Highly sensitive determination of total chromium in seawater by inductively coupled plasma-mass spectrometry with sample introduction of ultrasound nebulization-dielectric barrier discharge vapor generation

A highly sensitive method for total chromium (Cr) determination in seawater by inductively coupled plasma-mass spectrometry (ICP-MS) with sample introduction of ultrasound nebulization-dielectric barrier discharge (UNDBD) vapor generation is proposed in this work. Using this sample introduction system, the sensitivity of Cr is increased 56 folds compared with the common pneumatic nebulization sample introduction system, and the interferences from the seawater matrix at 500 mg L⁻¹ level are all found negligible for trace Cr determination. With these advantages, this method is proved to be applicable for rapid and accurate determination of total Cr in seawater, requiring only the oxidation of Cr(III) to Cr(VI) and dilution steps, without the matrix separation steps. The experimental parameters for Cr determination including the Cr species, the sample volume, the spray distance, the carrier gas flow rate, and the solution pH are evaluated in detail. Under optimal conditions, the relative standard deviation for Cr is 1.9% at the concentration of 5 μg L⁻¹ and the detection limit for Cr is 0.004 μg L⁻¹. The proposed method is thus successfully applied to determine total Cr in certified reference seawater samples and real seawater samples, all with satisfactory results. Comparing with other sample introduction systems, the proposed UNDBD sample introduction system not only has a much lower detection limit for Cr, but also can be operated with low sample consumption (40 μL) and low power (70 W).