# Reference method for dibenzofuran and dibenzo-p-dioxin in defoamers: section 4

## Section 4: Calculations

1. From the integrated ion chromatograms for the calibration runs, calculate the relative response factors for tire native DBD and DBF relative to the corresponding perdeuterated DBD and DBF internal standards (=RRFx) according to the following equation:

RRFx = (Aix/Ax)(Cx/Cix)

where:
Aix
peak area of the quantitation ion for the appropriate labelled internal standard (m/z 176 for DBF-d 8 and m/z 192 for DBD-d 8)
Ax
peak area of the quantitation ion for the native analyze "x" (m/z 168 for DBF and m/z 184 for DBD)
Cx
concentration of native analyte "x" pg/μL
Cix
concentration of appropriate internal standard "x", pg/μL

2. If the RRF for DBD and DBF are constant (relative standard deviation < 10%) over the working range, it can be assumed that the RRF is invariant and the average RRF can be used. Alternatively, the results can be used to plot a calibration curve of response ratios, Aix/Ax vs RRF.
3. Calculate the concentration of the native DBD and DBF in the sample, Csx, as follows:

Csx = (RRFx)(Ax/Aix)(Qix/W)

where:
Csx
concentration of native parameter "x" in the sample, ng/g
RRFx
response factor of native parameter "x" relative to its perdeuterated internal standard
Ax
peak area of the quantitation ion for native parameter "x" in the sample (m/z 168 for DBF and m/z 184 for DBD)
Aix
peak area of the quantitation ion for appropriate labeled internal standard "x" in the sample (m/z 176 for DBF-d 8 and m/z 192 for DBD-d 8)
Qix
amount in ng (i.e., 250 ng) of the appropriate labeled internal standard "x" added to the sample before extraction
W
weight of defoamer sample in grams

4. Calculate the percent recovery of the perdeuterated internal standards, % Rix, measured in the sample extract using the formula:

% Rix = [(Aix/Ar)sample][(Ar/Aix)standard](100)

where:
Ar
peak area of the quantitation ion (m/z 147) for haxamethylbenzene recovery standard
Aix
peak area of the quantitation ion for the appropriate labelled internal standard "x" (m/z 176 for DBF-d 8 and m/z 192 for DBD-d 8)

Date modified: