Sub-ppb detection limit of Cr, Pb, and Cu in water by surface-enhanced LIBS with femtosecond laser

Water pollution caused by heavy metal contamination significantly threatens human health. Detecting trace levels of heavy metals in water is of utmost importance. Surface-enhanced laser-induced breakdown spectroscopy (SE-LIBS) has become a reliable detection method. In this study, we improved the analytical sensitivity of trace heavy metals in water by introducing femtosecond lasers into the SE-LIBS technique, replacing the traditional nanosecond lasers. An aluminum plate was utilized as a substrate to transform the liquid into a solid, overcoming the inadequacy in sensitivity and precision of LIBS when applied to water samples. We developed individual calibration curves for Cr, Pb, and Cu to determine their respective limit of detection (LOD). The LODs obtained were 0.3, 2.5, and 0.08 ng/mL for Cr, Pb, and Cu, respectively. These LODs were lower than traditional nanosecond SE-LIBS, and even lower than the LODs obtained by combining other LIBS enhancement techniques and SE-LIBS. We also determined good accuracy through the coefficient of determination R2, which was 0.97, 0.99, and 0.97, respectively, for Cr, Pb, and Cu. These results provide valuable and insightful information for the sensitive analysis of trace heavy metals in water using SE-LIBS with a femtosecond laser.