BUCHI DuMaster D-480 - Manual (Page 144)

Operation Manual D-480 ©BÜCH Labortechnik AG
7 - Using the instrument 144
 The N integral values should be between 10 and 50 after stabilization. If your N integral values
are significantly higher than 50, repeat the blank value determination with methods which is
associated with an oxygen dosing time of 1second (e.g. "Blank without O2"). If the N integral
values are then normal, the oxygen was contaminated. Otherwise, the system has probably a
leak.
Sample additives or packing material
Blank samples are measured for blank value determination of sample additives (e.g. WO
3
powder) or
packing material:
 prepare blank samples:
 without sample substance.
 with equal amount of sample additives.
 with the same packing material and the same packing method.
 For the blank sample, use the same method used for the real sample.
 The mean value of the blank value integrals is then entered in the software and deducted from
the samples.
 Only if the blank value always remains the same by preparing the sample accordingly, it can also
be "calibrated" and does not have to be deducted. However, in this case standard substances
must be prepared in the same way as the samples for calibration and daily factors.
Determining blank values
Condition
The name of the blank sample must be defined in Options > Settings > Keywords. Ex works, "Blnk"
is already defined as the key word of the blank sample. If you want to change this, you must define
the new name via Options > Settings > Keywords.
Note
The first blank value is always too high after prolonged breaks between measurements or after
maintenance. If you want to perform an exact blank value determination, you must exclude the first
blank value from the calculation. Use a different name for the first blank value sample than the key
word in order to exclude the sample from the calculation.
Determining blank values
Proceed as follows:
 If you have not already done so, set the mode of blank value determination. For that purpose,
open the "Configure Calculations" dialog in the operating software by selecting Options >
Settings > Calculation.
 Define the mode of blank value determination:
If you select the following in "Blank value determination"
 ... ...select "sequentially" a separate blank value is computed for every element for every
group of blank value samples; this value is entered in the respective blank value column
until the next group of blank value samples.
 ... ...select "entirely" all blank value samples in the series are used to compute the blank
value. This blank value is then applied to all samples in the series.
 Then click OK to save your settings.
 Usually, do not place a sample on the carousel.
Only exception: When determining blank values of sample additives or packing materials, place a
blank sample on the carousel. Cf. Types of blank value determination and their settings (on
page 143).
 Enter the following for the sample in the sample view (text view) on the PC: