Evaluation of laser-induced breakdown spectroscopy (LIBS) signal enhancement for liquid and soft solid samples from room to low temperature

Abstract Laser-Induced Breakdown Spectroscopy (LIBS) is commonly used to identify elements for solid samples. However, it is a challenging issue for liquid samples due to the liquid sample effect. In this study, the interaction of high-power lasers and soft solid or liquid samples at varying temperatures is evaluated with the purpose of enhancing LIBS signals. The effects of liquid samples on the LIBS spectrum were minimized by using the thermoelectric cooling system. The Peltier Thermoelectric Cooler (TEC) was utilized to solidify the liquid sample and maintain its freezing point throughout the LIBS data collection process with the addition of the temperature controller and sensor. The LIBS emissions were acquired with varying temperatures of each of the samples to obtain the enhanced LIBS signal. Three different soft solid or liquid samples were used in this work, which were animal fat, honey, and coconut water. The samples were selected as they exhibit different states of matter based on different temperatures: soft solid/liquid at room temperature and solid at freezing temperature. The temperatures of the samples that were investigated were 0 °C to 25 °C with an interval of 5 °C. The results are then evaluated based on the intensity of the peaks of each LIBS spectrum. It was found that the temperature of the sample has a significant influence on the LIBS spectra of the sample. The LIBS spectra of the samples improved significantly in their solid form compared to their soft solid or liquid form.