Evaluation on the Uncertainty of Available Phosphorous Content in Compound Fertilizer

[Objective] The purpose was to establish an evaluation method for the uncertainty of available phosphorous(P) content in compound fertilizer.[Method] The available P content was measured by quinoline phosphomolybdate gravimetric method and the uncertainty of measured results was analyzed through establishing mathematic model.[Result] It could be concluded through analyzing the model that both the mass uncertainties of quinoline phosphomolybdate precipitates and tested samples were from the resolving power and precision of balance and its maximum tolerance in assay certificate;the uncertainty brought in by volumetric flask was from the permissible error of 250 ml volumetric flask,the operation of increasing the volume to scale of volumetric flask while diluting solution and the difference between experimental temperature and the temperature at the time when the volumetric flask was calibrated;the uncertainty brought in by pipette was from the permissible error of itself,the operation of increasing the volume to intake scale while taking solution and the difference between experimental temperature and the temperature at the time when the pipette was calibrated.At last,the uncertainty of measured results was calculated to be 16.3%±0.3%.[Conclusion] This experiment supplied scientific basis and methodological support for the quality evaluation of compound fertilizers.