pH assists simultaneous determination of folic acid and vitamin D 3 in biological fluids using a novel Tb 3+ -acyclovir optical biosensor.

An innovative, simple and cost effective Tb 3+ -acyclovir photo probe was designed and used as a core for a spectrofluorometric approach to sensitively determine two vital biological compounds in different matrices. The Tb 3+ -acyclovir complex displays a characteristic electrical band with λ em at 545 nm with significant luminescence intensity, which is quenched in the presence of folic acid and vitamin D 3 at pH 5.0 and 9.0, respectively. The conditions were optimized and the best solvent for operation was found to be acetonitrile and λ ex at 340 nm. folic acid was successfully estimated in tablet dosage form, urine and serum in the concentration range of 2.28 × 10 -6 to 1.49 × 10 -9 mol L -1 . Vitamin D 3 was also assessed in serum samples using the same optimal conditions within the concentration range of 3.2 × 10 -9 to 1.0 × 10 -6 mol L -1 . The proposed luminescence method was validated in accordance with ICH guidelines and found to be accurate, precise and specific and free from any interferences. The cost effectiveness and applicability of the method make it a good choice for routine analysis of the two compounds and early diagnosis of chronic diseases associated with abnormalities in their physiological levels.