Guidance for Preparing Standard Operating Procedures (SOPs)

Data ML005
Rev. # 0.0
Date: 11/00
Page 9 of 16
6.8 Analytical Spikes: Some tests (e.g., GFAA) make routine use of analytical spikes.
The limits on the recovery of the analytical spikes is given in the analysis SOP.
Verify that these limits are met, and that the software is flagging those outside the
limits.
6.9 Matrix Spikes: Verify that matrix spikes were analyzed at the required frequency,
and recoveries are within the limits stated in the analysis SOP. Laboratory policy
is to include a matrix spike/duplicate pair for every 10 samples, with a minimum of
one for each batch from a survey. This frequency may be increased or decreased at
the discretion of the client, group leader, or sample management. Preapproval is
required. The limits for recoveries are evaluated against the required acceptance
criteria in the QA Project Plan. A recovery outside of limits has a much greater
weight when the result for the analyte is near the action level given in the QA
Project Plan. The matrix duplicate has a bearing on the evaluation of the matrix
spike, as is explained in the next section.
6.10 Matrix Duplicates: Verify that the matrix duplicates are analyzed at the required
frequency, and RPDs or absolute differences are within the limits stated in the
analytical SOP. As for spikes, laboratory policy is to include a matrix
spike/duplicate pair for every 10 samples, with a minimum of one for each batch
from a survey. This frequency may be increased or decreased at the discretion of
the client, group leader, or sample management. Preapproval is required. The
limits for RPDs or absolute differences are evaluated against the acceptance
criteria in the QA Project Plan. A difference outside of limits has a much greater
weight when the result for the analyte is near the action level given in the QA
Project Plan. The matrix spike/duplicate pair should be evaluated together for
evidence of sample homogeneity problems. The sample description in the narrative
is of aid in this evaluation. A QA Project Plan may call for matrix spike duplicates
in place of separate matrix spikes and duplicates. In that event, the two matrix
spikes are evaluated separately as matrix spikes, and the pair is evaluated as above
for a sample/duplicate pair.
6.11 Digestion Blanks (LRB): Verify that digestion blanks were prepared and analyzed
at the required frequency. Ordinarily, this will be the same frequency as the matrix
spikes and duplicates. For large batches, a lesser number of blanks may be
prepared with pre-approval from the group leader, so long as it meets the needed
acceptance criteria. The limit for analytes reported to the reporting level is the
MDL. If all samples in the analysis run either in the grouping either just before or
just after a blank above the MDL are more than 10 times greater than the result in
QA/G-6 E-9
March 2001