准确检测牛奶中钙含量,进一步探究国标方法中干灰化法。方法通过单因素和正交试验,以牛奶中钙加标回收率为指标优化其检测方法,验证和应用该方法。试验结果表明镧溶液添加量2.5 mL,（1+1）硝酸溶液添加量5 mL,（180 ℃加热5 min、230 ℃加热5 min、300 ℃加热5 min、400 ℃加热10 min、500 ℃加热20 min）逐步升温炭化,550 ℃灰化4 h为最佳检测条件,可以保证检测结果的准确性。

Calcium content is an important indicator of milk.To accurately detect the calcium content in liquid milk, and further explore the dry ashing method in the national standard method.By conducting single factor and orthogonal experiments, the detection method was optimized using the spiked recovery rate as the indicator and validate and apply the method.The experimental results showed that：The amount of lanthanum solution added was 2.5 mL, nitric acid solution was 5 mL（1+1）, （Heating at 180 ℃ for 5 min 230 ℃ for 5 min, 300 ℃ for 5 min, 400 ℃ for 10 min, 500 ℃ for 20 min） gradually increase temperature and carbonize, ashing at 550 ℃ for 4 h was the optimal detection condition, the accuracy of the test results can be guaranteed。