"Multivariate calibration and differential kinetic analysis in flow systems with spectrophotometric detection" / "Calibração multivariada e cinética diferencial em sistemas de análises em fluxo com detecção espectrofotométrica"

AUTOR(ES)

Paula Regina Fortes

DATA DE PUBLICAÇÃO

2006

RESUMO

Differential kinetic analysis can be implemented in a flow system analyser, and this was demonstrated in designing an improved spectrophotometric catalytic determination of iron and vanadium in Fe-V alloys. The method relied on the influence of Fe2+ and VO2+ on the rate of the iodide oxidation by Cr2O7 under acidic conditions; therefore the Jones reductor was needed. To this end, a flow injection system (FIA) and a multi-pumping flow system (MPFS) were dimensioned and evaluated. In both systems, the alloy solution was inserted into an acidic KI solution that acted also as carrier stream, and a dichromate solution was added by confluence. Successive measurements were performed during sample passage through the detector, each one related to a different yet reproducible condition for reaction development. Data treatment involved multivariate calibration by the PLS algorithm. The FIA system was less recommended for multi-parametric determination, as the laminar flow regimen could not provide suitable kinetic information. On the other hand, a MPFS demonstrated that pulsed flow led to enhance figures of merit due to chaotic movement of its fluid elements. The proposed MPFS system is very simple and rugged, allowing 50 samples to be run per hour, meaning 48 mg KI per determination. The first two latent variables carry ca 94 % of the analytical information, pointing out that the intrinsic dimensionality of the data set is two. Results are in agreement with inductively coupled argon plasma – optical emission spectrometry.

ASSUNTO(S)

multi-pumping flow system métodos catalíticos catalytic methods flow analysis spectrophotometry espectrofotometria multi-impulsão mínimos quadrados parciais partial least squares cinética diferencial differential kinetic analysis sistemas de análises em fluxo

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