Dai Long Vu

Voltammetric Determination of Tannic Acid in Beverages using Pencil Graphite Electrode

Vu D.L., Ertek B., Dilgin Y., Cervenka L. (2015): Voltammetric determination of tannic acid in beverages using pencil graphite electrode. Czech J. Food Sci., 33: 72-76. The pretreated pencil graphite electrode (Pre-PGE) prepared by a chronoamperometry technique was applied for the determination of tannic acid using anodic stripping differential pulse voltammetry. The currents obtained from voltammetry measurements at optimum conditions were linearly correlated with the concentration of tannic acid. Calibration curve was obtained for tannic acid in the concentration range of 5.0-500 × 10 -9 mol/l. The limit of detec - tion was found to be 1.5 × 10 -9 mol/l. The content of tannic acid in beverage samples determined with Pre-PGE was in good agreement with that obtained by the standard spectrophotometric method.

Proteomic analysis of cerebrospinal fluid for relapsing-remitting multiple sclerosis and clinically isolated syndrome

Early diagnosis and treatment of multiple sclerosis (MS) in the initial stages of the disease can significantly retard its progression. The aim of the present study was to identify changes in the cerebrospinal fluid proteome in patients with relapsing-remitting MS and clinically isolated MS syndrome who are at high risk of developing MS (case group) compared to healthy population (control) in order to identify potential new markers, which could ultimately aid in early diagnosis of MS. The protein concentrations of each of the 11 case and 15 control samples were determined using a bicinchoninic acid assay. Nanoscale liquid chromatography coupled with tandem mass spectrometry was used for protein identification. Proteomics data were processed using the Perseus software suite and R. The results were filtered using the Benjamini-Hochberg procedure for the false discovery rate (FDR) correction (FDR<0.05). The results showed that, 26 proteins were significantly dysregulated in case samples compared to the controls. Nine proteins were found to be significantly less abundant in case samples, while the abundance of 17 proteins was significantly increased in case samples compared to controls. Three of the proteins were previously linked to RR MS, including immunoglobulin (Ig) γ-1 chain C region, Ig heavy chain V–III region BRO and Ig κ chain C region. Three proteins that were uniquely expressed in patients with RR MS were identified and these proteins may serve as prognostic biomarkers for identifying patients with a high risk of developing RR MS.

Determination of anti-cancer drug emodin using a silica-gel-modified carbon paste electrode

In this paper, a silica-gel-modified carbon paste electrode (Si-gel/CPE) was used to determine the anti-cancer drug emodin by anodic stripping differential pulse voltammetry (ASDPV). The effects of the silica-gel content, the pH of the supporting electrolyte, and the scan rate on the oxidation current of emodin were investigated. The oxidation currents of emodin obtained from ASDPV measurements were linearly correlated with the concentration in the range of 5.0 × 10-9 to 300.0 × 10-9 mol L-1. The limit of detection was determined to be 1.5 × 10-9 mol L-1. The current method was successfully applied to determine emodin in a knotweed root sample, with recovery rate of 92.5% to 98.3%.

Determination of ascorbic acid in pharmaceutical preparation and fruit juice using modified carbon paste electrode

Acrobic acid is key substance in the human metabolism and the rapid and accurate determination in food is of a great interest. Ascorbic acid is an electroactive compound, however poorly responded on the bare carbon paste electrodes. In this paper, brilliant cresyl blue and multi-walled carbon nanotubes were used for the modification of carbon paste electrode. Brilliant cresyl blue acts as a mediator improving the transition of electrons, whereas multiwalled carbon nanotubes increased the surface of the electrode. Both brilliant cresyl blue and multiwalled carbon nanotubes were added directly to the composite material. The electrochemical behavior of modified electode was determined in electrolyte at various pH, and the effect of the scan rate was also performed. It was shown that the electrochemical process on the surface of the modified carbon paste electrode was diffusion-controlled. The resulted modified carbon paste electrode showed a good electrocatalytic activity towards the oxidation of ascorbic acid at a reduced overpotential of +100 mV descreasing the risk of interferences. A linear response of the ascorbic acid oxidation current measured by the amperometry in the range of 0.1 - 350 µmol.L -1 was obtained applying the sensor for the standard solution. The limit of detection and limit of quantification was found to be 0.05 and 0.15 µmol.L -1 , respectively. The novel method was applied for the determination of ascorbic acid in pharmaceutical vitamin preparation and fruit juice, and the results were in good agreement with the standard HPLC method. The presented modification of carbon paste electrode is suitable for the fast, sensitive and very accurate determination of ascorbic acid in fruit juices and pharmaceutical preparation.