With the growing interest in new applications of metals in modern technologies, an increase in their concentration in the environment can be observed, which, in consequence, may constitute a hazard to human health. That is why it is of a great importance to establish “reference” levels of particular elements (essential or toxic) in human biological samples.The aim of this paper was to determine nickel in autopsy tissues of non-occupationally exposed subjects in Southern Poland (n = 60). Measurements were performed by means of electrothermal atomic absorption spectrometry after microwave-assisted acid digestion according to previously optimized and validated procedure. The results obtained indicate that data cover the wide range of concentrations and generally are consistent with other published findings. Nickel levels in the brain, stomach, liver, kidneys, lungs and heart (wet weight) were between 2.15–79.4 ng/g, 0.5–44.2 ng/g,7.85–519 ng/g, 12.8–725 ng/g, 8.47–333 ng/g and 2.3–97.7 ng/g, respectively. Females had generally lower levels of nickel in tissues than males (statistically significant relationships were found for the liver, kidneys and lungs), and median nickel concentrations in all studied material within all age groups had very similar values, with the exception of stomach.

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 concentration range of 0.1–10.0 µmol L⁻¹ (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L⁻¹ for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4–101.6%.

A novel calibration methodology named ‘the generalized calibration strategy’ (GCS) is presented that is aimed at verifying and improving the accuracy of analytical determinations. It is based on integration of calibration methods together with such operations as standard addition and sample dilution. At each stage of the sample dilution, the analytical result is estimated on the basis of six values, which are differently resistant to errors caused by interference and non-linearity effects. The process of stepwise elimination of both effects is controlled by comparison of these values. A dedicated flow system is presented. The GCS can be adapted to calibration by all well-known methods: conventional, internal standard, and indirect. This novel calibration strategy has been tested on indirect determination of chlorites in water samples by UV/Vis spectrophotometry.