Objective The microwave digestion procedure was not clearly described in the previous standard, which affected the systematic analysis of measurement factors. Methods The heavy metals in municipal sludge was determined by the microwave high-pressure digestion-ICP. A mathematical model for heavy metals measurement in the municipal sludge was established. Results The main sources of uncertainty come from ICP instrument, sample weighing and calibration curve fitting. Conclusion Countermeasures and suggestions for reducing the uncertainty were introduced, which may provided technical basis for improving the accuracy of heavy metals measurement.

microwave high-pressure digestion-ICP  /  municipal sludge  /  uncertainty