Quantitative application of the molecular absorption spectroscopy I: single component determination
The absorption of radiation by chemical species in solution is the basis of many quantitative analytical methods. In this process, the energy of the photons emitted by the radiation source, when absorbed by the analyte, causes a change from its state of lower energy (fundamental) to a state of highe...
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| Format: | Online |
| Language: | Portuguese |
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Universidade Estadual de Campinas
2024
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| Online Access: | https://econtents.sbu.unicamp.br/inpec/index.php/chemkeys/article/view/19959 |
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| Summary: | The absorption of radiation by chemical species in solution is the basis of many quantitative analytical methods. In this process, the energy of the photons emitted by the radiation source, when absorbed by the analyte, causes a change from its state of lower energy (fundamental) to a state of higher energy (excited) and, if the absorption of radiation occurs in the region UV-Vis, the observed phenomenon will have been caused by the electronic excitation of the absorbing species. Many compounds and ions in solution absorb in this range of the electromagnetic spectrum, where the main characteristic is the presence of very broad absorption bands. Furthermore, species that absorb little or nothing in this spectral region, if present, can interact with other molecules in the reaction medium and generate products that do so. Despite its limitations, molecular absorption spectroscopy is still widely used as an analysis method, routinely used in environmental, biological, industrial and forensic analyses. To associate theory with practice, this article presents a simple experimental guide, based on an experiment widely used in teaching activities, in which the spectrophotometric determination of iron in a real sample using the reagent 1,10-phenanthroline as a complexing agent is discussed. Based on the experimental results obtained during the laboratory practice, the parameters of a calibration curve that must be observed in quantitative determinations are detailed and the effects of experimental conditions on the linearity of Beer's Law are discussed. The practical utility of the proposed procedure is demonstrated in the quantitative determination of iron in a vitamin supplement sample.
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| ISSN: | 2595-7430 |
