Chemistry Institute, UNICAMP, Campinas, Brazil.
Department of Chemistry and Biochemistry, The University of South Carolina, Columbia, USA.
Appl Spectrosc. 2021 Nov;75(11):1374-1381. doi: 10.1177/00037028211035439. Epub 2021 Aug 4.
This paper describes the effects of laser pulse rate and solution flow rate on the determination of lithium at high pressure for water and 2.5% sodium chloride solutions using laser-induced breakdown spectroscopy (LIBS). Preliminary studies were performed with 0-40 mg L Li solutions, at ambient pressure and at 210 bar, and in static and flowing (6 mL · min) regimes, for a combination of four different measurement conditions. The sensitivity of calibration curves depended on the pressure and the flow rate, as well as the laser pulse rate. The sensitivity of the calibration curve increased about 10% and 18% when the pressure was changed from 1 to 210 bar for static and flowing conditions, respectively. However, an effect of flow rate at high pressure for both 2 and 10 Hz laser pulse rates was observed. At ambient pressure, the effect of flow rate was negligible, as the sensitivity of the calibration curve decreased around 2%, while at high pressure the sensitivity increased around 4% when measurements were performed in a flow regime. Therefore, it seems there is a synergistic effect between pressure and flow rate, as the sensitivity increases significantly when both changes are considered. When the pulse rate is changed from 2 to 10 Hz, the sensitivity increases 26-31%, depending on the pressure and flow conditions. For lithium detection limit studies, performed with a laser pulse energy of 2.5 mJ, repetition rate of 10 Hz, gate delay of 500 ns, gate width of 1000 ns, and 1000 accumulations, a value around 40 µg L was achieved for Li solutions in pure water for all four measurement conditions, while a detection limit of about 92 µg L was determined for Li in 2.5% sodium chloride solutions, when high pressure and flowing conditions were employed. The results obtained in the present work demonstrate that LIBS is a powerful tool for the determination of Li in deep ocean conditions such as those found around hydrothermal vent systems.
本文描述了激光脉冲率和溶液流速对激光诱导击穿光谱（LIBS）测定高压下水和 2.5%氯化钠溶液中锂离子的影响。在环境压力和 210 巴下，对 0-40mg/L Li 溶液进行了初步研究，采用了四种不同测量条件下的静态和流动（6mL·min）两种模式。校准曲线的灵敏度取决于压力、流速以及激光脉冲率。对于静态和流动两种条件，当压力从 1 增加到 210 巴时，校准曲线的灵敏度分别增加了约 10%和 18%。然而，在 2 和 10Hz 激光脉冲率下，均观察到高压下流速的影响。在环境压力下，流速的影响可以忽略不计，因为校准曲线的灵敏度下降了约 2%，而在高压下，当采用流动模式进行测量时，灵敏度增加了约 4%。因此，似乎存在压力和流速之间的协同效应，因为当同时考虑这两个变化时，灵敏度会显著增加。当脉冲率从 2 增加到 10Hz 时，灵敏度会根据压力和流速条件增加 26-31%。对于使用激光脉冲能量为 2.5mJ、重复率为 10Hz、门延迟为 500ns、门宽为 1000ns 和 1000 次累积的锂检测限研究，在所有四种测量条件下，纯水的 Li 溶液达到约 40μg/L，而在高压和流动条件下，Li 在 2.5%氯化钠溶液中的检测限约为 92μg/L。本工作的结果表明，LIBS 是一种强大的工具，可用于测定深海环境（如热液喷口系统周围的环境）中的 Li。
