Geoscience Reference
In-Depth Information
36
1.12
34
1.08
32
30
1.04
28
ExEm 265/490 nm
Temperature
26
1.00
0
2
4
6
8
Time (h)
1.12
1.08
1.04
1.00
28
30
32
34
36
Sensor Internal Tempertaure (°C)
Figure 6.9. (Top) Internal temperature and fluorescence signal increase during a laboratory experi-
ment using a WetLabs SAFIre fluorometer. (Bottom) Fluorescence as a function of instrument
temperature.
that employed 10 different sensors in varying environments, only 4 performed blank sub-
traction (
Table 6.2
) for their applications. The environmental considerations discussed in
Section 6.5
of this chapter may be of assistance in determining whether blank subtraction
is needed. Selection of the blank type is of great importance. Published blanking methods
have been routinely conducted with purified water, artificial seawater, and filtered seawater.
Which blank is appropriate (if any) must be determined by the analyst and requires a series
of experiments to establish the sensitivities and detection limits of the field sensors.
Once blank subtraction is deemed necessary, a blank may be acquired by either placing
the instrument into a blank solution (open-face design canisters) or pumping water through
the instrument (flow-through design canisters). In most cases the manufacturer's software
can be used to acquire signal output for a blank. However, some sensors have the ability to
measure the signal with a standard voltmeter. There are two accepted methods of applying
the blank: (1) saving the blank as a separate file to be applied during post-processing of
