Page:NIOSH Manual of Analytical Methods - 4000.pdf/3

 TOLUENE: METHOD 4000, Issue 2, dated 15 August 1994 - Page 3 of 4 7. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 8. Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 4000-1. 9. Inject sample aliquot manually using solvent flush technique or with an autosampler. NOTE: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid with CS2, reanalyze, and apply the appropriate dilution factor in calculations. 10. Measure peak area.

CALCULATIONS: 11. From the calibration graph and desorption volume, determine the mass, mg (corrected for DE), of toluene found on the sample collection element (W) and on the average media blank (B). NOTE: If W > sampler capacity x 0.33, the sampler may be saturated [4]. Evaluate each result on the basis of other organics present in the sampled atmosphere, the concentrations of all the adsorbable organics present, the ambient relative humidity, the sampling rate for the organics present and the sampling time. 12. Calculate concentration, C (mg/m3), of toluene in the air sampled:

C

where: NOTE:

( W

106

B) t K

, mg/m 3

t = length of sampling period (min) K = uptake constant (cm3 toluene/min). The uptake constant must be known accurately (either be supplied by the sampler manufacturer or determined by the user by calibration with standard toluene-in-air 2 mixtures [5]). K can be estimated from the diffusion coefficient, D (cm /min), the 2 cross-sectional area, A (cm), and the diffusion pathlength, L (cm), of the sampler:

K

D

A L

.

EVALUATION OF METHOD: Precisions and biases listed in the method were determined by analyzing generated atmospheres containing various concentrations of toluene at a range of humidities and in the presence of other volatile organics [3]. Generated concentrations were independently verified.

REFERENCES: [1] [2] [3] [4] [5]

Perkins, J. B., N. H. Price, L. Eggenberger and J. A. Burkart. Evaluation of Passive Organic Vapor Monitors, available as PB83-221028 from NTIS, Springfield, VA 22161 (1981). NIOSH Manual of Analytical Methods, 3rd ed., V. 2, NMAM 1500, 1501. U.S. Department of Health and Human Services, Publ. (NIOSH) 84-100 (1984). Rodriguez, S. T., D. W. Gosselink, and A. E. Mullins. "Determination of Desorption Efficiencies in the 3M 3500 Organic Vapor Monitor," Am. Ind. Hyg. Assoc. J., 43, 569-574 (1982). Woebkenberg, M. L. Unpublished data (1982). Cassinelli, M.E.; R.D. Hull; J.V. Crable; A.W. Teass, "Protocol for the Evaluation of Passive Monitors," In: Diffusive Sampling: An Alternative Approach to Workplace Air Monitoring. A. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition