Laser-induced breakdown spectroscopy assisted by acoustic levitation (LIBS-AL) for the calibration-free quantification of elements of interest in liquids – Case study of mineral waters

Bottled water is an essential commodity in modern life, and monitoring its composition is a critical necessity for public health; a task usually time-consuming with the current analytical techniques, when multi-elemental analysis is required. In this study, Laser-Induced Breakdown Spectroscopy assisted by acoustic levitation (LIBS-AL) was employed for the first time to quantify the elemental composition of complex liquid samples. This technique enables the analysis of liquid samples without interference or contamination from containers or substrates, allowing elemental quantification without any conventional pretreatment. This study was conducted using three bottled mineral water samples manufactured in Slovakia and the Czech Republic. Important minerals such as alkali (Na, K, Li) and alkali earth metals (Ca, Mg) were identified in the LIBS spectra and quantified by using calibration-free (CF-LIBS) approach for the first time in levitated liquid samples. The results demonstrated a good agreement with the reported values, with relative error in the concentrations between 3 and 27 % for the major elements (Na, Ca, Mg), while higher relative errors were noted for trace elements (Li, K). These findings validate the reliability of this methodology for monitoring liquid composition in a fast and environmentally friendly way, avoiding sample preparation steps with additional reagents or chemical waste during spectroscopic analysis.