Laser ablation-ICP-MS: particle size dependent elemental composition studies on filter-collected and online measured aerosols from glass

Abstract

In laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), the term elemental fractionation is normally used to summarize all non-stoichiometric effects occurring during sample ablation, aerosol transport and vaporization, atomisation and ionisation within the ICP. Nevertheless, there are different types of elemental fractionation occurring between different sized particles within an aerosol, as previously shown for metal alloy ablations. In the present work, laser generated aerosols from glass samples were filter collected before entering the ICP to study their total and particle size dependent composition. Furthermore, elemental concentrations in different particle size fractions on filters were compared with their response measured in the ICP. For the NIST SRM 610 glass, elemental fractionation effects between small particles (v125 nm and v340 nm), and the total aerosol containing all particle sizes up to 1 mm or even larger, were measured for 42 major and trace elements using a 266 nm Nd:YAG laser and scanning ablation conditions to produce the aerosol. Particles above 125 nm and 340 nm were separated from the aerosol by a particle separation device and the remaining particles were collected on a filter, digested and measured using solution nebulization ICP sector field MS (SFMS). Results show an enrichment of certain elements such as Cu, Zn, Ag, Tl, Pb and Bi of up to 90% relative to Ca within the small particle size fraction of an aerosol in comparison with the total composition of the aerosol. The same elements are depleted in large aerosol particles measured from deposited particles within the ablation cell. However, the total transportable aerosols produced using different laser wavelengths (193/266 nm), and gas environments (He/Ar), which were also filtered and digested show no significant deviation in their overall stoichiometry from the original sample (except Be, Fe, Cd for all lasers and gases) within the uncertainty of the measurements. Therefore, the composition of filter collected aerosol of glass samples indicates that the elemental fractionation in LA-ICP-MS, detected at the beginning of a 266 nm single hole ablation, is predominantly caused by incomplete vaporization of large particles within the ICP and is not dominated by non-stoichiometric ablation of the glass. 1 1 5 8 J . A n a l . A t . S p e c t r o m . , 2 0 0 4 , 1 9 , 1 1 5 8 -1 1 6 4 T h i s j o u r n a l i s ß T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4 J . A n a l . A t . S p e c t r o m . , 2 0 0 4 , 1 9 , 1 1 5 8 -1 1 6 4 J . A n a l . A t . S p e c t r o m . , 2 0 0 4 , 1 9 , 1 1 5 8 -1 1 6 4 View Article Online J . A n a l . A t . S p e c t r o m . , 2 0 0 4 , 1 9 , 1 1 5 8 -1 1 6 4 J . A n a l . A t . S p e c t r o m . , 2 0 0 4 , 1 9 , 1 1 5 8 -1 1 6 4

Inductively coupled plasma- and glow discharge plasma-sector field mass spectrometry : Part II. Applications

“…124 The analysis of CaF 2 , glass, quartz, ceramics, and other multi-component materials is hampered due to spectral interferences, which can be overcome by high mass resolution. [125][126][127][128] This was also recognised as an example for quality control in the steel industry, e.g., for the determination of phosphorus in steel and for the determination of 14 trace elements in cement. 129,130 Multi-element analysis of materials and objects in the context of forensic studies or provenance determination has been described in literature as well.…”

Development of an On-line Low Gas Pressure Cell for Laser Ablation-ICP-Mass Spectrometry

“…Even with a low laser energy fluence (< 1 J/cm 2 ), numerous signal spikes can be found in the measured intensity profile, suggesting the introduction of particles larger than the critical size into the ICP. 6,7 It should be noted that the signal stabilizer device, which acts as a particle filter, was used with the present system. Even with the stabilizer device, signal spikes could not be fully removed, and the number of signal spikes increased with a higher laser pulse energy, and therefore we could not apply a laser fluence of higher than 1 J/cm 2 .…”

“…10,18 For brass and glass materials, it is recognized that the total elemental composition of all transported particles represents the bulk composition of the solid sample, whereas individual particles possess a different elemental composition (deviating from the bulk composition). 6,19,20 Non-uniform gas flow in the large volume of an ablation cell can also cause an unstable signal intensity profile, 9,16 which indicates that the preferential introduction of a certain size of sample aerosol can cause elemental fractionation. Moreover, large-sized particles can pass through the ICP into the sampling orifice without being totally vaporized.…”

“…The size distribution of the sample aerosol is a critical parameter for the complete evaporation, atomization or ionization of the analytes; ablated particles larger than 150 nm for glass samples 6 and 400 nm for metals 7 are not completely vaporized and ionized in the ICP. The particle size distribution is a function of various parameters such as, the laser wavelength, [8][9][10][11] laser irradiance, 12,13 laser pulse length, 13,14 depth of the crater, cell geometry [15][16][17] or the type of carrier gas.…”

Evaluation of the Analytical Capability of NIR Femtosecond Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

“…12 However, even with the UV lasers, serious elemental fractionation occurs during laser ablation. It is recognized that the differences in elemental volatility, [6][7][8]13,14 or time-dependent changes in the particle size distribution [15][16][17][18][19] can cause elemental fractionation. Moreover, there are several other causes of elemental fractionation, such as differences in the transport efficiency of the particles, mass loading onto the ICP or amount of re-deposition.…”