pg | 19
fDOM
Sensor Overview
e EXO fDOM (Fluorescent Dissolved Organic Matter) sensor is a uorescence sensor which detects the
uorescent component of DOM (Dissolved Organic Matter) when exposed to near-ultraviolet (UV) light.
Colored Dissolved Organic Matter
Users might wish to quantify colored dissolved oxygen matter (CDOM) in order to determine the amount of
light which is absorbed by stained water and thus is not available for the photosynthesis process carried out
by subsurface aquatic plants and algae. In most cases, fDOM can be used as a surrogate for CDOM.
Quinine Sulfate
A surrogate for fDOM is Quinine Sulfate, which, in acid
solution, uoresces similarly to dissolved organic matter.
e units of fDOM are quinine sulfate units (QSUs) where
1 QSU = 1 ppb quinine sulfate and thus quinine sulfate is
really a double surrogate for the desired CDOM parameter.
e EXO fDOM sensor shows virtually perfect linearity
(R
2
=1.0000) on serial dilution of a colorless solution of
quinine sulfate. However, on serial dilution of stained water
eld samples, the sensor shows some underlinearity. e
point of underlinearity in field samples varies and is
1.8
Specifications
Units
Quinine Sulfate equivalents
(QSE), ppb
Temperature
Operating
Storage
-5 to
+
50°C
-20 to
+
80°C
Range
0 to 300 ppb QSE
Response
T63<2 sec
(see pg 12)
Resolution
0.01 ppb QSE
Sensor Type
Optical, fluorescence
Linearity
R
2
>0.999 for serial dilution
of 300 ppb Quinine Sulfate
solution
Detection Limit
0.07 ppb QSE
Optics:
Excitation
365±5 nm
Emission
480±40 nm
WARNING
UV LIGHT
Do not look
directly at light.
(continued)
599104
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