Thenoyltrifluoroacetone as a spectrophotometric reagent for determination of ascorbic acid

An extractive spectrophotometric method for the determination of microamounts of ascorbic acid is described. 1-[Thenoyl- (2')-3,3,3-trifluoro-acetone] (HTTA) is found to react with iron (111) in strongly acidic medium giving a red coloured complex. The method is based on the proportionate decrease in the colour intensity of Fe(III)-HTTA complex with the addition of ascorbic acid at 405 nm. Linear calibration curve is observed in the range 1.0-5.0 mug/mL of ascorbic acid. The molar absorptivity and Sandell's sensitivity are 5.3 x 10(4) L/mol/cm and 0.003mug/cm(2), respectively. The interference of sugars, vitamins, amino acids, mineral salts, sweetening agents etc. has been studied. The method is successfully used in the determination of ascorbic acid in pure vitamin C tablets, drops and multivitamin products.