Abstract: Traditional standard curve method and flow injection analysis method need to prepare series of standard solutions that generate problems of tedious manual preparation, easy to introduce manual error and large amount reagent consumption. To overcome these problems, a successive addition spectral analysis (SASA) system was developed for automated preparation of standard solutions, automated spectral acquisition, and automatic construction of calibration curves. In the SASA system, a stock solution is continuously and quantitatively pumped into a reaction vessel to prepare a series of standard solutions through successive dilution or to react with reagents to produce optically responsive compounds and obtain solutions with known concentrations. After that the spectra of the solutions are automatically collected. In addition, a quantitative analysis method incorporating calibration curve fitting and concentration calculation for unknown samples was established. The SASA system was applied to the quantitative determination of ammonium dihydrogen phosphate (NH?H?PO?) in dry chemical fire extinguishing agents. The results showed a good linear relationship between concentration and absorbance over the concentration range of 1.093–6.965 μg/mL, with a coefficient of determination (R2) of 0.9999 and a limit of detection of 0.0134 μg/mL. The results obtained by the proposed method were highly consistent with those obtained by the arbitration method, with detection errors ranging from 0.5% to 0.9%. These results demonstrate that the proposed method provides high accuracy, good repeatability, and high sensitivity, indicating its considerable potential for a wide range of quantitative analysis applications.

Key words: Successive addition spectral analysis（SASA）, Automation, NH4 H2 PO4 , Quantitative analysis