Reference method for dibenzofuran and dibenzo-p-dioxin in defoamers: section 4
Section 4: Calculations
- 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 (=RRF_{x}) according to the following equation:
RRF_{x} = (A_{ix}/A_{x})(C_{x}/C_{ix})
where:- A_{ix}
- 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})
- A_{x}
- peak area of the quantitation ion for the native analyze "x" (m/z 168 for DBF and m/z 184 for DBD)
- C_{x}
- concentration of native analyte "x" pg/μL
- C_{ix}
- concentration of appropriate internal standard "x", pg/μL
- 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, A_{ix}/A_{x} vs RRF.
- Calculate the concentration of the native DBD and DBF in the sample, C_{sx}, as follows:
C_{sx} = (RRF_{x})(A_{x}/A_{ix})(Q_{ix}/W)
where:- C_{sx}
- concentration of native parameter "x" in the sample, ng/g
- RRF_{x}
- response factor of native parameter "x" relative to its perdeuterated internal standard
- A_{x}
- peak area of the quantitation ion for native parameter "x" in the sample (m/z 168 for DBF and m/z 184 for DBD)
- A_{ix}
- 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})
- Q_{ix}
- 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
- Calculate the percent recovery of the perdeuterated internal standards, % R_{ix}, measured in the sample extract using the formula:
% R_{ix} = [(A_{ix}/A_{r})_{sample}][(A_{r}/A_{ix})_{standard}](100)
where:- A_{r}
- peak area of the quantitation ion (m/z 147) for haxamethylbenzene recovery standard
- A_{ix}
- 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})
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