Speciation analysis of inorganic antimony in soil using HPLC-ID-ICP-MS

Speciation analysis of Sb(III) and Sb(V) in a soil sample was performed through extraction and on-line isotope dilution concentration determination after a chromatographic separation. The total Sb concentration found in a through traffic contaminated soil sample was (4.17 mu g g(-1), 0.3 mu g g(-1) SD, n=6). It was determined using ICP-MS after soil digestion using the sodium peroxide sintering method. The optimized extraction procedure for speciation analysis was carried out using 100 mmol L-1 citric acid at pH 2.08 by applying an ultrasonic bath for 45 min at room temperature. The effects of citric acid concentration (0-500 mmol L-1), pH (1-6), and temperature (30-60 degrees C) on inorganic antimony species distribution in the examined sample were studied and optimized. The separation of Sb(III) and Sb(V) was achieved using an anion exchange column (PRP-X100) and 10 mmol L-1 EDTA and 1 mmol L-1 phthalic acid at pH 4.5 as a mobile phase. The eluent from the HPLC was mixed with an enriched (94.2%) Sb-123 spike solution that was pumped by a peristaltic pump with a constant flow rate (0.5 mL min(-1)) in a three-way valve. The blend passed directly to the Conikal nebulizer of the ICP-MS. By using the above extraction procedure and methodology, 43.2% Sb(V) (2.9% RSD, n=3) and 6.0% Sb(III) (1.3% RSD, n=3) of total Sb found in the sample could be detected. The detection limits achieved by the proposed method were 20 ng L-1 and 65 ng L-1 for Sb(V) and Sb(III), respectively. The precision, evaluated by using RSD with 100 ng L-1 calibration solutions, was 2.7% and 3.2% (n=6) for Sb(V) and Sb(III), respectively, in aqueous solutions.