Multielemental Laser-Enhanced Ionization Spectrometry for the Determination of Lead at the Trace Level in Pelletized Coal Using Laser Ablation and Internal Standard Signal Normalization

Abstract

Laser ablation laser-enhanced ionization (LA-LEI) was used for the simultaneous measurement of lead and indium in pelletized graphite and coal samples. UV Laser ablation of the solid samples was performed in an ablation cell and the ablated material was carried by a flow of gas to a miniature LEI flame where lead was detected. The influence of parameters such as binder content of the solid pellets and dispersion of the analytes spiked in the sample material, as well as the number of ablation pulses per crater on signal repeatability and on the size and shape of ejected particles was examined. Measurement repeatability values of 2 to 5% of relative standard deviation were obtained using indium as an internal standard to correct for variations in the ablation rate. A limit of detection of 120 nanograms per gram was calculated for the determination of Pb in high-purity graphite. The Pb concentration in the NIST 1632c Bituminous Coal certified reference material was determined to within 1% of its certified value, using graphite as the matrix-matching material and In as the internal standard in pelletized solid samples.

Study by focused shadowgraphy of the effect of laser irradiance on laser-induced plasma formation and ablation rate in various gases

“…low irradiance (Figs. [3][4][5] are very similar between all three gases. In this energy range, the plasma seems to expand as a blast wave producing a shockwave which is visible, in the case of argon and air, from 40 ns onward.…”

“…laser ablation) coupled to one among a variety of detection techniques (ICP-MS, ICP-OES, LEI, etc.) [1][2][3][4] or to provide the combined functions of sample ablation/vaporisation and thermal excitation in a laser-induced plasma (i.e. LIBS) [5][6][7].…”

Use of sol–gels as solid matrixes for laser-induced breakdown spectroscopy

“…The most popular approach involves the preparation of targets by mixing a suitable solid matrix with analytes in aqueous or solid form, followed by pelletization in an hydraulic press, either without a binder [11] or using KBr [12], powdered Ag [13], cellulose [14], graphitic carbon [15] or even glue [16]. However, many reports have questioned the reliability of the approaches described above, due to the signal fluctuations caused by the inhomogeneous dispersion of the spiked elements in the solid targets.…”

Prospects in analytical atomic spectrometry

“…216, 221 ± 223 As the laser-induced plasma creates high temperature and high densities of charged particles, one may opt to separate the sampling from the signal registration either temporally 221,222 or spatially. 216,223 In the latter case, the product of laser ablation (aerosol) is carried by the argon flow into the miniature flame where the LEIS signal is generated. This concept is similar to LA-ICP-MS and LA-ICP-AES.…”