Advancements in Chromium Analysis: Highly Sensitive Determination of Total Chromium in Seawater

Researchers from the University of Toyama in Japan and Qingdao National Laboratory for Marine Science and Technology in China developed a highly sensitive method for determining total chromium (Cr) in seawater using inductively coupled plasma-mass spectrometry (ICP-MS) with a novel sample introduction system known as ultrasound nebulization-dielectric barrier discharge (UNDBD) vapor generation (1). Their work was published in Spectrochimica Acta Part B: Atomic Spectroscopy, which explains how their method significantly improves chromium detection (1). The significance of this study is that the method introduced eliminates the need for complex matrix separation steps (1).

a person swimming in the ocean with corals and anemones on their sides photo by shutterstocker | Image Credit: © Golib Tolibov - stock.adobe.com

UNDBD vapor generation is a sample introduction system used in conjunction with ICP-MS for sensitive analysis of trace elements. The system employs ultrasonic nebulization to generate a fine aerosol mist from the sample solution (1). Then, the mist is integrated into a dielectric barrier discharge region; in this region, the aerosol droplets are vaporized and converted into a plasma state efficiently (1). The plasma that comes from this process is then placed inside the ICP-MS instrument for elemental analysis (1).

The research team proposed a new method that carries several benefits. As an example, the method allows for a 56-fold increase in sensitivity for chromium detection (1). Second, the new method allows for chromium detection at high seawater concentrations of 500 mg/L because it resolves seawater matrix interferences, which was an issue in previous methods (1). Third, the amount of sample preparation is needed is significantly reduced (1).

Several chromium determination experimental parameters were evaluated. These variables include chromium species, spray distance, solution pH, sample volume, and carrier gas flow rate (1). Under optimal conditions, the method achieved a relative standard deviation of 1.9% at a concentration of 5 μg/L and a detection limit for Cr as low as 0.004 μg/L (1). These results demonstrated that the method used in this study showcased excellent sensitivity (1).

To test whether their approach would be applicable, the research team used the UNDBD-ICP-MS method to test for chromium in certified reference seawater samples and real seawater samples (1). The results showed that improved detection limits for chromium can be realized with low power requirements (70 W) and minimal sample consumption (40 μL) (1).

This new detection method has important ramifications when studying marine ecosystems. Being able to detect complex chromium allows scientists to track the health of our oceans, which in turn allow them to see how chromium contamination is impacting oceans (1). By using this new method, the research team hopes that it could pave the way for the development of effective mitigation strategies that could help preserve our oceans for future generations (1).

Reference

(1) He, Q.; Li, C.; Zhang, J. 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. Spectrochimica Acta Part B: At. Spectrosc. 2023, 206, 106728. DOI: 10.1016/j.sab.2023.10672