Buchi DuMaster D-480, Operation Manual

Page: 180 / 354

Operating instructions DuMaster D-480 ©BÜCHI Labortechnik AG
8 - Maintaining the instrument 180
The following table explains the characteristics relating to the sample, as displayed in the above
picture:
Characteristic Description
Sample No. Shows the analysis number of the sample selected at the cursor.
Area Integral of the selected sample.
slope Slope of the curve at the calibration point of the selected sample.
{Element name}
theo
Theoretical absolute content of the selected sample
{Element name}
act
Absolute content of the selected sample, computed with the current curve
Diff. Difference between "theo" and "act", absolute
Diff. Difference between "theo" and "act", relative
Aids for assessing the calibration curve
The following aids are available for assessing the calibration curve:

Via
View > Zoom in / Zoom out
you can display the graph so that you can visually check the
curve.

You can click on the circle to select any sample. This displays the characteristics of the sample.

You can also select a sample using the buttons and . This displays the
characteristics of the sample.
Assessing the calibration curve
The following are used to assess the calibration curve:

Process standard deviation "Proc-SD"

Quality factor "r"

Coefficient "a", that corresponds to a calibrated blank value.
Process standard deviation "Proc-SD"
Use the following values for process standard deviation "Proc-SD" as guidelines:
Acceptable value
Proc-SD = ± 3 µg in the lower range
Proc-SD = ± 15 µg in the upper range
Very good value Proc-SD = ± 1 µg
Quality factor "r"
Use the following values for quality factor "r" as guidelines:
Good value for linear calibration function
r = 0.99 (r should tend to 1)
Good value for polynomial as calibration
function
r = < 2-4
Coefficient "a"
Use the following values for coefficient "a" as guidelines:
Acceptable range
a = 1 x 10 -3 to 3 x 10 -2 or smaller
The range given here applies to calibration with one calibration range and, when calibrating with two
calibration ranges, only for the lower range, while "a" may be greater in the second range.
If you do not approximately achieve the listed values you can assume that:

either you have selected the wrong calibration curve calculation mode,

or the calibration measurement has failed (weighing error, etc.).