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Appendix C
5/20/2009
10
concentration values in the appropriate units. Calculate the
MDL as follows:
MDL = S x 3
Where,
S = Standard Deviation of the
replicate analyses.
9.2.4
MDLs should be determined yearly.
9.3 Assessing Laboratory Performance
9.3.1
Laboratory Reagent Blank (LRB) – The laboratory must
analyze at least one LRB with each batch of samples. The
LRB consists of Nanopure water treated the same as the
samples. LRB data are used to assess contamination from
the laboratory environment.
9.3.2
Quality Control Sample (QCS)/ Standard Reference
Material (SRM) – when using this procedure, a quality
control sample is required to be analyzed at the beginning
of the run and end of the run, to verify data quality and
acceptable instrument performance. If the determined
concentrations are not within
±
3
σ
of the certified values,
performance of the determinative step of the method is
unacceptable. The source of the problem must be identified
and corrected before either proceeding with the initial
determination of MDLs or continuing with the analyses.
The results of these samples shall be used to determine
batch acceptance.
9.3.3
The QCS will be obtained from a source external to the
laboratory and different from the source of calibration
standards.
9.3.4
Control Charts – The SRM data is graphed, and the slope,
y-intercept, and r squared data are compiled and tracked.
9.3.5
Continuing Calibration Verification (CCV) – Following
every 12-15 samples, one or two CCVs are analyzed to
assess instrument performance. The CCVs are made from
the same material as calibration standards (KHP), and are
to be within TV
±
3
σ
. Failure to meet the criteria
constitutes correcting the problem and reanalyzing the
samples. If not enough sample exists, the data must be
qualified if reported.
9.4 Assessing Analyte Recovery
9.4.1
Matrix spikes are performed on a 20% QA/QC basis.
9.4.2
0.5 ml of the highest KHP standard in the curve is added to
5.0 ml of sample for a total volume of 5.5 ml.
9.4.3
0.5 ml standard
0.5/5.5 = 0.09