Abstract: Microwave digestion technique was used in the determination of calcium in milk by flame atomic spectrometry and the application of this technique in dairy products was optimized by one-factor-at-a-time and orthogonal array design methods. The optimal digestion conditions were 0.9 mL of nitric acid, 4.0 mL of hydrogen peroxide and 28 min of digestion time. The recovery rate was in range of 96.0%－98.1% for calcium in milk with RSD of 0.50%. Our study shows that microwave digestion allows rapid and large-scale sample pretreatment is helpful to increase the accuracy of determination for calcium because of less time consumption and complete digestion.

Key words: microwave digestion, flame atomic spectrometry, milk, calcium