Page:NIOSH Manual of Analytical Methods - 1615.pdf/2

 METHYL tert-BUTYL ETHER: METHOD 1615, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1. 2. 3.

4. 5. 6. 7.

EQUIPMENT:

Methyl tert-butyl ether,* reagent grade. Carbon disulfide,* reagent grade. Calibration stock solution, 7.41 mg/mL. Dilute 40 µL methyl tert-butyl ether to 4.00 mL with carbon disulfide. Helium, prepurified. Hydrogen, prepurified. Air, compressed, filtered. Liquid nitrogen or carbon dioxide for subambient cooling of GC oven.



See SPECIAL PRECAUTIONS.

1. Sampler: Two glass tubes in tandem, each 8 cm long, 8-mm OD, 6-mm ID, flame sealed ends with plastic caps, containing activated coconut shell charcoal held by plugs of silated glass wool (front tube = 400 mg, back tube = 200 mg). Pressure drop across tubes at 1 L/min airflow must be less than 3.4 kPa. 2. Personal sampling pump, 0.1 to 0.2 L/min with flexible connecting tubing. 3. Gas chromatograph with sub-ambient cooling, flame ionization detector (page 1615-1). 4. Vials, 5-mL, 2-mL with PTFE-lined crimp caps. 5. Pipettes, TD, 4-, 2- and 1-mL. 6. Syringes, 1-mL, 250-, 100-, 25-, and 10-µL.

SPECIAL PRECAUTIONS: Methyl tert-butyl ether and carbon disulfide are extremely flammable (flash points -28 °C and -30 °C, respectively. Carbon disulfide is also toxic. Work with these compounds in a hood.

SAMPLING: 1. 2. 3. 4.

Calibrate each personal sampling pump with a representative sampler in line. Immediately before sampling, break ends of sampler tubes. Connect smaller tube to personal sampling pump with flexible tubing and to larger tube with a short piece of plastic tubing. Sample at an accurately known flow rate of 0.1 to 0.2 L/min for a sample size of 2 to 96 L. Separate the tubes, cap, and pack securely for shipment. Chilling of the samples is necessary if they are not expected to be analyzed within five days.

SAMPLE PREPARATION: 5. 6. 7.

Add 2.0 mL carbon disulfide to 5-mL vials. Loosely cap vials. Place front and back sorbent sections in separate vials. Discard glass wool and foam plugs. Immediately cap each vial. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

9.

Calibrate daily with at least seven working standards. a. Prepare standards in capped vials by mixing various volumes (i.e., 5 to 230 µL) of calibration stock solution with carbon disulfide to a total volume of 4.00 mL to obtain concentrations in the range of 0.010 to 5 mg/mL. b. Analyze together with samples and blanks (steps 11 and 12). Determine the desorption efficiency (DE) at least once for each lot of charcoal used for sampling in the calibration range (step 8). Prepare three tubes at each level plus three media blanks. a. Use the 400-mg charcoal tube for DE determination. Hold charcoal in the tube by silanzied glass wool. b. Prepare three DE stock solutions by mixing 4, 40, and 160 µL of methyl tert-butyl ether and making up a total volume to 4.00 mL with carbon disulfide to produce corresponding concentrations of 0.741, 7.41 and 29.62 µg/µL. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94