Thermo Scientific SOLA II, User Manual

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Product Overview
Total Sulfur Measurement
Thermo Fisher Scientific SOLA II User Guide 2-3
enter the cell of the PUVF detector where they are exposed to ultraviolet (UV)
light. Absorption of UV light by SO
2
molecules results in an excited state of
the SO
2
molecules. The excited state SO
2
molecules exist at a higher energy
state (due to absorption of energy in the form of UV light) and rapidly relax
to their original energy level or ground state through the emission of light.
This process is called fluorescence. The intensity of the light emitted by SO
2
fluorescence is directly proportional to the SO
2
concentration. Pulsing the UV
light allows more energy (UV light) to be delivered to the sample, increasing
the fluorescence intensity for a given SO
2
concentration. This results in
increased overall sensitivity of the instrument.
At the PUVF detector, it is important to ensure that the measured light is
representative of only the SO
2
concentration and not some other species. SO
2
molecules emit light through fluorescence at a specific wavelength, and the
PUVF detector utilizes bandpass filters to ensure that only light from SO
2
is
measured. Once the proper wavelength of light is selected, its intensity is
measure by a photomultiplier tube (PMT). The PMT converts light energy to
electrical energy through manipulation of the photoelectric effect. The
electrical signal generated by the PMT is finally processed by the analyzer
electronics and software to determine and report the concentration of total
sulfur in the liquid petroleum fraction or gas sample.
The analyzer can be configured to report total sulfur in parts per million
(ppm), parts per billion (ppb), or milligrams per liter (mg/L).
λ
When using the ppm or ppb units of measure, you can choose to calibrate
the analyzer in terms of ppm (w/w), ppm (v/v), ppm (w/v), ppb (w/w),
ppb (v/v), or ppb (w/v).
λ
When using density compensation and the ppm or ppb units are selected,
the display shows ppm/weight or ppb/weight.
Units of concentration calculated on a weight/weight basis are sensitive to
sample density. If the density of the calibration standard is significantly
different from the density of the sample, a density correction should be
applied.
λ
If the sample density varies significantly, a density correction is also
necessary when using concentration units of ppm (w/w) or ppb (w/w).
λ
If using mg/L, ppm (w/v), ppm (v/v), ppb (w/v), or ppb (v/v), a density
correction is not required.