Page:NIOSH Manual of Analytical Methods - 2557.pdf/2

 DIACETYL: METHOD 2557, Issue 1, dated 15 August 1994 - Page 2 of 4

REAGENTS:

EQUIPMENT:

1.	Diacetyl, chromatographic grade* 2.	Acetone, pesticide grade* 3.	Methanol, pesticide grade* 4.	Helium, pre-purified and filtered 5.	Hydrogen, pre-purified and filtered 6.	Air, compressed, purified, and filtered 7.	Desorbing solvent: acetone/methanol (99:1) 8.	Calibration stock solution: Add known amount of diacetyl to desorbing solvent in 10- mL volumetric flask
 * See SPECIAL PRECAUTIONS

1.	Sampler: Anasorb CMS solid sorbent tube (SKC, Inc. # 226-121) or equivalent 2.	Personal sampling pump, 0.01 to 0.2 L/min, with flexible tubing 3.	Gas chromatograph equipped with FID, integrator, and capillary column with a deactivated glass inlet liner (page 2557-1) 4.	Vials, autosampler, 2-mL, amber glass, with PTFE-lined crimp caps 5.	Syringes, 10-μL, 25-μL, and 1-mL 6.	Pipettes, 3-mL and 5-mL 7.	Volumetric flasks, 10-mL, amber

AL

SPECIAL PRECAUTIONS:  Diacetyl is flammable, toxic, and forms explosive mixtures in air. Acetone and methanol are flammable and pose a fire hazard. Work with all chemicals in a well ventilated laboratory safety hood. SAMPLING:

ST OR

and are shipped cold (5 °C).

IC

1.	Calibrate each personal sampling pump with a representative sampler in line. 2.	Break the ends of the sampling tube immediately before sampling. Attach sampling tube to personal sampling pump with flexible tubing. 3.	Sample at an accurately know flow rate between 0.01 and 0.2 L/min for a total sample size of 10 L. 4.	Cap the samplers with plastic caps, pack in a manner to insure that the samplers are kept in the dark, SAMPLE PREPARATION:

5.	Place the front and back sorbent sections in separate amber vials (due to photosensitivity of diacetyl). Place the glass wool plug preceding the front section into the vial containing the front sorbent section. Discard the urethane foam plugs. 6.	Add 1.0 mL of the acetone/methanol (99:1) solvent into each vial. Securely attach crimp caps to each vial. 7.	Place each vial on a rotary mixer for 1.5 hours. CALIBRATION AND QUALITY CONTROL:

HI

8.	Calibrate daily with at least six working standards from below the LOD to 10 times the LOQ. If necessary, additional standards may be added to extend the calibration curve. a.	 Add known amounts of diacetyl to the solvent in a 10-m L volumetric flask and dilute to the mark. Prepare additional standards by serial dilution in 10-mL volumetric flasks. b.	 Analyze together with samples and blanks (steps 11 and 12). c.	 Prepare calibration graph (peak area vs μg diacetyl). 9.	Determine the desorption efficiency (DE) at least once for each lot of Anasorb CMS used for sampling in the calibration range (step 8). a.	 Prepare three tubes at each of five levels plus three media blanks. b.	 Inject a known amount (5 to 20 μL) of DE stock solution directly onto the front section of each Anasorb CMS tube with a microliter syringe. c.	 Allow the tubes to air equilibrate for several m inutes, then cap the ends of each tube and allow to stand overnight. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition