Square-wave voltammetry Dotaz Zobrazit nápovědu
Electrochemical behavior of folic acid (FA) was studied by cyclic voltammetry. An irreversible oxidation peak of FA was obtained at +0,85 V (Ag/AgCl, pH 5.0). The current dependence for square-wave voltammetry was linear at 1.0·10–7 – 17·10–4 M FA with a low detection limit of 3.0·10–8 M and good repeatability (RSD 2.8 %, n = 10). The method was used in analysis of tablets with recoveries 101.5 and 103.1 % and the determined values outside the confidence interval P = 95 %. The method is an alternative to widely used chromatographic methods.
- Klíčová slova
- square-wave voltampérometrie, borem dopovaná diamantová elektroda,
- MeSH
- bor MeSH
- elektrochemické techniky * metody statistika a číselné údaje metody statistika a číselné údaje MeSH
- elektrody MeSH
- kyselina listová * analýza chemie MeSH
- léčivé přípravky analýza chemie MeSH
- Publikační typ
- práce podpořená grantem MeSH
Compounds containing vicinal diol (glycol) groups, including saccharides, could be modified with sixvalent osmium complexes with nitrogenous ligands, particularly with N,N,N',N'-tetramethylethylenediamine (Os(VI)tem). The modification products are electrochemically active. Here we show that aminosaccharides can also be modified by Os(VI)tem. We studied chitosan oligosaccharides in their acetylated and deacetylated form in 0.2 M Na-phosphate, pH 6.9. Deacetylated chitosan oligosaccharides with free amino groups modified by Os(VI)tem yielded two peaks (peak I' at -0.15 V and peak II' at about -0.38 V) despite the fact that these oligomers contain only one glycol group on the non-reducing end of the molecule. The electrochemical behavior of Os(VI)tem modified deacetylated chitosan oligomers differs from Os(VI)tem modified simple saccharides, containing only glycol groups, predominantly in peak I'. Our results suggest that free amino groups are involved in Os(VI)tem modification of chitosan oligomers.
The pungency of chili peppers, the most popular hot spice used worldwide, is caused by capsaicinoids (CPDs), the content of which can vary greatly due to varietal differences and growing conditions. For the first time, a novel simple method for the fast determination of CPDs in chili peppers and chili products was developed based on adsorptive transfer cyclic square-wave voltammetry (AdTCSWV), using adsorption of lipophilic CPDs on an unmodified glassy carbon electrode surface from methanolic extracts of chili pepper samples. The CSWV is based on short oxidation of adsorbed CPDs to quinoid products, and their subsequent reduction and re-oxidation to provide specific analytical signals with a linear range from 0.05 to 1.00 mg L-1. This principle was also implemented in tandem coulometric and amperometric detection of CPDs after HPLC separation. The two-step electrochemical detection provides increased selectivity for CPDs in case of CPDs co-elution with other electrochemically oxidizable components that cannot be reversibly reduced.
To resolve the problem of the insufficient availability of seed cells and to provide seed cells for tissue engineering research, an immortalized human bone marrow stromal stem cell line (MSCxj cells) was established in our department to investigate the ectopic osteogenesis of MSCxj cells. MSCxjs were grown with a heterogeneous bone scaffold for 48 h. Three groups were included: A: MSCxjs of 35 PDs were maintained with heterogeneous bone; B: MSCxjs of 128 PDs were maintained with heterogeneous bone; and C: heterogeneous bone alone. Tetracycline fluorescence staining, H&E staining, and ponceau staining, immunohistochemistry and bone histomorphometry were performed. At the same time, scanning electron microscopy was conducted to detect the growth of MSCxjs and heterogeneous bone. Scanning electron microscopy showed favorable adherence of MSCxjs to heterogeneous bone. A large number of newly generated filamentous extracellular matrix and fine granular materials were found to cover the cells. The results from staining showed that the osteogenesis was not obvious in group A/B 4 weeks after transplantation. Eight weeks after implantation, osteoid matrix deposition was noted in and around the heterogeneous bone in group A/B. Twelve weeks after implantation, osteogenesis was increased in group A/B. There were no significant differences in the time course for bone formation and the amount of newly generated bone between group A/B. Like primary hBMSCs, MSCxj cells have favourable ectopic osteogenesis and can be applied as seeded cells in bone tissue engineering.
- MeSH
- antioxidancia chemie metabolismus MeSH
- biochemie metody MeSH
- biosenzitivní techniky přístrojové vybavení využití MeSH
- elektrochemie metody MeSH
- financování organizované MeSH
- glutathion chemie krev MeSH
- krev MeSH
- kyselina askorbová chemie krev MeSH
- kyselina močová chemie krev MeSH
- modely u zvířat MeSH
- oxidační stres fyziologie imunologie účinky léků MeSH
- ptáci krev MeSH
- reaktivní formy kyslíku chemie metabolismus MeSH
A new, rapid and very sensitive electrochemical method for the determination of a new pesticide clothianidin in tap and river water was developed. The electrochemical reduction and determination of clothianidin have been carried out at a hanging mercury drop electrode (HMDE) in various aqueous solutions in the pH range of 2–10 by cyclic voltammetry (CV) and cathodic stripping square wave voltammetry (SW CSV). The best results were obtained for the clothianidin determination by SW CSV method in 0.04 mol l–1 Britton Robinson buffer at pH 8.1. Various conditions of the procedure were checked. Elaborated electroanalytical procedure enable clothianidin determination in the concentration range of 2.0 × 10–8–9.9 × 10–7 mol l–1. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 2.00 × 10–9 and 2.36 × 10–8 mol l–1, respectively. Precision and accuracy of the developed method were checked by recovery studies in spiked tap and river water. The voltammetric determination has been validated using HPLC with UV detection.
Edukační publikace se zabývá v první části luminiscenčními metodami: luminiscencí lanthanidů rozloženou v čase, luminiscencí lanthanidů zesílenou enzymem, homogenní imunoanalýzou s pohlcením luminiscence, chemiluminiscencí, elektrochemiluminiscencí (kompetitivní i sendvičové uspořádání a metoda přímé interakce) a možnostmi simultánních imunoanalýz s elektrochemiluminiscenční detekcí. Druhá část je věnována imunoanalýzám s elektrochemickou detekcí, zejména anodickou rozpouštěcí voltametrií a square-wave voltametrií. Jako značky se používají různé nanomateriály: zlato, stříbro, polovodiče (CdS, PbS, ZnS, CuS), uhlíkové nanotrubičky (plněné enzymem), apoferitin (plněný ferokyanidem nebo ionty Cd 2+ nebo Pb 2+ ), liposomy (plněné ferokyanidem), křemenné částice (s kovalentně vázaným polyguaninem, nebo plněné peroxidázou a thioninem), mikrokrystaly ferrocenu a jiné.
The first part of the educational article deals with luminescence methods as follows: lanthanide-based time-resolved luminescence, enzyme-amplified lanthanide luminescence, homogeneous immunoassays with luminescence quenching, chemiluminescence, electrochemiluminescence (competitive assay, sandwich-type assay, and direct interaction) and simultaneous immunoassays options with electrochemical luminescence detection. The second part covers immunoassays with electrochemical detection, particularly anodic stripping voltammetry and square-wave voltammetry. Many kinds of nanomaterials are used as labels, e.g. gold, silver, semiconductors (CdS, PbS, ZnS, CuS), carbon nanotubes (enzyme-loaded), apoferritin (hexacyanoferrate loaded, in some cases Cd 2+ or Pb 2+ ions are used), liposomes (hexacyanoferrate loaded), silica particles (by covalently binding polyguanine or with peroxidase & thionine loaded), ferrocene microcrystals, etc. Keywords: Lanthanide-based luminescence, chemiluminescence, electrochemiluminescence, electrochemical immunoassays, nanomaterials.
Electrooxidation potentials of powdered green and black teas were determined by abrasive stripping voltammetry. A circular surface of paraffin-impregnated graphite rod was contaminated with tea microparticles and used as a chemically prepared working electrode in square-wave voltammetric experiments. The responses are ascribed to electrooxidation of flavanols in teas. Low oxidation potentials of some green teas were observed. An advantage of the proposed method is that no extraction of electroactive components is necessary.
Although ganciclovir (gan) as a purine analogue is a compound of biological interest (antiviral drug), it has been rarely electrochemically studied. In this paper surface catalytic electrode mechanism based on the hydrogen evolution reaction is analyzed under conditions of square-wave voltammetry and differential capacity curves of double layer measurements. The electrode mechanism is assumed to involve a preceding chemical reaction in which the adsorbed catalyst (ganads) is protonated at the electrode surface, i.e., ganads + H+aq › ganH+ads. The protonated form of the catalyst (ganH+ads) is irreversibly reduced at potential about –1.35 V vs Ag|AgCl, yielding the initial form of the catalyst and atomic hydrogen, i.e., ganH+ads + e › ganads + Haq. Changes of zero charge potential and surface tension point to the adsorption of ganciclovir molecule directed with guanine group to the mercury surface and suggests that ganciclovir molecules are not placed flat on the mercury surface. The effect of adsorption on mercury electrode was studied in detail in respect to analytical usefulness of the obtained results. A new catalytic method for voltammetric determination of ganciclovir was developed. The detection and quantification limits were 1.3 × 10–7 and 4.3 × 10–7 mol l–1 for square-wave voltammetry, and 1.4 × 10–7 and 4.7 × 10–7 mol l–1 for linear-sweep voltammetry.
Ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) is an alkaloid that has been isolated from plants of an Apocynaceae family. It is one of the simplest naturally occurring alkaloids with a planar structure. Over the past decades, ellipticine became a very promising antitumor agent. Interaction with DNA is one of the most studied ellipticine effects on cell division. This phenomenon is not clearly explained so far. In our experiments we studied interaction of ellipticine with single-stranded and double-stranded oligonucleotides by electrochemical methods on mercury electrode. Differential pulse voltammetry was applied for ellipticine (Elli) and CA peak detection. Square wave voltammetry was applied for G peak detection. The effect of the interaction time and ellipticine concentrations on interactions of ellipticine with single- and double-stranded oligonucleotides was tested too.
