36
y = a + bx
where
y
denotes the expected value.
The minimum number of calibrators for this fit type is two.
Extrapolation is only available for the linear regression fit type. The extrapolation result is merely
indicative and needs to be confirmed. Results using extrapolated data are marked with “*” in list
format. In matrix format the extrapolated results are not marked.
Four parameter logistic
The four-parameter logistic method uses the fit model below:
In the equation above,
y
is the signal,
x
the concentration,
a
the response at high asymptote,
b
the
response at low asymptote,
c
the 1/concentration
at the curve’s inflection point (i.e. where the
curvature changes from concave upwards to downwards, or vice versa), and
d
the slope factor at f(c).
The minimum number of calibrators for this fit type is five.
The Concentration logarithmic transformation is not available for this fit type.
Extrapolation is not available for the four-parameter logistic fit type.
Cubic spline
This method is a smoothed point-to-point method where the adjacent calibration points are connected
together using cubic polynomials (see the equation below) and optimizing the connecting points as
smoothly as possible to avoid sharp angles. The results are calculated by first searching for the
correct interval and then using a bisectional method to find the answer from the corresponding
equation. The minimum number of calibrators for this fit type is five.
y
i
= a
i
+ b
i
x
i
+ c
i
x
i
2
+ d
i
x
i
3
Only the means of the measured calibrator replicates can be used, not the individual replicate values.
Extrapolation is not available for the cubic spline fit type.
Point to point
The point-to-point method connects the adjacent response-concentrations coordinates, that is, the
calibration points, together using a straight line (see the equation below), which is different for each of
the intervals. The results are calculated by first searching for the correct interval and then using the
corresponding equation. The minimum number of calibrators for this fit type is two.
y
i
= a
i
+ b
i
x
i
Only the means of the measured calibrator replicates are used in the calculations. The replicates are
visible in the graph but they are not used in calculations.
Note!
The method always returns the first value found for a sample. Therefore, ensure that the
calibration points behave monotonously.
Extrapolation is not available for the point-to-point fit type.
Factor
Measured absorbances are multiplied with a factor given by the user to obtain the concentrations.
The concentration is calculated according to the following equation:
Concentration = Factor x absorbance
Stored curve
You can use a stored curve for an assay (a run). You can only use a stored curve with the protocol it
was created with. After the curve has been stored, the plate layout may be modified to contain, for
example, only unknowns. You can save the curve from the curve window using
FILE/
Save
calibrators
and load it using
FILE/
Load curve
.
d
xc
b
a
b
y
)
(
1
