Abstract: A mathematic model for evaluating the uncertainty in the determination procedure for calcium content in fruits by microwave digestion-flame atomic absorption spectrometry (FAAS) was established. The uncertainty sources for each parameter in the model were analyzed. The uncertainties of type A (based on the calculation of the statistical distribution of the determination results) type B (based on the estimation by experience and the probability distribution of other information) were evaluated. According to JJF 1059-1999, the component uncertainties were synthesized and extended. An expanded uncertainty of 1.18 mg/kg was obtained at the confidence probability of 95% and coverage factor of  k＝2. Based on the analysis of uncertainty, the preparation of standard solutions and the fitting of standard curves were the major sources of uncertainty, while sample weighing and the preparation of digestion solution revealed little effect on the final uncertainty. Meanwhile, some strategies for improving quality control were proposed.

Key words: microwave digestion-flame atomic absorption spectrometry, fruits, calcium, uncertainty