Second-order derivative of square-wave voltammetry for determination of vanillin at platinum electrode.

A simple and sensitive method of data treatment by second-order derivative square wave voltammetry (SD-SWV) was developed for the determination of vanillin at a platinum electrode. It was shown that the irreversible oxidation reaction is controlled by the adsorption and occurs following a mechanism involving two electrons, similar to other phenolic derivatives. The experimental parameters of SWV which exert influence on vanillin determination, such as frequency, pulse amplitude, or step potential, were optimized. The calibration curve shows a linear range between 50 and 430 nM vanillin with a detection limit of about 19 nM (signal/noise = 3). The mathematical treatment of experimental data leads to enhances the sensitivity of the determination and was successfully used for the estimation of vanillin in commercial food products.

Ochratoxin A Detection on Antibody- Immobilized on BSA-Functionalized Gold Electrodes.

Ochratoxin A (OTA)-a toxin produced by Aspergillus carbonarius, Aspergillus ochraceus, and Penicillium verrucosum-is one of the most-abundant food-contaminating mycotoxins. To avoid the risk of OTA consumption for humans and animals, the rapid detection and quantitation of OTA level in different commodities are of great importance. In this work, an impedimetric immunosensor for ochratoxin A (OTA) detection, a common toxic botanical contaminant, was developed via the immobilization of anti-OTA antibody on bovine serum albumin modified gold electrodes. A four-step reaction protocol was tested to modify the gold electrode and obtain the sensing substrate. All the steps of the immunosensor elaboration and also the immunochemical reaction between surface-bound antibody and ochratoxin A were analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. Modification of the impedance due to the specific antigen-antibody reaction at immunosensor surface, was used in order to detect ochratoxin A. Linear proportionality of the charge transfer resistance to the concentration of OTA allows ochratoxin A detection in the range of 2.5-100 ng/mL.

Lipophilicity of amine neurotransmitter precursors, metabolites and related drugs estimated on various TLC plates.

The retention behavior for a series of amine neurotransmitters, their precursors, metabolites and structurally related drugs has been investigated in reversed-phase thin-layer chromatography using RP-18, RP-8, RP-2, CN and Diol stationary phases and mixtures of phosphate buffer and methanol as mobile phase. According to the computed lipophilicity of the neutral form of the investigated compounds, the most lipophilic compound is dobutamine (log P(N) = 3.78), while the less lipophilic is norepinephrine (log P(N) = -0.14). The experimental results also show dobutamine as the most lipophilic compound in the case of RP-18 and CN stationary phases (RM0(RP-18) = 1.58 and RM(CN) = 1.21), while RP-8 indicates norepinephrine as the less lipophilic one (RM0(RP8) = -0.70). Both the theoretical computation and the experimental data revealed that only one ionic form of the compounds prevails in the used chromatographic conditions. In addition, the evaluation of the experimental results showed that a similar chromatographic behavior could be assumed in the case of RP-18, RP-8 and CN stationary phases. Moreover, the mRM (mean of the RM values) and PC1/RM (scores of the first principal component) experimental lipophilicity indices showed a high correlation with the computed lipophilicity indices.