Amperometry Dotaz Zobrazit nápovědu
This work describes the method for total antioxidant capacity (TAC) and/or total content of phenolics (TCP) analysis in wines using microdialysis online-coupled with amperometric detection using a carbon microfiber working electrode. The system was tested on 10 selected wine samples, and the results were compared with total reactive antioxidant potential (TRAP), oxygen radical absorbance capacity (ORAC), and chemiluminescent determination of total antioxidant capacity (CL-TAC) methods using Trolox and catechin as standards. Microdialysis online-coupled with amperometric detection gives similar results to the widely used cyclic voltammetry methodology and closely correlates with ORAC and TRAP. The problem of electrode fouling is overcome by the introduction of an electrochemical cleaning step (1-2 min at the potential of 0 V vs Ag/AgCl). Such a procedure is sufficient to fully regenerate the electrode response for both red and white wine samples as well as catechin/Trolox standards. The appropriate size of microdialysis probes enables easy automation of the electrochemical TAC/TCP measurement using 96-well microtitration plates.
Analyses of very complex samples involving capillary and chip electrophoresis often require dual (multiple) detection to attain sufficient selectivity of determination. The present work reviews and critically evaluates selected combinations of electrochemical detection techniques among themselves and with absorption spectrometric, fluorescence and luminescence techniques. Amperometry, contact and contactless conductometry, UV photometry and fluorescence measurements are paid special attention. Some information is also given on combinations of spectrometric techniques with mass spectrometry. The properties of the detection systems are critically discussed, examples are illustrated in figures and some details on the characteristics of dual detectors and their applications are tabulated.
We review the progress achieved during the recent five years in immunochemical biosensors (immunosensors) combined with nanoparticles for enhanced sensitivity. The initial part introduces antibodies as classic recognition elements. The optical sensing part describes fluorescent, luminescent, and surface plasmon resonance systems. Amperometry, voltammetry, and impedance spectroscopy represent electrochemical transducer methods; electrochemiluminescence with photoelectric conversion constitutes a widely utilized combined method. The transducing options function together with suitable nanoparticles: metallic and metal oxides, including magnetic ones, carbon-based nanotubes, graphene variants, luminescent carbon dots, nanocrystals as quantum dots, and photon up-converting particles. These sources merged together provide extreme variability of existing nanoimmunosensing options. Finally, applications in clinical analysis (markers, tumor cells, and pharmaceuticals) and in the detection of pathogenic microorganisms, toxic agents, and pesticides in the environmental field and food products are summarized.
- MeSH
- biosenzitivní techniky * MeSH
- imunoanalýza * MeSH
- lidé MeSH
- nanočástice chemie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Edukační publikace se zabývá v první části využitím čipů v imunochemii pro mikroanalýzu. Je uveden přehled podkladových materiálů a značek, jakož i senzitivita jednotlivých technologií. Vysvětluje se možnost imobilizace a detekce proteinů pomocí planárního vlnovodu. Ukazuje se používání čipů při paralelní kompetitivní imunoanalýze, sendvičové imunoanalýze a fluorescenční imunoanalýze na mikrokuličkách. Druhá část je věnována kapilární elektroforéze a jejímu využití k separaci po kompetitivní a nekompetitivní homogenní imunoanalýze, a heterogenní imunoanalýze. Diskutují se možnosti detekce analytu jako laserem indukovaná fluorescence, enzymové značky, chemiluminiscence, ampérometrie, UV/VIS absorbance, hmotnostní spektrometrie a povrchová plazmonová rezonance.
The first part of the educational article covers chip application for microarray in immunochemistry. An outline of surface chemistries and labelings is presented, as well as the sensitivity of various technologies. Protein immobilization and detection using planar waveguide technology is clarified. Chip applications are shown in parallel competitive immunoassay, sandwich immunoassay and fluorescent microsphere immunoassay. The second part covers capillary electrophoresis and its use for separation after competitive and non-competitive homogeneous immunoassay or heterogeneous immunoassay. The following possibilities of analyte detection are discussed: laser-induced fluorescence, enzyme labels, chemiluminiscence, amperometry, UV/VIS absorbance, mass spectrometry and surface plasmon resonance.
We report the first amperometric method for the simultaneous determination of tert-butylhydroquinone (tBHQ), propyl gallate (PG), and butylated hydroxyanisole (BHA) using flow injection analysis coupled to multiple-pulse amperometry. A sequence of potential pulses was selected in order to detect tBHQ, PG, and BHA separately in a single injection step at a glassy carbon electrode without the need of a preliminary separation. A mixture of methanol and 0.040M Britton-Robinson buffer was used both as a carrier solution and for dilution of analyzed solutions before injection. The method is precise (RSD < 5%, n = 10), fast (a frequency of 140 injections h-1), provides sufficiently low quantification limits (2.51, 1.45, and 0.85μmolL-1 for tBHQ, PG, and BHA, respectively) and can be easily applied without high demands on instrumentation. As a practical application, the determination of these antioxidants contained in commercial chewing gum samples was carried out by applying a simple extraction procedure.
The carbon fiber and silver microwire were used as working and pseudoreference electrode, respectively, and inserted into the ending of capillary to prepare monolithic capillary column with an integrated electrochemical detector. Prepared capillary devices offered stable and robust results with relative standard deviations of retention, resolution, and detection signal lower than 1.5, 5.5, and 5.0%, respectively. To further increase sensitivity of developed electrochemical microdetector, multiple pulse amperometry detection mode has been used. Optimized integrated device provided reliable chromatographic separation of mixture of neurotransmitters with calibration curve for dopamine linear from 0.5 to 20.0mgL-1 and an instrumental limit of detection as low as 24pg of injected dopamine. Finally, developed capillary column was applied to successful determination of dopamine in a human urine. By using both calibration curve and standard addition method, the dopamine level was determined to be 0.74±0.03mgL-1 and 0.71±0.02mgL-1, respectively. Triplicates of dopamine analysis provided relative standard deviations lower than 2.7% for intraday analyses, while interday relative standard deviations were lower than 3.6% for five consecutive days.
- MeSH
- dopamin analýza MeSH
- elektrochemické techniky přístrojové vybavení metody MeSH
- elektrody MeSH
- lidé MeSH
- neurotransmiterové látky analýza MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
The performances of ionic liquid (1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide, IL/CPE) and iron phthalocyanine (IP/CPE) modified carbon paste electrodes in electroanalytical determinations of rutin were evaluated and compared to the performance of unmodified carbon paste electrode (CPE). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), differential pulse adsorptive stripping voltammetry (DPAdSV), and amperometry were used for rutin analysis. The best current responses of rutin were obtained at pH 4.0 for all tested techniques. IL/CPE electrode was found to perform best with DPAdSV technique, where a detection limit (LOD) as low as 5 nmol L(-1) of rutin was found. On the other hand, IP/CPE showed itself to be an optimum choice for DPV technique, where LOD of 80 nmol L(-1) was obtained. Analytical applicability of newly prepared electrodes was demonstrated on determination of rutin in the model samples and the extracts of buckwheat seeds. To find an optimum method for buckwheat seeds extraction, a boiling water extraction (BWE), Soxhlet extraction (SE), pressurized solvent extraction (PSE), and supercritical fluid extraction (SFE) were tested.
- MeSH
- elektrochemie metody MeSH
- elektrody MeSH
- Fagopyrum chemie MeSH
- molekulární struktura MeSH
- rutin chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
This review (with 129 refs) summarizes the progress in electrochemical immunoassays combined with magnetic particles that was made in the past 5 years. The specifity of antibodies linked to electrochemical transduction (by amperometry, voltammetry, impedimetry or electrochemiluminescence) gains further attractive features by introducing magnetic nanoparticles (MNPs). This enables fairly easy preconcentration of analytes, minimizes matrix effects, and introduces an appropriate label. Following an introduction into the fundamentals of electrochemical immunoassays and on nanomaterials for respective uses, a large chapter addresses method for magnetic capture and preconcentration of analytes. A next chapter discusses commonly used labels such as dots, enzymes, metal and metal oxide nanoparticles and combined clusters. The large field of hybrid nanomaterials for use in such immunoassays is discussed next, with a focus on MNPs composites with various kinds of graphene variants, polydopamine, noble metal nanoparticles or nanotubes. Typical applications address clinical markers (mainly blood and urine parameters), diagnosis of cancer (markers and cells), detection of pathogens (with subsections on viruses and bacteria), and environmental and food contaminants as toxic agents and pesticides. A concluding section summarizes the present status, current challenges, and highlights future trends. Graphical abstract Magnetic nanoparticles (MNP) with antibodies (Ab) capture and preconcentrate analyte from sample (a) and afterwards become magnetically (b) or immunospecifically (c) bound at an electrode. Signal either increases due to the presence of alabel (b) or decreases as the redox probe is blocked (c).
This paper reports a simple electrochemical strategy for the determination of microRNAs (miRNAs) using a commercial His-Tag-Zinc finger protein (His-Tag-ZFP) that binds preferably (but non-sequence specifically) RNA hybrids over ssRNAs, ssDNAs, and dsDNAs. The strategy involves the use of magnetic beads (His-Tag-Isolation-MBs) as solid support to capture the conjugate formed in homogenous solution between His-Tag-ZFP and the dsRNA homohybrid formed between the target miRNA (miR-21 selected as a model) and a biotinylated synthetic complementary RNA detector probe (b-RNA-Dp) further conjugated with a streptavidin-horseradish peroxidase (Strep-HRP) conjugate. The electrochemical detection is carried out by amperometry at disposable screen-printed carbon electrodes (SPCEs) (- 0.20 V vs Ag pseudo-reference electrode) upon magnetic capture of the resultant magnetic bioconjugates and H2O2 addition in the presence of hydroquinone (HQ). The as-prepared biosensor exhibits a dynamic concentration range from 3.0 to 100 nM and a detection limit (LOD) of 0.91 nM for miR-21 in just ~ 2 h. An acceptable discrimination was achieved between the target miRNA and other non-target nucleic acids (ssDNA, dsDNA, ssRNA, DNA-RNA, miR-122, miR-205, and single central- or terminal-base mismatched sequences). The biosensor was applied to the analysis of miR-21 from total RNA (RNAt) extracted from epithelial non-tumorigenic and adenocarcinoma breast cells without target amplification, pre-concentration, or reverse transcription steps. The versatility of the methodology due to the ZFP's non-sequence-specific binding behavior makes it easily extendable to determine any target RNA only by modifying the biotinylated detector probe.
