Spark Discharge–Facilitated LIBS Coupled with Electrodeposition for Highly Sensitive Detection of Chromium Within Aqueous Matrices

In this study, electrodeposition (ED) combined with a spark discharge-facilitated laser-induced breakdown spectroscopy—referred to as SD-LIBS—was employed for highly sensitive detection of trace chromium (Cr) in aqueous solutions. First, trace Cr ions in water were preconcentrated on the outer surface of an ultra-pure aluminum base by ED, effectively addressing the issue of poor detection sensitivity when LIBS is applied directly to liquid samples. Subsequently, SD-LIBS was employed for the analysis of the chromium (Cr) deposited on the aluminum (Al) exterior, where the spark discharge significantly enhanced the emission intensities of the Cr (I) spectral lines centered at 425.43 nm, 427.48 nm, and 428.90 nm. Based on the calibration curves obtained from standard solutions, the limits for the detection (LoD) with respect to chromium (Cr) under different discharge voltages were determined. With the elevation of discharge voltage over the 0–2 kV range, the LoDs of the neutral chromium (Cr) line I corresponding to 425.43 nm and 428.90 nm, the concentration levels of 3.86 n and 5.13 ng decreased to 1.19 ng and 1.57 ng, respectively, with all values referenced per milliliter. These results demonstrate that spark discharge further improves the detection sensitivity of LIBS in aqueous environments. Overall, the combined ED+SD-LIBS approach exhibits excellent analytical performance for trace metal detection in water, offering promising potential for water quality monitoring applications.