Determination of Lithium in Lithium-Ionic Conductors by Laser-Enhanced Ionization Spectrometry with Laser Ablationстатья
Статья опубликована в высокорейтинговом журнале
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 13 марта 2014 г.
Аннотация:Laser-enhanced ionisation (LEI) with laser ablation (LA) into a methane-air flame was used for lithium determination in ferrites. Since there is a lack of certified reference materials, matrix-matched to ferrites powders, a set of spinel samples were synthesised by means of aerosol spray pyrolysis (ASP) or by annealing the mixture of Li and Fe (III) nitrates. Characterisation by X-ray diffraction showed that the annealed ceramics contained two phases, such as either α-LiFe5O8 and Fe2O3 or α-LiFeO2 and Fe2O3, while ASP ferrites consisted mainly of α-LiFe5O8. Total lithium content in samples was certified by conventional flame photometry after dissolution. We explained strong matrix effects on LA-LEI signal by the discrepancy of surface microstructure (and hardness) due to the difference in the conditions of sample preparation. Optoacoustic signal and emission line of Fe I at 382 nm were recorded simultaneously with LA-LEI signal in order to compensate for matrix effects. We suggest that the microstructure (ceramics or pellets from spherical microparticles) influences both mass removal (proportional to OA signal) and plasma temperature (proportional to AE signal). Correlation plot between OA and AE signals was deviated strongly from sample to sample, which was the basis for the application of a multivariate correction procedure to reduce strong matrix effects. 3D correlation plots (LEI vs. OA+AE) for each sample were built to obtain a new analytical signal, which represented a slope of correlation line to the plane of OA+AE signals. This normalised signal was free from matrix effects within a concentration range of 0.6-7.5 Li%. The proposed approach allows the use of ferrites synthesised by the various techniques as reference materials in order to build a unified calibration curve.