This study presents a detailed methodology, which combines high-precision thermogravimetry and FTIR spectroscopy, aiming to establish the most accurate and reliable means of measuring the molar absorption coefficients of adsorbed species. As the integrated molar absorption coefficients of Py complexes with Brønsted and Lewis acid sites, ɛ(Py-B) and ɛ(Py-L), are determined and the validity of the Beer-Lambert-Bouguer law for IR characterisation of solid acids is demonstrated, this work is setting a benchmark for the quantitative acidity measurements in zeolites and related materials. The following values of ɛ(Py-B) have been obtained at 150°C (band at ~1545 cm-1): 1.09±0.08 cm µmol-1 for ZSM-5; 1.12±0.16 cm µmol-1 for BEA; 1.29±0.04 cm µmol-1 for MOR and 1.54±0.15 cm µmol-1 for FAU. The value of ɛ(Py-L) (band at ~1455 cm-1 , which refers to different cations) measured at the same temperature is 1.71±0.1 cm µmol-1. Values of ɛ(Py-B) depend on the zeolite structure, in contrast to that for ɛ(Py-L). Clear correlations are presented between the temperature of the FTIR measurements and ɛ values for Py complexes and other species, which decrease by ~10% as the temperature increases by 100 o C. In addition, the effects of key experimental procedures, instrumentation design and sample preparation are established and quantified.
Selfplasticized, lumogallion-based fluorescent optical sensor for the determination of aluminium (III) with ultra-low detection limits, Analytica Chimica Acta,
We report on the development of a simple and cost-effective potentiometric sensor array that is based on manual “drawing” on the polymeric support with the pencils composed of graphite and different types of zeolites. The sensor array demonstrates distinct sensitivity towards a variety of inorganic ions in aqueous media. This multisensor system has been successfully applied to quantitative analysis of 100 real-life surface waters sampled in Mahananda and Hooghly rivers in the West Bengal state (India). Partial least squares regression has been utilized to relate responses of the sensors to the values of different water quality parameters. It has been found that the developed sensor array, or electronic tongue, is capable of quantifying total hardness, total alkalinity, and calcium content in the samples, with the mean relative errors below 18%.
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