Optimisation of parameters for determination of rubidium in spent CAPD fluids by flame and electrothermal atomic absorption spectrometry

An analytical procedure is reported for the determination of rubidium in sp ent continuous ambulatory peritoneal dialysis (CAPD) fluids by flame and el ectrothermal atomic absorption spectrometry (FAAS, ETAAS). Samples of spent CAPD fluids were collected as 5 mi aliquots in polyethylene tubes and stor ed in a freezer at - 20 degrees C. Before analysis, samples were equilibrat ed to room temperature and analysed within 8 h. A total of 2 mg ml(-1) of c aesium was added to each sample and standard solution to overcome interfere nces from ionisation. An air-acetylene flame was applied in FAAS determinat ions. Analysis was performed against aqueous standards. The calibration gra ph was linear from 30.0 up to 5000 mu g l(-1) Rb, while the limit of detect ion (3 s) was found to be 20.0 mu g l(-1) rubidium. Good repeatability of m easurement (RSD 1%) was obtained. Parameters were also optimised for determ ination of rubidium in spent CAPD fluids by ETAAS. Ten-fold diluted samples (3.5% nitric acid) were analysed applying standard addition calibration. T he calibration graph was linear from 2.0 up to 30.0 mu g l(-1) rubidium, wh ile the limit of detection (3 s) was found to be 1.0 mu g l(-1) rubidium (s ample volume 10 mu l). Good repeatability of measurement (RSD 5%) was obtai ned. The results of direct determination by FAAS and ETAAS were compared to those obtained after acid digestion of samples in Parr bombs. The accuracy of the procedure for direct determination was checked by spiking samples. In 73% of samples analysed, the differences between the results obtained by the two techniques, either for direct determinations of samples or for sam ples digested in a Parr bomb did not exceed +/- 10%. (C) 1999 Elsevier Scie nce B.V. All rights reserved.