Determination of ultra-trace level Cr(vi) in seawater using large-volume direct injection by LC-ICP-MS with in-line matrix elimination

In this study, we aimed to improve the detection of hexavalent chromium (Cr(VI)) in seawater by using large volume injection and in-line matrix elimination device in conjunction with LC-ICP-MS. Firstly, the sample solution was introduced into the chromatographic separation system through a 1000 μL quantitative loop. Then, the chromatographically separated solution was precisely introduced into the ICP-MS for analysis at the time of the Cr(VI) peak (2.8–4.2 min) by the valve switch in the in-line matrix elimination. And the separation of Cr(VI) was performed on a Dionex IonPac AG7 analytical column (50 mm × 4 mm, 10 μm) with 60 mmol L⁻¹ NH₄NO₃ as the mobile phase at a flow rate of 1.0 mL min⁻¹ for 5 min. The detection limits (LOD) and limit of quantitation (LOQ) were found to be 0.002 and 0.007 μg L⁻¹, respectively. Method precision and accuracy were satisfactory at 3.5% relative standard deviations (RSDs) for 0.1 μg L⁻¹ of Cr(VI), and 90% ∼ 105% recoveries for real samples. The developed method was successfully applied for the analysis of Cr(VI) in environmental seawater samples.