Automatic On-line Solid-phase Extraction–Electrothermal Atomic Absorption Spectrometry Exploiting Sequential Injection Analysis for Trace Vanadium, Cadmium and Lead Determination in Human Urine Samples

Abstract

A fully automated sequential injection column preconcentration method for the on-line determination of trace vanadium, cadmium and lead in urine samples was successfully developed, utilizing electrothermal atomic absorption spectrometry (ETAAS). Polyamino-polycarboxylic acid chelating resin (Nobias chelate PA-1) packed into a handmade minicolumn was used as a sorbent material. Effective on-line retention of chelate complexes of analytes was achieved at pH 6.0, while the highest elution effectiveness was observed with 1.0 mol L⁻¹ HNO₃ in the reverse phase. Several analytical parameters, like the sample acidity, concentration and volume of the eluent as well as the loading/elution flow rates, have been studied, regarding the efficiency of the method, providing appropriate conditions for the analysis of real samples. For a 4.5 mL sample volume, the sampling frequency was 27 h⁻¹. The detection limits were found to be 3.0, 0.06 and 2.0 ng L⁻¹ for V(V), Cd(II) and Pb(II), respectively, with the relative standard deviations ranging between 1.9 – 3.7%. The accuracy of the proposed method was evaluated by analyzing a certified reference material (Seronorm^TM trace elements urine) and spiked urine samples.