Determination of soil total phosphorus by autoanalyzer

Determination method of soil total phosphorus by AA3 Continuous Flow Analytical System was investigated.The results showed that through sucking certain concentration sulfuric acid to the machine with another pump,instead of directly adding sulfuric acid to ammonium molybdate in order to moderate the pH of reaction solution,AA3 CFA can be used to assay soil total phosphorus accurately,and avoid the blue reaction after adding a little of sulfuric acid to the ammonium molybdate.The result of this method was not significantly different from the traditional colorimetry.In the linear area,the correlation efficiency for the standard curve was as high as over 0.999,the recovery percentage of standard sample was 97.9%～102.1%,and the detection limit of the sample was 0.012 mg/L.