ETHYLENE OXIDE: METHOD 1614, Issue 2, dated 15 August 1994 - Page 3 of 6
4.
to 24 L. Cap each tube. Pack securely for shipment.
SAMPLE PREPARATION: 5. 6. 7. 8. 9.
10. 11. 12.
Score each sampler with a file. Break sampler at score line. Transfer front sorbent section and first glass wool plug to a 2-mL vial. Transfer middle glass wool plug and back sorbent section to a separate vial. Add 1.0 mL DMF to each vial. Cap each vial. Shake at least 10 sec. Allow to stand at least 5 min. Pipet a 20-µL aliquot of the DMF solution to another 5-mL vial containing 2.0 mL 2% HFBl (v/v) in isooctane. NOTE: Pipet 20 µL of each working standard (step 13) into vials containing 2% HFBl at this step. Cap and shake 1 min: Allow to stand at room temperature at least 5 min. Add 2.0 mL high purity water. Mix 1 min to ensure complete hydrolysis of excess HFBl. Transfer at least 1.0 mL of isooctane (top) layer to 2-mL vial. NOTE: If the sample concentration is higher than the standards, dilute an aliquot of sample with DMF, reanalyze starting at step 9, and apply the appropriate dilution factor in calculations. The desorbed sample (in DMF) keeps well in a freezer [1].
CALIBRATION AND QUALITY CONTROL: 13.
Calibrate daily with at least six working standards over the range 1 to 42 µg EtO per sample. For example: a. Pipet 1.0 mL 2-BrEt (density 1.763 g/mL @ 20 C) into a 10-mL volumetric flask. Dilute to volume with DMF. This is stock solution "A." Dilute 3 mL of "A" to 25 mL with DMF to give standard "B." Dilute 1 mL of "B" to 10 mL with DMF to give standard "C." NOTE: A sample calculation with 95% pure 2-BrEt (MW = 124.98) expressed as its equivalent weight in EtO (MW = 44.05) is: Standard Solution "A": 1.763 g 2 BrEt 10 mL
0.95
44.05 124.97
106 µg
59,036 µg EtO/mL.
Standard Solution "B": 3 mL • 59,030/25 mL = 7084 µg EtO/mL. Standard Solution "C": 1 mL • 7084/10 mL 708.4 µg EtO mL. b. Prepare working standards by injecting microliter volumes of "B" and "C" into vials containing 1.0 mL DMF. The following serial dilution scheme is suggested: Working Standard D E F G H I J
Aliquot added to 1.0 mL DMF
Final µg EtO/mL
2.5 µL "C" 5.0 µL "C" 10.0 µL "C" 2.5 µL "B" 3.5 µL "B" 5.0 µL "B" 6.0 µL "B"
1.77 3.54 7.08 17.7 24.8 35.4 42.5
Higher standards may be used if detector output remains acceptable. (Some detectors may become saturated at higher levels.) c. Analyze working standards together with samples and blanks. d. Prepare calibration graph (µg EtO per sample vs. peak area). Use a nonlinear (e.g., NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
