Abstract
The analysis of hexavalent chromium, Cr(VI), in soil and sediment samples has been predominantly carried out in materials containing elevated levels. Reliable analysis of trace-level of Cr(VI) in sediment samples remains challenging. Cr(VI) analyses with multipoint calibration and speciated isotope dilution (SID) adapted from U.S. EPA method 6800 were used to measure lower-level Cr(VI) on an ion chromatograph coupled with a tandem mass spectrometer (IC-MS/MS). Lake sediment samples were collected from various locations in Northern Ontario and Cr(VI) was extracted using both alkaline digestion and ethylene diaminetetraacetic acid (EDTA) extraction. Certified reference materials were extracted and analyzed by IC-MS/MS and UV-VIS detection. The SID-MS approach allowed for the quantification of Cr(VI) in samples with concentration levels below 0.5 μg.g-1 wet weight.
Highlights
Chromium has been heavily used in metallurgical, chemical and refractory industries, for example for the production of stainless steel, chrome-plating or leather tanning
Anion exchange chromatography allowed for the separation of the two chromium species from each other and from most interfering inorganic and organic sample components
Considering an extraction volume of 0.05 L, a sample amount of 2.5 g and a dilution factor of 100 to reduce chromatographic interferences with extraction solvent used for alkaline digestion, this value translates to 0.014 μg∙g−1 wet weight Cr(VI) in solid matrices
Summary
Chromium has been heavily used in metallurgical, chemical and refractory industries, for example for the production of stainless steel, chrome-plating or leather tanning. Simultaneous complexation of Cr(III) by EDTA further stabilizes the chromium species equilibrium as it minimizes the oxidation of the trivalent metal ion. The SID-MS strategy has been shown to compensate for species interconversion during alkaline digestion based on U.S EPA 3060A for NIST standard reference materials (SRM), aggregate materials and sediments [33]. The latter were found to contain very little to no Cr(VI). Alonso and coworkers successfully applied the SID-MS approach in combination with IC-ICP-MS to NIST standard reference materials containing high levels of Cr(VI) and demonstrated the efficiency of the extraction solvent EDTA in complexing Cr(III) and preventing its oxidation [24]. Linear calibration curves, as well as an adapted SID-MS approach were applied
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