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Advisory Committee on Health Effects of Endocrine Disruptors
The Supplement II to the Intermediary Report
1.2.3.1 |
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4. Analytical procedure
4.1. Sample preparation: cleaning up and concentration
1) Perform a blank test to confirm that the procedure does not
contaminate the sample.
2) Preclude contamination during concentration by the rotary
evaporator, Kuderna Danish concentrator, or nitrogen blowing.
4.2. Measurement: maintenance, calibration and cleaning of
instruments
1) Status check and configuration of the gas chromatograph/mass
spectrometer (GC/MS): Configure the GC/MS as appropriate to the
analyte. Check for appropriate reproducibility and sensitivity.
2) Status check and configuration of the HPLC: Configure the
HPLC as appropriate to the analyte. Check for appropriate
reproducibility and sensitivity.
3) The isotope dilution technique is recommended for GC/MS or
LC/MS measurements.
5. Detection limit
5.1. Detection limit of instruments
1) Detection limit in the sense of analytical chemistry: The
detection limit of an instrument (HPLC, GC, GC/MS, LC/MS, etc.)
is defined as the absolute quantity of a standard sample that
yields a peak height corresponding to S/N = 3. Alternatively,
the limit may be defined as three times the standard deviation
for at least five measurements of a dilute standard solution
which has a concentration close to the detection limit.
2) Detection limit of specific samples: The detection limit of a
specific sample is calculated from the peak height given by the
sample, quantity of the sample used, and the concentration of
the standard substance in the sample that would give a peak
height corresponding to S/N = 3. For a compound which gives no
peak in the measurement of the sample, estimate the peak height
corresponding to S/N = 3 from the peak height of the standard
sample, and use the concentration of the standard substance in
the sample that would give a peak of that height in the same
calculation.
The lower detection limit of specific samples should be lower
than the target detection limit. |
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