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Lauric acid was used to synthesize the low-molecular-weight organogelators (LMOGs), derivatives of two endogenous (L)-alanine, (L)-leucine, and three exogenous (L)-valine, (L)-phenylalanine, and (L)-proline amino acids. The nature of processes responsible for the gel formation both in polar and in apolar solvents of such compounds is still under investigation. Knowing that the organization of surfactant molecules affects the properties of nano scale materials and gels, we decided to elucidate this problem using crystallographic diffraction and energy frameworks analysis. The single crystals of the mentioned compounds were produced successfully from heptane/tBuOMe mixture. The compounds form lamellar self-assemblies in crystals. The energetic landscapes of single crystals of a series of studied amphiphilic gelators have been analyzed to explore the gelling properties. The presented results may be used as model systems to understand which supramolecular interactions observed in the solid state and what energy contributions are desired in the designing of new low-molecular-weight organic gelators.

For the fast and simple sensing of the arsenic drug roxarsone (ROX), the development of a glassy carbon electrode (GCE) modified with cationic surfactant (cetyltrimethylammonium bromide, CTAB) material is critical. The CTAB-modified glassy carbon electrode, in contrast to the unmodified one, showed excellent behavior for electrochemical reduction of ROX using cyclic voltammetry (CV) and square-wave adsorptive stripping voltammetry (SWAdSV) techniques. CV studies reveal an irreversible reduction process of NO2 to NH–OH in the ROX molecule in NaAc–HAc buffer (pH = 5.6). The electrode material was characterized using CV and electrochemical impedance spectroscopy. The experiments show that the surfactant-modified material has faster electron transfer and a higher active surface area, and permits a diffusion–adsorption-controlled process. After optimization, the SWAdSV procedure with GCE/CTAB has linear ranges of 0.001–0.02 and 0.02–20 µM, and a detection limit of 0.13 nM. Furthermore, the procedure successfully determined roxarsone in river water samples.

3-(4-Nitrophenyl)-8-(2,3-dimethylphenyl)-7,8-dihydroimidazo[2,1-c][1,2,4]triazin-4(6H)-one (NDIT) is one of the most promising candidates for anticancer agents. Hence, a sensitive and selective sodium dodecyl sulfate-modified screen-printed carbon sensor (SPCE/SDS) was used for its quantitative analysis. The SPCE/SDS, in contrast to the SPCE, showed excellent behavior in the electrochemical reduction of NDIT by differential-pulse adsorptive stripping voltammetry (DPAdSV). Cyclic voltammetric (CV) studies reveal an irreversible, two-stage and not purely diffusion-controlled reduction process in 0.01 M HNO3. The sensor was characterized by CV and electrochemical impedance spectroscopy (EIS). Under the optimized conditions (t 45 s, ΔE 175 mV, ν 150 mV/s, and tm 5 ms), the DPAdSV procedure with the SPCE/SDS presented a very wide linear range from 1 to 2000 nM and a low detection limit of 0.29 nM. A 1000-fold excess concentration of potential interferents commonly present in biological samples did not significantly alter the peak current of NDIT. The practical application of the proposed DPAdSV procedure with the SPCE/SDS was successfully checked by analyzing spiked human serum samples.

In this paper, we report a highly sensitive voltammetric sensor for the determination of the anti-cancer antibiotic bleomycin (BLM) based on a screen-printed carbon sensor that is electrochemically pretreated and decorated with lead nanoparticles in the sample solution (pSPCE/PbNPs). These sensor surface manipulations contribute to significant amplification of the analytical signal and improvement of its shape and repeatability. The effect of the electrochemical behavior of BLM on the pSPCE/PbNPs was examined by electrochemical strategies. CV, EIS, and XPS were used to compare the sensor surface modifications. The effects of the type and pH of the supporting electrolyte and the procedure parameters were optimized. The features of the proposed procedure include: (a) very low limits of detection and quantification (2.8 × 10−11 and 9.3 × 10−11 M, respectively), (b) linear ranges (1.0 × 10−10–2.0 × 10−9 M and 2.0 × 10−9–2.0 × 10−8 M, and (c) a high sensitivity of 0.32 µA/nM. The electrochemical sensor was successfully applied for the determination of BLM in wastewater and reference material of human urine samples.

Testosterone (TST), despite its good properties, may be harmful to the human organism and the environment. Therefore, monitoring biological fluids and environmental samples is important. An electrochemically pretreated screen-printed carbon sensor modified with Pb nanoparticles (pSPCE/PbNPs) was successfully prepared and used for the determination of TST. The surface morphology and electrochemical properties of unmodified and modified sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive X-ray spectroscopy (EDS). Selective determinations of TST at the pSPCE/PbNPs were carried out by differential pulse adsorptive stripping voltammetry (DPAdSV, EPb dep.and TST acc. of −1.1 V, t Pb dep.and TST acc. of 120 s, ΔEA of 50 mV, ν of 175 mV s−1, and tm of 5 ms) in a solution containing 0.075 mol L−1 acetate buffer of pH = 4.6 ± 0.1, and 7.5 × 10−5 mol L−1 Pb(NO3)2. The analytical signal obtained at the potential around −1.42 V (vs. silver pseudo-reference electrode) is related to the reduction process of TST adsorbed onto the electrode surface. The use of pSPCE/PbNPs allows obtaining a very low limit of TST detection (2.2 × 10−12 mol L−1) and wide linear ranges of the calibration graph (1.0 × 10−11–1.0 × 10−10, 1.0 × 10−10–2.0 × 10−9, and 2.0 × 10−9–2.0 × 10−8 mol L−1). The pSPCE/PbNPs were successfully applied for the determination of TST in reference material of human urine and wastewater purified in a sewage treatment plant without preliminary preparation.

In this paper, we propose the first analytical procedure—using a screen-printed carbon electrode modified with carbon nanofibers (SPCE/CNFs)—for the detection and quantitative determination of an electroactive disubstituted fused triazinone, namely 4-Cl-PIMT, which is a promising anticancer drug candidate. The electrochemical performances of the sensor were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square-wave adsorptive stripping voltammetry (SWAdSV). The presence of carbon nanofibers on the sensor surface caused a decrease in charge-transfer resistance and an increase in the active surface compared to the bare SPCE. Under the optimised experimental conditions, the proposed voltammetric procedure possesses a good linear response for the determination of 4-Cl-PIMT in the two linear ranges of 0.5–10 nM and 10–100 nM. The low limits of detection and quantification were calculated at 0.099 and 0.33 nM, respectively. In addition, the sensor displays high reproducibility and repeatability, as well as good selectivity. The selectivity was improved through the use of a flow system and a short accumulation time. The SWAdSV procedure with SPCE/CNFs was applied to determine 4-Cl-PIMT in human serum samples. The SWAdSV results were compared to those obtained by the ultra-high-performance liquid chromatography coupled with electrospray ionization/single-quadrupole mass spectrometry (UHPLC-ESI-MS) method.

The dynamic production and usage of pharmaceuticals, mainly painkillers, indicates the growing problem of environmental contamination. Therefore, the monitoring of pharmaceutical concentrations in environmental samples, mostly aquatic, is necessary. This article focuses on applying screen-printed voltammetric sensors for the voltammetric determination of painkillers residues, including non-steroidal anti-inflammatory drugs, paracetamol, and tramadol in environmental water samples. The main advantages of these electrodes are simplicity, reliability, portability, small instrumental setups comprising the three electrodes, and modest cost. Moreover, the electroconductivity, catalytic activity, and surface area can be easily improved by modifying the electrode surface with carbon nanomaterials, polymer films, or electrochemical activation.

Water is the most important life-giving resource on earth. Nowadays, intensive growth of the world population has resulted in increased water consumption and the production of wastewater. Additionally, the presence of pharmaceuticals in treated conventional wastewater or even in the environment is strictly indicating that present techniques of wastewater treatment are not efficient enough and are not designed to remove such pollutants. Scarce water resources in the world are the main driving force for the innovation of novel techniques of water and wastewater treatment. Photocatalysis, as one of the advanced oxidation processes, enables the transformation of recalcitrant and toxic pollutants into CO2, water, and inorganic salts. In the present paper, the photocatalytic oxidation of β-blockers—metoprolol and propranolol—are described. For photocatalytic oxidation, novel TiO2 photocatalysts modified with biochar were used. Photocatalysts were prepared by sol-gel method and the effect of photocatalysts type, presence of inorganic ions, dissolved organic matter, and different water matrix was established. The results indicate that using only the decrease in the tested pollutant concentration is not effective enough in establishing the treatment method’s safety. There is a need to use additional testing such as ecotoxicity tests; however, the key parameter is the properly chosen tested organism.

Polyaniline (PANI) is one of the best known and widely studied conducting polymers with multiple applications and unique physicochemical properties. Due to its porous structure and relatively high surface area as well as the affinity toward many analytes related to the ability to establish different types of interactions, PANI has a great potential as a sorbent in sample pretreatment before instrumental analyses. This study provides an overview of the applications of polyaniline and polyaniline composites as sorbents in sample preparation techniques based on solid-phase extraction, including conventional solid-phase extraction (SPE) and its modifications, solid-phase microextraction (SPME), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE) and stir-bar sorptive extraction (SBSE). The utility of PANI-based sorbents in chromatography was also summarized. It has been shown that polyaniline is willingly combined with other components and PANI-based materials may be formed in a variety of shapes. Polyaniline alone and PANI-based composites were successfully applied for sample preparation before determination of various analytes, both metal ions and organic compounds, in different matrices such as environmental samples, food, human plasma, urine, and blood.

In this paper, a dicyandiamide-impregnated mesoporous carbon (N-CMK-3), electrochemically modified in situ with lead film (Pb-N-CMK-3), was tested as an electrode material for U(VI) ultratrace determination. The prepared carbon material was characterized by XRD, SEM-EDX, Raman, FT-IR, XPS analysis and nitrogen sorption measurements. The changes of electrochemical properties of glassy carbon electrodes (GCE) after the N-CMK-3 and Pb-N-CMK-3 modification were studied using CV and EIS methods. The modification of the GCE surface by the N-CMK-3 material and Pb film increases the electroactive area of the electrode and decreases the charge transfer residence and is likely responsible for the electrochemical improvement of the U(VI) analytical signal. Using square-wave adsorptive stripping voltammetry (SWAdSV), two linear calibration ranges extending from 0.05 to 1.0 nM and from 1.0 to 10.0 nM were observed, coupled with the detection and quantification limits of 0.014 and 0.047 nM, respectively. The Pb-N-CMK-3/GCE was successfully applied for U(VI) determination in reference materials (estuarine water SLEW-3 and trace elements in natural water SRM 1640a).

Electrochemical stripping analysis is recognized as a powerful technique for trace metals owing its remarkable sensitivity, relatively inexpensive instrumentation, ability for multielement determination and capable of determining elements accurately at trace and ultra-trace levels. The success of voltammetric sensing procedure depends mainly on the proper choice and preparation of the working electrode. The article reviews the development and application of metal film electrodes (bismuth, lead, and antimony film electrodes) prepared with a reversibly deposited mediator for stripping voltammetric determination of metal ions (Ni(II), Sn(IV), Hg(II), U(VI), Cd(II), Pb(II), and Cr(VI)). In this electrochemical, defect-mediated, thin-film growth method, the mediator is periodically deposited and the stripped from the surface, and this serves to significantly increase the density of islands of atoms of interest metal, what in consequence improves the electrochemical properties of these electrodes, because of the increase in the active surface area of electrode.

Acetaminophen (APAP), a non-steroidal anti-inflammatory drug, is the most commonly detected wastewater contaminant together with caffeine (CAF), that is used both in beverages and food but also in medicine. The presence of pharmaceuticals in the wastewater effluent have confirmed that nowadays existing wastewater treatment methods are not effective enough in pharmaceuticals removal. The aim of presented studies was the determination of the photocatalytic efficiency of TiO2 based nanocomposites in the removal of APAP and CAF from water under visible light irradiation. The process of photocatalytic removal of APAP from water in the presence of CAF was performed using TiO2-SiO2 photocatalysts containing multiwalled carbon nanotubes (MWCNT) characterized by high surface area (up to 420.8 ± 12.6 m2 g−1), narrow pore diameter (3–4 nm) and uniform anatase TiO2 crystallites (5–6 nm) with reduced band gap energy (up to 2.82 eV). The high resistance of CAF to photocatalytic decomposition under visible light irradiation was noted. Slight removal of CAF (29.4 ± 2.7%) was observed after 60 min of irradiation using nanocomposite with lowest MWCNT addition (0.15 wt%). The presence of CAF hindered APAP photocatalytic oxidation. CNT10, nanocomposite that was the most effective in APAP removal (81.6 ± 0.6%) enabled to remove APAP in the presence of CAF only by 48.0 ± 4.3% during visible light irradiation. The best results of APAP removal in the presence of CAF were obtained over CNT1 (47.6 ± 2.4%), that contained 0.15 wt% of MWCNT. The kinetics of APAP, CAF and APAP with CAF photocatalytic degradation and mineralization proceeded according to a pseudo-first-order reaction model and APAP kDOC was significantly reduced in the CAF presence (up to almost 4 times). The photocatalytic APAP removal in the presence of CAF over MWCNT-TiO2-SiO2 proceeded via photo generated holes and, in lower extend, OH radicals. Photocatalytically treated model water containing APAP and CAF revealed no toxicity to Vibrio fischeri.

For the first time the application of unmodified boron doped diamond electrode for dopamine (DA) and paracetamol (PA) determination in biological samples and pharmaceutical preparations with the use of differential pulse voltammetry was demonstrated in the present work. The wide linear range of calibration graphs: from 1 × 10−7 to 2 × 10−4 mol L−1 for DA and PA, and very low detection limits were achieved, equaling 1.87 × 10−8 mol L−1 for DA and 1.35 × 10−8 mol L−1 for PA. The proposed sensor was successfully applied for determination of dopamine in urine samples, paracetamol in syrups for children, and for simultaneous determination of paracetamol and dopamine in blood and serum samples.

A commercially available screen-printed carbon electrode coated with carbon nanofibers (SPCE/CNFs) and differential-pulse adsorptive stripping voltammetry (DPAdSV) were used to determination of caffeine. The process of electrochemical oxidation of caffeine in 0.1 mol L−1 sulfuric acid at the SPCE/CNFs surface was investigated by cyclic voltammetry (CV). The effect of the supporting electrolyte type, pH and concentration, time and potential of accumulation, amplitude and scan rate were studied to select the optimum experimental conditions. Under the optimized conditions, the well-defined caffeine peak was observed at 1.25 V (vs. screen-printed silver reference electrode) in 0.1 mol L−1 sulfuric acid. The caffeine was accumulated at − 0.8 V for 60 s. The oxidation peak current was proportional to concentration of caffeine from 2.0 × 10−7 to 1.0 × 10−6 mol L−1 with detection limit of 5.6 × 10−8 mol L−1. The presented method has been successfully applied for the determination of caffeine in beverage samples.

In this paper, a screen-printed boron-doped electrode (aSPBDDE) was subjected to electrochemical activation by cyclic voltammetry (CV) in 0.1 M NaOH and the response to rifampicin (RIF) oxidation was used as a testing probe. Changes in surface morphology and electrochemical behaviour of RIF before and after the electrochemical activation of SPBDDE were studied by scanning electron microscopy (SEM), CV and electrochemical impedance spectroscopy (EIS). The increase in number and size of pores in the modifier layer and reduction of charge transfer residence were likely responsible for electrochemical improvement of the analytical signal from RIF at the SPBDDE. Quantitative analysis of RIF by using differential pulse adsorptive stripping voltammetry in 0.1 mol L−1 solution of PBS of pH 3.0 ± 0.1 at the aSPBDDE was carried out. Using optimized conditions (Eacc of −0.45 V, tacc of 120 s, ΔEA of 150 mV, ν of 100 mV s−1 and tm of 5 ms), the RIF peak current increased linearly with the concentration in the four ranges: 0.002–0.02, 0.02–0.2, 0.2–2.0, and 2.0–20.0 nM. The limits of detection and quantification were calculated at 0.22 and 0.73 pM. The aSPBDDE showed satisfactory repeatability, reproducibility, and selectivity towards potential interferences. The applicability of the aSPBDDE for control analysis of RIF was demonstrated using river water samples and certified reference material of bovine urine.

A carbon nanofibers modified screen-printed carbon sensor (SPCE/CNFs) was applied for the determination of a novel promising anticancer agent candidate (ethyl 8-(4-methoxyphenyl)-4-oxo-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3-carboxylate, EIMTC) using square-wave voltammetry (SWV). It is the first method for the quantitative determination of EIMTC. The modified screen-printed sensor exhibited excellent electrochemical activity in reducing EIMTC. The peak current of EIMTC was found to be linear in two concentration ranges of 2.0 &times, 10&minus, 9 &ndash, 2.0 &times, 8 mol L&minus, 1 and 2.0 &times, 8 &ndash, 7 mol L&minus, 1, with a detection limit of 5.0 &times, 10 mol L&minus, 1. The connection of flow-cell for the SPCE/CNFs with SWV detection allowed for the successful determination of EIMTC in human serum samples. Ultra-high-performance liquid chromatography coupled to electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-MS/MS) acted as a comparative method in the serum samples analysis.

A differential-pulse adsorptive stripping voltammetric (DPAdSV) procedure with the use of pulsed potential accumulation and carboxyl functionalized multiwalled carbon nanotubes modified screen-printed carbon electrode (SPCE/MWCNTs-COOH) was delineated for simultaneous analysis of paracetamol (PA) and diclofenac (DF). The use of carboxyl functionalized MWCNTs and pulsed potential accumulation improves the analytical signals of PA and DF, and minimizes interferences from surfactants. After optimization of analytical conditions for this sensor, the peak currents of the two compounds were found to increase linearly with the increase in their concentration (5.0 &times, 10&minus, 9&ndash, 5.0 &times, 6 mol L&minus, 1 with a detection limit of 1.4 &times, 9 mol L&minus, 1 for PA, and 1.0 &times, 10&ndash, 2.0 &times, 8 mol L&minus, 1 with a detection limit of 3.0 &times, 11 mol L&minus, 1 for DF). For the first time, the electrochemical sensor allows simultaneous determination of PA and DF at concentrations of 24.3 &plusmn, 0.5 nmol L&minus, 1 and 3.7 &plusmn, 0.7 nmol L&minus, 1, respectively, in wastewater samples purified in a sewage treatment plant.

Monolithic fillings used in chromatography are of great interest among scientists since the first reports of their synthesis and use were published. In the 20 years since silica-based monolithic columns were introduced into the commercial market, numerous papers describing their chromatographical properties and utility in various branches of industry and scientific investigations were presented. This review is focused on possible applications of commercially available silica-based HPLC monolithic columns in the analysis of biological samples.

In this work, a fast and low-cost voltammetric methodology for determination of carlina oxide in plant extracts was developed. The best results were obtained using a boron-doped diamond electrode (BDDE). The voltammetric measurements of carlina oxide were performed in a 0.1 mol/L solution of sulphuric acid. After 30 s of stirring the solution, differential pulse voltammograms (DPVs) were recorded from 0.5 to 1.8 V. The amplitude was 75 mV and the scan rate was 175 mV/s. Measurements were recorded in non-deaerated solutions. The background current was subtracted from each registered voltammogram; then they were cut from 0.5 to 1.5 V. The detection and quantification limits were 0.28 and 0.93 μg/L, respectively, and repeatability expressed as the relative standard deviation of 0.1 mg/L of carlina oxide was 1.9% (n = 5). The results were compared with those obtained using gas chromatography with a flame ionization detector and high performance liquid chromatography with a photodiode array detector.

A simple, sensitive and time-saving differential-pulse adsorptive stripping voltammetric (DPAdSV) procedure using a screen-printed carbon electrode modified with carboxyl functionalized multiwalled carbon nanotubes (SPCE/MWCNTs-COOH) for the determination of diclofenac (DF) is presented. The sensor was characterized using optical profilometry, SEM, and cyclic voltammetry (CV). The use of carboxyl functionalized MWCNTs as a SPCE modifier improved the electron transfer process and the active surface area of sensor. Under optimum conditions, very sensitive results were obtained with a linear range of 0.1&ndash, 10.0 nmol L&minus, 1 and a limit of detection value of 0.028 nmol L&minus, 1. The SPCE/MWCNTs-COOH also exhibited satisfactory repeatability, reproducibility, and selectivity towards potential interferences. Moreover, for the first time, the electrochemical sensor allows determining the real concentrations of DF in environmental water samples without sample pretreatment steps.

In the present paper, for the first time, the integrated three-electrode screen-printed sensor with in situ plated bismuth film carbon working electrode was applied for the ultratrace determination of thallium(I) (Tl(I)). Under optimized conditions extremely low limits of detection were reached, 8.47 × 10−10 and 6.71 × 10−12 mol L−1 for the deposition times of 60 s and 300 s, respectively. The influences of foreign metal ions and surfactants on the voltammetric signal of thallium in natural samples were minimized using 1 × 10−5 mol L−1 EDTA and Amberlite XAD-7 resin added to the buffer solution (CH3COONH4, CH3COOH and NH4Cl) of pH = 4.6 ± 0.1. The developed voltammetric method with integrated three-electrode screen-printed sensor was validated with use of certified reference materials (surface, rain and natural water) and can be in future applied to field analyses of Tl(I).

The presence of acetaminophen (APAP) in water and wastewater indicates its low susceptibility to conventional treatment. The application of new TiO2 nanocomposites containing pristine carbon nanotubes (MWCNT, 0.15–8.78 wt%) prepared by solgel method in acetaminophen removal from water was tested. The studied nanocomposites possessed a high surface area (348–421 m2·g−1) with uniform framework-confined mesopores (primary mesopores) with an average pore width of about 3 nm. TiO2 was present as anatase with crystal size ∼ 5–6 nm. The nanocomposites had an exposed more graphitized MWCNT surface with a lower content of C O and O C O surface groups. The addition of MWCNT reduced the band gap of TiO2 from 3.2 eV to 2.82 eV. Dark adsorption resulted in insignificant changes in APAP concentration. The greatest changes in APAP concentration during Vis irradiation over the tested nanocomposites were observed using CNT10 (Fig. 10B). The highest efficiency was exhibited by the nanocomposite containing 1.72 wt% of MWCNT that enabled 81.6 ± 0.6% removal of APAP from water. Generally, an increase of MWCNT concentration up to 1.72 wt% in the nanocomposites induced APAP removal. The nanocomposites possessing higher MWCNT addition were, however, not so efficient (63.2 ± 2.4% and 62.2 ± 4.2% removal). The enhanced photocatalytic activity of different nanocomposites is observed only in the narrow range. The obtained results confirmed that photogenerated holes and, to a lower extent, O2− and OH radicals played the key role in photocatalytic APAP removal over MWCNT-TiO2-SiO2. The studies using Vibrio fischeri have confirmed that photocatalytic oxidation is an effective method for reducing water toxicity.

A bismuth film electrode prepared in situ with a reversibly deposited mediator (Zn) applied for ultrasensitive determination of Cr(VI) using differential pulse catalytic adsorptive stripping voltammetry is presented. The optimization of experimental conditions such as composition of the supporting electrolyte, potential and time of bismuth film formation as well as analyte accumulation, and DP mode parameters is reported. For 180 s accumulation time, very low limits of detection and quantification of Cr(VI) were obtained, with 5.8 × 10–14 and 1.9 × 10–13 mol L−1, respectively. The relative standard deviation for 5.0 × 10–13 mol L−1 of Cr(VI) was 3.9% (n = 5). Finally, the proposed procedure was applied to determine Cr(VI) in the certified reference materials – NASS-6 (seawater), SLEW-3 (estuarine water) and TMRAIN-04 (rainwater) – as well as in river water samples. Furthermore, the obtained results show that the proposed voltammetric procedure employing the bismuth film electrode prepared with mediator appears to form a very promising tool for the speciation of chromium at ultratrace level.

A glassy carbon electrode covered with thiol-functionalized polysiloxane film modified by electrodeposited lead nanoparticles was used for determination of Ag(I) by square-wave anodic stripping voltammetry. The sol-gel methodology based on co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of cetyltrimethylammonium bromide (CTAB) was applied to synthesize an organosilica sol that was used to modify electrode surface. Silver ions were accumulated on the electrode surface by complexation with thiol groups and then simultaneously deposited with Pb nanoparticles by reduction at − 0.85 V. The Pb nanoparticles used as modifier of polyslioxane film significantly improved the electrochemical performance of the sensor. Under optimized conditions, the voltammetric signal was proportional to the Ag(I) concentration in the range of 0.0093 to 1.85 nmol L− 1 with excellent limits of detection and quantification of 1.2 pmol L− 1 and 4.1 pmol L− 1 after 90 s of accumulation on the electrode surface covered with thiol-functionalized polysiloxane film, respectively. The proposed method was applied for determination of Ag(I) in river water samples collected from Bystrzyca and Vistula without mineralization and a total silver concentration in commercially available silver-containing products.

In the work presented, a lead film electrode was prepared in situ on a screen-printed carbon support using a reversibly deposited mediator (Zn) and applied to the determination of Cd(II) by anodic stripping voltammetry. The electrochemical method for lead film formation is based on a co-deposition of a metal of interest (Pb), with a reversibly deposited zinc mediator, followed by oxidation of zinc, with additional deposition of lead at the appropriate potential. It serves to increase the density of lead particles, promoting lead film growth, and consequently helps to improve the electrochemical properties of the electrode. This was confirmed by microscopic and voltammetric studies. The obtained detection limit of Cd(II) is equal to 6.6 × 10−9 mol L−1 (−1.6 V for 180 s and then −0.95 V for 5 s). The presented procedure was successfully applied to cadmium determination in Bystrzyca River water samples.

The paper outlines the first report of application of a differential pulse voltammetry for simultaneous quantification of clinically important molecular markers – tryptophan and its metabolite – kynurenine. The analytes were determined in less than 60 s at the boron-doped diamond electrode modified in situ with bismuth film (BiF/BDDE). Proper adjustment of a supporting electrolyte composition allowed to obtain good separation of tryptophan and kynurenine oxidation peaks that appeared at potential of 0.88 and 1.05 V (vs. Ag/AgCl), respectively. Studies using an optical profilometer have confirmed an increase in electrode surface area after deposition of Bi film. At the optimized conditions, the obtained detection limits of tryptophan and kynurenine were at 30 nM concentrations. The method was validated for linearity, precision, accuracy, selectivity and recovery. We have investigated an impact of numerous relevant interfering organic compounds (including amino acids and different tryptophan metabolites of kynurenine pathway) on voltammetric signals of the measured analytes. Finally, for proof˗of˗technology, the sensor was used for tryptophan and kynurenine quantification in culture medium collected from human cancer cell lines (breast MDA–MB–231 and ovary SK–OV–3). The target molecules were analyzed directly, without any sample preparation step. The sensor showed good accuracy in presence of the sample matrix components that was confirmed by high performance liquid chromatography measurements. Our work emphasizes the advantages of application of the herein proposed, easy to fabricate voltammetric sensor, instead of popular chromatographic assays or previously proposed potentiometric immunosensor. The method might serve for rapid assessment of kynurenine pathway activity in cancer cells.

In this work, an electrochemically activated screen-printed carbon electrode modified with sodium dodecyl sulfate (aSPCE/SDS) was proposed for the simultaneous determination of paracetamol (PA), diclofenac (DF), and tramadol (TR). Changes of surface morphology and electrochemical behaviour of the electrode after the electrochemical activation with H2O2 and SDS surface modification were studied by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The influence of various parameters on the responses of the aSPCE/SDS such as pH and concentration of the buffer, SDS concentration, and techniques parameters were investigated. Using optimised conditions (Eacc. of −0.4 V, tacc. of 120 s, ΔEA of 150 mV, ν of 250 mV s−1, and tm of 10 ms), the aSPCE/SDS showed a good linear response in the concentration ranges of 5.0 × 10−8–2.0 × 10−5 for PA, 1.0 × 10−9–2.0 × 10−7 for DF, and 1.0 × 10−8–2.0 × 10−7 and 2.0 × 10−7–2.0 × 10−6 mol L−1 for TR. The limits of detection obtained during the simultaneous determination of PA, DF, and TR are 1.49 × 10−8 mol L−1, 2.10 × 10−10 mol L−1, and 1.71 × 10−9 mol L−1, respectively. The selectivity of the aSPCE/SDS was evaluated by examination of the impact of some inorganic and organic substances that are commonly present in environmental and biological samples on the responses of PA, DF, and TR. Finally, the differential pulse adsorptive stripping voltammetric (DPAdSV) procedure using the aSPCE/SDS was successfully applied for the determination of PA, DF, and TR in river water and serum samples as well as pharmaceuticals.

Thallium is an element classified as a heavy metal. In chemical compounds it occurs on +1 and +3 oxidation levels. In the context of the toxicity of this element, Tl(I) is most often referred to. The similarity of Tl+ ions to K+ ions is the basis of the mechanism of toxic action of Tl(I) on the human body. The main features of thallium poisoning in humans are gastroenteritis, polyneuropathy and alopecia Thallium in the environment comes from both natural and anthropogenic sources. Due to the high toxicity of thallium and its easy absorption by the human and animal organisms, it is extremely important to monitor the amount of this element, including in water. The purpose of this work is to present a new method for determination of thallium in water samples using a screen-printed sensor with carbon working electrode modified with multiwalled carbon nanotubes and in-situ plated bismuth film. The measurements were carried out using square wave anodic stripping voltammetry (SWASV) method. Simultaneous deposition of bismuth and thallium took place at a potential of -0.9 V for 180 s. Under optimized conditions a linear calibration curve was obtained in the range of Tl(I) concentrations from 1·10-8 to 1·10-6 mol L-1. The procedure allows to achieve the limits of detection and quantification of Tl(I), 2.8 × 10-9 and 9.3 × 10-9 mol L-1 respectively. The method was applied for determination of Tl(I) in spiked water samples from Vistula river. [1] Kozak, J., Tyszczuk-Rotko, K., Rotko, M. Physicochemical Problems of Mineral Processing 2019 , 55(6), 1422-1428.

The subject of this study is a chemical compound called ethyl 8-(4-methoxyphenyl)-4-oxo-4,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3-carboxylate (EIMTC). This substance was found to have good bioavailability as well as low toxicity both in vitro and in vivo. This work presents for the first time a sensitive voltammetric procedure for the determination of a compound with anticancer activity in human serum using a screen-printed sensor with a carbon working electrode modified with carbon nanofibers. After optimizing the procedure, a linear calibration curve was obtained in two concentration ranges from 2 × 10-9 to 2 × 10-8 mol L-1 and from 2 × 10-8 to 2 × 10-7 mol L-1. The calculated limits of detection and quantification were 5.0 × 10-10 and 1.7 × 10-9 mol L-1 respectively. The method was applied for the determination of the EIMTC in human serum samples after the previous removal of the protein using trichloroacetic acid (TCA). [1] Tyszczuk-Rotko, K., Kozak, J., Sztanke, M., Sztanke, K., Sadok, I. Sensors 2020 , 20(18), 5217-5227.

The paper presents the interactions between rutin and nonionic surfactant Triton X-114 in ethanol, which were investigated by means of the UV–Visible spectrometry, fluorescence spectroscopy, speed of the sound, surface tension and adsorptive stripping voltammetric measurements. An attempt was made to examine the effect of flavonoid and surfactant concentration on the interactions between each compound in alcohol – water solutions. The obtained results show that the interactions in the examined mixtures change with the increase of the surfactant concentration in the solution and the surfactant adsorption capacity onto the electrode surface decreases over time and after micellization.