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EFFECT OF RUTHENIUM ON THE FLUORESCENCE OF SALICYLIC ACID

Salicylic acid and its derivates are an important class of pharmacological active compounds with wide range of use e.g. in reducing pain or swelling and as anti-inflammatory agent. It is also used as a food preservative, as an antiseptic in toothpaste, in aspirin production, etc. However, salicylic acid is toxic if ingested in large quantities. Salicylic acid is a simple analogue of humic acid (HA) and has been commonly used as modelling substance for HA. Recently, salicylic acid and its derivatives find useful application in analysis of metal ions. Simple and sensitive spectrophotometric and spectrofluorimetric methods for determination of iron(III), (1, 2) aluminium(III), (3, 4) and cooper(II)(4) ions can be found in literature. In order to understand the contribution of the metal coordination and the type of interaction between salicylic acid and metal ion, the reaction of the ruthenium(III) with salicylic acid in water-alcoholic solution using spectrofluorimetric method was investigated in this study. The fluorescence of salicylic acid was strongly quenched by ruthenium(III), and the quenching was highest at pH = 5.5–8 (controlled by acetate and phosphate buffers) at lex = 290 nm, lem = 405 nm. The decrease in the emission intensity was linearly proportional to the ruthenium(III) concentration in the 0.5–14.2 ug cm(-3) range when the salicylic acid concentration was 5x10(-6) mol dm(-3) at constant ionic strength of 0.2 mol dm(-3) (adjusted with NaCl), and the ratio of ethanol 65 %. The advantage of present method when compared to other commonly used methods is that the reaction occurs at room temperature which makes the method time-saving. Also, the presented method has a good sensitivity. References: (1) A. Asan, M. Andac, and I. Isildac, Chem. Pap. 64 (2010) 424-428. (2) B. Oktavia, L. M. Lim and T. Takeuchi, Anal. Sci. 24 (2008) 1487-1492. (3) C. Brach-Papa, B. Coulomb, C. Branger, A. Margaillan, F. Thereeaulaz, P. Van Loot and and J.L. Boudenne, Anal. Bioanal. Chem. 378 (2004) 1652-1658. (4) M. M. Seleim, M. S. Abu Bakr, E. Y. Hashem and A. M. El-Zohry, Anal. Lett. 43 (2010) 85-96.

ruthenium; salicylic acid; quenching of the fluorescence

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