Adsorption-desorption processes of aluminium, zinc and copper on plastic tubing in haemodialysis monitors

This study was performed to identify the source of contamination of dialysate with trace elements which had been observed in some haemodialysis centres in Slovenia. A possible explanation of this phenomenon was adsorption-desorption processes occurring on the plastic tubing in which dialysate was circulating in the haemodialysis monitors during dialysis. To confirm this, contamination of tubing with trace elements was simulated in vitro. After contamination, acetate or bicarbonate dialysates were prepared by the conventional procedure and samples of each dialysate collected in 1 ml fractions. Trace elements were measured by atomic absorption spectrometry. The haemodialysis tubing was contaminated for 0.5 or 4.5 h with 1.85 or 7.41 μmol/l of aluminium, 38.24 or 76.48 μmol/l of zinc and 7.87 or 15.74 μmol/l of copper. Steady state concentrations were reached after 5 min and ranged for aluminium from 0.18 to 0.67 μmol/l, for zinc from 0.31 to 0.92 μmol/l and for copper from 0.13 to 0.28 μmol/l in acetate dialysate, and 0.15 to 0.56 μmol/l of aluminium, 0.46 to 1.53 μmol/l of zinc and 0.06 to 0.47 μmol/l of copper in bicarbonate dialysate. The results suggested that adsorption-desorption processes are a probable source of contamination of the dialysate that could affect the health of haemodialysis patients.