783620H / 1013 6. ANALYSIS METHODS
3) Determine the (decimal representation) FWHM of this peak (based on the FWHM calibration at the centroid channel).
4) Determine half of the FWHM range (denoted as I
L
), which is calculated as the integer representation of (1.25 * FWHM + 0.5). Note that this value is capped at 100.
5) Determine the centroid for integration (denoted as C
I
), which is simply the centroid channel determined in step (2) rounded to the closest whole (integer) number.
6) Determine a lower channel of integration (denoted as C
Low
) as follows. This value has a minimum value of 4.
C
Low
= C
I
- I
L
+ 1
7) Determine an upper channel of integration (denoted as C
High
) as follows:
C
High
= C
I
+ I
L
- 1
8) A
3
is then simply the sum of all channels from C
Low
to C
High
.
6.9.1.2. Background Methods
B
1
Background reported in the Identified Peak Summary (counts). These backgrounds are used in Methods 1, 2, 5, 6, 7, 8, 12, and 16 below. For some MDA methods, if the peak fails validity tests, B
1
= B
1
+ peak area.
B
2
The average of three high-energy channels and three low-energy channels as part of peak area method A
3
(counts). Backgrounds computed in this manner are used in Method 13 below.
B
3
The sum of the counts on the high-energy portion of the peak and the low-energy portion of the peak. The boundary of the peak is established as described for A
1
. Backgrounds computed in this manner are used in Methods 14 and 15 below.
To determine the area:
1) Determine the (decimal representation) centroid energy of the peak.
2) Determine the (decimal representation) channel of this centroid (based on the energy calibration).
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3) Determine the (decimal representation) FWHM of this peak (based on the FWHM calibration at the centroid channel).
4) Determine the integer value representation of the centroid channel (denoted as C
Int
) simply by rounding the centroid channel down to the closest whole (integer) number.
5) Determine the width of 2.5 times the FWHM (denoted as I
B
, range 4 to 100), then round to next integer; e.g., round 5.0 to 5, and 5.0001 to 6.0 to 6. This value is calculated as follows:
I
B
= (Integer) 2.5 * FWHM + 0.9999
6) Determine half the I
B
range (denoted as L) as follows and rounded down to the next closest whole integer:
L = (Integer) I
B
/ 2
7) Determine the start channel of the main peak region (denoted as Pk
Start
). This value is set at the minimum value of 1, and is calculated as:
Pk
Start
= C
Int
- (integer) (-0.45 + IB / 2)
8) Determine the end channel of the main peak region (denoted as Pk
End
) as follows:
Pk
Start
= C
Int
+ L
9) Determine the starting channel for N1 integration (denoted as N1
Low
) as follows:
N1Low = Pk
Start
- L
10) Determine the ending channel for N1 integration (denoted as N1
High
) as follows:
N1High = Pk
Start
- 1
11) N1 is then the summation of all counts from channel N1
Low
to N1
High
.
12) Determine the starting channel for N2 integration (denoted as N2
Low
) as follows:
N2Low = Pk
Start
+ 1
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