Selective Determination of Cr(VI) by FAAS After Solid Phase Extraction on Bis(3-aminopropyl)amine-Bonded Silica Gel

In this study, a novel method was developed for the selective determination of Cr(VI) based on column solid phase extraction (SPE) using bis(3-aminopropyl) amine-bonded silica gel (BAPASG). To optimize the SPE procedure, the effects of various variables, including pH, sample volume, eluent type and volume, matrix ions and sample flow rate, were studied. The column SPE studies showed that BAPA-SG could selectively collect Cr(VI) ions at the pH of 2.0 from a sample volume up to 1000 mL in the presence of Cr(III). The recovery of the Cr(VI) ions was not affected by anions and cations widely found in environmental water samples. Adsorbed Cr(VI) on the column could be easily eluted using 5.0 mL of a 2.0M HCl solution. Cr(VI) adsorption dynamics onto BAPA-SG were also studied batch-wise by investigating the effects of contact time, initial Cr(VI) concentration, and temperature. Increasing the temperature showed adverse effects on the adsorption of Cr(VI). A Langmuir model best fit the experimental data. The maximum adsorption capacity was 75.5 mg g(-1). The developed SPE procedure was successfully applied to the determination of Cr(VI) in spiked solutions by flame atomic absorption spectrometry. The pre-concentration factor of 200 permitted a detection limit of 0.11 ng/mL.