Study on Signal Enhancement Technology for Atomic Fluorescence Spectrometry Based on Digital Micromirror Device

A dispersive detection system based on ultraviolet digital micromirror device (DMD) was used for hydride generation atomic fluorescence spectrometer (HG-AFS) on the basis of the original non-dispersion detection system. The dispersion system was used to suppress the interference when spectral interference from the light source or scattering interference exists. The limit of detection (LOD) of the dispersive system was worse than the non-dispersive one due to the addition of the dispersive components (DMD and grating , etc) . In this work , to improve the analytical performance of the dispersive detection method , a cylindrical mirror was installed in front of the photomultiplier tube (PMT) , the minimum effective area of the PMT was expanded to enhance the signal intensity, a better fixed location mode of DMD rotation was proposed, and the analysis methods such as peak selection and the instrument parameters affecting the signal intensity were optimized. The results showed that the signal intensity within 180-320 nm was increased more than 2 times , and the spectral resolution was increased more than 1.2 times. Moreover, the emission lines and excitation fluorescence lines of Cd, Te, Sn and Zn were obtained, and the LODs were respectively less than 0. 005 ng/mL for Cd, 0. 02 ng/mL for Sn, 0. 1 ng/mL for As, Bi and Hg, 0. 05 ng/mL for Sb , Pb and Te, and 0. 2 ng/mL for Se and Zn. The spiked recoveries and the RSDs of As were 93% - 101% and 0. 6% - 3. 3% in living and drinking water samples , and 95% - 106% and 0. 9% - 3. 4% in food samples , respectively. The LOD and resolution of the dispersive system were effectively improved because of the improvement of the ultraviolet DMD spectrometer, the upgrade of the DMD rotation detection mode and the optimization of the analysis method. As a result, the dispersive system met the detection requirements of toxicological index limits in the Standards 14 Drinking Water Quality (GB 5749-2006) , and also had good accuracy, sensitivity and stability in actual food sample analysis.