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9.2.3 DEMONSTRATION OF ACCURACY - Using the same set of replicate data
generated for Section 9.2.2, calculate the average percent recovery. The average
recovery must be within 80-120% for both the LFB and the LFSSM data.
Calculate percent recovery (%R) using the following equation:
%R = average measured concentration X 100
fortification concentration
9.2.4 MINIMUM REPORTING LEVEL (MRL) CONFIRMATION - Select a target
concentration for the MRL based on the intended use of the method. Establish
an Initial Calibration following the procedure outlined in Section 10.3. The
lowest calibration standard used to establish the Initial Calibration in
Section 10.3 (as well as the low-level CCC) must be at or below the
concentration of the target MRL. Establishing the MRL concentration too low
may cause repeated failure of on-going QC requirements. Confirm the targeted
MRL following the procedure outlined below.
9.2.4.1 Prepare and analyze seven replicate LFBs at the target MRL
concentration. All samples must be processed using the sample
collection devices described in Section 8.1.4.1. Calculate the mean
(Mean) and standard deviation for these replicates using the m/z 101 ion.
Determine the Half Range for the prediction interval of results (HR PIR )
using the equation below:
HR PIR = 3.963 X S
where,
S is the standard deviation, and 3.963 is a constant value for seven
replicates.
9.2.4.2 Confirm that the upper and lower limits for the Prediction Interval of
Results (PIR = Mean + HR PIR ) meet the upper and lower recovery limits
as shown below:
The Upper PIR Limit must be < 150% recovery.
Mean + HR PIR X 100 < 150%
Fortified Concentration
The Lower PIR Limit must be > 50% recovery.
Mean - HR PIR X 100 > 50%
Fortified Concentration
332.0-18