Teledyne T200, Operation Manual, Page: 291 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Principles of Operation
289
Quenching is an unwanted phenomenon and the extent to which it occurs depends on the
properties of the collision partner.

Larger, more polarized molecules such as H
2
O and CO
2
are the most significant
quenching interferents of NO chemiluminescence.

The influence of water vapor on the T200 measurement can be eliminated with
an optional, internal sample gas dryer (see Section 3.3.2.6).

The interference of varying CO
2
amounts at low concentrations (less that 0.5%)
is negligible.

In cases with excessively high CO
2
concentrations (larger than 0.5%), the effect
can be calibrated out by using calibration gases with a CO
2
content equal to the
measured air.

Only very high and highly variable CO
2
concentrations will then cause a
measurable interference. For those applications, it is recommended to use
other analyzer models. Please consult Teledyne API's Sales Department or our
website (see Section 12.10).

Smaller less polar and electronically “harder” molecules such as N
2
and O
2
can
cause interference of this type as well, however, the concentrations of N
2
and O
2
are virtually constant in ambient air measurements, hence provide a constant
amount of quenching that is accounted for in the calibration of the instrument .
13.1.5.3. LIGHT LEAKS
The T200 sensitivity curve includes a small portion of the visible light spectrum (see
Figure 13-2), therefore it is important to ensure that the reaction cell is completely
sealed with respect to light. To ensure this:

All pneumatic tubing leading into the reaction cell is opaque in order to prevent light
from entering the cell.

Light penetration is prevented by stainless steel filters and orifices.
06858E DCN7057