Use of Multichannel Microgravimetry for Assessing the Properties of Organic Phosphors of the Azolotriazine Class

Abstract

The article is devoted to the use of multichannel microgravimetry for assessing the functional properties of organic phosphors of the azolotriazine class as promising analytical reagents for test systems for liquid and gas media. The promise of using azolotriazines of various structures as analytical reagents in test systems for liquid and gas media is estimated. The primary objectives of the study were to identify the most stable and selective structures of the synthesized organic compounds based on heterocyclic ring systems of imidazo-, pyrazolo-, and triazolotriazines; to assess their properties and potential use as analytical reagents for volatile organic and some inorganic (water, ammonia) compounds (VCs) for use in portable test systems. The study covered two fields: the assessment of changes in the optical properties of the reagents in various media (solutions, solid substrates) for visual test systems, and an analysis of the kinetics of sorption of VC vapors by piezoelectric quartz resonators (FLU-1 array) modified with fluorimetric reagents in the injection and frontal sample introduction modes in combination with highly sensitive microgravimetry. Compounds of the highest stability in solution and on a solid support (4-(6-oxo-2-phenylimidazo[1,2-b]pyrido[4,3-e][1,2,4]triazin-7(6H)-yl)butanoic acid (I), 3-hydroxy-2-(6-oxo-2-phenylimidazo[1,2-b]pyrido[4,3-e][1,2,4]triazin-7(6H)-yl)propanoic acid, 3-methyl-6-phenylimidazo[1,2-b][1,2,4]triazine-2-carbohydrazide) were identified, as well as those demonstrating selectivity to the key analytes formed during food spoilage, i.e., butyric acid, propionic aldehyde, cyclohexanone, and aromatic amines. The results indicate that azolotriazines ensure the differential recognition of complex VC mixtures, including real samples, by interpreting paired sensitivity spectra A(_i/j) and kinetic “visual fingerprints” of the signals of sensor with the selected best phases. A chemometric RGB space method with integral color labels of the results of vapor detection by piezoelectric quartz microbalances with new sorbents confirmed the applicability of compounds I and 7-(2-aminophenyl)pyrazolo[5,1-c]pyrido[4,3-e][1,2,4]triazin-6(7H)-one to the identification of water, ethanol, and organic acids. However, to ensure the accuracy of an analysis, it is important to completely remove residual polar solvents (DMSO) affecting phase selectivity. A protocol was proposed for the rapid screening of luminophore, with the assessment of visual brightness, stability, and gravimetric vapor weighing efficiency under both batch and dynamic conditions. This step confirmed the feasibility of integrating individual azolotriazines into sensor platforms for monitoring the quality of food and biomedical systems and indicated a direction for optimizing the structures of potential reagents by adjusting donor–acceptor properties of the substituents in the luminophore molecule and minimizing artifacts associated with the residual synthesis components and the nature of the substrates. The data obtained provide a basis for the development of portable analytical facilities with multimodal response, overcoming the limitations of the traditional fluorescence systems, such as reduced selectivity in multicomponent media and instability under operation conditions.