Handling complex effects in slurry-sampling-electrothermal atomic absorption spectrometry by multivariate calibration.

Analysis of solid samples by slurry-sampling-electrothermal atomic absorption spectrometry (SS-ETAAS) can imply spectral and chemical interferences caused by the large amount of concomitants introduced into the graphite furnace. Sometimes they cannot be solved using stabilized temperature platform furnace (STPF) conditions or typical approaches (previous sample ashing, use of chemical modifiers, etc.), which are time consuming and quite expensive. A new approach to handle interferences using multivariate calibrations (partial least squares, PLS, and artificial neural networks, ANN) is presented and exemplified with a real problem consisting on determining Sb in several solid matrices (soils, sediments and coal fly ash) as slurries by ETAAS. Experimental designs were implemented at different levels of Sb to develop the calibration matrix and assess which concomitants (seven ions were considered) modified the atomic signal mostly. They were Na+ and Ca2+ and they induced simultaneous displacement, depletion (enhancement) and broadening of the atomic peak. Here it is shown that these complex effects can be handled in a reliable, fast and cost-effective way to predict the concentration of Sb in slurry samples of several solid matrices. The method was validated predicting the concentrations of five certified reference materials (CRMs) and studying its robustness to current ETAAS problems. It is also shown that linear PLS can handle eventual non-linearities and that its results are comparable to more complex (non-linear) models, as those from ANNs.

Slurry sampling for direct analysis of solid materials by electrothermal atomic absorption spectrometry (ETAAS). A literature review from 1990 to 2000.

The determination of trace metals in solid samples has traditionally been performed by acid digestion and subsequent measurement by a suitable instrumental technique. This dissolution step is time-consuming and it shows important drawbacks. For these reasons, in the past years many efforts have been focused on the direct analysis of solid samples. Among the developed methodologies, slurry sampling-electrothermal atomic absorption spectrometry combines the significant advantages of the solid and liquid sampling methods, and it can be already considered as a mature technique, that is widely utilized for metal determination in both organic and inorganic matrices, even for routine analysis. Accordingly, this work gives a retrospective view of the progresses of this technique during the past decade (1990-2000).