Appendix A
|
General Instrument Information
210
|
Orion AquaMate Spectrophotometer User Manual
Thermo Scientific
Calculation
Calculation Equation
Segmented model
The segmented model requires:
•
Data for at least two standard data points with different concentration and
absorbance
•
Slopes of all segments must be ascending (positive) or descending
(negative)
Validity of standard
curves
A(c
1
) > A(c
2
) for all c
1
> c
2
or
A(c
1
) < A(c
2
) for all c
1
> c
2
Where:
A = absorbance
c
1
, c
2
= concentration
Graph of Valid Nonlinear Standard Curve:
If this is not the case, there will be more than one solution within the specified
domain and the message “Curve cannot be used to determine sample
concentrations – it may produce ambiguous results” will appear when the curve
is viewed.
Graph of Invalid Nonlinear Standard Curve: