Novel insights into solute non-uniformity in liquid-solid LIBS detection: Minimal impact on quantitative accuracy

Abstract

Accurate detection of heavy metals is crucial for ensuring water safety. However, the impact of sample preparation non-uniformity and different scanning strategies on liquid-solid Laser-induced Breakdown Spectroscopy (LIBS) detection has not been fully explored. This study comprehensively analyzes how various solute distribution characteristics, such as solute area, shape, and uniformity, as well as different scanning strategies, impact spectral stability and quantitative accuracy. The analysis was conducted through theoretical modeling, simulations, and experimental validation. Experimental results revealed that for nine samples with same concentrations but varying morphologies, the average spectral intensity fluctuation was only 2.74 %. The findings show that solute non-uniformity has a minimal effect on spectral intensity, offering valuable insights into the actual impact of solute distribution. Among the scanning strategies evaluated, namely full coverage scanning, solute region scanning, and internal matrix array scanning, the solute region scanning strategy demonstrated superior performance. Evaluated using cadmium (Cd), manganese (Mn), and chromium (Cr), this method achieved an average $R^2$ value of 0.992 and a detection limit (LOD) of 56.41 μg/L, representing a 43.40 % reduction in LOD compared to full coverage scanning. These results highlight the significance of optimizing scanning strategies over focusing solely on uniform solute distribution, paving the way for more effective and practical applications of LIBS in water quality monitoring.