Page:NIOSH Manual of Analytical Methods - 2549.pdf/2

 VOLATILE ORGANIC COMPOUNDS (SCREENING): METHOD 2549, Issue 1, dated 15 May 1996 - Page 2 of 8

REAGENTS:

EQUIPMENT:

1. Air, dry 2. Helium, high purity 3. Organic compounds of interest for mass spectra verification (See Table 1).* 4. Solvents for preparing spiking solutions: carbon disulfide (low benzene chromatographic grade), methanol, etc.(99+% purity)

1. Sampler: Thermal sampling tube, ¼” s.s. tube, multi-bed sorbents capable of trapping organic compounds in the C3-C16 range. Exact sampler configuration depends on thermal desorber system used. See Figure 1 for example. 2. Personal sampling pump, 0.01 to 0.05 L/min, with flexible tubing. 3. Shipping containers for thermal desorber sampling tubes. 4. Instrumentation: thermal desorption system, focusing capability, desorption temperature appropriate to sorbents in tube (~300 C), and interfaced directly to a GC-MS system. 5. Gas chromatograph with injector fitted with 1/4" column adapter, 1/4" Swagelok nuts and Teflon ferrules (or equivalent). 6. Syringes: 1-µL, 10-µL (liquid); 100-µL, 500-µL (gas tight) 7. Volumetric Flasks, 10-mL. 8. Gas bulb, 2 L


 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Some solvents are flammable and should be handled with caution in a fume hood. Precautions should be taken to avoid inhalation of the vapors from solvents as well. Skin contact should be avoided. SAMPLING: NOTE:

1. 2.

3.

4.

5. 6.

Prior to field use, clean all thermal desorption tubes thoroughly by heating at or above the intended tube desorption temperature for 1-2 hours with carrier gas flowing at a rate of at least 50 mL/min. Always store tubes with long-term storage caps attached, or in containers that prevent contamination. Identify each tube uniquely with a permanent number on either the tube or tube container. Under no circumstances should tape or labels be applied directly to the thermal desorption tubes. Calibrate each personal sampling pump with a representative sampler in line. Remove the caps of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. NOTE: With a multi-bed sorbent tube, it is extremely important to sample in the correct direction, from least to maximum strength sorbent. For general screening, sample at 0.01 to 0.05 L/min for a maximum sample volume of 6 L. Replace caps immediately after sampling. Keep field blanks capped at all times. Tubes can act as diffusive samplers if left uncapped in a contaminated environment. Collect a "humidity test" sample to determine if the thermal adsorption tubes have a high water background. NOTE: At higher sample volumes, additional analyte and water (from humidity) may be collected on the sampling tube. At sufficiently high levels of analyte or water in the sample, the mass spectrometer may malfunction during analysis resulting in loss of data for a given sample. Collect a "control" sample. For indoor air samples this could be either an outside sample at the same location or an indoor sample taken in a non-complaint area. Ship in sample storage containers at ambient temperature. Store at -10 C.

SAMPLE PREPARATION: 7.

Allow samples to equilibrate to room temperature prior to analysis. Remove each sampler from its storage container.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 5/15/96