In this study, the peroxidase-like activity of zirconium (IV) oxide nanoparticles (nZr) is reported. Peroxidases catalyze the oxidation of their substrate in the presence of peroxide species. 3,3′,5,5′-tetramethylbenzidine (TMB) is a peroxidase substrate, and we have demonstrated that nZr oxidizes the TMB in the presence of hydrogen peroxide resulting in a colored (TMBox) product. The reaction was tested in various buffers, and sodium acetate with pH 4 was observed to be an ideal buffer for the enzymatic reaction and the dispersity of the nZr in the solution. The nanozyme behavior was studied systematically at three different temperatures (25, 35 and 45 °C) and a wide range of H2O2 concentrations. The dependence of the enzymatic reaction on temperature, nZr content and H2O2 concentration was observed. The enzymatic reaction was tested in different protein solutions and no noticeable interference was observed with these proteins. Overall, we demonstrate that nZr, which is often used for industrial applications, mimics peroxidase enzyme and catalyzes oxidation of its substrate in the presence of peroxide species.

Naturally produced hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been extensively studied in the lower end of the Baltic Sea food web. Certain OH-PBDE congeners have displayed increasing concentrations over the last 30 years in herring (Clupea harengus) from the Baltic proper. However, studies on the top carnivores in the Baltic Sea are scarce. Quantitative data on OH-PBDEs exist for ringed seal (Pusa hispida) from the Gulf of Bothnia, but only a limited amount of data have been produced with regard to Baltic grey seal (Halichoerus grypus), and seals from the Baltic proper. A method was developed and evaluated for quantification of OH-PBDEs in coagulated whole blood. The method was applied on blood obtained from dead grey seals originating from different parts of the Baltic Sea. The levels of OH-PBDEs were observed to be low in the analyzed seals in comparison with reported levels in white-tailed sea eagle nestlings (Halizeetus albicilla), and some Baltic fish species. The levels of the dominant congener, 6-OH-BDE47, were statistically significantly higher in seals from the Baltic proper than in seals from the Gulf of Bothnia. Hydroxylated polychlorinated biphenyls (OH-PCBs) were observed to be of much higher concentration than the OH-PBDEs in the analyzed seals. The average concentration of the dominant OH-PCB congener, 4-OH-CB107, was one order of magnitude greater than that of 6-OH-BDE47.

A combined approach of target, suspected target and non-target screening using liquid chromatography –high-resolution mass spectrometry (LC–HRMS) was used to develop a new concept for water monitoring. With the current LC–MS/MS target approach for water monitoring, all targets can be quantified, but no additional information about the sample is collected. With the new concept, it is possible to detect 97% of the target compounds with a simplified quantification method without losing accuracy. Furthermore, a suspect target screening can be performed to get broader qualitative information about the water samples. In addition, the non-target screening offers the possibility to identify unknown micropollutants. All three evaluation steps depend on the same analytical measurement so that a lot of measurement and quality assurance effort can be saved. This concept could change water monitoring and assessment, and make it much more efficiently without losing information. There is a chance to measure less but learn more about the water bodies.

This study describes the preparation of zinc oxide nanoparticle–chitosan as a solid-phase adsorbent for separation and preconcentration of trace amount of chromium and nickel from environmental water samples and their determination by inductively coupled plasma optical emission spectrometry. Important factors including pH, amount of adsorbent, amount of 1-(2-pyridylazo)-2-naphthol, sample volume, eluent concentration and extraction time were investigated and optimized. The equilibrium data according to the Freundlich’s and Langmuir models were processed. The results showed that the equilibrium data were well fitted with Langmuir isotherm model. The best fit of adsorption kinetics was attained with a second-order equation. Under the optimum conditions, the detection limits for chromium and nickel were 0.041 and 0.039 µg L−1, respectively, and the relative standard deviations (RSD %) were 1.5% and 1.3% (n = 10, c = 50 µg L−1) for chromium and nickel, respectively. This procedure was then used for preconcentration and determination of target compounds from environmental water samples.

Using C4–C25 fatty acid methyl esters (C4–C25 FAMEs) as a sample reference series, a method was developed to generalize the reference system for calculating the second dimension retention index (2I) of compounds analyzed by comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC–MS). The second dimension elution temperature (2Te), second dimension unadjusted retention time (2tR), and the linear retention index (IT) of C4–C25 FAMEs were used to form a second dimension retention index surface (2IS) via a three-dimensional surface fitting model. The 2I of an analyte analyzed by GC × GC–MS was then calculated from the 2IS based on its 2tR and 2Te. The developed method was validated by calculating the 2I of n-alkanes, 80 compounds, and two commercially available mixtures (MegaMix A and MegaMix B). Compared to the conventional method, the developed method keeps the 2I in n-alkane retention index scale, and enables using any compounds as references to obtain a much increased separation space in the second dimension GC.

The zwitterionic compound, levofloxacin, was determined for the first time at different pH values in pure samples, pharmaceutical preparations and spiked serum and urine samples. Different types of potentiometric sensors including poly (vinyl chloride) membrane electrode, carbon paste electrode and screen printed electrode, containing the ion pair levofloxacinium-phosphomolybdate as the electroactaive species, were used for this purpose. The effect of pH is the key factor in determining the ratio of the different species that can exist in the medium (zwitterionic, monocationic, dicationic, anionic and neutral), and so it is the controller of the electrochemical performance. The different sensors were fully characterized and optimized in terms of composition, pH effect, selectivity, response and lifetimes. The different sensors showed reliable reversibility and could be utilized for the determination of the drug in real spiked physiological fluids with reliable recovery values.

The development of transition metal complex-based luminescent chemosensors has recently aroused increasing interest for protein biomarker labelling and detection, especially for the real-time diagnosis and treatment of disease. This is owing to their unique photophysical properties, particularly their long-lived and environmentally sensitive emission, which can be easily controlled via the structural modification of ligands. In this overview, we highlight recent examples of protein biomarker detection using group 8–9 metal-based luminescent chemosensors, including the frequently employed ruthenium(II) and iridium(III) complexes. Various mechanisms and sensing modes are described and compared, and the outlook and future directions of this field are discussed as well.

We report on a highly sensitive chemiluminescence (CL) assay for the detection of specific DNA sequence, where streptavidin-modified polystyrene microspheres (PS–SA) coupled with hybridization chain reaction (HCR) were employed as dual amplification platform. Briefly, a “sandwich-type” detection strategy was proposed in our design, which involved capture probe DNA immobilized on the surface of carboxyl-terminated magnetic beads (MB) and the reporter DNA combined with the HCR trigger immobilized on the surface of PS–SA. After that, two hairpin-type monomers were added to initiate the HCR. In the detection system, CL signal was obtained via the instantaneous derivatization reaction between 3,4,5-trimethoxylphenylglyoxal (TMPG) and guanine bases in the target and the HCR complex binding on the magnetic beads. As compared to traditional sandwich type (capture/target/reporter) assays, this dual-amplified strategy for sequence-specific DNA detection showed better specificity, lower detection limit and wider linear response range (linear range of 0.01 fmol–10 pmol and a low detection limit of 5 amol). Moreover, this approach could be easily extended to detect a wide range of specific DNA sequences by modification of the hybridization region. We believe this simple technique will present a significant step towards early diagnoses of diseases.

We reported an unprecedented chemiluminescence (CL) behavior of polyamine-functionalized carbon dots induced by Fe3+–H2O2 Fenton-like system. The first-step CL intensity increased with the increasing of the concentration of H2O2 and Fe3+, when the Fe3+ concentration came to 10−3 M, the unprecedented two-step CL behavior appeared. The CL intensity of BPEI-CDs induced by Fenton-like system was about 10 times stronger than that of naked CDs. The possible two-step CL mechanism was speculated based on the photoluminescence spectra, CL emission spectra, and the effects of radical scavengers on the CL intensity. Radiative recombination of the injected holes by strong oxidant perferrate formed through Fe3+–H2O2 reaction and the ·OH generated from successive Fenton reaction with the thermally excited electrons was proposed, which further facilitate full understanding about the optical properties of carbon dots.