Basic HTML Version
57
Method Detection Limit -
A statistically derived estimate of the lowest concentration or mass
detectable under method conditions at the concentration evaluated. A series of standards at an
estimated limit of detection is analyzed multiple times (usually 7), a standard deviation of these
seven replicate analyses is determined and the standard deviation is multiplied by the Student's t-
distribution statistic at 6 degrees of freedom.
Practical Quantitation Limit (PQL)
- A measure of the lowest limit of detection under the
conditions of a particular method. The PQL is often determined by multiplying the MDL by a
factor of between 3 and 10.
Reporting Limit (RL) -
For a target analyte, the reporting limit is instrument dependent and
based on the lowest point on the calibration curve.
Duplicate Analysis
- A measure of precision determined by analyzing samples twice or by analyzing a
second sample taken from the same source at the same time and analyzed under identical conditions.
There are several different types of duplicate samples that provide information on the precision of specific
types of data:
Field Duplicates
- Independent samples that are collected as close as possible to the same point
in time and space. They are two separate samples taken from the same source, stored in separate
containers and analyzed independently. These types of duplicates are useful in characterizing the
precision of the sampling process.
Matrix Duplicates -
An intra-laboratory split sample that is used to document the precision of a
method in a given sample matrix.
Split Samples
- Two or more representative portions taken from one sample in the field or in the
laboratory and analyzed by different analysts or laboratories. Split samples are quality control
(QC) samples that are used to assess analytical variability and comparability.
Duplicate Samples
- Two samples taken from and representative of the same population and carried
through all steps of the sampling and analytical procedures in an identical manner. Duplicate samples are
used to assess variance of the total method, including sampling and analysis.
Existing data -
Existing data are data or information that will be used that have not been newly generated
by the BWTS test. They may also be known as secondary data or non-direct measurement.
Field (Matrix) Spike
- A sample prepared at the sampling point (i.e., in the field) by adding a known
mass of the target analyte to a specified amount of the sample. Field matrix spikes are used, for example,
to determine the effect of the sample preservation, shipment, storage, and preparation on analyte recovery
efficiency (the analytical bias).
Performance Evaluation (PE)
- A type of audit in which the quantitative data generated in a
measurement system are obtained independently and compared with routinely obtained data to evaluate
the proficiency of an analyst or laboratory.
Precision
- A measure of mutual agreement among individual measurements of the same property,
usually under prescribed similar conditions expressed generally in terms of the standard deviation.
Quality Assurance (QA)
- An integrated system of management activities involving planning,
implementation, assessment, reporting, and quality improvement to ensure that a process, item, or service
is of the type and quality needed and expected.
Quality Assurance Project Plan (QAPP)
- A formal document describing in comprehensive detail the
necessary quality assurance (QA), quality control (QC), and other technical activities that must be