Abstract
A new method was developed in this work to account for inorganic Sb species interconversion during soil sample preparation and subsequent separation steps. The Sb(III) and Sb(V) concentrations at each investigated step in the analytical procedure were determined using species specific spikes (121Sb(III) with 81.18% and 123Sb(V) with 74.04% enrichment). The spiking of these enriched isotopes species solutions was done separately before soil sample extraction and before HPLC separation. Simply by subtracting the final concentration of each species done by on-line isotope dilution (ID) from its concentration at different stages of the analytical procedure done by species specific ID, the influence of each step on species transformation can be estimated. After optimization, the extraction procedure for inorganic Sb species 6% Sb(III) (1.3 RSD, n = 3) and 43.2% Sb(V) (2.9% RSD, n = 3) as percent of total Sb were detected in the examined soil sample using online ID. Using the above described methodology we found that there was no reduction of Sb(V) to Sb(III) during sample preparation or species separation. While about 9.3% of extractable Sb (4.6% of total) was converted from Sb(III) to Sb(V) during the extraction step, no conversion during HPLC separation step was observed. By compensating for Sb(III) transformation during the sample preparation step; the extractable Sb(III) and Sb(V) as percent of total Sb yielded 10.6% and 38.7%, respectively.
Highlights
Antimony and its compounds are considered to be priority pollutants by Environmental Protection Agency of the United States (USEPA) and European Union (EU) [1] Sb toxicity depends on its oxidation state; Sb(III) compounds are ten times as toxic as Sb(V) compounds [2,3]
By subtracting the final concentration of each species done by on-line isotope dilution (ID) from its concentration at different stages of the analytical procedure done by species specific ID, the influence of each step on species transformation can be estimated
The high accuracy and precision provided by ID-ICP-MS in the species-specific spiking mode can used to correct for the majority of systematic errors occurred in speciation analysis
Summary
Antimony and its compounds are considered to be priority pollutants by Environmental Protection Agency of the United States (USEPA) and European Union (EU) [1] Sb toxicity depends on its oxidation state; Sb(III) compounds are ten times as toxic as Sb(V) compounds [2,3]. The sample preparation is the most challengeable step of the analytical speciation procedures preventing that reliable enough speciation results can be achieved routinely This statement refers specially to the speciation of elements in the solid samples where the major difficulty is not the quantification itself but the quantitative extraction of those compounds from the complex solid sample matrix without degradation or species transformation [8]. Evaluating and correcting for these species transformations in the sample preparation step could be attained if a spike solution containing inorganic antimony species isotopically labeled with different antimony isotopes This can not be done in a similar way to previous studies which applied SIDMS successfully for the elements having more than two naturally isotopes like Cr [12], since Sb has only two isotopes. The influence of each step on species transformation can be estimated by subtracting the final concentration of each species done by on-line ID from its concentration done by species specific ID at the investigated step of analytical procedure
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