Resonance Scattering Ratio Spectrometric Study on the Interaction of Sodium Dodecylbenzene Sulfonate with Quinidine

It was found that due to the interaction of sodium dodecyl benzene sulfonate (SDBS) with quinidine in a B-R buffer medium of pH 1.81, signals of resonance scattering intensity were significantly enhanced as measured at the wavelengths of 377.0 nm or 278.0 nm. When the concentration of SDBS for the reaction was taken as 3.0×10-4mol·L-1, values of scattering intensity (I) measured at the above mentioned wavelengths (I278.0 or I277.0) were found to keep linear relationships with concentration of quinidine in the ranges of 0.067-40 μmol·L-1 and 0.062-40 μmol·L-1 with detection limits (3σ) of 6.71 nmol·L-1 and 6.15 nmol·L-1 respectively. Based on these findings, single wavelength resonance scattering spectrometric determination of quinidine could be done. It was found further that by applying the dual wavelength technique, and taking the ratios of intensities measured at the wavelengths at wave crest and trough, i.e., I240.0/I275.0, as parameter in the determination of quinidine, linearity range of 0.007-75 μmol·L-1 and detection limit (3σ) of 0.691 nmol·L-1 were obtained. Hence, the dual wavelength resonance scattering ratio spectrometry was more preferrable to be used.