Resonance Rayleigh Scattering Spectrometric Determination of Doxepin Hydrochloride by Its Reaction with Erythrosine

In a B-R buffer medium of pH 4.5, an appropriate amount of doxepin hydrochloride sample solution was reacted with 1.0 mL of 1.0×10-4mol·L-1 erythrosine solution in a total volume of 10 mL, to form an ion association complex, of which the intensity of resonance Rayleigh scattering (IRRS) was measured at the wavelength of 284 nm. Values of ΔIRRS (difference between values of IRRS of sample and blank) was found to keep linear relationship with values of mass concentration of doxepin hydrochloride in the range of 0.10-4.2 mg·L-1, with limit of detection (3s/k) of 9.01 μg·L-1. The proposed method was applied to the determination of doxepin hydrochloride in sample of medicine, results obtained by this method were found to check quite well with the results found by the method of pharmacopeia. Values of recovery found were in the range of 98.9%-102%.