ICP-MS 用EPA的方法测试MDL

请教各位，我现在需要用Aglient 8800做MDL，参照了EPA的方法。我配制7个相同浓度的样品，测试完成后算MDL。在这个过程中，我加标的浓度是否可以低于我检量线的最小浓度，是否需要先做仪器的IDL，测试结果是否需要减去空白?谢谢！

Step	Action
1	Estimate the expected MDL.
2	Calculate the desired spike level such that MDL is between 10 to 100% of the spike.
3	Spike at least 7 replicate samples with analytes of interest. Complete the sample preparation steps for each replicate.
4	Calibrate the measurement tool. Measure the analytes. This is done within 1 day.
5	Calculate the standard deviation of the 7 measurements. (s)
6	Determine the correct t-statistic *t_{df, 99}* Determine degrees of freedom (df=n-1) Find the one-tailed t-statistic for 99% confidence level · t-stat is 3.143 for 7 measurements.
7	Calculate MDL = t statistic x standard deviation x dilution factor (if not already included in the data).
8	Verify: 10% Spike level £ MDL £ Spike level
9	Validate that the calculated MDL makes sense.