Bone disease in long-term hemodialysis patients with low dialysate aluminium

Speciation of Al in human serum by convective-interaction media fast-monolithic chromatography with inductively coupled plasma mass spectrometric detection

A new analytical procedure using anion-exchange separation support based on convective-interaction media (CIM) was developed for the speciation of Al in human serum. The separation of proteins was performed on a weak anion-exchange CIM diethylamine (DEAE) fast-monolithic disk. To prevent co-elution of low molecular mass (LMM) Al species with high molecular mass (HMM) Al compounds on CIM disk serum proteins were first separated from LMM-Al species by the use of size exclusion chromatography (SEC). For this purpose 1 mL of serum was injected onto SEC (Superdex 75 HR 10/30) column. Isocratic elution using 0.05 M TRIS-HCl+0.03 M NaHCO(3) was applied and separation of proteins was followed by UV detection at 278 nm. It was experimentally proven that proteins were eluted in 5.5 mL peak that was collected into a polyethylene cup. A 0.1 mL of the sample aliquot was then injected onto the CIM DEAE disk. The separation of serum proteins was obtained in 10 min by applying linear gradient elution from 100% buffer A (0.05 M TRIS-HCl+0.03 M NaHCO(3)) to 100% buffer B (A+1M NH(4)Cl) and followed by UV detection at 278 nm. Separated Al species were detected on-line by inductively coupled plasma mass spectrometry (ICP-MS). Well-resolved protein peaks were obtained. It was experimentally proven that 90+/-3% of Al in spiked serum of renal patient was eluted under the transferrin peak. The proposed speciation procedure removes LMM-Al species and enables reliable determination of the concentration and composition of Al bound to proteins by CIM DEAE-ICP-MS when the concentration of Al in serum is higher than 5 ng mL(-1). In comparison to chromatographic columns CIM disks enable faster separation and simpler manipulation during cleaning procedure and coupling to ICP-MS.

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.