Fish samples. The fish were bought from local supermarket in Poland. The fish stored at 20 C prior analysis. Then the muscle
fishes were separated and freeze-dried. For lead analysis 0.5 g of the samples was digested in 6 mL of concentrated nitric acid using a microwave mineralizer (time: 10 min, power: 100%, max. pressure 45 atm). Next, the digested samples were diluted to a final volume of 50 mL with deionised water, and Pb(II) ions were preconcentrated using the DMSPE procedure described above.