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Appendix D
5/20/2009
5
3.35
Precision – The degree to which a set of observations or measurements
of the same property, obtained under similar conditions, conform to
themselves; a data quality indicator. Precision is usually expressed as
standard deviation, variance or range, in either absolute or relative terms.
(NELAC)
3.36
Preservation – Refrigeration, freezing, and/or reagents added at the time
of sample collection (or later) to maintain the chemical and or biological
integrity of the sample.
3.37
Quality Control Sample (QCS) – A sample of analytes of known and
certified concentrations. The QCS is obtained from a source external to
the laboratory and different from the source of calibration standards. It
is used to check laboratory performance with externally prepared test
materials.
3.38
Quenching – A phenomenon which occurs when the fluorescence
measurements decrease even though the analyte concentration is
increasing. (Turner Designs TD700 manual)
3.39
Raw fluorescence – Refers to the “relative” fluorescence of a substance
being read, rather than the actual concentration. (Turner Designs TD700
manual)
3.40
Run – One sample analysis from start to finish, including printout.
3.41
Run Cycle – Typically a day of operation – the entire analytical
sequence of runs from the first run to the last run and including the
transfer of run cycle data to the disc.
3.42
Sample Volume – Volume of water filtered.
3.43
Sensitivity – The capability of a test method or instrument to
discriminate between measurement responses representing different
levels (concentrations) of a variable of interest.
3.44
Shall – Denotes a requirement that is mandatory whenever the criterion
for conformance with the specification requires that there be no
deviation. (ANSI)
3.45
Should – Denotes a guideline or recommendation whenever
noncompliance with the specification is permissible. (ANSI)
3.46
Standard Reference Material (SRM) – Material which has been certified
for specific analytes by a variety of analytical techniques and/or by
numerous laboratories using similar analytical techniques. These may
consist of pure chemicals, buffers, or compositional standards. The
materials are used as an indication of the accuracy of a specific
analytical technique.
4.
INTERFERENCES
4.1
Light and heat cause the chlorophyll molecule to break down.
Therefore, the samples should be kept cold in the dark and care should
be taken when grinding the samples so as not to overheat the sample.
Chlorophyll
b
also fluoresces within an overlapping range of
wavelengths, possibly leading to an overestimation of chlorophyll
α
.