence of some parameters: temperature, monomer and supporting electrolyte concentration, polarization potential and hydrodynamic conditions on electrodeposition process were investigated. Obtained layers were preliminary tested in construction of an amperometric biosensor based on enzyme tyrosinase, which response was tested using catechol as a substrate

Meldola's Blue : doped titania sol-gel sensor for NADH determination

Titania layers obtained by a sol-gel technique doped with redox mediator, Meldola’s Blue, were employed for construction of a new NADH senor. Optimization of preparation process as well as experimental conditions affecting the response of the sensor were examined. Under optimal conditions NADH could be determined in the wide linear range from 90 to 2300 μM with detection limit 12 μM and a high sensitivity 12.5 nA μM-1. The usefulness of developed sensor was preliminarily checked in determination of NADH forming during enzymatic oxidation of ethanol catalyzed by alcohol dehydrogenase (ADH

A new capacitive sensor based on electrostriction phenomenon : application for determination of ionic surfactants

The aim of the work was to develop a new capacitive sensor based on the electrostriction phenomenon observed in membranes deposited on solid electrodes in contact with an electrolyte solution. The functioning of the sensor was checked in determination of ionic surfactants. The sensor was based on self-assembled monolayers (SAM’s) of thiol supported on the surface of a gold electrode. Two thiols, 1-octadecanethiol and 1-hexadecanethiol, and two surfactants, anionic sodium dodecyl sulfate and cationic hexadecyltrimethylammonium bromide, were chosen for studies. Different shapes of capacitance-potential curves with hysteresis were revealed. After an addition of a surfactant, the height of hystheresis changed, enabling construction of linear relationship between the hystheresis’ height and concentration of surfactant

Visualization of amphetamine and its analogues in TLC

Derivatisation followed by iodine azide reaction was employed for detection of amphetamines and its analogues in TLC. The derivatisation reaction with phenyl isothiocyanate took place directly on the TLC plate before the developing step. Afterwards, the plate was sprayed with a mixture of sodium azide and starch solution and then exposed to iodine vapour. The obtained limits of detection were compared with other commonly visualization techniques: UV, iodine vapour, Marquis and Simon’s reagents, ninhydrin, Fast Black K