Abstract

In the present study, an on-line preconcentration system for the determination of Cd and Zn was developed. This system involves solid-phase extraction of metals using a minicolumn filled with Amberlite XAD-2 modified with 2-(5-bromo-2- pyridylazo)-5-diethylaminophenol (Br-PADAP) and detected by flame atomic absorption spectrometry (FAAS). After the preconcentration step, hydrochloric acid was used in the elution process, in order to transport the analytes directly to the spectrometer flame. A Doehlert design was used to optimize the variables involved in the preconcentration performance. The developed system provides enrichment factors of 30 and 88 fold, limit of detection of 0.63 and 0.38 µgL^-1 and precision (RSD, 20.0 µgL^-1, N = 10) of 4.3 and 5.4% for Cd and Zn, respectively. The optimized procedures were applied in the determination of Cd in fertilizer samples and Zn in drinking water. Accuracy was accessed by Cd determination in a certified reference material (NIST SRM 1573a, tomato leaves) and using a spike test for zinc in water samples. A test was applied to compare the results obtained in this study with the values of the certified reference materials and the results are not significantly different (95% confidence level), which confirms the accuracy of the developed procedures.

Keywords: Doehlert design, solid-phase extraction, XAD-2/Br-PADAP resin, cadmium, zinc.

Graphical Abstract