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Figure 31 TOC Concentration vs. CO
100%
80%
60%
40%
20%
Zero or Baseline
UVTOCOperation.fm
(0,y
) and is called the baseline. The higher point (x
1
span reading, though it is not always done at the full scale of the analyzer.
The slope of the interpolated/extrapolated line is the gain of the analyzer
in ppm/mg/L (gas/TOC). See
y
2
Gain
=
------------------ -
ppm
2
(0, y )
1
0
40%
0
20%
For example, if a 0–1000 mg/L analyzer is calibrated with 800 mg/L the
calibration might be defined as (0, 25) and (800, 7602). This would give a
gain of (7602-25)/800 i.e 9.475 ppm/mg/L. The gain of each analyzer will vary
slowly with time due to aging of peristaltic pump tubing and also the aging of
the UV lamps. Following any manual calibration or auto-calibration, this aging
can be identified by the % in the Pri v cal screen (see
page
93). An online TOC measurement of a sample is produced by
measuring the CO
up the TOC mg/L. If the calibration set (0,y
two point active calibration:
Online sample TOC (mg/L)
Where:
y
is the CO
s
At any point in time, four distinct calibrations are stored separately in the
database of the analyzer. Only one is used at any time to calculate the online
Figure
31.
y
–
1
x
2
(x , y )
2
60%
80%
TOC µg/L or mg/L
gas ppm and using the straight line to mathematically look
2
(
y
y
–
s
1
=
----------------------------------- -
(
y
y
–
2
ppm being produced by the sample.
2
Section 6
,y
) is normally called the
2
2
2
Span
100%
section 6.7.3.1 on
) and (x
,y
) are being used as the
1
2
2
) x
•
2
)
1
Calibration Menu
Page 97
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