Papers by Radosław Porada
Journal of Hazardous Materials
Applied Nanoscience, Feb 13, 2023
Bi(III) ions electroreduction in the presence of N-acetylcysteine (ACYS)at the nanostructured R-A... more Bi(III) ions electroreduction in the presence of N-acetylcysteine (ACYS)at the nanostructured R-AgLAFE electrode has been studied by the voltammetric and impedance measurements. The experimental data indicates the multistage character of the electrode process and the catalytic influence of N-acetylcysteine on the Bi(III) ions electroreduction rate. It was found that this process is controlled by the chemical reaction of the Bi(III)-Hg(SR) 2 activecomplexes formation on the electrode surface, which mediates electron transfer. Active complexes are a substrate in the process of electroreduction, and their different structure and properties are the reason for the diverse catalytic activity of N-acetylcysteine.
Vitamin K2 (VK2) is one of two natural forms of vitamin K, necessary for the proper functioning o... more Vitamin K2 (VK2) is one of two natural forms of vitamin K, necessary for the proper functioning of organisms. Currently, it is sourced from chemical synthesis, nonetheless, it is worth reaching out to its natural sources. The aim of the study was to devise a voltammetric procedure for the determination of vitamin K2 (VK2) produced by bacteria in order to find the strain that exhibits the highest efficiency of VK2 production. Bacillus subtilis, isolated from traditional Japanese food (Nattō), was chosen as a model strain. Employment of the Controlled Growth Mercury Drop Electrode (CGMDE) was crucial, as it is the only electrode that allows performing the measurement on the surface specifically renewed directly before, thus minimizing the influence of interferents. This new method was successfully applied for VK2 determination in supernatant samples. Developed procedure is robust and easily adjustable for the variety of biological matrixes. Strong differences in VK2 production dependi...
Colorectal cancer (CRC) is one of the foremost causes of cancer-related deaths. Lately, a close c... more Colorectal cancer (CRC) is one of the foremost causes of cancer-related deaths. Lately, a close connection between the course of CRC and the intestinal microbiota has been revealed. Vitamin K₂ (VK₂) is a bacterially derived compound that plays a crucial role in the human body. Its significant anti-cancer properties may result, inter alia, from a quinone ring possessing a specific chemical structure found in many chemotherapeutics. VK₂ can be supplied to our body exogenously, i.e., through dietary supplements or fermented food (e.g., yellow cheese, fermented soybeans -Natto), and endogenously, i.e., through the production of bacteria that constantly colonize the human microbiome of the large intestine. This paper focuses on endogenous K₂ synthesized by the most active members of the human gut microbiome. This analysis tested 86 intestinally derived bacterial strains, among which the largest VK₂ producers (Lactobacillus, Bifidobacterium, Bacillus) were selected. Moreover, based on the...
Monatshefte für Chemie - Chemical Monthly
Due to the indubitable role of vitamins in maintaining human health, a lot of attention has been ... more Due to the indubitable role of vitamins in maintaining human health, a lot of attention has been paid to the methods and analytical procedures of their determination. Voltammetric methods are of particular interest as they do not involve complex sample preparation, however, close values of the redox potential of some vitamins may result in peak overlapping, hindering the quantitative analysis. This paper addresses the separation of overlapped reduction peak of vitamins B1 and B3 by means of Continuous Wavelet Transform (with appropriately selected mother wavelets) and differentiation of the recorded voltammograms. These numerical algorithms allowed to obtained linear, single-variable calibration functions that comply with the applied in analytical chemistry criteria regarding the correlation coefficients and the limit of detection and quantification. Their relatively simple implementation does not include any manual interpretation step; thus, these algorithms provide impartial and r...
Molecules
A novel voltammetric method for the sensitive and selective determination of cadmium and lead ion... more A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder–Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentrati...
ABSTRAKT: Celem pracy było zbadanie zawartości kadmu i ołowiu, przy użyciu anodowej woltamperomet... more ABSTRAKT: Celem pracy było zbadanie zawartości kadmu i ołowiu, przy użyciu anodowej woltamperometrii stripingowej, w próbkach wody surowej, pobranych ze Zbiornika Dobczyckiego oraz w wodzie po zakończonym procesie uzdatniania. Kolejno starano się oszacować wydajność procesu filtrowania za pomocą antracytu oraz jego wpływ na stężenie Pb 2+ i Cd 2+ w wodzie. Uzyskane wyniki nie przekraczały wartości 1 μg/L, zatem mieszczą się w granicach wyznaczonych przez normę. Stwierdzono również, że filtracja na złożu antracytowym przyczynia się do wzrostu stężenia jonów oznaczanych metali ciężkich. ABSTRACT: This research aims at examining the cadmium and lead ions concentrations, with the use of differential pulse anodic stripping voltammetry, in the raw water samples from the Dobczyce Reservoir and the water samples after completion of the water purification process. Furthermore, this paper attempts to assess efficiency of the filtration method involving use of anthracite and its influence on t...
Electrochemistry Communications, 2022
Microchimica Acta, 2021
A voltammetric sensor has been developed based on glassy carbon electrode (GCE) modification with... more A voltammetric sensor has been developed based on glassy carbon electrode (GCE) modification with nanocomposite consisting of manganese-based metal-organic framework (JUK-2), multi-walled carbon nanotubes (MWCNTs), and gold nanoparticles (AuNPs) for detection of citalopram (CIT). The composition and morphology of JUK-2-MWCNTs-AuNPs/GCE were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy dispersion spectroscopy (EDS), and scanning electron microscopy (SEM). The electrochemical properties investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) indicated that the fabricated hybrid material exhibits the properties of mixed ion-electron conductor (MIEC). Using staircase voltammetry (SCV), under optimized conditions, the fabricated sensor shows a linear response in three CIT concentration ranges, 0.05–1.0, 1.0–10.0 and 15.0–115.0 μmol L−1, with a detection limit of 0.011 μmol L−1. The JUK-2-MWCNT...
Talanta, 2021
Urinalysis is a simple and non-invasive approach for the diagnosis and monitoring of various heal... more Urinalysis is a simple and non-invasive approach for the diagnosis and monitoring of various health disorders. While urinalysis is predominantly confined to clinical laboratories the non-invasive sample collection makes it applicable in wide range of settings outside of central laboratory confinements. In this respect, 3D printed devices integrating sensors for measuring multiple parameters may be one of the most viable approaches to ensure costeffectiveness for widespread use. Here we evaluated such a system for the multiplexed determination of sodium, potassium and calcium ions in urine samples with ion-selective electrodes based on state of the art octadecylamine-functionalized multi-walled carbon nanotube (OD-MWCNT) solid contacts. The electrodes were tested in the clinically relevant concentration range, i.e. ca. 10 − 4-10 − 1 mol L − 1 and were proven to have Nernstian responses under flow injection conditions. The applicability of the 3D printed flow manifold was investigated through the analysis of synthetic samples and two certified reference materials. The obtained results confirm the suitability of the proposed system for multiplexed ion analysis in urine.
Measurement, 2021
Abstract This paper reports the fabrication of a new, portable, and user-friendly zeolite-based s... more Abstract This paper reports the fabrication of a new, portable, and user-friendly zeolite-based sensor – the Mn-zeolite/graphite modified Screen-printed Carbon Electrode (MnZG-SPCE) and its application in the highly-sensitive determination of folic acid (FA) by differential pulse voltammetry (DPV). The X-ray spectroscopy measurements proved the incorporation of Mn cations into the zeolite framework, whereas the SEM images and cyclic voltammograms provided intel about morphology and electrochemical properties of the modifying layer. The developed method for FA determination exhibited the linear response from 0.004 to 0.99 mg L-1 (R=0.9998) and the limit of detection (LOD, S/N=3) of 1.3 ug L-1 (2.9 nM). The major improvement was observed in the sensitivity equaled 6.93 µA L mg-1, which translates into a higher resolution, thus the possibility to detect small changes in FA concentration. Employment of MnZG-SPCE in the determination of FA in pharmaceuticals delivered reliable results, as verified by the reference method (UV-Vis spectroscopy).
Microchimica Acta, 2021
The utilization of environmentally friendly nanoporous natural zeolite exchanged with Ni2+ ions (... more The utilization of environmentally friendly nanoporous natural zeolite exchanged with Ni2+ ions (NiZ) and conductive carbon black (CB) in the fabrication of a novel and selective voltammetric sensor of vitamin B6 (VB6) is presented. The used clinoptilolite-rich zeolite material and CB were characterized in terms of morphology and textural properties. The superior properties of Ni-zeolite/carbon black modified glassy carbon electrode (NiZCB-GCE), arising from the synergistic effect of combining the unique features of zeolite and conductive carbon black, were confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. In the determination of VB6 with the use of differential pulse voltammetry (DPV), the optimization of the pH value of supporting electrolyte and instrumental parameters, as well as the interference study were performed. Under optimized conditions, the oxidation peak current at the potential +0.72 V vs. Ag | AgCl | 3 M KCl reference...
Microchemical Journal, 2021
The biosynthetic pathway, unraveled three decades ago, is a model for related transformations to ... more The biosynthetic pathway, unraveled three decades ago, is a model for related transformations to anti-infl ammatory mediators including the lipoxins, eoxins, resolvins, protectins, and maresins (2-5). 5-Lipoxygenase (5-LOX) catalyzes the fi rst two steps in leukotriene biosynthesis, namely the stereospecifi c oxygenation of arachidonic acid to 5 S-hydroperoxy-eicosatetraenoic acid (5 S-HPETE), and dehydration of the hydroperoxide to LTA 4 , the allylic 5,6-trans-epoxide from which the bioactive leukotrienes are derived (Fig. 1) (6-9). The importance of this pivotal intermediate is refl ected in the extensive efforts directed toward perfecting the total synthesis of LTA 4 and of closely related 5,6-epoxide isomers (as reviewed in Refs. 10-12). LTA 4 is highly unstable in physiological buffer at pH 7.4, with a half-life estimated as approximately 3 s at 25°C and 18 s at 4°C (13). Despite this instability, LTA 4 was detected as an evanescent intermediate in short-term incubations of arachidonic acid with human leukocytes (6), and the radiolabeled product was isolated and, as the methyl ester derivative, shown to have similar chromatographic mobility and hydrolysis under acidic conditions as a synthetic standard (14). The stereochemistry has heretofore not been established directly on the biosynthetic product but was deduced from an understanding of the biosynthetic pathway and by study of the reactions of synthetic LTA 4 and related isomers in transformations to the stable, bioactive leukotrienes LTB 4 and LTC 4 (15-17). Herein we report the isolation and purifi cation of LTA epoxides as products of LOX enzymes in quantities suffi cient for NMR analysis of the stereoconfi gurations. The isolation method Abstract Leukotriene (LT)A 4 and closely related allylic epoxides are pivotal intermediates in lipoxygenase (LOX) pathways to bioactive lipid mediators that include the leukotrienes, lipoxins, eoxins, resolvins, and protectins. Although the structure and stereochemistry of the 5-LOX product LTA 4 is established through comparison to synthetic standards, this is the exception, and none of these highly unstable epoxides has been analyzed in detail from enzymatic synthesis. Understanding of the mechanistic basis of the cis or trans epoxide confi guration is also limited. To address these issues, we developed methods involving biphasic reaction conditions for the LOX-catalyzed synthesis of LTA epoxides in quantities suffi cient for NMR analysis. As proof of concept, human 15-LOX-1 was shown to convert 15 S-hydroperoxy-eicosatetraenoic acid (15 S-HPETE) to the LTA analog 14 S ,15 S-trans-epoxy-eicosa-5 Z ,8 Z ,10 E ,12 E-tetraenoate, confi rming the proposed structure of eoxin A 4. Using this methodology we then showed that recombinant Arabidopsis AtLOX1, an arachidonate 5-LOX, converts 5 S-HPETE to the trans epoxide LTA 4 and converts 5 R-HPETE to the cis epoxide 5-epi-LTA 4 , establishing substrate chirality as a determinant of the cis or trans epoxide confi guration. The results are reconciled with a mechanism based on a dual role of the LOX nonheme iron in LTA epoxide biosynthesis, providing a rational basis for understanding the stereochemistry of LTA epoxide intermediates in LOX-catalyzed transformations.-Jin, J., Y. Zheng, W. E. Boeglin, and A. R. Brash. Biosynthesis, isolation, and NMR analysis of leukotriene A epoxides: substrate chirality as a determinant of the cis or trans epoxide confi guration.
Journal of The Electrochemical Society, 2020
Voltammetric sensors with laterally placed working electrode are an interesting alternative to cl... more Voltammetric sensors with laterally placed working electrode are an interesting alternative to classic electrodes since they offer enhanced performance in electroanalysis. Their characteristics include easier preparation for measurement, removal of interferences and gas bubbles, amplification of mass-transport, and possibility of miniaturization and automation. In this review, construction and characteristics of the custom-designed in our team cyclically renewable, silver, gold, bismuth, glassy carbon, ceramic and amalgam annular band, bi-band, ring, and multidisc electrodes are discussed in detail. They represent the current trends in electroanalysis, aimed at reducing of amount of the used toxic electrode materials, like mercury and its compounds, and organic solvents used for a sample preparation, and are coherent with the concept of Green Chemistry. For each sensor type available strategies for mechanical and electrochemical surface renovation/activation before measurement are e...
Sensors and Actuators B: Chemical, 2019
In this work a new type of working electrode for voltammetrythe bi-band silver microelectrode (b-... more In this work a new type of working electrode for voltammetrythe bi-band silver microelectrode (b-BAgmE)is presented for the first time. The sensor consists of two Ag bands 25 μm thick and 4.5 mm long. The bands are arranged symmetrically and contrariwise, along the lateral, cylindrical surface of the Ag guide, coated with a thin layer of epoxy resin. Simple and inexpensive microelectrode construction ensures its reliability of use as well as wide possibilities of application in electroanalysis. Electrochemical properties of the sensor were tested by means of the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) in the [Ru(NH 3) 6 ] 2+/3+ redox system. Comparative experiments, carried out simultaneously on a homemade silver annular band electrode (AgABE), commercially available silver microelectrode (AgmE) and b-BAgmE, confirmed occurrence of the microelectrode effect in case of the AgmE and b-BAgmE. Moreover, the b-BAgmE is characterized by significantly lower value of charge-transfer resistance R ct = 179 ± 6 Ω in comparison to AgmE R ct = 6.0 ± 0.4 MΩ. The practical usefulness of the b-BAgmE was confirmed by determination of Pb 2+ , Tl + , In 3+ and vitamin B 2 using the differential pulse (DP) voltammetric technique.
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Papers by Radosław Porada