Self test 5.2B – MOOC: Validation of liquid chromatography mass spectrometry (LC-MS) methods (analytical chemistry) course

You are validating a LC/MS analysis of L-PFOS in ground water and for trueness evaluation, you are analyzing a commercial CRM sample.

You are using matrix matched calibration.

Your analysis data is:

Number of result	C (ng/L)
1	13.96
2	14.00
3	12.51

Calculate bias (unit: ng/L):

Relative bias (unit: %):

For evalution of your bias, calculate zeta-score.

[accordion][acctitle]Clue 1[/acctitle]For u(lab) use standard deviation of your parallel measurements[/accordion]

[accordion][acctitle]Clue 2[/acctitle]For u(ref) use expanded uncertainty in the certificate divided by 2 (k = 2)[/accordion]

Result is:

[accordion][acctitle]Clue[/acctitle]∣z∣≤ 2 means satisfactory results; 2<∣z∣≤3 means questionable results and ∣z∣>3 means unsatisfactory result.[/accordion]

Satisfactory

Questionable

Unsatisfactory

Possible reasons for unsatisfactory results (click all that apply):

CRM sample matrix has less matrix components than a matrix matched calibration solution.

CRM sample has more matrix components than you matrix matched calibration solution.

Your calibration solution has degraded.

You are running your analysis on a dirty instrument.

Method bias is:

Statistically significant

Not statistically significant

Could this CRM be used for evaluating L-PFOS method bias in the case of sea water?

Yes