A wide dynamic range detection of biopolymer medicines with resonance light scattering and absorption ratiometry Original Research Article

Using the interaction of heparin with Janus Green Blue (JGB) as an example, herein a dual-wavelength resonance lighting scattering (RLS) ratiometric method and an absorbance ratiometric one are developed to detect biopolymer medicines based on their bindings with organic dyes. In aqueous solution, heparin could interact with JGB, displaying significantly enhanced RLS signals in UV–vis region. By measuring the RLS intensity ratio (Rratio) and absorbance ratio (Aratio) at the wavelengths of 285 nm over that at 345 nm, respectively, heparin over a wide dynamic range of content could be detected. Typically, when JGB concentration is kept at 1.00 × 10−5 mol l−1, using Rratio could detect heparin over a range of 0.30–2000 ng ml−1 with a limit of determination of 30 pg ml−1, while using Aratio could detect heparin over the range of 0.01–2000.0 ng ml−1 with a limit of determination of 1 pg ml−1. The wavelength-dependent RLS and absorption ratiometric methods were found to have much better flexibility for a series of common influences, such as pH, and dye concentration, than that of RLS method at a single wavelength. The interaction nature was investigated through size measurements and RLS imaging detections.