Self test 4.4A – Validation of liquid chromatography mass spectrometry (LC-MS) methods

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:

No	C_thiomethoxam (ng/L)
No	16-Oct-2015	6-Nov-2015	26-Nov-2015	27-Nov-2015
1	7.6	11	9.5	11.3
2	8.2	11.2	8.8	10.2
3	14.9	10.7	8.6	11.3
4	9.5	11.1	9.1
5	11.4		9.1

Insert results with units!

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

No

Yes

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

Please give the answer with one decimal place.

3.

Is the obtained repeatability on 26^th of November acceptable?

No

Yes

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.

True

False

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?

No

Yes

Depends on the guidelines