Detection of Hexavalent Chromium by Copper Sulfide Nanocomposites

Chromium (Cr) is a vital environmental contaminant. In environmental matrixes, Cr presents dominantly in hexavalent chromium [Cr(VI)] and trivalent chromium [Cr(III)], which are two different inorganic states. Cr(VI) is a well-known human carcinogen, while Cr(III) is a naturally occurring micronutrient for the human body. Hence, speciation of Cr is crucial for ensuring environmental water and food safety. The distinction between each chromium species is almost impossible with commonly used methods like atomic spectrometric techniques, due to the low level of Cr and the high complexity of the matrix. Typically, a preconcentration step is required prior to determining and improving the selectivity and detection limit of the inspection instrument. For this process, nanocomposites, which are emerging high-quality adsorbents are used. However, preparation of previous nanocomposites suffered from a trivial synthesis process, had high reagent consumption, and was time-consuming. Therefore, we succinctly designed and fabricated the novel triadic silica gel-supported copper sulfide (CuS) nanocomposites for ultrasensitive detection of Cr(VI). CuS nanocomposites in a solid phase system were successfully applied to extract Cr(VI) in reference materials, such as food and water samples. Cr(VI) were detected by use of flame atomic absorption spectrometry (FAAS). By loading 30 mL of sample solution, a linear range of 0.5-300 μg L^-1 with R = 0.998, a detection limit of 0.15 μg L^-1, and an accuracy of 1.7% (20 μg L^-1, n = 11) were obtained by this method. The detection limit and the precision of this procedure are superior to those reported in the literature with the same detection technique, indicating that CuS nanocomposites have a good potential for Cr(VI) detection which is essential for food safety and human health.