Resonance Rayleigh scattering spectra for studying the interaction of heparin with some basic phenothiazine dyes and their analytical applications

In near neutral medium, binding of heparin with some basic phenothiazine dyes such as methylene blue (MB), Azure B or toluidine blue (TB) can result in a significant enhancement of resonance Rayleigh scattering (RRS) and appearance of a new RRS spectrum. Their maximum scattered wavelengths appear at 346, 338 and 329nm for MB, Azure B and TB, respectively. The optimum conditions of these reactions, the influencing factors and the relationship between the RRS intensity and the concentration of heparin have been investigated. A new method for the determination of trace amounts of heparin based on the RRS method has been developed. The methods exhibit high sensitivities, the detection limits for heparin are 9.0ngml^-1 for MB, 14.5ngml^-1 for Azure B and 26.0ngml^-1 for TB. Among them the MB is the most sensitive and has better selectivity, so it was applied to the determination of heparin in heparin sodium injection samples with satisfactory results. The mechanisms of the effect are discussed.