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i
nterference
Chemical interferences are give in the table below for both types
of hydrogen sulfide sensors .
In addition, Type II sensors are sensitive to light because ferro
cyanide reacts in light, especially blue (short-wave) light, which
gives a false H
S signal . This reaction causes the zero current to
2
increase leading to an overestimation of the H
light . Thus, when measuring through a light gradient (e .g . when
measuring into an illuminated biofilm) the signal will decrease
slightly, when entering the biofilm . In many systems the light will
be almost completely attenuated within the first few hundred
microns .
The sensor has been painted black to reduce this phenomenon,
however light may still enter the sensor through the tip, which is
not possible to paint .
n
ame
m
ethane
c
arbon dioxide
n
itrogen
o
xygen
a
ir
n
itrous oxide
a
mmonia
h
ydrogen
c
arbon monoxide
d
imethyl sulfide
m
ethyl mercaPtan
e
thyl mercaPtan
s
ulfur dioxide
Given as signal for the interfering species in % of H
1
Given as signal for the interfering species in % of H
2
i
nterferences for gases
in gas Phase
Formula
SULF
CH
0
4
CO
0
2
N
0
2
O
0
2
O
, N
, Ar
0
2
2
N
O
0
2
NH
0
3
H
0 . 8
2
CO
0 . 6
(CH
)
S
18
3
2
CH
SH
174
3
C
H
S
13
2
6
SO
40
2
S concentration in
2
i
nterferences for gases
(%)
1
dissolved in water
H
S
2
0
0
0
0
0
0
0
0 . 0 3
4
3
117
8
34
S signal at equal partial pressures
2
S signal at equal molar concentrations
2
Micromanipulator
(%)
2
SULF
H
S
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
96
4
77
487
18
3
44
30
14
9
1
1
19
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