SAMPLE PREPARATION:
4. Using tweezers, transfer each sample or blank filter to a vial. Add 10.0 mL CCl4
. Cap and shake
vigorously.
CALIBRATION AND QUALITY CONTROL:
5. Calibrate daily with at least six working standards.
a.Add known amounts of stock mineral oil standard to CCl4
in 10-m L volumetric flasks and dilute
to the mark to obtain mineral oil concentrations in the range 5 to 250 µg/mL.
b.Analyze with samples and blanks (step 8).
c.Prepare calibration graph (peak absorbance vs. :g mineral oil).
6. Determine recovery (R) at least once for each lot of filters used for sampling in the range of
interest. Prepare three filters at each of five levels plus three media blanks.
a.Deposit a known amount of stock mineral oil standard onto the filter. Allow solvent to
evaporate.
b.Store samples overnight in filter cassettes.
c.Prepare and analyze with working standards.
d.Prepare a graph of R vs. µg mineral oil recovered.
7. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration
graph and R graph are in control.
MEASUREMENT:
8. Scan each standard solution and each blank or sample filter extract from 3200 to 2700 cm-1 in
absorbance mode vs. CCl4
in reference beam. Record absorbance at wavelength of largest
absorbance near 2940 cm-1 (± 11.8%).
CALCULATIONS:
9. Determine the mass, µg (corrected for R), of mineral oil found in the sample (W ) and in the
average media blank (B) from the calibration graph.
10. Calculate concentration, C, of mineral oil in the air volume sam pled, V (L)