MOOC: Validation of liquid chromatography mass spectrometry (LC-MS) methods (analytical chemistry) course

Self test 4.4A

1.

1.    You are validating a method for analysing several analytes in surface water.
Using data from analyzing one water sample on different days, evalute the repeatability of Thiomethoxam determination:

No Cthiomethoxam (ng/L)
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!

2.

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

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



[accordion][acctitle]Clue 1[/acctitle]Did you use data from the correct date?[/accordion]

[accordion][acctitle]Clue 2[/acctitle]Standard deviation is 0.34 ng/L[/accordion]

4.

Is the obtained repeatability on 26th of November acceptable?

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



[accordion][acctitle]Clue 1[/acctitle]Standard deviations are 2,95 ng/L; 0,22 ng/L; 0,34 ng/L and 0,64 ng/L[/accordion]

[accordion][acctitle]Clue 2[/acctitle]Degrees of freedom is the number on parallel measurements -1[/accordion]

6.

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

7. Calculate pooled relative standard deviation (in %):

8.

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


 

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