Metrohm 746 VA Trace Analyzer - Manual (Page 491)

6 Data processing and evaluation
746 VA Trace Analyzer / 747 VA Stand
6-28
1 Measurement of the calibration solutions
The calibration solutions of known mass concentration
ρ
nn
are each meas-
ured several times. This gives:
EV
n
Evaluation quantity for n th calibration solution
EV
n
.mean Mean value of the evaluation quantities for n th calibra-
tion solution
Std.dev. Standard deviation of the n th individual value EV
n
ρ
eff,s eff,s
Effective mass concentrations of the calibration solu-
tions (calculated from ρ
nn
taking the dilution into ac-
count)
2 Determination of the calibration curve
The parameters of the four possible model functions
y = a + bx Straight line
y = bx Straight line through zero point
y = a + bx + cx 4 Nonlinear curve of 4 th degree
y = bx + cx 4 Nonlinear curve of 4 th degree through zero point
are determined by the procedure described in section 6.9.3 with y = EV and
x = ρ
eff eff
by weighted least squares minimization. These parameters are
displayed on the "RESULTS/Calibrations" page and have the following
meaning:
a Y.reg/offset Intercept of calibration curve
b Slope Slope of calibration curve in the linear region
c Nonlin. Non-linearity factor
3 Display of the calibration curve
The calibration curve
EV vs ρ
eff eff
is displayed and plotted by the 746 VA Trace
Analyzer:
Y.offset
EV
0
0
cal.crv.
linear
nonlin
0/linear
0/nonlin
Slope
4 Measurement of the sample solution
The sample solution with the unknown mass concentration
ρ
eff,s eff,s
of the sam-
ple is measured one or more times. This gives:
EV
s
Evaluation quantity for sample
EV
s
.mean
Mean value of the evaluation quantity for sample
Std.dev. Standard deviation of the individual value EV
s
ρρ
eff eff