Some micro- and trace elements in selected bottled natural waters from the Polish market evaluated by electrochemical methods

Although beneficial properties of mineral waters are acknowledged by law in many countries, the use of water for medicinal purposes is not universally accepted. Notably numerous waters (especially mineral and curative ones) have high concentrations of mineral and trace elements. These mineral waters are common on the market and their availability is not regulated by law. Due to the hazard of overdosing, quantification of trace elements and minerals seems to be necessary. The World Health Organization, European Standards and Polish Standards recommend different methods for elemental determination, i.e. spectrometry, photometry for zinc determination, colorimetry or spectrometry for copper, and ionic chromatography for calcium, chloride and fluoride. In this paper, alternative, electrochemical methods have been applied to determine zinc, copper, calcium, chloride and fluoride in most popular natural and curative waters from southern Poland. The determined elemental content varied between 3.85-33.54 μg L-1 for zinc, 85-15.33 μg L-1 for copper, 2.8-2433.63 mg L-1 for chloride, 0.4-1.66 mg L-1 for fluoride and 11.05-478.48 mg L-1 for calcium. The voltammetric method was tested according to the validation procedures, taking into account the following parametes: linearity range, limit of detection and limit of quantification and precision. The results show that the applied electroanalytical methods are suitable for determination of the selected elements in waters of natural origin, ensuring low instrumental and analysis costs while providing results comparable with ones achieved with recommended methods.