Green quantitative spectrofluorimetric analysis of rupatadine and montelukast at nanogram scale using direct and synchronous techniques

Two green sensitive spectrofluorimetric methods at nanogram scale were investigated for the determination of rupatadine fumarate (RUP) [method I] and its binary mixture with montelukast (MKT) [method II]. Method I is concerned with measuring the native fluorescence of RUP in presence of 0.10 M H2SO4 and 0.10 % w/v sodium dodecyl sulfate at 455 nm after excitation at 277 nm. The linearity range of the first method was 0.20-2.00 µg/mL with detection and quantitation limits of 11.00 ng/mL and 36.00 ng/mL, respectively. The second method includes the concurrent estimation of RUP and MKT in their co-formulated tablet preparation by applying first derivative synchronous spectrofluorimetric technique. The derivative intensities were measured for the two drugs in aqueous solution containing Mcllvaine’s buffer pH 2.60 at fixed wavelength difference (Δλ) of 140 nm. Each drug was estimated at the zero contribution of the other. For RUP, the intensity was measured at 261 nm while MKT was quantitate...