Metrohm viva 1.1 (ProLab) - Manual (Page 685)

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5 Method
viva 1.1 (for process analysis)
￭￭￭￭￭￭￭￭ 673
Linear interpolation y = CALC 0 + CALC 1 ⋅
x
≥ 2
At least three points are required for being able to generate a nonlinear or
quadratic calibration. A suitable curve fit (quadratic or nonlinear) must be
placed on the points so that the calibration curve is available in the curve
display and/or the calibration curve can be calculated. Fig. 1 shows the
first three points of the calibration, which lie upon a line. This curve can-
not be evaluated with a nonlinear or quadratic curve type. For the purpo-
ses of evaluation, the calibration curve must intersect the line with the
evaluation ratio and may not lie parallel to it.
Figure 1 Fig.: 1
An additional, fourth point is required for the calibration so that the non-
linear or quadratic function can be placed on the points and extrapolated
to the intersection point with the evaluation ratio (see Figure 2, page
673).
Figure 2 Fig.: 2
NOTE
The curve type for the standard solution and the curve type for the
sample need not be identical.