Fdom - Xylem EXO Series User Manual

fDOM

1.8
Sensor Overview
The EXO fDOM (Fluorescent Dissolved Organic Matter) sensor is a fluorescence sensor which detects the
fluorescent 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.
A
directly at light.
599104
WARNING
UV LIGHT
Do not look
Quinine Sulfate
A surrogate for fDOM is Quinine Sulfate, which, in acid
solution, fluoresces similarly to dissolved organic matter.
The 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.
The EXO fDOM sensor shows virtually perfect linearity
(R =1.0000) on serial dilution of a colorless solution of
2
quinine sulfate. However, on serial dilution of stained water
field samples, the sensor shows some underlinearity. The
point of underlinearity in field samples varies and is
Specifications
Quinine Sulfate equivalents
Units
(QSE), ppb
Temperature
-5 to + 50°C
Operating
-20 to + 80°C
Storage
0 to 300 ppb QSE
Range
T63<2 sec
Response
0.01 ppb QSE
Resolution
Sensor Type Optical, fluorescence
R >0.999 for serial dilution
2
Linearity of 300 ppb Quinine Sulfate
solution
Detection Limit 0.07 ppb QSE
Optics:
365±5 nm
Excitation
Emission 480±40 nm
(continued)
(see pg 12)
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