Determination of DNA with imidacloprid by a resonance light scattering technique at nanogram levels and its application

In this paper, we have set up a determination method of nucleic acids at nanogram levels by using a common spectrofluorometer to detect intensity of resonance light scattering (RLS). We have also studied the characteristics of RLS spectra of Imidacloprid with nucleic acids, the effective factors, and the optimum conditions. The RLS of imidacloprid was greatly enhanced by DNA in the range of pH 1.5-1.7. A RLS peak at 310nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DNA. The linear range of the calibration curve was 0-5.0 mug mL(-1), 5.0-20.0 mug mL(-1) for calf thymus DNA, 0-1.0 mug mL(-1) for thermally denatured calf thymus DNA, 0-14.6 mug mL(-1) for salmon sperm DNA (ssDNA), and 4.0-7.0 mug mL(-1) for yeast RNA (yRNA). The limits of detection (LOD, 3sigma) were 12.8, 8.7, 29.5, and 35.5 ng mL(-1), respectively. The nucleic acids in six synthetic samples and in three real samples were determined. The results were satisfactory, and the recovery rates were in the range of 99-106%, 91-109%, respectively. Compared with other methods, this method has larger detective range, which can reduce the interference of background and increase the intensity of RLS.