Europium-Enoxacin Complex as Fluorescence Probe for the Determination of Folic Acid in Pharmaceutical and Biological Samples

A simple, rapid and sensitive spectrofluorometric method was developed for the determination of folic acid (FA), based on its quenching effect on the fluorescence intensity of enoxacin (ENX)-europium (Eu3+) complex as a fluorescent probe. Fluorometric interaction between ENX-Eu3+ complex and FA was studied using UV-visible and fluorescence spectroscopy. The quenched fluorescence intensity at an emission wavelength of 614 nm was proportional to the concentration of FA. Optimum conditions for the determination of FA were investigated. Under optimal conditions, the reduced fluorescence intensity at 614 nm was responded linearly with the concentration of FA. The linearity was maintained in the range of 1.25 x 10(-9) to 1.50 x 10(-7) M (R = 0.9986) with the limit of detection (3S(b)/m) (where S-b is the standard deviation of blank and m is the slop of linear calibration curve) of 6.94 x 10(-10) M. The relative standard deviation (RSD) for 9 repeated measurements of 1.0 x 10(-9) M FA was 1.42%. This method was simple, cost effective, and relatively free of interference from coexisting substances. Successful determinations of FA in pharmaceutical formulation and biological samples with the developed method were demonstrated.