Development of quantitative analytical methods using diffuse reflectance in the UV-visible

• Grant number: 05/01531-3
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2006
• End date: March 31, 2009
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
• Principal Investigator: Matthieu Tubino
• Grantee: Matthieu Tubino
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Reflectance quantitative methods, in visible range of the spectrum, have been studied in our laboratory there is already some time. We have also constructed a very simple portable reflectometer for quantitative analysis that can be used also in spot-test procedures (Matias, Vila e Tubino, 2003; Tubino, Rossi e Magalhães, 1997 ).The first article we published about this subject (Tubino, Rossi e Magalhães, 1997) was well received in the Analytical Chemistry community. It caused the appearing of other related works (Ghauch et al., 1999, 2000; Gotardo et al. 2004). Apparently, this article o four authorship is one of the first, maybe the first, describing a quantitative analytical method using diffuse reflection in the visible. Observing the literature of the recent years, after the publishing of our work, it can be noted a discrete but constant in the number of publications about the subject. Until now, we published five articles directly related with the subject (Matias, Vila e Tubino, 2003, 2004; Fávero e Tubino, 2003; Matias e Tubino, 2001; Tubino, Rossi e Magalhães, 1997) and other one will be soon submitted and a PhD. thesis (Matias, 1999) and a MSc. dissertation (Souza, 2004), were presented. In the reflectometric methods developed in our laboratory, essentially two different procedures were used. On of them uses to immobilize the analyte, or a derived compound, on a solid support, for example paper. In the other case, the colored substance was suspended in the solvent, water. It is known that the use of diffuse reflectance in the visible, using solid surfaces, is not common in Analytical Chemistry; rarer is the use of this technique with solids suspended in the solvent. Therefore, in a certain way, the adopted procedures bring proposals with innovative content. Someone could ask what are the advantages of the reflectance techniques, in the uv-visible region, compared with transmittance methods. First, it is possible, by this way, to analyze by non destructive procedures, a surface on which it was deposed any colored substance. With respect to the analysis of soluble colored substances, it is possible to develop reflectometric procedures that avoid a variety of interferences that appear when transmittance methods. In other cases, it is possible to analyze substances in suspension where turbidimetry and nefelometry are not applicable.The objective of this work is to develop quantitative analytical methods using diffuse reflectance in the uv-visible range of the spectrum, in order to contribute for the development of this technique that can be used for the determination of organic and inorganic analytes in a variety of matrixes. (AU)