Quantitative analysis of sodium in aqueous samples using laser-induced breakdown spectroscopy with a thermoelectric cooler as the sample preparation method

In this work, a microcontroller-based thermoelectric cooler (TEC) system was proposed as a sample pretreatment method to freeze liquid samples prior to laser-Induced breakdown spectroscopy (LIBS) analysis. Initially, direct laser irradiation of liquid and frozen NaCl solutions were analyzed, and later analyses were focused on laser irradiation of the frozen NaCl solutions under different temperatures. The direct irradiation on aqueous NaCl was carried out at concentrations ranging from 0.2 to 2.5 mol/L. The irradiation of the frozen NaCl solutions showed a much lower detection limit (2.5x), higher signal-to-noise ratio (S/N) (3x), and improved precision and accuracy. The analysis of the frozen NaCl solutions at different temperature led to higher S/N as the temperature was kept constant at the freezing point of -1, -2, and -3 °C for each 0.2, 0.5, and 1.0 mol/L frozen samples, respectively