FluoroCheck II Revision 3.0 Page 8 | 25
3.0 FLUOROMETRY PRINCIPLES AND METHOD OVERVIEW
3.1 FLUORESCENCE MEASUREMENT
The fluorescence principle is based on the science that certain compounds, when subjected to a
specific wavelength of light energy (excitation) and can re-emit this light energy at one, or more, higher
wavelengths (emission). These emission wavelengths are registered as peaks.
Aromatic hydrocarbons, when subjected to a specific wavelength, will fluoresce an emission at a
predictable wavelength. This is considered it's signature wavelength. When the sample is in the cuvet
well of the instrument, it is is exposed to UV light energy (360-370 nm) from a high precision filtered
LED light source. This light energy excites the hydrocarbon molecules in the sample, which then emit
energy at peaks of approximately 450 nm. An emission filter in front of the photodetector allows only
fluorescence at 450 nm +/- 40nm to register, minimizing background interference caused by other
wavelengths. Through the instrument calibration, the measured fluorescence provides a direct
indication of the hydrocarbon concentration in the engineered units of your choice.
The ratio of aromatics to total oil is registered through a customer site calibration or Arjay factory
calibration to provide a display of total oil.
Since different oil types may yield different fluorescent intensities at similar concentrations, an
instrument calibration can be made specific to your application.
3.1.1 DIRECT WATER SAMPLE OVERVIEW
A direct water sample can be tested in the FluoroCheck. This is ideal for fast screening of aromatics in
a water sample without any sample conditioning. The Factory Calibration for refined or crude oils
eliminates the need for a site calibration. The results are more qualitative than quantitative but are
effective for trending and comparison of multiple tests. Samples are tested in the supplied 12mm
diameter (2 MIL) disposable cuvets.
3.1.2 SOLVENT EXTRACTED SAMPLE OVERVIEW
A solvent extraction procedure using Hexane or Pentane as indicated by EPA 1664 Rev 1 and ISO
9377-2 provides high accuracy results. The hydrocarbons are extracted from the water using solvent.
This clarifies and defines the sample to be tested. Background influences are left behind in the water
sample. The FluoroCheck can be calibrated against your local laboratory methods for correlated
results. The supplied disposable 4mm diameter (200 uL) cuvets are used for crude oil testing and the
12mm diameter (2 MIL) disposable cuvets are used for refined oil testing.
3.2 INSTRUMENT OPERATION OVERVIEW
The cuvets provided are disposable to avoid cross-contamination between samples. These are low
wavelength, high transmission disposable borosilicate cuvets. Use only Arjay supplied or
recommended cuvets. Inappropriate cuvets may not have the light transmission suitable for this
instrument or may not resist solvents.
Although the unit is shipped with factory preset calibrations to allow out-of-the-box use, for best
accuracy, the unit should be calibrated against a sample that has been tested by your local lab. This
will correlate the unit to your process water conditions and to your local lab methodology.
The FluoroCheck can store up to 10 different calibrations:
• Location 0 (DIESEL1) is factory calibrated for solvent extraction testing of refined oils.
• Location 1 (CRUDE1) is factory calibrated for solvent extraction testing of crude oils.
