Buchi DuMaster D-480, Руководство по эксплуатации

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Operating instructions DuMaster D-480 ©BÜCHI Labortechnik AG
7 - Using the instrument 130
Defining the Kjeldahl factor
What is the Kjeldahl factor used for?
It has been well documented that measurement bias exists between the classic wet chemical Kjeldahl
method and the high temperature combustion Dumas method (cube instruments). Bias has also been
documented between Kjeldahl methods using mercury based catalysts and other less toxic catalysts.
The basis of the bias is generally believed due to the less than 100% recovery for the Kjeldahl
method for certain forms of nitrogen. So, the Dumas method will often measure a higher value of
nitrogen compared to Kjeldahl.
Certain industries still require nitrogen values based on the historical Kjeldahl recovery. The “Kjeldahl
Factor” may be used to normalize the nitrogen results measured by the D-480 to their Kjeldahl
equivalent values.
A Kjeldahl factor can be assigned to each Method. This factor (typically between 0.99 to 0.97) is
multiplied to the nitrogen (and protein) results. The Kjeldahl factor however does not influence the
values for standard samples. If the Kjeldahl factor is set to 1.00, no Kjeldahl adjustment will be made.
The inclusion of the Kjeldahl factor into the methods allows users to specify different factors for
different types of samples.
Defining Kjeldahl factor in a method
Proceed as follows:

Open the "Methods" dialog in the operating software by selecting
Options > Settings >
Methods
.

In the left field, select the appropriate method.

Enter the appropriate value in field "Kjeldahl factor".

Then click
Save
. Your modifications will be saved.

Click
Close
to close the dialog. You have now defined the Kjeldahl factor in a method.
Copy methods
Defining custom methods
The existing method can be copied with the option "Copy methods" and subsequently the parameters
of the corresponding requirements can be changed accordingy. In a lot of cases this is more efficient
than creating a new method and entering all parameters.
Copy methods
Proceed as follows:

Open the "Methods" dialog in the operating software by selecting
Options > Settings >
Methods
.

Select a method from a list in the left area which parameters are most similar to the new method.
Enter the parameters of the method to be newly defined:

Enter the following:

Enter the name of the new method in the "ID" field.

Enter the purpose of the method, for example, in the "Description" field.

Change the corresponding method parameters in the other boxes accordingly.

Click
Create
. Your new method will now be included in the list in the left area of the dialog. You
have now successfully copied and defined the method.

Click
Close
to close the dialog.