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Chapter 5: Calibration and Verification
Two-Point Calibration
The concentrations of the two points should be selected to bracket the range of concentrations expected in the
samples that will be subsequently analyzed.
As in all calibrations involving more than a single point, the point having the lowest concentration is measured
first. In most cases the Analyzer will be used to analyze samples containing substantial TOC concentrations.
However, if the Analyzer will be used to measure samples having very low TOC concentrations, then Point 1 may
have to be reagent water (TOC 0.1 ppm) in order to bracket the concentrations of the samples.
When you plan on measuring TOC(TC-IC) in your samples, it is recommended that the first calibration point for
the TC and IC portions be reagent water. This will ensure that the best linear response will be achieved for both
TC and IC regardless of the variability of the individual concentrations.
Figure 32
depicts a two-point calibration in which point 1 is not reagent water, but rather a standard of the
known TOC concentration. The concentrations of both points are entered into the calibration protocol.
The response of the Analyzer is defined by the equation:
C = a + b*R
where,
R = Mass Response, μg
a = Calibration intercept
b = Calibration constant (slope)
C = mg/L Carbon, ppm
GE Analytical Instruments ©2016
Figure 32: Two-Point Calibration (Point 1 is Standard)
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DLM 68100-09 EN Rev. A
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