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Appendix D
5/20/2009
9
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
analyses.
9.2.3
Method Detection Limits (MDLs) – MDLs should be
established for chlα using a low level ambient water
sample. To determine the MDL values, analyze seven
replicate aliquots of water. Perform all calculations defined
in the procedure (Section 11) and report the 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 90% acetone 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
Continuing Calibration Verification (CCV) – The CCV is
the solid secondary standard which is also the quality
control sample. . If the high std is off by 2.5% or more,
reset the calibration to the high solid standard reading
acquired at calibration, using the calibration function.
Failure to meet the criteria constitutes correcting the