Detection of chromium in different valence states in water and soil using laser-induced breakdown spectroscopy combined with an ion enrichment chip

In the environment, chromium usually exists in both the trivalent and hexavalent states. Cr(VI) is of particular concern because it is highly toxic. However, it remains challenging to conduct field detection for trace concentrations of different valence states of Cr. Here, we propose a method based on laser-induced breakdown spectroscopy (LIBS) combined with an ion enrichment chip (IEC) to rapidly and sensitively detect the total Cr and Cr(VI) in water and soil. This method was termed IEC–LIBS. A chip with a millimetric channel was used for separating and enriching total Cr and Cr(VI) and LIBS was used for detection. The limits of detection (LoDs) of total Cr and Cr(VI) in water were 10 μg L−1 and 4 μg L−1, respectively, and the recoveries from spiked pool water ranged from 90 to 114%. The method also had good quantitative ability for soil detection, with total Cr and Cr(VI) LoDs of 13.6 mg kg−1 and 3.8 mg kg−1, respectively. The detection sensitivity of this method met the Cr environmental quality standards in China, and the detection time was within 20 min. IEC–LIBS is a simple and environmentally friendly method for detecting trace Cr in different valence states, and it is expected to be useful for field application.