Investigation of volatile aliphatic and aromatic amine detection using a fluorescent pH indicator ethyl eosin in polymer matrices

Abstract

Changes in the fluorescence spectra (F) of ethyl eosin (EE) embedded into polymer matrices of different compositions, gas permeability, and polarity under the action of gaseous aliphatic and aromatic amines (dimethylamine (DMA), trimethylamine (TMA), and pyridine (Pyr)), depending on the pH and the structure of polymer matrix, were investigated. Organic methanesulfonic acid was used to adjust pH in a polymer matrix. Cellulose acetate-propionate (CAP), polyvinyl trimethylsilane (PVTMS), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP), as well as mesoporous silica gel microspheres, were used as polymer matrices. Absorption and fluorescence maxima of EE in solution and in most polymers are in the region of 505 nm and 550 nm, respectively. The maximum of EE fluorescence intensity increases in all polymer matrices except for PVP in the presence of amines, while the F decreases in the PVP matrix and silica gel microspheres. The fluorescence response to DMA is higher than to TMA and Pyr for all the polymers; the F response is two-phase in the case of Pyr: an increase in F followed by a decrease. Characteristic response times for different matrices change in a sequence: CAP < PVP < PEO < MS < PVTMS. These differences are probably due to the different contributions to the process of the analyte diffusion, its affinity to the polymer, and the internal polarity of the polymer matrix for different polymers.