Determine the slope, m, of the calibration graph in counts/:g. The intercept, b, on the abscissa
should be within ± 5 :g of zero.
NOTE: A large intercept indicates an error in determining the background, i.e., an incorrect
baseline or interference by another phase.
10. NOTE: The following procedure for absorption correction is not necessary in situations that have been previously documented as requiring no corrections.
Select six silver mem brane filters as media blanks randomly from the same box of filters to be used for
depositing the samples. These will be used to test for sample self-absorption. Mount each of the media
blanks on the filtration apparatus and apply vacuum to draw 5 to 10 m L 2-propanol through the filter.
Remove, let dry, and mount on XRD holders. Determine the net normalized count for the silver peak,
îAg, for each m edia blank (step 12.g). Obtain an average value for the six m edia blank s, ÎA
o
g
.
NOTE: The analyst is a critical part of this analytical procedure [12]. A high level of analyst expertise
is required to optimize instrument parameters and correct for matrix interferences either during
the sample preparation phase or the data analysis and interpretation phase [15]. The analyst
should have some training (university or short course) in mineralogy or crystallography in order
to have a background in crystal structure, diffraction patterns and mineral transform ation. In
addition, an intensive short course in the fundamentals of X-ray diffraction can be useful.