Horiba Scientific Quanta-phi F-3029, Operation Manual

Page: 23 / 98

Quanta-
φ
rev. C (23 Apr 2010) Theory of Operation
1-9
Influence of OD on fluorescence emission of quinine sulfate dissolved in 0.1
N H
2
SO
4
.
In both compounds there is no correlation of

with concentration because rhodamine
101 has a
υ ≈ 93% and quinine sulfate (

≈ 55%) shows no re-absorption. Yet when the
sample’s intrinsic υ
100 % and self-absorption is strong, the measured
υ
will be
influenced in proportion to the absorbance (OD) of the sample.
In contrast to rhodamine
101 and quinine sulfate,
the figure to the right de-
picts the observed rela-
tionships between the in-
tegrated fluoresence area,
the absorbance, and quan-
tum yield (%) of fluo-
rescein in 0.1
N NaOH.
Clearly as the OD in-
creases beyond 0.1 units,
the relationship between
the fluorescence area
(hollow symbols) and
quantum yield (filled
symbols) becomes increasingly non-linear. Likewise the observed quantum yield be-
comes depressed with increasing OD, consistent with the inner-filter effects.
Similar to the fluorescein data above, self-absorption is also a problem with many solid
samples and powders whose ODs cannot easily be determined. As with liquid samples,
in solid and powder samples, when possible, HORIBA Scientific advises you to vary