Detection of Low Lithium Concentrations Using Laser-Induced Breakdown Spectroscopy (LIBS) in High-Pressure and High-Flow Conditions

Abstract

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−1 Li solutions, at ambient pressure and at 210 bar, and in static and flowing (6 mL · min−1) 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−1 was achieved for Li solutions in pure water for all four measurement conditions, while a detection limit of about 92 µg L−1 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.

Underwater determination of calcium and strontium ions in oilfield produced water by laser-induced breakdown spectroscopy (LIBS)

“…The signal increase as a function of the pulse repetition is also shown in Fig. 8, and the results are in accordance with those previously described by Raimundo et al , 8 who proposed the formation of an emulsion of gas bubbles in the liquid, facilitating the formation of the plasma, with a consequent increase in its temperature, therefore increasing the emission signal. This statement was ratified by Young et al , 35 who verified by means of a shadowgraph that microbubbles are formed after the cavitation bubble has collapsed, lasting for a few seconds.…”

“…This result is related to the fact that higher repetition rates produce a greater number of bubbles, which can impair laser focusing, decreasing the energy of the pulse, and affecting the sensitivity of the measurements. 8 Regarding the SNR shown in Fig. 8c and d, higher values were obtained at repetition rates above 7 Hz with a laser pulse number above 60.…”

“…6 Based on this scenario, the use of sensing technologies or the exploration of conditions in ordinary laboratories of analyses with the objective of developing these technologies is a remarkable perspective to solve problems of industrial interest. [7][8][9] Therefore, technologies that allow realtime monitoring of the ionic composition of water are of great benet to the oil industry.…”

Laser-induced breakdown spectroscopy for quantitative lithium monitoring in geothermal brines for lithium extraction

“…While LIBS is known for its sensitivity to Li, its application in liquid analysis has traditionally been limited due to rapid plasma cooling and subsequent signal attenuation [10]. To address these limitations, recent studies have explored innovative approaches such as creating aerosols or jets from the liquid [11; 12] or employing double-pulse laser techniques to enhance LIBS performance in liquid analysis [13].…”