Turner Designs Inc.
845 W.Maude Ave Sunnyvale, CA 94085
toll free (877)316-8049 / (408)749-0994 / fax (408)749-0998
Three Turner Designs sensors (CDOM, Crude Oil, and Refined Fuels) were evaluated by ACT for
response, linearity, accuracy/precision, and reliability. To facilitate testing for all test sites and modes, the
three sensors were housed in a C3 Submersible Fluorometer that allowed functions such as calibration,
auto-ranging, data logging and streaming, and simultaneous measurement of data from all three sensors.
A few important notes to keep in mind when viewing results from this evaluation: 1) a good amount of
research should be done when selecting a calibration standard so as to obtain comparable or meaningful
results, 2) there are potential interference factors that convolute the overall response from fluorophores of
interest, more so when using fluorimetry for fluorescence detection from UV absorbing material, and 3)
because of the various types of materials, all which have different excitation/emission properties eliciting a
wide range of fluorescence yields, data collected from these types of sensors are qualitative in nature and
can only be approximated at best. Our recommendation regarding the most appropriate way to view these
data is looking at absence/presence and trend analysis of fluorescence response in an effort to determine
relative changes in a fluorophore of interest rather than ground truth concentrations of specific compounds.
Response/Linearity
The necessity for testing linearity is more so for the purpose of establishing linear detection limits or
saturation points for certain compounds or applications, which we feel is important to research and
understand prior to sampling. Based on results from this evaluation, we would expect the Crude Oil sensor
to be more sensitive than the CDOM sensor to the presence of oil in water and equivalent in sensitivity
when no oil is present. The three sensors’ response to actual fuel compound confirmed both the ability for
our refined fuel’s sensor to detect fuel compounds rendered undetectable by the CDOM or Crude Oil
sensors and the minimal to no interference observed from CDOM or Crude Oil sensors when fuel is present
in significant concentrations. Turbidity rejection in all three sensors was excellent; no scattering detected at
~8.0 NTU equivalent, BB3 concentration.
Accuracy/Precision
Precision of measured responses were more a focus of this evaluation, rather than accuracy as the ability
to estimate concentrations accurately. Measurements of specific concentrations for multiple challenge
compounds taken for a total of 10 minutes showed low signal variation allowing a clear separation among
concentrations above detection limits.
Range
Detection limits (full range of detection, minimum detection limit, saturation) for CDOM, Crude Oils, and
Refined Fuels are compound dependant and will also vary with water types. For example, the maximum
total hydrocarbon detected during the moored sampling mode was ~35 ppb, well below our specified
detection limit, but the potential for this fuel compound to have a high fluorescence yield may have
attributed to the observed response. The variability among the compounds found in natural environments
makes it a difficult task to specify with certainty instrument capabilities, with respect to limits and detection
ranges, therefore we do our best to specify limits for lab standards which we believe can be easily obtained
by users for the purpose of verifying functionality of the instrument rather than definite calibrations for
estimating concentrations.
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