Analytical properties of pyridine-2,4,6-tricarboxylic acid: Determination of iron in food samples and quantification of tetracyclines

Pyridine-2,4,6-tricarboxylic acid is proposed as a new and sensitive reagent for the determination of Fe(H). The tridentate ligand combines with iron(II) in the acidic media at the pH of 2.2 to readily form an intense coloured red-purple iron(II) complex with an absorbance maximum at 488 nm in the first order derivative spectrum. The complex is stable for 3-4 h with no increase in the absorbance value. Beer's law is obeyed for iron(II) concentrations from 3.0-425.0 mu g mL(-1). The molar absorptivity was found in the range of 0.186 x 10(3) L mol(-1) cm(-1). The method has been successfully applied for the determination of iron(II) in food samples as well as indirect quantification of tetracycline class of antibiotics. Use of derivative spectroscopy eliminates commonly encountered spectral interferences in this determination due to impurities, excepients and additives in food and pharmaceutical samples.