Determination of trace elements in a large series of spent peritoneal dialysis fluids by atomic absorption spectrometry

An analytical procedure is reported for the determination of six elements in a large series of spent dialysis fluid samples. Determinations of aluminium, chromium, copper, manganese and iron were made by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman background correction, while zinc was analysed by flame atomic absorption spectrometry (FAAS). Because of the complex matrix with high salt content and a high content of proteins, the measurement parameters were optimised for each particular element determined by ETAAS. The samples were collected in polyethylene eppendorf cups and stored in a freezer at −20°C. When the elements were determined by ETAAS the standard addition method was applied in the calibration procedure. The sample (10 μl) was injected into a cuvette and careful drying and long ashing of samples at temperatures between 850 and 1000°C performed. Triton X-100 was added before each determination to reduce the matrix effects of the proteins. Zinc was determined by FAAS in an air–acetylene flame under the usual recommended procedure, calibrating with aqueous standards. The limits of detection (3σ basis) were 1.0 μg l⁻¹ for aluminium, 0.20 μg l⁻¹ for chromium, 0.40 μg l⁻¹ for copper, 0.20 μg l⁻¹ for manganese, 0.50 μg l⁻¹ for iron and 5.0 μg l⁻¹ for zinc. The reproducibility of the measurements for aluminium, copper, iron and zinc was better than ±3.0%. It was worse for manganese and chromium (±6.0 and ±12.0%, respectively), since these two elements were present in very low concentrations in all the samples analysed.