ИСТИНА

Optoacoustic technique (OA) for concentrated, strongly light-absorbing solutions and monitoring the course of reactions at this concentration level is proposed for increasingly developed branch of chemical analysis of high concentrations. Expanding the range of reliably measured concentrations is one of the primary tasks of analytical chemistry. The problem of high concentrations seems to be shadowed by the trace analysis. However, it appears to be a very complex conglomerate of various chemical, methodological, and technical problems. It turns out equally multifactor and sophisticated as trace analysis, and shows a lower number, but no less important. The existing applications of methods of analytical chemistry for complex concentrated systems (like technological, biological, or clinical samples) showed that many previously developed methodological approaches require reconsideration or reworking due to changes in the chemistry, the necessity to take into account a larger number of components, the different role of matrix, etc. In addition, the problem of analysis and probing of highly concentrated solutions is not a single task, but rather a number of various and different analytical challenges. OA spectroscopy is suitable for all the types of such problems. The used technique is based on the wide-band detection of temporal profiles of laser-generated ultrasonic pulses (optoacoustic signals) in a medium under study [1]. The leading edge of the optoacoustic signal repeats the distribution of the laser fluence in the medium, which makes it possible to determine its optical absorption in a wide range of strongly absorbing samples [2]. The idea of the work is to apply this technique with the the developments in the methodology of analytical chemistry and investigate the changes in the optical-absorption coefficient during a chemical reaction for obtaining the chemical information. In order to determine the principal possibility of the OA technique, several relevant photometric reactions and their performance parameters of them are considered. We use a wide range of chemically relevant processes: complexation (1,10-phenanthroline with iron(II) [3] and other metals and ligands); organic and inorganic redox reactions; acid-base equilibria, and the behavior and characterization of disperse systems (nanodiamonds and fullerenes). Investigation will include obtaining chemical-analytical, physical and physicochemical information for low and high concentrations, and the elucidation of kinetics and thermodynamics of these reaction at high reactant concentrations. In already studied photometric systems the linear absorptivity was achieved for the level of 10–400 cm–1 for Fuchsine (10–4–10–2 M) and 1-100 cm–1 for Phenol Red (10–5–10–3 M). Such linear absorptivities cannot be reliably monitored with other methods except special ATR-probes, but the information content in OA experiments is much wider. To prove our concept further, kinetic, solubility measurements for different photometric reactions will be studied in various solvents and compared with conventional spectrophotometry data obtained at lower concentrations. REFERENCES 1. T. Khokhlova, I. Pelivanov, A. Karabutov, Acoustical Physics, 55 (2009) 674-684. 2. I.M. Pelivanov, M.I. Barskaya, N.B. Podymova, T.D. Khokhlova, A.A. Karabutov, Quantum Electronics, 39 (2009) 835. 3. T. Filimonova, D. Volkov, M. Proskurnin, I. Pelivanov, Photoacoustics, 2 (2013) in press