Study on Enhancing the Quantitative Performance of LIBS for Cu Element in Liquids Based on the Chitosan-Parafilm Enrichment Method

Abstract

Abstract To enhance the accuracy of laser-induced breakdown spectroscopy (LIBS) in detecting heavy metal elements in solutions, a Chitosan (CS)-Parafilm (PM) enrichment method is proposed. This method involves drying chitosan-heavy metal complexes on a Parafilm substrate. During the drying of droplets, electrostatic attraction and chelation by CS effectively concentrate analytes. Additionally, the hydrophobic effect of the PM substrate induces Marangoni flow, which drags analytes from the bottom edge to the central top of the droplet surface, effectively suppressing the coffee ring effect (CRE).LIBS spectra were collected in a uniform array on the surface of sediments, and spectral stability was assessed through cumulative excitation spectra measurements. The results showed that the spectral stability of emission lines Cu I 324.754 nm and Cu I 327.396 nm decreased to 3.85% and 3.78%, respectively, indicating that the CS-PM enrichment method allows for uniform deposition of analytes within samples, effectively enhancing detection repeatability.Quantitative analysis of Cu elements using the CS-PM enrichment method was conducted using PSO-SVM, PSO-BPNN, and RF algorithms. The RF algorithm demonstrated the best predictive performance with Rp² of 0.979, RMSEP of 4.60 mg/L, MAE of 3.19 mg/L, and RPD of 6.75. These results indicate that CS-PM effectively improves spectral stability and quantitative analysis accuracy, providing a technical reference for enhancing the stability and quantitative performance of element analysis in liquids using LIBS.