Synchronous fluorescence techniques for the detection and monitoring of selected fluorescent dyes in binary and multifluorophoric mixtures

The present study deals with non-destructive conventional emission, constant-wavelength synchronous fluorescence spectroscopy (CWSFS) and first derivative of CWSFS for selective estimation of two fluorescent xanthene dyes viz. rhodamine B (RhB) and fluorescein (Fls) in their binary and multifluorophoric mixtures via spike method in an aqueous environment. Various parameters (Δλ, pH, ionic strength, etc.) affecting these methods were optimized. Based on the results, measurement of RhB and Fls were performed at Δλ, 20.0 nm, pH 7.0, 25.0 ⁰C temperature and scan rate of 240.0 nm/min without their prior separation in mixtures. CWSFS and first derivative CWSFS measurements were carried out at 556.0 nm and 547.0 nm for RhB (R2 = 0.988 and 0.983) and 493.0 nm and 484.0 nm for Fls (R2 = 0.999 and 0.999) over the concentration range of both dyes at 0.10–0.70 mg/L. The mean percentage recoveries from aqueous binary mixtures of RhB and Fls were found to be 98.95, 99.97 (RhB) and 100.68, 100.73 (Fls) for CWSFS and first derivative CWSFS respectively. Results were statistically analyzed in terms of accuracy and precision.