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7. If using QuickFlask, there are 3 methods to verify that it contains
1000+/10ml: scale, meniscus-lines, and drain port:
a. Place the provided kitchen scale on a flat surface. A level note-
book computer is ideal, but not so much in the rain. The top of the
DuckBox has enough flat surface to use, but care must be taken
when positioning the feet to ensure that nothing is touching any of
the box ridges. After the scale is powered on, place the QuickFlask
on the scale and tare it. You have a limited amount of time before
the scale automatically powers down, which can be extended by
pressing the scale surface.
b. Open the port and dunk the flask in the stream. While holding the
handle such that the flask is plumb, allow the sample to drain out
. The QuickFlask has a calibrated handle. Hold the handle at the
approximate water temperature. Water is most dense at 4oC, as
shown in Figure 4 above, until the meniscus is below the black
lines
9
. Close the port.
c. Place the flask on the scale. Water at room temperature (20˚C) will
weigh 997g. Water below 10˚C will weigh 1000g. We aim to have
the weight within 5g (0.5% error). This error is taken into account
in the derived SDIQ Uncertainty and can be set in Setup>Meta
Settings>Uncert CF.T%. The total CF.T% is set at 2.0% as default
for plasticware. If lower uncertainty is required, the user must go to
volumetric glassware, which can achieve 1.4% uncertainty.
8. Note the EC.T
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when the probes are in the stream. Now put the EC.T
probes into QuickFlask and note the EC.T. It may increase by a few μS/
cm. In theory, a slightly higher (i.e. <1%) ECT should not affect the CFT.
But residual salt in the flask for example, can contaminate the results and
if the ECT increases by more than 1%, step 7 should be repeated. Push
the button to set the first EC.T in the calibration. As calibration points are
collected, they are displayed. Often, the first injection results in an unac-
ceptably high or low CFT. If it is less than 0.44 or higher than 0.55, press
and hold the button to remove the last point and start again. If you miss
pressing a button after an injection, you can press and hold multiple times
to restart the CF.T calibration. Only a few ml have been injected, after all,
and can either be removed with the pipettor or ignored if you just start
the CF.T again without refilling the flask.
9. Inject 1 ml of standard and mix until the EC.T stabilizes (about 50 vigor-
ous up & down motions). Push the button to accept this value. Repeat for
3 more injections. After the last button push, QiQuac will calculate and
display the final CF.T for each active channel. Nothing needs to be done
with these numbers, they will be saved to RAM, but you may wish to write
them down, or take a photo, for your field notes.
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The accuracy of the stream sample volume will depend on this step and the user should try several test runs with QuickFlask and a scale to
determine the volume and uncertainty of the sample.
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EC.T is Electrical Conductivity.Temperature Compensated in μS/cm at 25°C using NLF (Non-Linear Function based on EU standard 27888).
C H A P T E R 3: OPE R AT ION
