OSCAR G2
Manual
D01-44en201810
Software V.1.1.6
(C)TriOS Mess- und Datentechnik GmbH
Bürgermeister-Brötje-Str. 25
D- 26180 Rastede/Germany
16 / 62
when later preparing the calibration solutions. Calibration solutions with an absorption
coefficient (
a
578
nm
) between 0.5 and 2 m
-
1
(on the
log
n
scale) are prepared by diluting a few
milliliters of the stock solution in ca. 2000 ml purified water. The exact spectral absorption
coefficients of this Nigrosine in solution is determined photometrically in the range of ca. 350
to 800 nm using a 10 cm cuvette and purified water as the reference.
The transmission measurements in the PSICAM are conducted by determining the light
intensity inside the cavity when the cavity is first filled with purified water
F
w
, and second with
the calibration solution
F
nig
. In each case the temperature of the fluid (
t
w
and
t
nig
) inside the
cavity should be recorded for a later temperature correction of the pure water absorption. For
field applications the parallel application of a CTD probe is recommended.
After the calibration solution has been measured, the PSICAM has to be cleaned as the stain
adsorbs considerably fast on the cavity wall of the PSICAM. Therefore the PSICAM is
bleached for 15 min with a 0.1 % sodium hypochlorite solution (NaOCl). Afterward the bleach
is removed from the PSICAM by washing the cavity several times with purified water.
The reflectivity is calculated for the pair of pure water/calibration solution using the pure
water absorption as
a
B
, and the sum of absorptions of pure water and Nigrosine as
a
A
. The
pure water absorption is calculated beforehand for each fluid using the specific fluid
temperature.
2.1.4 Calibration procedure in short
1) preparation of approx. 100 ml Nigrosine stock solution (
a
580nm
1cm
ca. 3 OD)
2) preparation of 2000 ml Nigrosine calibration solution
a
580nm
= 0.5
– 2 m
-1
3) determination of Nigrosine absorption,
a
nig
, of the calibration solution (10 cm cuvette
in spectrophotometer or using a LWCC system (liquid waveguide capillary cell), 3x)
4)
determination of “transmission” (nigrosine solution vs. purified water) in the PSICAM,
5) cleaning and bleaching of the cavity after the measurement of the nigrosine solution
6) calculation of reflectivity (after temperature correction of pure water absorption),
where
