Determination of Total Phosphorus in Soil and Plants By Using the AA3 Continuous Flow Analyzer

The AA3 continuous flow analyzer (CFA) was applied to the determination of total phosphorus in soil and plants.Sample of either the soil or the plant was pretreated by drying at 60 ℃ and grinding to pass through screen with mesh of 0.25 mm.The pretreated sample was digested with HClO4-H2SO4 mixture for soil sample and with H2SO4-H2O2 mixture for plant sample.An aliquot of the sample solution was taken,and the acidity of solution in the reaction coil was controlled at c(1/2 H2SO4)=0.39 mol·L-1.Molybdenum blue photometric method was adopted in CFA,and wavelength of 660 nm was used for absorbance measurements (in terms of peak heights).Linearity was kept both in analysis of soil and plants,giving correlation coefficients (r) of 0.999 2 and 0.999 6,with detection limits of 0.010 mg·L-1 and 0.013 mg·L-1 respectively.Values of RSD (n=6) and recovery obtained were less than 2% and in the range of 98.0%-100.5%.