Sequential-Pulse Laser-Induced Breakdown Spectroscopy of High-Pressure Bulk Aqueous Solutions

Abstract

Sequential-pulse (or dual-pulse) laser-induced breakdown spectroscopy (DP-LIBS) with an orthogonal spark orientation is described for elemental analysis of bulk aqueous solutions at pressures up to approximately 138 x 10(5) Pa (138 bar). The use of sequential laser pulses for excitation, when compared to single-pulse LIBS excitation (SP-LIBS), provides significant emission intensity enhancements for a wide range of elements in bulk solution and allows additional elements to be measured using LIBS. Our current investigations of high-pressure solutions reveal that increasing solution pressure leads to a significant decrease in DP-LIBS emission enhancements for all elements examined, such that we see little or no emission enhancements for pressures above 100 bar. Observed pressure effects on DP-LIBS enhancements are thought to result from pressure effects on the laser-induced bubble formed by the first laser pulse. These results provide insight into the feasibility and limitations of DP-LIBS for in situ multi-elemental detection in high-pressure aqueous environments like the deep ocean.

LIBS Analysis of Liquids and of Materials Inside Liquids

“…The corresponding lines become strong under DP excitation and the maximum enhancement was obtained for Dt = 18 ls. Similar results were reported in [75], where H and Zn lines originating from high excited states were detected only by DP excitation and over a limited range of interpulse delays corresponding to a large, already developed LFB. Systematic measurements of DP LIBS signal as a function of Dt for two collinear beams reveal a complex dependence [85] similar to that shown in Fig.…”

“…For these reasons, DP LIBS losses efficiency at high liquid pressures. The signal enhancement was almost absent above the static pressure of 100 bar for the bubble generated with a laser pulse of 30 mJ [75]. Here, it has been suggested that the pressure range for the LIBS signal enhancement by DP excitation might be achieved by an increase of the first pulse energy or by multi-pulse laser excitation, the both aimed to obtain a larger vapor bubble.…”

“…An increase of the static liquid pressures leads to a smaller radius and to a shorter lifetime of the LFB [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75]. As a result, the optimum Dt in DP laser excitation shifts towards shorter intervals.…”

Ultrasonic nebulization-sample introduction system for quantitative analysis of liquid samples by laser-induced breakdown spectroscopy

“…In order to overcome those difficulties experienced in liquid analysis, plasma formation on liquid surfaces [3,4], on droplets [5,6], on flowing-jet liquids [7,8] and in cavitation bubbles [9] has been employed. Use of double pulses for plasma formation [10][11][12] has also been realized in liquid analysis by LIBS, with high sensitivity. Aerosol formation by suitable nebulization techniques [13][14][15][16][17][18][19] is another approach to liquid analysis by LIBS.…”

Laboratory evaluation of laser-induced breakdown spectroscopy (LIBS) as a new in situ chemical sensing technique for the deep ocean

“…As a result, the highest intensity peaks that are observed occur when two pulses are close together, similar to a single pulse. Lawrence-Snyder et al [30] suggest that at higher solution pressures (8 x 107 Pa), the bubble formed by the first laser pulse is confined by its surrounding pressure. As a result, the bubble never expands to the maximum volume that is observed at lower pressures.…”