ONLINE SEPARATION AND SPECTROPHOTOMETRIC DETERMINATION OF LOW-LEVELS OF ALUMINUM IN HIGH-SALT CONTENT SAMPLES - APPLICATION TO ANALYSIS OF HEMODIALYSIS FLUIDS

An on-line preconcentration and matrix separation procedure for the sp ectrophotometric determination of low levels of aluminum in aqueous an d high-salt content matrices was developed. Aluminum was preconcentrat ed on polyethylene powder as a complex with Chrome azurol S and, after elution, the complex was spectrophotometrically determined, without i nterference of the matrix. The assayed salts were sodium, potassium, m agnesium and calcium chlorides and sodium acetate, usually employed in hemodialysis fluids. A polyethylene powder column was incorporated to the flow system by using a microcolumn as the loop of a six-port valv e connected to an injector and to the spectrophotometric detector. Eff ects of eluent composition and concentration, reactor length and influ ence of the presence of salts on the preconcentration and elution step s were investigated. The proposed method was characterized by a precis ion of about 90% and a detection limit of 17 ng Al (6x10(-10) mol). Re coveries from spiked samples of the salts were between 87-110%, and re sults were in agreement with determinations by graphite furnace atomic absorption spectrometry. The method was applied to the analysis of sa line concentrates and water for hemodialysis. (C) 1998 Elsevier Scienc e B.V.