The relationship between the mercury concentration in fish muscles and scales/fins and its significance

The determination of mercury in fish typically involves analysis of muscles. For predicting the concentration of mercury in fish muscle on the basis of the analysis of fish scales or fins, the relationship between total mercury concentrations in fish muscles and in fish scales and fins was studied. Mercury content in fish muscles, scales and fins was determined by atomic absorption spectrometry with thermal decomposition of the sample in a flow of oxygen. A number of scale treatments were applied in order to remove impurities and to enhance the prediction quality. For scale treatment, 40 min of washing with DI water in an ultrasonic bath is recommended. A coefficient of determination r²= 0.93 for the relationship between Hg concentrations in muscles and scales was achieved for 40 fish among the different fish species tested (European bream, perch, roach) from the Hamry Reservoir, Czech Republic. With respect to fin sampling, the coefficient of determination r² for these fish was 0.86. The analysis of fish scales and caudal fins is a useful screening tool for assessing the relative mercury contamination of monitored fish. The method of sampling scales is not suitable for fish species with small scales such as brown trout.      

Determination and identification of synthetic cannabinoids and their metabolites in different matrices by modern analytical techniques – a review

Synthetic cannabinoids have gained popularity due to their easy accessibility and psychoactive effects. Furthermore, they cannot be detected in urine by routine drug monitoring. The wide range of active ingredients in analyzed matrices hinders the development of a standard analytical method for their determination. Moreover, their possible side effects are not well known which increases the danger.     

Improving the detection limit in capillary isotachophoresis using asymmetric neutralisation reaction boundary

An online method involving transient electrokinetic dosing and ITP with neutralization reaction boundary (NRB) and/or carrier ampholyte-free isoelectric focusing (CAF IEF) was developed for the preconcentration, preseparation, and analytical determination of glyphosate in aqueous samples containing low concentrations of the analyte of interest. Various parameters were investigated in the framework of an optimization study with the aim of achieving the maximum concentration limit of detection (cLOD) decrease in minimum time. The proposed method used CAF IEF and/or ITP with NRB. The sample was dosed to the column on the stationary reaction boundary (CAF IEF) and/or moving reaction boundary (ITP with NRB), whereat a sharp pH step exists. Here, charge reversal was due to the ampholytes, and/or acid accumulation occurred because of charge loss. Similarly, the accumulated sample was mobilized with TE and analyzed using classical ITP in the second analytical column. Glyphosate (GLY), the analyte of interest, was chosen as a model substance for ITP with NRB and preconcentration as well as focusing preconcentration and CAF IEF using the asymmetric purpose-built NRB. On one side of the asymmetric boundary was the zone of acidic pH; while the opposite side comprised a neutral/basic non-conductive zone of the ampholyte—in this case, GLY. Such an arrangement enables the use of a lower pH on the acidic side, which allows the focusing of strongly acidic ampholytes and the accumulation of weak acids. The electrolyte composition and the dosing time were optimized, and a 14-fold accumulation was achieved in 25 min compared to that by classical ITP and a 180-fold accumulation was achieved through CAF IEF and preconcentration with a glyphosate sample. Both methods are simple and can be conducted using all commercial ITP systems.     

On the Energy Growth of Some Periodically Driven Quantum Systems with Shrinking Gaps in the Spectrum

We consider quantum Hamiltonians of the form H(t)=H+V(t) where the spectrum of H is semibounded and discrete, and the eigenvalues behave as E _n ∼n ^α , with 0<α<1. In particular, the gaps between successive eigenvalues decay as n ^α−1. V(t) is supposed to be periodic, bounded, continuously differentiable in the strong sense and such that the matrix entries with respect to the spectral decomposition of H obey the estimate ‖V(t) _m,n ‖≤ε|m−n|^−p max {m,n}^−2γ for m≠n, where ε>0, p≥1 and γ=(1−α)/2. We show that the energy diffusion exponent can be arbitrarily small provided p is sufficiently large and ε is small enough. More precisely, for any initial condition Ψ∈Dom(H ^1/2), the diffusion of energy is bounded from above as 〈H〉 _Ψ (t)=O(t ^σ ), where . As an application we consider the Hamiltonian H(t)=|p| ^α +ε v(θ,t) on L ²(S ¹,dθ) which was discussed earlier in the literature by Howland.     

Removal of chlorinated solvents from carbonate-buffered water by zero-valent iron

The performance of a ground level reactive cell, filled with Fe⁰, designed for the treatment of water contaminated by chlorinated solvents, having a total input concentration of approximately 2 mg 1⁻¹ of the principal contaminants trichloroethene and perchloroethene, was tested at the Milovice site in the Czech Republic. A residence time of 1.62 days in the box was sufficient to reduce concentrations to a fraction less than 0.015 of the initial concentration. However, incomplete degradation of cis-1,2-DCE was observed. Reactions approximated first-order kinetics. The principal changes of concentrations of inorganic dissolved species in the reactive cell occurred for Ca²⁺, HCO ₃ ⁻ , NO ₃ ⁻ (decreased) and for Fe (initially increased, then decreased). Changes for Ca²⁺ and HCO ₃ ⁻ were caused by the precipitation of secondary carbonate mineral phases such as aragonite and siderite with the minor presence of green rust-CO₃. Concentration changes were gradual, along the complete length of the cell with a maximum at the inlet zone. The observations were attributed to minor increases of pH and slow kinetics of precipitation in the carbonate-buffered system. The average porosity loss was estimated to be approximately 2.7 % of the initial porosity per year, suggesting the long-term function of the permeable reactive barrier.      

The non-newtonian creeping flow around a rotating spheroidal spindle

The rotational flow in a region bounded by two axisymmetric closed surfaces has been studied by variational methods. The approach is described in detail for the global power-law representation of a viscosity function. Numerical, as well as simple, analytical results applicable to immersion rotational viscometry are given for the spheroidal geometry of bounding surfaces.     

Optical single-particle detection in nanoholes towards simple parallel detection of molecular binding events

A novel scheme for the optical detection of a few or even single gold nanoparticle labels is introduced. It utilizes sub-wavelength holes in a chromium layer on a glass substrate, where a bioaffinity reaction could take place and the outcome (regarding particle label binding) can be monitored using optical means. Experiments in combination with simulations demonstrate that the presence of particles in such a chromium hole can be simply detected by using the color information of images by a charge couple device (CCD) camera without the need for additional spectroscopy setups. The presence of gold nanoparticles leads to a detectable red-shift in the images of the respective nanohole, which is the sensing principle of the sensor.