Minimizing Matrix Effect by Femtosecond Laser Ablation and Ionization in Elemental Determination

Abstract

Matrix effect is unavoidable in direct solid analysis, which usually is a leading cause of the nonstoichiometric effect in quantitative analysis. In this research, experiments were carried out to study the overall characteristics of atomization and ionization in laser-solid interaction. Both nanosecond (ns) and femtosecond (fs) lasers were applied in a buffer-gas-assisted ionization source coupled with an orthogonal time-of-flight mass spectrometer. Twenty-nine solid standards of ten different matrices, including six metals and four dielectrics, were analyzed. The results indicate that the fs-laser mode offers more stable relative sensitivity coefficients (RSCs) with irradiance higher than 7 × 10(13) W·cm(-2), which could be more reliable in the determination of element composition of solids. The matrix effect is reduced by half when the fs-laser is employed, owing to the fact that the fs-laser ablation and ionization (fs-LAI) incurs an almost heat-free ablation process and creates a dense plasma for the stable ionization.

Laser Ablation/Ionisation Mass Spectrometry: Sensitive and Quantitative Chemical Depth Profiling of Solid Materials

“…[4,17,26,37] Since parameters such as size, power consumption and mass are highly limited on a spacecraft the LMS mass analyser has the dimensions of only 160 mm × 60 mm. the elements, [14,17] which together with the ability of clean material ablation [19][20][21][22] and high pulse-to-pulse reproducibility enable a laser ablation in a highly controlled manner. [4,17] So far, various LIMS systems have been designed and constructed specifically to investigate different scientific questions and for the application in variable environments, ranging from elemental mapping [8,23] to depth profiling analyses, [4,16] from laboratory [7,8,12,[14][15][16]24,25] instruments to instruments with the capability to operate on planetary objects.…”

“…[4,17] So far, various LIMS systems have been designed and constructed specifically to investigate different scientific questions and for the application in variable environments, ranging from elemental mapping [8,23] to depth profiling analyses, [4,16] from laboratory [7,8,12,[14][15][16]24,25] instruments to instruments with the capability to operate on planetary objects. [17,[26][27][28][29][30][31] However, and to our best current knowledge, only the designs from the research groups of Huang, [8,14,15,24] Cui et al, [16] and Wurz, [4,13,17,23,32] have reached the measurement capabilities and performance comparable to the state-of-the-art measurement techniques for chemical analysis with high spatial resolution. All these systems consist of a TOF mass analyser, a sophisticated detector system and are equipped with a femtosecond laser ablation/ionisation source and differ only in their technical realisation.…”

“…All these systems consist of a TOF mass analyser, a sophisticated detector system and are equipped with a femtosecond laser ablation/ionisation source and differ only in their technical realisation. In the following the LIMS systems from Cui et al [16] and the Huang group [8,14,15,24] are discussed only briefly. Readers should consult the listed references for further information.…”

“…data acquisition system) and laser systems with significantly increased performance, Laser Ablation/Ionisation Mass Spectrometry (LIMS) has proved, in the last decade, to be a truly alternative measurement technique for the sensitive and quantitative chemical investigation of solid materials with high spatial resolution and figures of merit comparable to state-of-the-art measurement techniques, such as SIMS, LA-ICP-MS or GD-TOF-MS. [4,7,[13][14][15][16] The implementation of ultrafast pulsed laser systems used as ablation and ionisation source with pulse widths within the femtosecond regime and pulse to pulse energy stability better than the %-level (e.g. CPA system, Clark-MXR Inc., USA) has allowed the measurement performance and capabilities of LIMS to be significantly increased.…”

“…CPA system, Clark-MXR Inc., USA) has allowed the measurement performance and capabilities of LIMS to be significantly increased. [4,14,17] In comparison to laser systems providing longer pulses the application of a femtosecond laser ablation/ionisation source has various analytical advantages, including e.g. minimised elemental fractionation due to reduced thermal heating of the sample material (heat affected zone, HAZ) [18] and the lack of interaction between the ejected plasma during the laser ablation process and the laser pulse.…”