BUCHI DuMaster D-480 - Manual (Page 57)

Operation Manual D-480 ©BÜCH Labortechnik AG
4 - Understanding the instrument and planning its use 57
Routine measuring work is performed at set intervals or on defined occasions before, during or after a
series of measurements with real samples.
Instrument blank values
Determination of the instrument blank value depends on your needs. The following overview shows
the type and purpose of the individual determinations.
Purpose Sample Occasion
Checking gas-tightness none after maintenance work
Blank value determination of
sample additives and packing
materials
 Sample additive
 Packing material
to allow for sample additives or packing
material
For details on determining blank values, cf. Types of blank value determination and their settings
(on page 143).
Conditioning samples
Conditioning samples are measured with standard substances at the start of every series of analyses.
They are used to check...
 ... the correct run of the analysis.
 ... the proper condition of the instrument.
 ... flow and pressure behavior of the gases.
Daily factor determinations
Determination of the daily factor serves...
 ... to fine-tune instrument calibration to room conditions at the time of analysis.
 ... to assess the condition of the instrument by observing daily factor fluctuations and drift trends.
When to perform routine measuring work
Perform routine measuring work...
 ... at least once a day.
 ... additionally when measuring breaks last longer than 2 hours.
If a series of analyses exceeds a duration of 5-6 hours (carousel completely loaded), it is advisable to
determine the daily factor additionally at the end of the series.
Formulae for blank value determination and compensation
Blank samples and blank values
Blank samples are samples...
 ... that do not contain sample substance.
 ... that have a key word for identification by the software as blind samples.
Despite the lack of sample substance, a peak area value is computed on the basis of various factors
when analyzing blank samples. This peak area value is referred to as a blank value. In order to
compensate for this, the averaged blank value is subtracted from the measured peak area value of
every individual analysis sample.