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 mumol/l of aluminium, 38.24 or 76.48 mumol/l of zinc and 7.87 or 15.74 mumol/l of copper. Steady state concentrations were reached after 5 min and ranged for aluminium from 0.18 to 0.67 mumol/l, for zinc from 0.31 to 0.92 mumol/l and for copper from 0.13 to 0.28 mumol/l in acetate dialysate, and 0.15 to 0.56 mumol/l of aluminium, 0.46 to 1.53 mumol/l of zinc and 0.06 to 0.47 mumol/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.