4.5 mL of 50 mg L−1 Mn/ZnS QDs solution, 5.0 mL of PBS (pH 8.0), 50 μL of 0.10 mM AA standard and 50 μL of different concentrations of interfering components were introduced into a 10 mL calibrated test tube. Then the mixture was diluted to the volume with high-purity water and mixed thoroughly. The tube was stood for 10 min and a portion of the solution was transferred into a 10-mm silica cuvette for phosphorescence measurement. RTP was taken at an excitation wavelength of 306 or 315 nm with excitation and emission slit widths of 10 nm.