Effect of Sodium Chloride Concentration on Elemental Analysis of Brines by Laser-Induced Breakdown Spectroscopy (LIBS)

Abstract

Leakage of injected carbon dioxide (CO2) or resident fluids, such as brine, is a major concern associated with the injection of large volumes of CO2 into deep saline formations. Migration of brine could contaminate drinking water resources by increasing their salinity or endanger vegetation and animal life as well as human health. The main objective of this study was to investigate the effect of sodium chloride (NaCl) concentration on the detection of calcium and potassium in brine samples using laser-induced breakdown spectroscopy (LIBS). The ultimate goals were to determine the suitability of the LIBS technique for in situ measurements of metal ion concentrations in NaCl-rich solution and to develop a chemical sensor that can provide the early detection of brine intrusion into formations used for domestic or agricultural water production. Several brine samples of NaCl-CaCl2 and NaCl-KCl were prepared at NaCl concentrations between 0.0 and 3.0 M. The effect of NaCl concentration on the signal-to-background ratio (SBR) and signal-to-noise ratio (SNR) for calcium (422.67 nm) and potassium (769.49 nm) emission lines was evaluated. Results show that, for a delay time of 300 ns and a gate width of 3 μs, the presence of and changes in NaCl concentration significantly affect the SBR and SNR for both emission lines. An increase in NaCl concentration from 0.0 to 3.0 M produced an increase in the SNR, whereas the SBR dropped continuously. The detection limits obtained for both elements were in the milligrams per liter range, suggesting that a NaCl-rich solution does not severely limit the ability of LIBS to detect trace amount of metal ions.

Development of laser-induced breakdown spectroscopy sensor to assess groundwater quality impacts resulting from geologic carbon sequestration

“…24 This paper reviews the work carried out in our laboratory to obtain high-precision quantitative data on trace mineral composition of aqueous solutions using single-pulse LIBS measurements. We demonstrate that LIBS can 1) perform trace metal quantification in freshwater samples, 2) analyze highly saline brines, as might be found in sub-surface aquifers 22 , and 3) measure elemental concentrations at elevated temperatures and pressures that might be present in subsurface aquifers. 23 Having shown the applicability of the LIBS for sensing trace metals in aqueous solutions, we introduce fabrication of an experimental laser unit capable of carrying out real-time LIBS measurements in downhole environment.…”

“…21 In fact, generation of the laser spark and the subsequent LIBS analysis in liquid samples is more difficult, as compared to solid and gas sample analysis. [22][23] However, a number of researchers have used double-pulsed LIBS to overcome some of those limitations. 24 This paper reviews the work carried out in our laboratory to obtain high-precision quantitative data on trace mineral composition of aqueous solutions using single-pulse LIBS measurements.…”

EXPRESS: Effects of Ambient Temperature on Laser-Induced Plasma in Bulk Water

“…Indeed, some studies have paid close attentions to the hydrostatic pressure and salinity effects on underwater LIBS, due to the fact that the pressure has great impact on the plasma expansion, collision, and quenching process, 11–13 and salinity is primarily related to the matrix effect of LIBS. 14–16…”

Sensitive determinations of Cu, Pb, Cd, and Cr elements in aqueous solutions using chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy

“…However, the detection sensitivity of LIBS is still unsatisfactory when directly analyzing liquid samples because it suffers from several problems, e.g., water splashing, surface ripples, and quenching of intensity [7,8]. To address these problems, various sampling configurations including liquid flow [9,10] . Although a limit of detection (LoD) of 6 μg/g for manganese (Mn) could be achieved, the static liquid-liquid microextraction as a pretreatment method requires additional reagents and the whole sample preparation time is longer than 15 minutes.…”