Validation of liquid chromatography mass spectrometry (LC-MS) methods

Self test 4.4A

You are validating a method for analysing several analytes in surface water.
Using data from analyzing one water sample on different days, evaluate the repeatability of Thiomethoxam determination:
NoCthiomethoxam (ng/L)
16-Oct-20156-Nov-201526-Nov-201527-Nov-2015
17.6119.511.3
28.211.28.810.2
314.910.78.611.3
49.511.19.1
511.49.1
 

1. Is it important to know the exact concentration of Thiomethoxam in the sample?

2. What is the relative standard deviation on 26th of November (in %)?



Please give the answer with one decimal place.

3. Is the obtained repeatability on 26th of November acceptable?

4. What is the pooled repeatability over all the days (in ng/L)?



Please give the answer with 2 decimal places.

5. Pooled standard deviation can be used for evaluating repeatability over multiple days and at any concentrations.

6. Calculate pooled relative standard deviation (in %). Please give the answer with 1 decimal place.

7. Is the obtained value acceptable if the expected LoQ is 0.01 ng/L?


 

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