783620H / 1013 6. ANALYSIS METHODS
background.
PEAK CENTROID BACKGROUND NET AREA INTENSITY UNCERT FWHM
CHANNEL ENERGY COUNTS COUNTS CTS/SEC 1 SIGMA % keV
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Background width: best method (based on spectrum).
2939.64
718.00
1514.
79.
.009
70.82
1.517
Background width: average of five points.
2939.64
718.00
1372.
12.
.001
422.37
1.517
Background width: average of three points.
2939.64
718.00
1299.
43.
.005
Background width: minimum data point.
2939.64
718.00
1214.
72.
.008
119.77
69.70
1.517
1.517
Fig. 237. Example of Different Background Method Results.
6.3.2. Peak Area — Singlets
6.3.2.1. Total Summation Method
The gross area of the peak is the sum of the contents of each channel between the background channels (including the two background channels) as follows:
(30)
where:
A g
= the gross area
C i
= the data value of channel i
l
= the center channel of the background calculation width at the low energy side of the spectrum
h
= the center channel of the background calculation width at the high energy side of the spectrum
This peak area calculation method (referred to as total summation) maintains precision as the peak gets smaller, is less sensitive to random fluctuations in the data, and is less sensitive to the differences between the spectrum peak shape and the calibrated peak shape.
Refer to Fig. 235, Fig. 236, and Table 5 to calculate the gross area for the example peak. The integral from channel 2276 to 2311 is 18143 counts.
The net area is the gross area minus the background in those channels (Fig. 238).
243
