Application of one-point calibration LIBS for quantification of analytes in samples with distinct matrix characteristics: a case study with Hg

Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique for elemental analysis, but matrix effects can significantly affect its accuracy. In this work, we propose the use of calibration-free LIBS (CF-LIBS) with the one-point calibration (OPC) method to reduce matrix effects in the quantification of mercury (Hg) for seven soil and eleven landfill leachate samples, with Hg concentration ranging from 50 to 1000 mg kg(-1). To improve sensitivity, we employed a double-pulse LIBS system with parameters optimized for each of the two sample matrices. A single soil sample was used to calibrate the OPC factors, which were then applied to the CF-LIBS calculations for the other samples. Using CF-LIBS corrected with the OPC method, we achieved an average error of 4.3% in the quantification of Hg for the two sample sets. This result indicates that these methods have the potential not only to reduce matrix effects but also to compensate for variations in LIBS system optimization for either matrix (soils and leachates) in the quantification of Hg. Therefore, the combination of these methods opens new possibilities for LIBS analyses, where the system can be optimized for each element and sample matrix, and the quantification can be performed with CF-LIBS, as long as the requirements for local thermodynamic equilibrium are fulfilled. Further studies with other elements, matrices, and measurement conditions are needed to validate and expand these findings.

Automated summary

In this study, calibration-free LIBS with the one-point calibration method was used to reduce matrix effects in the quantification of mercury in soil and landfill leachate samples. By optimizing the LIBS system parameters for each sample matrix and applying the OPC factors, an average error of 4.3% was achieved in the quantification of Hg.