Determination of iron (III) in environmental objects by photometric method with acetylacetone derivatives

Organic reagents containing three carbonyl groups based on acetylacetone, 2,4-diacetyl-3-phenyl-5-methyl-5-hydroxyhexanone (R1), 2,4-diacetyl-3-(3'-nitrophenyl)-5-hydroxy-5-methylcyclohexanone (R2) and 3-acetyl-4,6-diphenylgensandione-2,6 (R3), were synthesized. Their absorption spectra were studied at various pH values of the medium, and the acidity constants were determined by potentiometric titration. It was found that the reagents are monobasic acids and, depending on the acidity of the medium, can be in the molecular (HR) or anionic (R-) form. Formation of iron (III) complexes with synthesized reagents in the presence of hydrophobic amines, 1,10-phenanthroline (Phen), diantipyrylmethane (DAM) and diantipyrylphenylmethane (DAPM) was studied. It was established that mixed ligand complexes with the components ratio of 1:1:1 were formed in the presence of hydrophobic amines. At the same time bathochromic shifts in the absorption spectra were observed and the maximum yield was noted in a more acidic medium compared to the corresponding single ligand complexes. The influence of the reagents concentration, time and temperature on the formation of mixed ligand complexes was studied, and the stability constants were determined by various methods. It was shown that iron (III) in the form of mixed ligand complexes, Fe(III)-R1-DAM, Fe(III)-R2-Phen and Fe(III)-R3-DAM, can be determined with high selectivity in the presence of large excess of other metal cations. The developed methods were tested on fruits – strawberries, apricots, cherries, white cherries and two varieties of apples (Golden Ahmadi and Simirenko), and natural waters – drinking water taken from a tap in the BSU laboratory and Caspian Sea water taken near the Turkan village of Baku city.