Site-Specific Health and Safety Plan (HASP) - Laschools.org

A column test procedure for determining sorbed hexavalent chromium is included as
Appendix A.
6.2 DETECTION AND QUANTITATION LIMITS
This section describes the terms, definitions, and formulas that will be used for detection
and quantitation limits.
6.2.1 Method Detection Limit
The method detection limit (MDL) is the lowest concentration at which a specific analyte
in a matrix can be measured and reported with 99-percent confidence that the analyte
concentration is greater than zero. MDLs are experimentally determined and verified for
each target analyte of the methods in the sampling program. Instrument-specific MDLs
are analyzed in accordance with 40 CFR Part 136. The lab will spike at a level equal to
the lowest calibration standard. In order to maintain reporting consistency, if multiple
instruments are used for the same method, the lab will report down to the highest MDL
between all instruments so that all MDLs for a given analyte are at or below the reported
MDL. MDLs are verified quarterly with a spike at ½ of the low calibration standard.
Since MDLs are verified quarterly and in accordance with California Department of
Health Services Environmental Laboratory Accreditation Program (ELAP) policy on
Method Detection Limits, annual MDL studies are not performed unless a problem is
identified during the quarterly verification process. MDLs are based on the results of
seven matrix spikes at 2 times the estimated PQL, and are statistically calculated in
accordance with the Title 40, Code of Federal Regulations Part 136 (40 CFR 136),
Appendix B. The standard deviation of the seven replicates is determined and multiplied
by 3.14 (i.e., the 99-percent confidence interval from the one-sided student t-test). Where
practicable, MDLs must be lower than the risk-based criteria determined for the project.
The MDLs to be used are intended to allow that both nondetected and detected target
compound results will be usable to the fullest extent possible for the project. An MDL
check sample, an interference-free MS with all method target compounds, must be
analyzed following the MDL study to determine if reasonable MDL concentrations have
been achieved. The MDL check sample should be at a concentration of approximately
two times the MDL. If any target compound is not recovered, the MDL study must be
repeated. In this case, the repeated MDL study should be performed with a higher
concentration, based on the analyst's judgment, of the target compounds which failed in
the MDL check sample. The MDLs shall be verified quarterly by running a standard at
½ the concentration of the lowest standard of the initial calibration. If the verification
analysis shows lack of adherence to the determined MDLs, then the MDL study shall be
repeated.
6.2.2 Sample Quantitation Limit
Sample quantitation limits (SQLs) are defined as the MDL multiplied by the dilution
factor (DF) required to analyze the sample, and corrected for moisture or sample size.
These adjustments may be due to matrix effects or to the high concentrations of some
analytes. For example, if an analyte is present at a concentration that is greater than the
linear range of the analytical method, the sample must be diluted for accurate
quantitation. The DF raises the reporting limit, which then becomes the SQL. Because
6-2
K:\Depts\Dept48\LAUSD\MSA WORK\QAPP\Draft Final QAPP to DTSC\QAPP for OU 1 RAP.DOC
303