Fluorescence Based Turn-on Probe for the Determination of Caffeine Using Europium-Tetracycline as Energy Transfer Complex

Abstract

The study describes a simple and sensitive fluorometric sensor based on the enhancement of fluorescence intensity of Europium ion (Eu(3+)) - tetracycline (TC) charge transfer complex on addition of caffeine. The Eu(3+)-TC ternary complex has a characteristic emission peak at 615 nm (λex = 375 nm), the intensity of which increases with increase in concentration of caffeine. The caffeine sensor assay was found to be linear in the range of 0.0515 mM to 51.5 mM. The limit of detection and quantification were found to be 0.0515 mM and 0.382 mM, respectively. A caffeine recovery of 90 to 110 % in biological samples (serum and urine) indicated minimal interference by commonly present excipients in the samples. Rosenthal plots to calculate the binding capacity of caffeine with the Eu(3+)- TC complex revealed an association constant (K) of 238 x 10(3) L/mol and binding number (N) of 1.9. Bland-Altman plot comparing the developed assay and HPLC showed good agreement between values obtained by both the methods. The proposed fluorescent chemical sensor is a rapid and convenient method to determine caffeine with excellent recovery and low detection limit. The probable reaction mechanism for the formation of the turn on fluorescent probe enhancer is discussed.

Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

“…Numerous techniques and analytical procedures have been developed for caffeine determination in various matrix environments including biological fluids, pharmaceutical formulations, plants and commercial food products. These include chromatography [8][9][10], voltammetry [11,12], amperometry [13], fluorescence [14], spectrophotometry [15], potentiometry [16], electrospray ionization ion mobility spectrometry [17], capillary electrophoresis [18] and electrochemical methods [19][20][21][22]. However, these methods turn out to be expensive and time consuming due to complex fabrication designs, longer duration and complicated steps for pretreatment and extraction of samples, involvement of lot of chemicals and instrumentation and mediocre stability and reproducibility.…”