Buchi DuMaster D-480, Operation Manual

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Operating instructions DuMaster D-480 ©BÜCHI Labortechnik AG
4 - Understanding the instrument and planning its use 55
The correlation coefficient is computed according to this formula:
where:
r 2 = correlation coefficient
x
i
= peak area of the corresponding sample
y
i
= absolute content of the corresponding
sample
n = number of samples
i = index from 1 to n
Computing the quality factor for polynomials of a higher degree
In order to assess how well the calibration curve described by the polynomial follows the actual
development of the pairs of values, the software computes a quality factor for each calibration
process. For a polynomial of a higher degree, this quality factor corresponds to the sum of the error
squares. The closer the sum of error squares tends to 0, the better the fit.
The sum of error squares is computed with these formulae:
where:
q = quality
ssq = sum of error squares
act
i
= actual absolute content computed respectively
theo
i
= theoretical absolute content respectively
n = number of samples
i = index from 1 to n
Routine measuring work
Definitions
Routine measuring work comprises the following activities:

Determination of instrument blank values.

Instrument conditioning with conditioning samples.

Determination of daily factors.
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.