BUCHI DuMaster D-480 - Manual (Page 132)

Operation Manual D-480 ©BÜCH Labortechnik AG
7 - Using the instrument 132
 Open the "Methods" dialog in the operating software by selecting Options > Settings >
Methods.
 In the left field, select the appropriate method. In the fields at the right side the parameters of the
selected method are now displayed.
 Click Close to close the dialog again.
Defining custom methods
Proceed as follows:
 Open the "Methods" dialog in the operating software by selecting Options > Settings >
Methods.
 Click New. The input boxes on the right of the dialog are now empty. Enter the parameters of the
method to be newly defined:
 Enter the following:
 Enter the name of your method in the "ID" field.
 Enter the purpose of the method, for example, in the "Description" field.
 Input the corresponding method parameters in the other boxes.
 Click Create. Your new method will now be included in the list in the left area of the dialog. You
have now defined the method.
 Click Close to close the dialog.
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.