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SAMPLING
QUALITY ASSURANCE
CodyHart
sampling quality assurance includes:
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Testing deionised water used for rinsing equipment to ensure it is
<5 µS/cm at the start of each sampling day. The result is
noted on the field parameter forms for the day.
-
Checking that repeated readings of field analyte values at the end
of a purge, or from the four field surface water samples taken at
each sampling point, are reasonably close and not exceeding a Relative
Percentage Deviation (RPD) of 20% where RPD = {(A-B)/ [(A+B)/2]} x
100.
-
Conducting field blank tests of EC regularly throughout the sampling
day, that is, after the final deionised water decontamination rinse
at a sampling point, deionised water is swilled in a sampling beaker
or other piece of sampling equipment and its EC tested. Results were
noted on the field parameter forms.
- Noting
low EC readings of the remaining deionised water in the pump at the
start of the purge for each well.
-
Logging field lab calibrations.
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Logging gas monitor calibrations.
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Completing sampling point specific field parameter forms as sampling
progresses and including them in quarterly reports.
-
Using chain of custody forms for pick up and delivery of samples to
document the lack of tampering with sample containers from and samples
to the laboratory. These forms will also be included in the quarterly
report addendum.
-
Having two field personnel who work together and review one another’s
work practices.
ANALYTICAL
QUALITY ASSURANCE
Australian
Laboratory Services (ALS) quality assurance includes:
- NATA
registration for the analyses
- A
method blank of all inorganic analytes. A known analyte free matrix
is processed and analysed in the same manner as the samples.
-
A Lot Control Spike (LCS) of most inorganic analytes, the number depending
on the range of analytes in the set of 20 samples of similar matrix
being analysed by ALS at the time of submission of samples. A spike
of target analytes is placed into a known, interference free matrix
which is processed as per a set of 20 samples of similar matrix (a
sample lot) which may be from different batches but are processed
together for Quality Control purposes. The known true value of the
spiked concentration is compared with its tested result (% recovery),
to note the accuracy of the equipment and methodology. No more than
20% on either side of 100% is generally regarded as acceptable.
-
If clients wish, the sampling team will collect one duplicate (split
sample – the water is poured from a sampling beaker into two
containers) per ten sampling points for a full range of analytes and
send them to the laboratory marked D. An RPD of µ20% is expected,
except for trace analytes where the RPD is likely to be greater. To
assist impartial analysis, the laboratory is not given the time of
sampling or the duplicate sampling point making it difficult for laboratory
personnel to determine the duplicate’s sampling point origin.
Extra cost is incurred for this additional quality assurance.
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